JP4231422B2 - Vehicle steering device - Google Patents

Description

  The present invention relates to a steering wheel operated by a driver to steer a vehicle, a steering actuator for steering a steered wheel, and a steered wheel by driving and controlling the steered actuator according to the operation of the steering handle. The present invention relates to a steering device for a steering-by-wire vehicle including a steering control device for steering the vehicle.

  In recent years, the development of steering devices that employ this type of steering-by-wire system has been actively carried out. For example, Patent Document 1 below detects a steering angle and a vehicle speed, calculates a transmission ratio that decreases as the steering angle increases and increases as the vehicle speed increases, and divides the steering angle by this transmission ratio, thereby dividing the front wheel A steering device is shown in which a turning angle (amount of rack shaft displacement) is calculated and the front wheels are turned to the calculated turning angle. Further, in this steering device, the steering response and followability of the front wheels are improved by correcting the calculated turning angle in accordance with the steering speed obtained by time-differentiating the detected steering angle. Further, by calculating the target yaw rate using the detected vehicle speed and the detected steering angle, and correcting the calculated turning angle according to the difference between the calculated target yaw rate and the detected actual yaw rate, the vehicle behavior state Steering control that takes into account is realized.

  Further, in Patent Document 2 below, the steering torque and the steering angle of the steering wheel are detected, two turning angles that increase as the steering torque and the steering wheel steering angle increase are calculated, and these calculated turning angles are added. A steering device is shown in which the front wheels are steered at the steered angle. In this steering apparatus, the vehicle speed is also detected, the both turning angles are corrected based on the detected vehicle speed, and the turning characteristics are changed according to the vehicle speed.

  However, in any of the above-described conventional devices, the steering angle and the steering torque, which are the operation input values for the steering wheel by the driver for steering the vehicle, are detected, and the front wheels are detected using the detected steering angle and steering torque. The steering angle is directly calculated, and the front wheels are steered to the calculated steering angle. However, although the steering control of these front wheels has removed the mechanical connection between the conventional steering wheel and the steered wheels, the response of the steering of the front wheels to the operation of the steering wheel is the operation position of the steering wheel. Alternatively, the basic technical idea of determining the front wheel turning angle according to the operating force is exactly the same, and in these turning methods, the front wheel turning angle is determined according to human sensory characteristics. It was difficult to drive the vehicle.

  That is, in the above-described conventional device, the turning angle that cannot be perceived by the driver is determined directly in response to the operation of the steering wheel, and the vehicle turns by turning the front wheels according to the turning angle. . The driver senses the lateral acceleration, yaw rate, and turning curvature of the vehicle due to the turning of the vehicle by touch or vision, and feeds back to the operation of the steering handle to turn the vehicle in a desired manner. In other words, since the turning angle of the front wheels with respect to the steering wheel operation by the driver is a physical quantity that cannot be perceived by humans, the turning angle that is directly determined by the driver's steering operation is the driver's perception. It was not determined according to the characteristics, and this made it difficult to drive the vehicle.

  Further, in the above-described conventional apparatus, the determined turning angle is corrected according to the difference between the target yaw rate calculated using the detected vehicle speed and the detected steering wheel angle, and the detected actual yaw rate. This is merely correction of the turning angle in consideration of the behavior state of the vehicle, and does not determine the turning angle according to the yaw rate that the driver will perceive by operating the steering wheel. Accordingly, in this case as well, the turning angle determined for the driver's steering operation is not determined in accordance with the driver's perceptual characteristics, making it difficult to drive the vehicle.

  Further, the conventional apparatus does not include means for notifying the driver of the abnormality that has occurred when an abnormality has occurred in the steering device itself. In general, in a steering apparatus that employs a steering-by-wire system, a system is multiplexed as a fail-safe mechanism. If an abnormality occurs in the main steering system that is normally used, for example, the vehicle can be safely driven by switching to the standby system. At this time, as means for notifying the driver that an abnormality has occurred, for example, increasing the reaction torque (steering torque) of the steering wheel can be considered.

  However, in the conventional steering device, when the reaction torque (steering torque) of the steering wheel is simply changed, the operating state of the steering actuator of the steering device may be changed in accordance with this change. In other words, the conventional steering device determines the turning angle of the steered wheels in response to the steering wheel operating position or operating force as the response of the steered wheels to the steering wheel operation. When it becomes difficult to steer the steering wheel, the operation amount of the steering actuator is limited accordingly. For this reason, the vehicle performance (for example, the return of the steering wheel, the straightness, etc.) may be greatly affected, and the motion characteristics of the vehicle may be deteriorated. On the other hand, if the steering torque is increased to such an extent that it does not affect the vehicle performance, it may not function as an abnormality alarm for the driver.

JP 2000-85604 A Japanese Patent Laid-Open No. 11-124047

  In order to cope with the above problem, the present inventors have worked on research on a vehicle steering apparatus that can steer a vehicle in accordance with human perceptual characteristics in response to a steering wheel operation by a driver. Regarding such human perception characteristics, according to Weber-Fechner's law, it is said that the human sensory quantity is proportional to the logarithm of the physical quantity of the given stimulus. In other words, if the physical quantity of a stimulus given to a human being is changed exponentially with respect to the human operating quantity, the relationship between the operating quantity and the physical quantity can be matched to the human perceptual characteristics. The present inventors have applied the Weber-Hefner's law to a vehicle steering system and discovered the following.

  When driving a vehicle, the vehicle turns by operating the steering handle, and the vehicle's motion state quantities such as lateral acceleration, yaw rate, and turning curvature change as the vehicle turns, and the driver senses the motion state quantity of the vehicle. And it feels more visually. Accordingly, if the amount of motion state of the vehicle that can be perceived by the driver is changed exponentially with respect to the driver's operation on the steering wheel, the driver's operation on the steering wheel is not changed by the driver. The vehicle can be operated according to the perceptual characteristics.

  The present invention is based on the above discovery. The purpose of the present invention is to make the vehicle easier to drive and to generate an abnormality by steering the vehicle in accordance with human perceptual characteristics in response to the operation of the steering wheel by the driver. An object of the present invention is to provide a vehicle steering apparatus capable of reliably reporting an abnormality that has occurred without impairing human perception characteristics and vehicle movement characteristics.

In order to achieve the above object, the present invention is characterized in that a steering handle operated by a driver to steer a vehicle, a steering actuator for turning a steered wheel, and an operation of the steering handle. a vehicle steering apparatus of a steer-by-wire system and a steering control system for steering the steerable wheels of the steering actuator drive control to Te, the steering control system detects a displacement amount of the steering wheel A displacement amount sensor, conversion means for converting the detected displacement amount into an operating force applied to the steering wheel, and a vehicle driving state amount that can be perceived by the driver in relation to turning of the vehicle. And a power function of the operating force with an index obtained by dividing a predetermined Weber ratio related to the motion state quantity by a predetermined Weber ratio related to the operating force. The anticipated motion state quantity of the vehicle that is, rotation of the the motion state quantity calculating means for calculating using the converted operation force, the steerable wheels necessary for the vehicle to move in anticipated motion state quantity that is the calculated A turning angle calculation means for calculating a steering angle using the calculated expected motion state quantity, and the turning wheel is controlled by controlling the turning actuator according to the calculated turning angle. Steering control means for steering to a steered angle, and steered control means for controlling the steered actuator in accordance with the calculated steered angle and steering the steered wheels to the steered angle calculated. If, by keeping an abnormality detecting means for detecting an abnormality relating to the steering of the steered wheels, the power function of the operating force and the anticipated motion state quantity of the previous SL vehicle, the steering anomalies detected by said abnormality detecting means An error to notify the driver via the steering wheel In that it includes a notification unit. In this case, the expected motion state quantity is one of a lateral acceleration, a yaw rate, and a turning curvature of the vehicle .

In the present invention configured as described above, first, the operation force of the driver against the steering wheel is, the driver in relation to the turning of the vehicle is represent a motion state of the vehicle that may be perceived, to the motion state quantity Expected motion state quantity of the vehicle (lateral acceleration, yaw rate, turning curvature, etc.) defined as a power function of the operating force with an index obtained by dividing a predetermined Weber ratio by a predetermined Weber ratio related to the operating force ). Then, based on the converted expected motion state quantity, the turning angle of the steered wheel necessary for the vehicle to move with the expected motion state quantity is calculated, and the steered wheel is added to the calculated turning angle. Steered. Therefore, when the vehicle turns by turning the steered wheels, the driver is given the expected motion state quantity as the “physical quantity of the applied stimulus” according to the Weber-Hefner law. Then, the anticipated motion state quantity, since it is intended to change in the base Ki-th power relationship to the operation force of the steering wheel, the driver, while perceiving the motion state quantity that matches the human perception characteristics, steering The handle can be operated. The lateral acceleration and yaw rate can be sensed tactilely by the driver in contact with each part in the vehicle. Further, the turning curvature can be visually perceived by the driver due to changes in the situation within the field of view of the vehicle. As a result, according to the present invention, the driver can operate the steering wheel in accordance with human perceptual characteristics, so that driving of the vehicle is simplified.

Further, when an abnormality relating to turning of the steered wheels is detected, the detected abnormality is maintained in a state in which a power function of the driver's operating force with respect to the steering wheel and the expected motion state quantity that can be perceived by the driver is maintained. Is notified via the steering wheel. For this reason, the driver can reliably recognize the occurrence of an abnormality through the steering wheel and can operate the steering wheel while perceiving a motion state amount that matches human perception characteristics. Therefore, in order to notify the occurrence of an abnormality related to turning of the steered wheels, it is possible to notify the driver with certainty without deteriorating the motion characteristics of the vehicle, which is preferable.

According to another aspect of the present invention, in the steering device for a steering-by-wire vehicle, a reaction force having an exponential relationship with a displacement amount of the steering wheel detected by the displacement amount sensor is applied to the operation of the steering wheel. Reaction force applying means is provided, and when the abnormality detecting means detects an abnormality related to turning of a steered wheel by the abnormality detecting means, the amount of displacement of the steering wheel and the reaction force applying means are applied to the steering handle. While changing the exponential relationship with the reaction force, the reaction force applying means may apply the changed reaction force in the changed exponential relationship to the steering wheel. In this case, the abnormality notifying means indicates an exponential relationship between the displacement amount of the steering handle and the reaction force applied to the steering handle by the reaction force applying means, with respect to the operation of the steering handle by the reaction force applying means. It is better to change to an exponential relationship for applying a predetermined amount of reaction force.

  According to this, the abnormality related to the turning of the steered wheels is notified by appropriately changing the magnitude of the reaction force applied to the steering wheel in accordance with the Weber-Hefner law. For this reason, the driver can recognize that an abnormality has occurred reliably when the magnitude of the reaction force (or steering force) of the steering wheel changes according to human perceptual characteristics while the vehicle is traveling. In this case, the driver can recognize the occurrence of the abnormality more reliably by notifying the occurrence of the abnormality by changing the reaction force (or the steering force) to be larger than that in the normal state. Even in this case, the driver can surely recognize the occurrence of the abnormality through the steering wheel and can operate the steering wheel while perceiving the amount of motion state that matches human perceptual characteristics. Therefore, in order to notify the occurrence of an abnormality related to turning of the steered wheels, it is possible to notify the driver with certainty without deteriorating the motion characteristics of the vehicle.

  According to another aspect of the present invention, in the steering device for a steering-by-wire vehicle, when the abnormality notification unit detects an abnormality related to turning of the steered wheels by the abnormality detection unit, the neutral position of the steering handle is set. There are also changes. In this case, the abnormality notification unit may change the neutral position of the steering handle in a stepwise manner in accordance with the degree of abnormality related to turning of the steered wheels detected by the abnormality detection unit.

  According to these, the abnormality relating to the turning of the steered wheels is notified by changing the neutral position of the steering wheel. For this reason, since the driver recognizes that the neutral position of the steering wheel has been changed as a visual discomfort, it is possible to reliably notify the occurrence of an abnormality. In addition, by changing the neutral position of the steering wheel in a stepwise manner according to the degree of abnormality that has occurred, the driver can recognize the degree of abnormality through visual discomfort. At this time, since the steering apparatus and the steered wheels are mechanically disconnected from each other, the neutral position of the steered wheels is not changed with the change of the neutral position of the steering handle. For this reason, the motion characteristics of the vehicle are not deteriorated. Therefore, in this case as well, the driver can reliably recognize the occurrence of abnormality via the steering handle and can operate the steering handle while perceiving the amount of motion state that matches human perceptual characteristics.

a. First Embodiment Hereinafter, a vehicle steering apparatus according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 schematically shows a vehicle steering apparatus according to the first embodiment.

  The steering apparatus includes a steering handle 11 as an operation unit that is turned by a driver to steer left and right front wheels FW1 and FW2 as steered wheels. The steering handle 11 is fixed to the upper end of the steering input shaft 12, and the lower end of the steering input shaft 12 is connected to a reaction force actuator 13 including an electric motor and a speed reduction mechanism. The reaction force actuator 13 applies a reaction force to the turning operation of the steering handle 11 by the driver.

  In addition, the steering device includes a steering actuator 21 including an electric motor and a speed reduction mechanism. The turning force by the turning actuator 21 is transmitted to the left and right front wheels FW1 and FW2 via the turning output shaft 22, the pinion gear 23, and the rack bar 24. With this configuration, the rotational force from the steering actuator 21 is transmitted to the pinion gear 23 via the steering output shaft 22, and the rack bar 24 is displaced in the axial direction by the rotation of the pinion gear 23. Due to the displacement in the axial direction, the left and right front wheels FW1, FW2 are steered left and right.

  Furthermore, this steering device includes an electric motor, a speed reduction mechanism, and a clutch, and includes a standby system steering actuator 25 as a fail safe that starts operation when an abnormality (failure) occurs in the steering actuator 21. The standby system steering actuator 25 is configured such that the clutch is operated when a failure is detected in the operation of the steering actuator 21 by an electric control device to be described later, and the steering force by the standby system steering actuator 25 is changed. It is transmitted to the pinion gear 23 via the rudder output shaft 22. The operation of the standby system steering actuator 25 is the same as the operation of the steering actuator 21 except that the actuator 23 operates when a failure occurs in the steering actuator 21. For this reason, a detailed description of the operation of the standby system steering actuator 25 will be omitted by describing the operation of the steering actuator 21.

  Next, an electric control device that controls the operations of the reaction force actuator 13, the turning actuator 21, and the standby turning actuator 25 will be described. The electric control device includes a steering angle sensor 31, a turning angle sensor 32, a vehicle speed sensor 33, and a lateral acceleration sensor 34.

  The steering angle sensor 31 is assembled to the steering input shaft 12, detects the rotation angle from the neutral position of the steering handle 11, and outputs it as the steering angle θ. The steered angle sensor 32 is assembled to the steered output shaft 22, detects the rotational angle from the neutral position of the steered output shaft 22, and corresponds to the actual steered angle δ (the steered angle of the left and right front wheels FW1, FW2). ). Note that the steering angle θ and the actual turning angle δ are represented by setting the neutral position to “0”, the left rotation angle as a positive value, and the right rotation angle as a negative value. The vehicle speed sensor 33 detects and outputs the vehicle speed V. The lateral acceleration sensor 34 detects and outputs the actual lateral acceleration G of the vehicle. The actual lateral acceleration G also represents leftward acceleration as positive and rightward acceleration as negative.

  These sensors 31 to 34 are connected to the electronic control unit 35. The electronic control unit 35 includes a microcomputer including a CPU, a ROM, a RAM, and the like as main components, and controls operations of the reaction force actuator 13, the steering actuator 21, and the standby system steering actuator 25 by executing a program. To do. An abnormality notification program described later is stored in advance in the ROM, and the electronic control unit 35 (specifically, the CPU) executes each step of the program to notify the driver of the failure that has occurred. Drive circuits 36 and 37 for driving the reaction force actuator 13 and the steering actuator 21 (standby steering actuator 25) are connected to the output side of the electronic control unit 35, respectively. In the drive circuits 36 and 37, current detectors 36a and 37a for detecting a drive current flowing through the electric motor in the reaction force actuator 13 and the turning actuator 21 (standby turning actuator 25) are provided. . The drive current detected by the current detectors 36a and 37a is fed back to the electronic control unit 35 in order to control the drive of both electric motors.

  Next, regarding the steering device of the first embodiment configured as described above, first, the function of FIG. 2 representing the function realized by computer program processing in the electronic control unit 35 for the steering operation of the device. This will be described with reference to a block diagram. The electronic control unit 35 includes a reaction force control unit 40 for controlling the reaction force applied to the steering handle 11, and the left and right front wheels FW1 and FW2 corresponding to the driver's sensory characteristics based on the turning operation of the steering handle 11. A sensory adaptation control unit 50 for determining the target turning angle δd and a steering control unit 60 for controlling the steering of the left and right front wheels FW1, FW2 based on the target turning angle δd.

When the steering handle 11 is turned by the driver, the steering angle sensor 31 detects the steering angle θ, which is the rotation angle of the steering handle 11, and uses the detected steering angle θ as the reaction force control unit 40 and the sense. Each is output to the matching control unit 50. In the reaction force control unit 40, the displacement-torque conversion unit 41 calculates a reaction force torque Tz that is an exponential function of the steering angle θ by using the following equation (1).
Tz ＝ To ・ exp (K1 ・ θ)… Formula 1
However, To and K1 in the formula 1 are constants, and these values will be described in detail when the sensory adaptation control unit 50 described later is described. Further, the steering angle θ in the equation 1 represents the absolute value of the detected steering angle θ. If the detected steering angle θ is positive, the constant To is set to a negative value, and the detected steering angle θ is If negative, the constant To is a positive value having the same absolute value as the negative constant To. Here, it is also possible to calculate the reaction force torque Tz using a conversion table having characteristics as shown in FIG. 3 in which the reaction force torque Tz with respect to the steering angle θ is stored, instead of the calculation of the equation (1). For this reason, in the description of the abnormality notification program detailed later in this specification, the conversion table will be used for description.

  The calculated reaction force torque Tz is supplied to the drive control unit 42. The drive control unit 42 inputs a drive current flowing from the drive circuit 36 to the electric motor in the reaction force actuator 13 and feedback-controls the drive circuit 36 so that a drive current corresponding to the reaction force torque Tz flows through the electric motor. . By the drive control of the electric motor in the reaction force actuator 13, the electric motor applies a reaction force torque Tz to the steering handle 11 via the steering input shaft 12. Therefore, the driver feels the reaction force torque Tz that changes exponentially with respect to the steering angle θ, in other words, while applying a steering torque equal to the reaction force torque Tz to the steering handle 11, It will rotate. The relationship between the steering angle θ and the reaction torque Tz also follows the above-mentioned Weber-Hefner law, and the driver rotates the steering handle 11 while receiving a sense from the steering handle 11 that matches human perception characteristics. Can be operated.

On the other hand, with respect to the steering angle θ input to the sensory adaptation control unit 50, the displacement-torque conversion unit 51 calculates the steering torque Td according to the following equation 2 similar to the equation 1.
Td ＝ To ・ exp (K1 ・ θ)… Formula 2
Also in this case, To and K1 in the formula 2 are constants similar to those in the formula 1. However, the steering angle θ in Equation 2 represents the absolute value of the detected steering angle θ. If the detected steering angle θ is positive, the constant To is set to a positive value, and the detected steering angle is If θ is negative, the constant To is a negative value having the same absolute value as the positive constant To. Here, in this case as well, the steering torque Td may be calculated using a conversion table having characteristics as shown in FIG. 3 in which the steering torque Td with respect to the steering angle θ is stored, instead of the calculation of the expression 2. Good. For this reason, in this specification, the abnormality notification program described in detail later will be described using this conversion table.

The calculated steering torque Td is supplied to the torque-lateral acceleration conversion unit 52. If the absolute value of the steering torque Td is less than a predetermined positive value To, the torque-lateral acceleration conversion unit 52 calculates the expected lateral acceleration Gd that the driver expects through the turning operation of the steering handle 11 according to the following formula 3. Thus, when the absolute value of the steering torque Td is not less than a predetermined positive value To, the expected lateral acceleration Gd, which is a power function of the steering torque Td, is calculated according to the following equation 4.
Gd = 0 (| Td | <To)… Formula 3
Gd = C · Td ^K2 (To ≦ | Td |) Equation 4
However, C and K2 in Formula 4 are constants. Further, the steering torque Td in the equation 4 represents the absolute value of the steering torque Td calculated using the equation 2, and if the calculated steering torque Td is positive, the constant C is a positive value. If the calculated steering torque Td is negative, the constant C is set to a negative value having the same absolute value as the positive constant C. In this case as well, the steering torque Td is calculated by using a conversion table having characteristics as shown in FIG. 4 in which the expected lateral acceleration Gd with respect to the steering torque Td is stored instead of the calculations of the expressions 3 and 4. May be.

Here, Formula 4 will be described. When the steering torque Td is eliminated using the above equation 2, the following equation 5 is obtained.
Gd = C (To · exp (K1 · θ)) ^K2 = C · To ^K2 · exp (K1, K2 · θ) = Go · exp (K1, K2 · θ)
In Equation 5, Go is a constant C · To ^K2 , and Equation 5 indicates that the expected lateral acceleration Gd varies exponentially with respect to the steering angle θ of the steering wheel 11 by the driver. The expected lateral acceleration Gd is a physical quantity that can be perceived by the driver due to the contact of a part of the driver's body with a predetermined part in the vehicle, and follows the aforementioned Weber-Hefner law. Therefore, if the driver can turn the steering handle 11 while perceiving a lateral acceleration equal to the expected lateral acceleration Gd, the relationship between the turning operation of the steering handle 11 and the steering of the vehicle can be expressed by human perception characteristics. It can be made to correspond.

As described above, the expected lateral acceleration Gd shown in the equation 4 (that is, the equation 5) changes exponentially with respect to the steering angle θ, which is the operation amount of the steering wheel 11, and thus the human perception specification is performed. It is suitable for. Further, the simplest method for the turning operation of the steering handle 11 by the driver is to turn the steering handle 11 at a constant speed ω (θ = ω · t). The acceleration Gd changes exponentially with respect to time t as shown in the following equation (6). Therefore, it will be understood that if the steering handle 11 can be rotated while perceiving a lateral acceleration equal to the expected lateral acceleration Gd, the driver can easily rotate the steering handle 11.
Gd = Go · exp (K0 · ω · t) ... Equation 6
However, K0 is a constant having a relationship of K0 = K1 · K2.

Further, as shown in Equation 3, when the steering torque Td is less than the predetermined value To, the expected lateral acceleration Gd is kept at “0”. This is because, even when the steering angle θ is “0”, that is, when the steering wheel 11 is kept at the neutral position, the steering torque Td becomes a positive predetermined value To by the calculation of the above equation 2, and this steering torque Td If (= To) is applied to the calculation of Equation 4, the expected lateral acceleration Gd becomes a positive value C · To ^K2 , which is not realistic. However, as described above, if the steering torque Td is less than the predetermined value To, the expected lateral acceleration Gd is “0”, so this problem is solved.

In this case, if the minimum perceived lateral acceleration that the driver can perceive is Go and the predetermined value To has a relationship of Go = C · To ^K2 , the steering torque Td becomes the predetermined value To. That is, the expected lateral acceleration Gd of the vehicle is kept at “0” until the driver feels the lateral acceleration generated in the vehicle by turning the vehicle by operating the steering handle 11. According to this, only when the steering handle 11 is steered at the minimum steering torque To or more, the left and right front wheels FW1, FW2 are steered by the steered angle required to generate the expected lateral acceleration Gd. Will correspond exactly to the steering of the vehicle.

  Next, how to determine the parameters K1, K2, and C (predetermined values K1, K2, and C) used in the expressions 1 to 6 will be described. In the description of how to determine the parameters K1, K2, and C, the steering torque Td and the expected lateral acceleration Gd in the expressions 2 to 6 are handled as the steering torque T and the lateral acceleration G. According to the aforementioned Weber-Hefner law, “the ratio ΔS / S between the minimum physical quantity change ΔS perceivable by humans and the physical quantity S at that time is constant regardless of the value of the physical quantity S, and the ratio ΔS / S is called the Weber ratio. The present inventors confirmed that the above-mentioned Weber-Hefner's law is established with respect to steering torque and lateral acceleration, and in order to determine the Weber ratio, the following experiments were conducted for men and women, age, and vehicle driving. I went to various people with different histories.

  Regarding the steering torque, a torque sensor is assembled to the steering handle of the vehicle, a test torque is applied to the steering handle from the outside, and the test torque is changed in various manners, and a human being resists this test torque. Measured the human's ability to adjust the steering torque to adjust the steering handle so that it does not rotate by applying an operating force to the steering handle. That is, in the above situation, when the detected operation torque at a certain time is T, and the minimum steering torque change amount that can be perceived as a change from the detected steering torque T is ΔT, the ratio value ΔT / T, that is, Weber The ratio was measured for various humans. According to this experimental result, the Weber ratio ΔT / T was approximately constant 0.03 regardless of the operation direction of the steering wheel, the state of the hand holding the steering wheel, and the magnitude and direction of the inspection torque. .

  Regarding the lateral acceleration, a wall member is provided on the side of the driver's seat, and a force sensor for detecting the pressing force of the human shoulder is assembled to the wall member. The wall member is made to contact the wall member against the inspection force while applying the inspection force to the wall member from the outside in the lateral direction and changing the inspection force in various modes. It was adjusted so that the wall member does not move by pushing, that is, the human side force adjustment ability to maintain the posture was measured. That is, under the above situation, F is the detection force that can withstand lateral force from the outside at a certain time and maintain the posture, and the minimum force change amount ΔF that can perceive the change from the detection force F The ratio value ΔF / F, the Weber ratio, was measured for various humans. According to the results of this experiment, the Weber ratio ΔF / F was a substantially constant value of about 0.09 regardless of the magnitude and direction of the reference force applied to the wall member.

On the other hand, when the formula 2 is differentiated and the formula 2 is considered in the differentiated formula, the following formula 7 is established.
ΔT ＝ To ・ exp (K1 ・ θ) ・ K1 ・ Δθ = T ・ K1 ・ Δθ
When the equation 7 is modified and the Weber ratio ΔT / T related to the steering torque obtained by the experiment is Kt, the following equation 8 is established.
K1 = ΔT / (T · Δθ) = Kt / Δθ Equation 8

If the maximum steering torque is Tmax, the following formula 9 is established from the above formula 2.
Tmax ＝ To ・ exp (K1 ・ θmax) ... Equation 9
If Equation 9 is modified, the following Equation 10 is established.
K1 = log (Tmax / To) / θmax Equation 10
Then, the following formula 11 is derived from the formula 8 and the formula 10.
Δθ = Kt / K1 = Kt · θmax / log (Tmax / To) (Formula 11)
In Equation 11, Kt is the Weber ratio of the steering torque T, θmax is the maximum value of the steering angle, Tmax is the maximum value of the steering torque, and To is the minimum perceptible horizontal that can be perceived by humans as described above. Since the values Kt, θmax, Tmax, and To are all constants determined by experiments and the system, the differential value Δθ is calculated using the equation (11). Can be calculated. Then, a predetermined value (coefficient) K1 can also be calculated based on Equation 8 using the differential value Δθ using the Weber ratio Kt.

In addition, when the expression 4 is differentiated and the expression 4 is considered in the differentiated expression, the following expression 12 is established.
ΔG = C ・ K2 ・ T ^K2-1 ΔT = G ・ K2 ・ ΔT / T
When Expression 12 is modified and the Weber ratio ΔT / T related to the steering torque obtained by the experiment is set to Kt and the Weber ratio ΔF / F related to the lateral acceleration is set to Ka, the following Expressions 13 and 14 are established.
ΔG / G = K2 · ΔT / T Equation 13
K2 = Ka / Kt ... Formula 14
In this equation 14, Kt is the Weber ratio related to the steering torque, and Ka is the Weber ratio related to the lateral acceleration, both of which are given as constants. Therefore, using these Weber ratios Kt and Ka, the above equation is used. 14 can also calculate the coefficient K2.

If the maximum value of the lateral acceleration is Gmax and the maximum value of the steering torque is Tmax, the following equation 15 is derived from the equation 4.
C = Gmax / Tmax ^K2 Equation 15
In Equation 15, Gmax and Tmax are constants determined by experiments and systems, and K2 is calculated by Equation 14, so that a constant (coefficient) C can also be calculated.

  As described above, the maximum value θmax of the steering angle θ, the maximum value Tmax of the steering torque T, the maximum value Gmax of the lateral acceleration G, the minimum steering torque To, the minimum sensed lateral acceleration Go, the Weber ratio Kt and the lateral acceleration relating to the steering torque T. If the Weber ratio Ka is determined by experiment and system, the coefficients K1, K2, and C in the equations 1 to 5 can be determined in advance by calculation. Here, a preferable numerical example by experiment is shown. In a vehicle having a wheelbase L of 2.67 m, θmax = π / 2, Tmax = 3.5 Nm, Gmax = 9.8 m / s / s, To = 0.76 Nm, Go = 0.1 m / s / s, Kt = 0.03, Ka = 0.09. In this case, K1 = 0.17, K2 = 3.0, C = 0.23 It is. In this case, Δθ = 0.18. Accordingly, in the displacement-torque conversion units 41 and 51 and the torque-lateral acceleration conversion unit 52, the reaction force torque Tz, the steering torque Td, and the expected lateral acceleration that match the driver's perceptual characteristics are obtained using the equations 1-5. Gd can be calculated.

  Returning to the description of FIG. 2 again, the expected lateral acceleration Gd calculated by the torque-lateral acceleration conversion unit 52 is supplied to the turning angle conversion unit 53. The turning angle conversion unit 53 calculates the target turning angle δd of the left and right front wheels FW1 and FW2 necessary for generating the expected lateral acceleration Gd, and changes according to the vehicle speed V as shown in FIG. And a table representing a change characteristic of the target turning angle δd with respect to the expected lateral acceleration Gd. This table is a set of data collected by running the vehicle while changing the vehicle speed V and actually measuring the turning angle δ and the lateral acceleration G of the left and right front wheels FW1, FW2. Then, the turning angle conversion unit 53 refers to this table and calculates a target turning angle δd corresponding to the input expected lateral acceleration Gd and the detected vehicle speed V input from the vehicle speed sensor 33. Further, the lateral acceleration G (expected lateral acceleration Gd) and the target turning angle δd stored in the table are both positive, but the expected lateral acceleration Gd supplied from the turning angle conversion unit 53 is negative. In this case, the output target turning angle δd is also negative.

Since the target turning angle δd is a function of the vehicle speed V and the lateral acceleration G as shown in the following formula 16, it can be calculated by executing the calculation of the following formula 16 instead of referring to the table. it can.
δd = L · (1 + A · V ² ) · Gd / V ² Equation 16
However, L in the equation 16 is a predetermined value (for example, 2.67 m) indicating the wheel base of the vehicle, and A is a predetermined value (for example, 0.00187).

The calculated target turning angle δd is supplied to the turning angle correction unit 61 of the turning control unit 60. The turning angle correction unit 61 receives the expected lateral acceleration Gd from the torque-lateral acceleration conversion unit 52 and also the actual lateral acceleration G detected by the lateral acceleration sensor 34, and calculates the following equation (17). The corrected target turning angle δda is calculated by correcting the inputted target turning angle δd.
δda = δd + K3 · (Gd−G) Equation 17
However, the coefficient K3 is a predetermined positive constant. When the actual lateral acceleration G is less than the expected lateral acceleration Gd, the coefficient K3 is corrected so that the absolute value of the corrected target turning angle δda is increased. . When the actual lateral acceleration G exceeds the expected lateral acceleration Gd, the corrected target turning angle δda is corrected to be smaller. By this correction, the target turning angle δd of the left and right front wheels FW1, FW2 necessary for the expected lateral acceleration Gd can be ensured with higher accuracy.

  The calculated corrected target turning angle δda is supplied to the drive control unit 62. The drive control unit 62 inputs the actual turning angle δ detected by the turning angle sensor 32, and turns the steering actuator 21 (standby system) so that the left and right front wheels FW1, FW2 are turned to the corrected target turning angle δda. The rotation of the electric motor in the steering actuator 25) is feedback controlled. The drive control unit 62 also inputs a drive current flowing from the drive circuit 37 to the electric motor in the steering actuator 21 (standby system steering actuator 25), and drives the electric motor with a magnitude corresponding to the steering torque. The drive circuit 37 is feedback controlled so that the current flows appropriately. Due to the drive control of the electric motor in the steered actuator 21 (standby steered actuator 25), the rotation of the electric motor is transmitted to the pinion gear 23 via the steered output shaft 22, and the rack bar is rotated by the pinion gear 23. 24 is displaced in the axial direction. As the rack bar 24 is displaced in the axial direction, the left and right front wheels FW1 and FW2 are steered to the corrected target turning angle δda.

  Next, in the state where the left and right front wheels FW1, FW2 are steered to the corrected target turning angle δda with respect to the steering angle θ input to the steering handle 11 of the driver as described above, the electronic control unit 35 is An abnormality notification program shown in FIG. 6 is repeatedly executed every predetermined short time to detect an abnormality (failure) related to turning of the left and right front wheels FW1 and FW2 as the steered wheels and notify the driver. Hereinafter, the abnormality notification program will be described in detail.

  The abnormality notification program starts to be executed in step S10, and in step S11, the electronic control unit 35 determines whether or not a failure has occurred regarding the steering of the left and right front wheels FW1 and FW2. That is, the electronic control unit 35 determines whether or not the fail determination flag FRG acquired from the drive circuit 37 is “1”. The fail determination flag FRG is a flag indicating a failure occurrence state by being set to “1” and indicating a normal state by being set to “0”.

  Specifically, the drive circuit 37 will fail if there is a problem with the operation of the electric motor in the steering actuator 21 and the drive current of the electric motor detected by the current detector 37a is abnormal. The determination flag FRG is set to “1”. Then, the fail determination flag FRG set to “1” is output to the electronic control unit 35. Thus, if the output failure determination flag FRG is “1”, the electronic control unit 35 determines “Yes” because the failure has occurred in the steering actuator 21 of the steering device, and the step Proceed to S12.

  In step S12, the electronic control unit 35 has a large steering torque Td (reaction force torque Tz) based on the conversion table of the steering torque Td (reaction force torque Tz) with respect to the steering angle θ shown in FIG. The map M2 is adopted and changed. This map M2 has a characteristic that the steering torque Td (reaction force torque Tz) increases exponentially with respect to the steering angle θ, similarly to the map M1 indicated by a broken line that is adopted when normal, that is, when no failure occurs. The steering torque Td (reaction torque Tz) is the same as that of the map M1 at the neutral position of the steering handle 11, and the steering torque Td (reaction torque) of the map M1 increases as the steering angle θ increases. Greater than (Tz).

  For this reason, in a state where a failure has occurred, that is, in a state where the failure determination flag FRG is set to “1”, the driver steers the steering handle 11 with a larger steering torque Td than the normal time, and uses it as an operation input value. The steering angle θ is input. Then, the electronic control unit 35 adopts and changes the map M2 of the conversion table of the steering torque Td (reaction torque Tz) with respect to the steering angle θ, and changes the steering angle θ input based on the adopted map M2. The steering torque Td (reaction force torque Tz) is determined, and the process proceeds to step S14. Here, since the steering device employs the steer-by-wire system, even if the steering torque Td is largely changed, the operation state of the steering actuator 21 described above is not affected at all. That is, the driver turns the steering wheel 11 according to human perceptual characteristics while feeling the expected lateral acceleration Gd according to the Weber-Hefner law corresponding to the inputted steering angle θ, except that the steering torque Td is increased. The vehicle can be turned by moving the vehicle.

  On the other hand, if the fail determination flag FRG is not “1” in step S11, that is, if the fail determination flag FRG is “0”, the electronic control unit 35 determines “No” because no file is generated. Determine and proceed to step S13. In step S13, the electronic control unit 35 employs a map M1 in which the steering torque Td (reaction torque Tz) has a normal magnitude based on the conversion table of the steering torque Td (reaction torque Tz) with respect to the steering angle θ. . Then, the electronic control unit 35 determines the steering torque Td (reaction force torque Tz) for the steering angle θ input based on the adopted map M1, and proceeds to step S14.

  In step S14 and step S15, the expected lateral acceleration Gd and the target turning angle δd are determined in the same manner as the description of the turning operation of the turning device described above. That is, in step S14, the expected lateral acceleration Gd is determined using the conversion table shown in FIG. 4 based on the steering torque Td (reaction torque Tz) determined in step S12 or step S13. In step S15, the target turning angle δd is determined using the conversion table shown in FIG. 5 based on the expected lateral acceleration Gd determined in step S14.

  After the processing of step S14 and step S15, the process proceeds to step S16, and the electronic control unit 35 once resets the fail determination flag FRG, that is, sets it to “0”, and temporarily ends the execution of the abnormality notification program in step S17. .

  As can be understood from the above description of the operation, according to the first embodiment, the steering angle θ as the operation input value of the driver with respect to the steering handle 11 is converted into the steering torque Td by the displacement-torque conversion unit 51 and the same. The converted steering torque Td is converted into the expected lateral acceleration Gd by the torque-lateral acceleration conversion unit 52, and the left and right front wheels FW1, FW2 are estimated by the turning angle conversion unit 53, the turning angle correction unit 61, and the drive control unit 62. The vehicle is steered to the corrected target turning angle δda necessary for generating the lateral acceleration Gd.

  In this case, since the steering torque Td is equal to the reaction force torque Tz, it is a physical quantity that can be perceived by the driver from the steering wheel 11 due to the action of the reaction force actuator 13 and changes exponentially with respect to the steering angle θ. Therefore, the driver can turn the steering handle 11 according to the human perceptual characteristic while feeling the reaction force according to the Weber-Hefner law. The actual lateral acceleration G generated in the vehicle by turning the left and right front wheels FW1 and FW2 is a physical quantity that can be perceived, and the actual lateral acceleration G is controlled to be equal to the expected lateral acceleration Gd. Further, the expected lateral acceleration Gd also changes exponentially with respect to the steering angle θ input by the driver (exponentially by changing Expression 4 to Expression 5). Accordingly, the driver can turn the steering wheel 11 by turning the steering handle 11 according to the human perceptual characteristic while feeling the lateral acceleration according to the Weber-Hefner law. As a result, the driver can operate the steering handle 11 in accordance with human perceptual characteristics, and thus driving of the vehicle is simplified.

  Further, the turning angle correction unit 61 corrects the target turning angle δd so that the actual lateral acceleration G actually generated in the vehicle accurately corresponds to the steering angle θ of the steering handle 11, so that the vehicle An actual lateral acceleration G accurately corresponding to the steering angle θ of the steering handle 11 is generated. As a result, the driver can operate the steering wheel 11 while perceiving the lateral acceleration more accurately according to the human perceptual characteristics, so that the driving of the vehicle becomes easier.

  Further, when an abnormality (failure) related to steering of the steering apparatus occurs, the driver inputs the steering angle θ as a steering input value while feeling a steering torque Td that is larger than that in the normal state. Thus, the driver can recognize that a failure has occurred by feeling a steering feeling that changes exponentially and is different from the normal time. In this case, even if the steering torque Td increases, the vehicle can be turned without changing other perceptual characteristics, that is, the perceptual characteristics of the expected lateral acceleration Gd. As a result, the driver can operate the steering handle 11 in accordance with the human perceptual characteristics, so that the driver can be surely notified without damaging the motion characteristics of the vehicle before and after the occurrence of a failure. is there.

b. Second Embodiment In the first embodiment described above, the magnitude of the steering torque Td (reaction torque Tz) is detected when a failure related to the steering of the left and right front wheels FW1, FW2 as the steered wheels is detected and notified to the driver. By increasing (heavy) (heavy) and giving a sense of incongruity to the driver's steering feeling, a notification was made that a failure occurred. Instead of this, or in addition to this, it is also possible to notify the driver in a stepwise manner according to the level of the failure that has occurred and to predict the failure that has occurred. Hereinafter, although this 2nd Embodiment is described in detail, since it is the same as that of the said 1st Embodiment regarding the structure and steering operation of a steering device, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

  In the second embodiment, the abnormality notification program shown in FIG. 7 is executed by the electronic control unit 35 when a failure occurs. The abnormality notification program is started in step S50, and in step S51, the electronic control unit 35 determines whether or not a failure has occurred regarding the steering of the left and right front wheels FW1 and FW2. That is, the electronic control unit 35 determines whether or not the fail determination flag FRG acquired from the drive circuit 37 is “1”. The fail determination flag FRG is the same flag as the abnormality notification program of the first embodiment. Then, if the fail determination flag FRG is “0”, that is, if no failure has occurred, the determination is “No”, and the process proceeds to step S 52, in accordance with the human perceptual characteristics, as in the first embodiment described above. The left and right front wheels FW1, FW2 are steered by the turning operation, and the execution of the abnormality notification program is temporarily terminated in step S60.

  On the other hand, if the fail determination flag FRG is “1” in step S51, that is, if a failure has occurred, “Yes” is determined, and in step S53, the electronic control unit 35 determines the level of the failure that has occurred. To determine whether or not the vehicle can continue to travel. In this level determination, it is determined whether or not the generated failure makes the vehicle travel impossible. When the travel is possible, the fail level is determined according to a margin until the travel is impossible.

  That is, the electronic control unit 35 can operate the steering actuator 21, but, for example, the main line of the multiple communication lines including three lines set between the electronic control unit 35 and the steering actuator 21 may be disconnected (allowance). If the fail level is 1), the main line and the second line are disconnected (fail level 2 if the margin is small), it is determined that the vehicle can continue to travel and “Yes” is determined. In step S54, the neutral position of the steering wheel 11 is changed by offset by an offset amount θoff (for example, 0 <θoff <π / 6). This will be described in detail with reference to FIGS. 8 and 9 by taking the disconnection of the multiplex communication line as an example.

  When the multiplex communication line is normal, that is, when the multiplex communication line is not disconnected, the electronic control unit 35 sets the offset amount θoff to “0” as shown in the normal region of FIG. The neutral position is set to a normal state as shown in FIG. When the state where the main line of the multiplex communication line is disconnected, that is, the fail level 1 is detected from this normal state, the electronic control unit 35 sets the offset amount θoff corresponding to the fail level 1 as shown in the notification area of FIG. Then, as shown in FIG. 9B, the neutral position of the steering handle 11 is offset by the offset amount θoff set as the notification state.

  More specifically, the electronic control unit 35 drives the reaction force actuator 13 via the drive circuit 36 to rotate the steering handle 11 until the neutral position becomes the set offset amount θoff. Thereby, the electronic control unit 35 resets the offset position rotated by the offset amount θoff as a new neutral position, and detects the steering angle θ input by the driver as θ = θ−θoff. In this way, by offsetting the neutral position of the steering handle 11, the driver can visually feel a sense of incongruity and recognize that an abnormality has occurred in the steering device. In this case, since the steering device employs a steer-by-wire system, it does not affect the neutral positions of the left and right front wheels FW1, FW2. For this reason, the driver feels the lateral acceleration according to the Weber-Hefner's law by opening the steering handle 11 from the newly set neutral position, and rotates the steering handle 11 according to the human perceptual characteristics. It can be operated to turn the vehicle.

  Further, when the electronic control unit 35 detects the state where the main line and the second line of the communication line are disconnected, that is, the fail level 2, the electronic control unit 35 supports the fail level 2 as shown in the notification area of FIG. Set the offset amount θoff. Then, similarly to the above-described fail level 1, the neutral position of the steering handle 11 is rotated until the offset amount θoff corresponding to the set fail level 2 is reached, and the rotational position is set as a new neutral position. Here, the offset amount θoff of the fail level 2 is set larger than the offset amount θoff of the fail level 1. As described above, by increasing the offset amount θoff as the fail level increases, the driver feels visually more uncomfortable and can recognize the failure occurring in the steering device step by step. it can.

  Here, when the main line of the multiplex communication line is disconnected and fail level 1 is detected, and then the second line of the multiplex communication line is disconnected and fail level 2 is detected, the electronic control unit 35 The neutral position of the steering handle 11 is offset in stages. That is, when the fail level 1 is detected, the electronic control unit 35 determines the offset amount θoff corresponding to the fail level 1 and offsets the neutral position of the steering wheel 11. In this state, when the second line is further disconnected and the fail level 2 is detected, the electronic control unit 35 rotates the steering handle 11 from the neutral position corresponding to the fail level 1 to the neutral position corresponding to the fail level 2. Let As described above, the electronic control unit 35 offsets the steering handle 11 stepwise in accordance with the generated fail level.

  After the setting process in step S54, in step S55, the electronic control unit 35 considers the offset amount θoff set in step S54 in the conversion table of the steering torque Td (reaction torque Tz) with respect to the steering angle θ. The steering torque Td (reaction force torque Tz) is determined based on the changed conversion table. That is, when the neutral position of the steering wheel 11 is offset in step S54, the electronic control unit 35 translates the conversion table by the offset amount θoff relative to the steering angle θ (in this embodiment, steering) (Change in parallel to the positive direction of the angle θ). Then, the electronic control unit 35 determines the steering torque Td (reaction force torque Tz) corresponding to the input steering angle θ based on the changed conversion table.

  In subsequent steps S56 and S57, the expected lateral acceleration Gd and the target turning angle δd are determined in the same manner as in steps S14 and S15 of the abnormality notification program in the first embodiment. That is, in step S56, the expected lateral acceleration Gd is determined based on the steering torque Td (reaction torque Tz) determined in step S55. In step S57, the target turning angle δd is determined based on the expected lateral acceleration Gd determined in step S56.

  After the processing of step S56 and step S57, the process proceeds to step S58, where the electronic control unit 35 temporarily resets the fail determination flag FRG, that is, sets it to “0”, and temporarily ends the execution of the abnormality notification program in step S60. .

  On the other hand, in step S53, the electronic control unit 35, for example, disconnects all the multiple communication lines set between the electronic control unit 35 and the steering actuator 21 (failure level 3 because communication is not possible), thereby turning the steering actuator 21. When the operation of the vehicle is impossible, it is determined that the vehicle cannot continue running due to the malfunction of the actuator 21, and the determination is “No”. In step S59, as a failure process, the operation is switched to the operation of the standby system turning actuator 25, and the neutral position of the steering handle 11 is offset to the maximum to notify that a failure has occurred in the steering system. That is, since all the multiple communication lines are disconnected, the electronic control unit 35 offsets the neutral position of the steering handle 11 by the maximum offset amount θoff as shown in the failure region of FIG. Thereby, the user can know through the visual sense of incongruity that an abnormality has occurred in the steering apparatus of the vehicle. In step S60, the execution of the abnormality notification program is temporarily terminated.

  As can be understood from the above description, according to the second embodiment, the neutral position of the steering handle 11 can be offset according to the level of the generated failure. Thereby, it is possible to give a visually uncomfortable feeling to the driver and to reliably notify the generated failure. In addition, after the steering handle 11 is offset, this offset position is reset as the neutral position. Therefore, the expected lateral acceleration Gd with respect to the steering angle θ as the operation input value of the driver is before and after the neutral position offset of the steering handle 11. Perceived by the driver as well. For this reason, even if it is in the state where the failure was effectively notified to the driver, the motion characteristic of the vehicle can be ensured satisfactorily.

c. First Modification The abnormality notification program according to the first embodiment and the second embodiment is applied to a steering apparatus that employs lateral acceleration as a motion state quantity. Instead of this, it is also possible to implement the abnormality notification program by applying it to a steering device that employs a yaw rate as the amount of motion state. Hereinafter, this first modification will be described. In the first modification, as shown by a broken line in FIG. 1, the steering device is an amount of motion state that can be perceived by the driver instead of the lateral acceleration sensor 34 in the first embodiment and the second embodiment. A yaw rate sensor 38 for detecting a certain actual yaw rate γ is provided. About another structure, it is the same as the said 1st Embodiment and 2nd Embodiment, However Regarding the steering operation, the computer program run in the electronic control unit 35 is the said 1st Embodiment and 2nd Embodiment. The case is slightly different. Moreover, since the abnormality notification program applied to the steering device that uses the yaw rate according to the first modification as the motion state quantity is the same as the abnormality notification program of the first embodiment and the second embodiment, the details thereof are described. Description is omitted.

  In the first modification, the computer program executed by the electronic control unit 35 with respect to the steering operation is shown in the functional block diagram of FIG. In this case, in the sensory adaptation control unit 50, the displacement-torque conversion unit 51 functions in the same manner as in the first embodiment and the second embodiment, but the torque-lateral acceleration conversion in the first embodiment and the second embodiment. Instead of the unit 52, a torque-yaw rate conversion unit 54 is provided.

The torque-yaw rate conversion unit 54 uses the steering torque Td calculated by the displacement-torque conversion unit 51 to calculate the expected yaw rate γd that the driver expects from the turning operation of the steering handle 11 to the steering torque Td. If the absolute value is less than the positive small predetermined value To, the value is set to “0” as shown in the following formula 18. If the absolute value of the steering torque Td is greater than the positive small predetermined value To, the calculation is performed according to the following formula 19.
γd = 0 (| Td | <To) Equation 18
γd = C · Td ^K2 (To ≦ | Td |) Equation 19
However, C and K2 in Equation 19 are constants as in the first and second embodiments. Also in this case, the steering torque Td in the equation 19 represents the absolute value of the steering torque Td calculated using the above equation 2. If the calculated steering torque Td is positive, the constant C Is a positive value, and if the calculated steering torque Td is negative, the constant C is a negative value having the same absolute value as the positive constant C. In this case, the expected yaw rate γd may be calculated using a conversion table having characteristics as shown in FIG. 11 in which the expected yaw rate γd with respect to the steering torque Td is stored instead of the calculations of the equations 18 and 19. Good.

  Further, the turning angle conversion unit 55 calculates the target turning angle δd of the left and right front wheels FW1 and FW2 necessary for generating the expected yaw rate γd, and changes according to the vehicle speed V as shown in FIG. And a table representing the change characteristic of the target turning angle δd with respect to the expected yaw rate γd. This table is a set of data collected by actually measuring the turning angle δ and yaw rate γ of the left and right front wheels FW1 and FW2 while driving the vehicle while changing the vehicle speed V. Then, the turning angle conversion unit 55 refers to this table and calculates the target turning angle δd corresponding to the input expected yaw rate γd and the detected vehicle speed V input from the vehicle speed sensor 33. Further, the yaw rate γ (expected yaw rate γd) and the target turning angle δd stored in the table are both positive, but if the expected yaw rate γd supplied from the turning angle conversion unit 55 is negative, The output target turning angle δd is also negative.

Since the target turning angle δd is a function of the vehicle speed V and the yaw rate γ as shown in the following equation 20, it can be calculated by executing the calculation of the following equation 20 instead of referring to the table. .
δd = L · (1 + A · V ² ) · γd / V Equation 20
However, also in Equation 20, L is a predetermined value (for example, 2.67 m) indicating the wheel base, and A is a predetermined value (for example, 0.00187).

The calculated target turning angle δd is supplied to the turning angle correction unit 63 of the turning control unit 60. The turning angle correction unit 63 receives the expected yaw rate γd from the torque-yaw rate conversion unit 54 and also the actual yaw rate γ detected by the yaw rate sensor 38, and executes the calculation of the following equation (21). The corrected target turning angle δda is calculated by correcting the input target turning angle δd.
δda = δd + K4 · (γd−γ) Equation 21
However, the coefficient K4 is a predetermined positive constant, and when the actual yaw rate γ is less than the expected yaw rate γd, the coefficient K4 is corrected so that the absolute value of the corrected target turning angle δda becomes larger. Further, when the actual yaw rate γ exceeds the expected yaw rate γd, the correction target turning angle δda is corrected to be smaller. By this correction, the turning angles of the left and right front wheels FW1, FW2 necessary for the expected yaw rate γd are more accurately ensured.

  Further, other program processes executed by the electronic control unit 35 are the same as those in the first embodiment and the second embodiment. In the functional block diagram of FIG. 10, the same reference numerals as those in FIG. 2 of the first embodiment and the second embodiment are attached, and the description thereof is omitted.

  In the first modified example described above, the steering angle θ as an operation input value of the driver with respect to the steering handle 11 is converted into the steering torque Td by the displacement-torque converter 51, and the converted steering torque is also converted. Td is converted to the expected yaw rate γd by the torque-yaw rate conversion unit 54, and the left and right front wheels FW1, FW2 are corrected to generate the expected yaw rate γd by the turning angle conversion unit 55, the turning angle correction unit 63, and the drive control unit 62. The vehicle is steered to the target turning angle δda. Also in this case, since the steering torque Td is equal to the reaction force torque Tz, it is a physical quantity that can be perceived by the driver from the steering handle 11 by the action of the reaction force actuator 13, and changes exponentially with respect to the steering angle θ. Therefore, the driver can turn the steering handle 11 according to the human perceptual characteristic while feeling the reaction force according to the Weber-Hefner law.

  Further, the yaw rate γ generated in the vehicle by the steering of the left and right front wheels FW1 and FW2 is a physical quantity that can be perceived, and the yaw rate γ is controlled to be equal to the expected yaw rate γd. It changes exponentially with respect to θ (exponentially by changing equation 19 in the same way as changing from equation 4 to equation 5 in the first embodiment). Therefore, the driver can turn the steering wheel 11 by turning the steering handle 11 according to the human perception characteristic while feeling the yaw rate according to the Weber-Hefner law. As a result, the driver can operate the steering handle 11 in accordance with the human perceptual characteristics, as in the case of the first embodiment and the second embodiment, so that the driving of the vehicle is simplified.

  Also in this first modified example, when an abnormality (failure) related to steering of the steering apparatus occurs, the driver resists the steering torque Td that is larger than the normal time, and steers as a steering input value. Enter the angle θ. As a result, the driver can surely know that a failure has occurred by feeling a steering feeling that changes exponentially and is different from the normal time. In this case, even if the steering torque Td increases, the vehicle can be turned without changing other perceptual characteristics, that is, the perceptual characteristics of the expected lateral acceleration Gd. As a result, the driver can operate the steering handle 11 in accordance with the human perceptual characteristics, and thus can easily drive the vehicle without impairing the motion characteristics of the vehicle.

  Furthermore, the neutral position of the steering handle 11 can be offset according to the level of the failure that has occurred. Thereby, it is possible to give a visually uncomfortable feeling to the driver and to reliably notify the generated failure. In addition, after the steering handle 11 is offset, this offset position is reset as the neutral position. Therefore, the expected lateral acceleration Gd with respect to the steering angle θ as the operation input value of the driver is before and after the neutral position offset of the steering handle 11. Perceived by the driver as well. For this reason, even if it is in the state where the failure was effectively notified to the driver, the motion characteristic of the vehicle can be ensured satisfactorily.

c. Second Modification Next, the abnormality notification program in the first embodiment and the second embodiment is applied to a steering apparatus that employs lateral acceleration as a motion state quantity. In addition, the abnormality notification program in the first modified example is applied to a steering apparatus that employs a yaw rate as a motion state quantity. Instead of these, the present invention can also be applied to a steering apparatus that employs a turning curvature as a motion state quantity. Hereinafter, this second modification will be described. Also in the second modified example, the steering device is configured as shown in FIG. 1 as in the first and second embodiments. However, regarding the turning operation, the computer program executed by the electronic control unit 35 is slightly different from the case of the first embodiment and the second embodiment. Further, the abnormality notification program applied to the steering device having the turning curvature as the motion state quantity according to the second modification is the same as the abnormality notification program of the first embodiment and the second embodiment, and therefore the details thereof. The detailed explanation is omitted.

  In the second modification, the computer program executed by the electronic control unit 35 with respect to the steering operation is shown in the functional block diagram of FIG. In this case, in the sensory adaptation control unit 50, the displacement-torque conversion unit 51 functions in the same manner as in the first embodiment and the second embodiment, but the torque-lateral acceleration conversion in the first embodiment and the second embodiment. Instead of the unit 52, a torque-turning curvature converting unit 56 is provided.

The torque-turning curvature conversion unit 56 uses the steering torque Td calculated by the displacement-torque conversion unit 51 to convert the expected turning curvature ρd that the driver expects by turning the steering handle 11 into the steering torque. If the absolute value of Td is less than a small positive predetermined value To, it is set to “0” as shown in Equation 22 below, and if the absolute value of the steering torque Td is greater than or equal to a positive small predetermined value To, it is calculated according to Equation 23 below.
ρd = 0 (| Td | <To) Equation 22
ρd = C · Td ^K2 (To ≦ | Td |) Equation 23
However, C and K2 in Equation 23 are constants as in the first and second embodiments. Also in this case, the steering torque Td in the equation 23 represents the absolute value of the steering torque Td calculated using the above equation 2. If the calculated steering torque Td is positive, the constant C Is a positive value, and if the calculated steering torque Td is positive, the constant C is a negative value having the same absolute value as the positive constant C. In this case, the expected turning curvature ρd is calculated using a conversion table having characteristics as shown in FIG. 14 in which the expected turning curvature ρd with respect to the steering torque Td is stored in place of the calculations of the equations 22 and 23. May be.

  Further, the turning angle conversion unit 57 calculates the target turning angle δd of the left and right front wheels FW1, FW2 necessary for generating the expected turning curvature ρd, and according to the vehicle speed V as shown in FIG. There is a table that changes and represents the change characteristic of the target turning angle δd with respect to the expected turning curvature ρd. This table is a set of data collected by actually measuring the turning angle δ and the turning curvature ρ of the left and right front wheels FW1 and FW2 while the vehicle is running while changing the vehicle speed V. Then, the turning angle conversion unit 57 refers to this table and calculates the target turning angle δd corresponding to the input expected turning curvature ρd and the detected vehicle speed V input from the vehicle speed sensor 33. The turning curvature ρ (expected turning curvature ρd) and the target turning angle δd stored in the table are both positive, but the expected turning curvature ρd supplied from the torque-turning curvature conversion unit 56 is negative. If so, the output target turning angle δd is also negative.

Since the target turning angle δd is a function of the vehicle speed V and the turning curvature ρ as shown in the following equation 24, the target turning angle δd can be calculated by executing the operation of the following equation 24 instead of referring to the table. it can.
δd = L · (1 + A · V ² ) · ρd Equation 24
However, also in the formula 24, L is a predetermined value (eg, 2.67 m) representing the wheel base, and A is a predetermined value (eg, 0.00187).

The calculated target turning angle δd is supplied to the turning angle correction unit 64 of the turning control unit 60. The turning angle correction unit 64 receives the expected turning curvature ρd from the torque-turning curvature conversion unit 56 and also receives the actual turning curvature ρ from the turning curvature calculation unit 65. The turning curvature calculation unit 65 uses the lateral acceleration G detected by the lateral acceleration sensor 34 or the yaw rate γ detected by the yaw rate sensor 38 and the vehicle speed V detected by the vehicle speed sensor 33 to calculate the following Expression 25. The actual turning curvature ρ is calculated by execution and output to the turning angle correction unit 64.
ρ = G / V ² or ρ = γ / V Equation 25

And the turning angle correction | amendment part 64 performs the calculation of following formula 26, correct | amends the input target turning angle (delta) d, and calculates corrected target turning angle (delta) da.
δda = δd + K5 · (ρd−ρ) Equation 26
However, the coefficient K5 is a predetermined positive constant, and when the actual turning curvature ρ is less than the expected turning curvature ρd, the coefficient K5 is corrected so that the absolute value of the corrected target turning angle δda is increased. When the actual turning curvature ρ exceeds the expected turning curvature ρd, the absolute value of the corrected target turning angle δda is corrected to be smaller. By this correction, the turning angles of the left and right front wheels FW1, FW2 necessary for the expected turning curvature ρd are more accurately ensured.

  Further, other program processes executed by the electronic control unit 35 are the same as those in the first embodiment and the second embodiment. And in the functional block diagram of FIG. 13, the code | symbol same as FIG. 2 of the said 1st Embodiment and 2nd Embodiment is attached | subjected, and the description is abbreviate | omitted.

  Also in the second modified example described above, the steering angle θ as the operation input value of the driver with respect to the steering handle 11 is converted into the steering torque Td by the displacement-torque converter 51, and the converted steering torque is also converted. Td is converted to the expected turning curvature ρd by the torque-turning curvature conversion unit 56, and the left and right front wheels FW1, FW2 generate the expected turning curvature ρd by the turning angle conversion unit 57, the turning angle correction unit 64, and the drive control unit 62. To the corrected target turning angle δda required for Also in this case, since the steering torque Td is equal to the reaction force torque Tz, it is a physical quantity that can be perceived by the driver from the steering handle 11 by the action of the reaction force actuator 13, and changes exponentially with respect to the steering angle θ. Therefore, the driver can turn the steering handle 11 according to the human perceptual characteristic while feeling the reaction force according to the Weber-Hefner law.

  Further, the turning curvature due to the turning of the left and right front wheels FW1 and FW2 is also a physical quantity that can be visually perceived, and this turning curvature ρ is controlled to be equal to the expected turning curvature ρd, and the expected turning curvature ρd is also steered. It changes exponentially with respect to the angle θ (exponentially by changing the expression 23 in the same way as changing the expression 4 to the expression 5 in the first embodiment). Accordingly, the driver can turn the vehicle by turning the steering handle 11 according to human perceptual characteristics while visually perceiving the turning curvature according to the Weber-Hefner's law. As a result, the driver can operate the steering wheel 11 in accordance with the human perceptual characteristics, as in the first and second embodiments, so that driving of the vehicle is simplified.

  Further, the turning angle correction unit 64 corrects the target turning angle δd so that the actual turning curvature ρ actually generated in the vehicle accurately corresponds to the steering angle θ of the steering handle 11, so that the vehicle is steered. The vehicle turns with an actual turning curvature ρ that accurately corresponds to the steering angle θ of the handle 11. As a result, the driver can operate the steering wheel 11 while perceiving a turning curvature that more accurately matches the human perceptual characteristics, and thus the driving of the vehicle is further simplified. Further, the specific operational effects are the same except that the lateral acceleration of the first embodiment and the second embodiment is changed to the turning curvature.

  Also in this second modified example, when an abnormality (failure) related to the steering of the steering device occurs, the driver resists the steering torque Td which is larger than the normal time, and steers as a steering input value. Enter the angle θ. As a result, the driver can surely know that a failure has occurred by feeling a steering feeling that changes exponentially and is different from the normal time. In this case, even if the steering torque Td increases, the vehicle can be turned without changing other perceptual characteristics, that is, the perceptual characteristics of the expected lateral acceleration Gd. As a result, the driver can operate the steering handle 11 in accordance with human perceptual characteristics, so that the vehicle can be easily driven without impairing the motion characteristics of the vehicle.

  Furthermore, the neutral position of the steering handle 11 can be offset according to the level of the failure that has occurred. Thereby, it is possible to give a visually uncomfortable feeling to the driver and to reliably notify the generated failure. In addition, after the steering handle 11 is offset, this offset position is reset as the neutral position. Therefore, the expected lateral acceleration Gd with respect to the steering angle θ as the operation input value of the driver is before and after the neutral position offset of the steering handle 11. Perceived by the driver as well. For this reason, even if it is in the state where the failure was effectively notified to the driver, the motion characteristic of the vehicle can be ensured satisfactorily.

  Furthermore, in carrying out the present invention, the present invention is not limited to the first and second embodiments and the respective modifications, and various modifications can be made without departing from the object of the present invention.

  For example, in the first and second embodiments and the modifications, the steering handle 11 that is turned to steer the vehicle is used. However, instead of this, for example, a joystick-type steering handle that is linearly displaced may be used, or any other one that can be operated by the driver and instructed to steer the vehicle is used. May be.

  In the first and second embodiments and the modifications, the left and right front wheels FW1 and FW2 are steered by rotating the steered output shaft 22 using the steered actuator 21. However, instead of this, the left and right front wheels FW1, FW2 may be steered by linearly displacing the rack bar 23 using the steered actuator 21.

  Further, in the first and second embodiments and the modifications, the lateral acceleration, the yaw rate, and the turning curvature are each independently used as the vehicle motion state quantity that can be perceived by humans. However, the vehicle steering control may be performed by switching the amount of motion state of these vehicles by a selection operation by the driver or automatically switching according to the traveling state of the vehicle. When switching automatically according to the traveling state of the vehicle, for example, when the vehicle is traveling at a low speed (for example, less than 40 km / h), the turning curvature is used as the motion state quantity, and the vehicle is traveling at a medium speed (for example, 40 km). / H or more and less than 100 km / h), the yaw rate is used as the motion state quantity, and lateral acceleration is used as the motion state quantity when the vehicle is traveling at a high speed (for example, 100 km / h or more). According to this, appropriate steering control of the vehicle is performed according to the running state of the vehicle, and the driving of the vehicle becomes easier.

1 is a schematic diagram of a vehicle steering apparatus common to first and second embodiments of the present invention. FIG. FIG. 4 is a functional block diagram functionally representing a computer program process of turning control executed by the electronic control unit of FIG. 1 according to the first and second embodiments of the present invention. It is a graph which shows the relationship between a steering angle and a steering torque. It is a graph which shows the relationship between steering torque and estimated lateral acceleration. It is a graph which shows the relationship between a prospective lateral acceleration and a target turning angle. 2 is a flowchart showing an abnormality notification program executed by the electronic control unit of FIG. 1 according to the first embodiment of the present invention. It is a flowchart which shows the abnormality alerting program which concerns on 2nd Embodiment of this invention and is performed in the electronic control unit of FIG. It is a figure for demonstrating the offset amount set according to a fail level. (A) has shown the neutral position of the steering wheel of a normal state, (b) is the schematic which shows the neutral position of the steering wheel at the time of a failure. It is a functional block diagram functionally showing the computer program process of the steering control performed in the electronic control unit of FIG. 1 according to the first modification of the present invention. It is a graph which shows the relationship between steering torque and estimated yaw rate. It is a graph which shows the relationship between an expected yaw rate and a target turning angle. FIG. 10 is a functional block diagram functionally representing a computer program process of turning control executed by the electronic control unit of FIG. 1 according to a second modification of the present invention. It is a graph which shows the relationship between steering torque and prospective turning curvature. It is a graph which shows the relationship between a prospective turning curvature and a target turning angle.

Explanation of symbols

FW1, FW2 ... front left and right wheels, 11 ... steering handle, 12 ... steering input shaft, 13 ... reaction force actuator, 21 ... steering actuator, 22 ... steering output shaft, 25 ... standby steering actuator, 31 ... steering angle sensor 32 ... Steering angle sensor, 33 ... Vehicle speed sensor, 34 ... Lateral acceleration sensor, 35 ... Electronic control unit, 38 ... Yaw rate sensor, 40 ... Reaction force control unit, 50 ... Sensory adaptation control unit, 51 ... Displacement-torque conversion , 52 ... torque-lateral acceleration converter, 53, 55, 57 ... turning angle converter, 54 ... torque-yaw rate converter, 56 ... torque-turning curvature converter, 60 ... steering controller, 61, 63 , 64 ... Steering angle correction unit

Claims (6)

A steering wheel operated by a driver to steer the vehicle, a steering actuator for steering the steered wheel, and the steered actuator according to the operation of the steering handle to drive and control the steered wheel. In a steering device for a steering-by-wire vehicle equipped with a steering control device for steering, the steering control device includes :
A displacement amount sensor for detecting a displacement amount of the steering wheel;
Conversion means for converting the detected displacement amount into an operating force applied to the steering wheel;
A vehicle driving state quantity that can be perceived by the driver in relation to turning of the vehicle, and a value obtained by dividing a predetermined Weber ratio related to the movement state quantity by a predetermined Weber ratio related to the operating force. A motion state quantity calculating means for calculating a predicted motion state quantity of the vehicle, which is defined as a power function of the operating force as an index , using the converted operating force ;
A turning angle calculation means for calculating a turning angle of the steered wheels necessary for the vehicle to move with the calculated expected motion state quantity, using the calculated expected motion state quantity;
Steering control means for controlling the steered actuator according to the calculated steered angle and steering the steered wheel to the steered angle calculated by the same,
Steering control means for controlling the steered actuator according to the calculated steered angle and steering the steered wheel to the steered angle calculated by the same,
An abnormality detection means for detecting an abnormality related to turning of the steered wheels;
And maintaining the power function of the operating force and the anticipated motion state quantity of the previous SL vehicle, the abnormality detected by the abnormality detecting means comprises an abnormality informing means for informing the driver through the steering wheel A steering-by-wire vehicle steering apparatus characterized by the above. The steering apparatus for a steering-by-wire vehicle according to claim 1,
A reaction force applying means for applying a reaction force in an exponential relationship with a displacement amount of the steering wheel detected by the displacement amount sensor to the operation of the steering wheel;
The abnormality notification means includes
When an abnormality relating to turning of the steered wheels is detected by the abnormality detection means, the exponential relationship between the amount of displacement of the steering wheel and the reaction force applied to the steering handle by the reaction force application means is changed, and the reaction force A steering-by-wire steering apparatus for a vehicle, wherein a reaction force having the changed exponential relationship is applied to the steering handle by an applying means. In the steering device for a steering-by-wire vehicle according to claim 2,
The abnormality notification means includes
The reaction force applying means gives a reaction force larger by a predetermined amount to the operation of the steering handle, as an exponential relationship between the displacement amount of the steering handle and the reaction force applied to the steering handle by the reaction force applying means. A steering-by-wire vehicle steering apparatus characterized by changing to an exponential relationship. The steering apparatus for a steering-by-wire vehicle according to claim 1,
The abnormality notification means changes a neutral position of the steering handle when the abnormality detection means detects an abnormality related to turning of the steered wheels. In the steering device for a steering-by-wire vehicle according to claim 4,
The abnormality notification means changes the neutral position of the steering handle stepwise according to the degree of abnormality related to turning of the steered wheels detected by the abnormality detection means. apparatus. The steering apparatus for a steering-by-wire vehicle according to claim 1,
The predicted motion state quantity is a steering-by-wire vehicle steering apparatus that is one of a lateral acceleration, a yaw rate, and a turning curvature of the vehicle.

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