JP6048253B2 - Steering control device - Google Patents

Description

  The present invention relates to a steering control device, and more particularly to a steering control device having an electric power steering system.

  2. Description of the Related Art Conventionally, an electric power steering (EPS) system including an actuator that assists the steering force of a steering wheel based on a detected value of steering torque output from a torque sensor is known. As a rear wheel steering system, an active rear steering (ARS) system is also known in which a steering angle of a rear wheel is controlled by an actuator in accordance with a steering state of a front wheel and a vehicle behavior.

  Generally, an EPS system performs steering force assist control based on a steering torque detected by a torque sensor and a vehicle speed detected by a wheel speed sensor. Patent Document 1 discloses an electric power steering device that performs steering assist control based on the steering angle of the steering wheel, the angular velocity of the steering angle, and the vehicle speed when a torque sensor fails.

JP 2004-114755 A

  By the way, in a vehicle equipped with an ARS system that is a rear wheel steering system, if an abnormality occurs in the ARS system, the rear wheel may be fixed in a steered state depending on the type of abnormality. When the driver tries to maintain the vehicle in a straight traveling state with the steering angle of the rear wheel locked, the driver operates the steering handle to adjust the steering angle of the front wheel to the steering angle of the rear wheel.

  Since the EPS system assists the driver's steering, the importance as the steering control device is high, and it is preferable to perform the steering assist control as much as possible. However, it is not preferable to generate unnecessary assist force. For example, it is not preferable to generate assist force in a state where the vehicle is traveling straight ahead.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a steering control technique for prohibiting or restricting generation of unnecessary assist force.

In order to solve the above-described problems, a steering control device according to an aspect of the present invention performs a torque detection unit that detects a steering torque applied to a steering member, and a first steering assist control based on the detected steering torque. A first control unit that performs a second steering assist control based on a state quantity indicating that the vehicle is turning when an abnormality occurs in the torque detection unit. A second control unit to be implemented; a rear wheel steering system capable of steering the vehicle rear wheel; a rear wheel steering angle detection unit that detects a rear wheel steering angle; a speed detection unit that detects a wheel speed; and a rear wheel steering Abnormality in the rear wheel steering system when the difference between the detected rear wheel angle detected by the angle detector and the estimated rear wheel angle calculated from the rear wheel speed detected by the speed detector is greater than a predetermined threshold A second abnormality determining unit for determining , Upon occurrence of abnormality in the rear wheel steering system, to prohibit or restrict the second steering assist control.

According to this aspect, since the second steering assist control is prohibited or restricted when an abnormality has occurred in the rear wheel steering system, it is possible to avoid generation of inappropriate assist force. Limiting the second steering assist control means generating an assist force that is smaller than the assist force calculated based on the state quantity indicating that the vehicle is turning. When the second abnormality determination unit estimates the abnormality of the rear wheel steering system from the state quantity of the vehicle, the second control unit can suitably prohibit or restrict the second steering assist control.

  A 2nd abnormality determination part may determine the abnormality of a rear-wheel steering system, if an abnormality detection signal is received from a rear-wheel steering system. When the rear wheel steering system detects its own abnormality and the second abnormality determination unit receives a signal indicating the abnormality, the second abnormality determination unit can accurately determine the abnormality of the rear wheel steering system. It becomes.

  The steering control device may further include a correction information acquisition unit that acquires information indicating that the output correction of the speed detection unit has been performed. The second abnormality determination unit may make the threshold compared with the difference when the output correction of the speed detection unit is performed smaller than the threshold compared with the difference when the output correction is not performed. Thus, when output correction is performed, the second abnormality determination unit can estimate an abnormality of the rear wheel steering system at an early stage.

  The second abnormality determination unit is a case where the turning state of the vehicle is not an understeer state or an oversteer state, and the difference between the detected rear wheel angle and the estimated rear wheel angle is greater than a predetermined threshold value. An abnormality in the wheel steering system may be determined. Thereby, the second abnormality determination unit can improve the abnormality determination accuracy of the rear wheel steering system.

  ADVANTAGE OF THE INVENTION According to this invention, the steering control technique which prohibits or restrict | limits the production | generation of an unnecessary assist force can be provided.

It is a figure which shows roughly the vehicle by which a vehicle steering control apparatus is mounted. It is a figure which shows the functional block of the vehicle steering control apparatus of a present Example. (A) is a figure which shows an example of the 1st assist map which defined assist force with respect to steering angle (theta) str and vehicle speed V, (b) is a figure which shows the correspondence of slip state quantity (DELTA) (theta) and the correction gain C. is there. (A) is a figure which shows a mode that the rear wheel RW1 and RW2 were fixed in the state steered, (b) shows a mode that the vehicle is going straight ahead by steering the front wheel FW1 and FW2. FIG. It is a figure which shows the flowchart of the steering control in an Example.

  FIG. 1 schematically shows a vehicle on which a vehicle steering control device 1 is mounted. The vehicle steering control device 1 includes a steering handle 10 that is a steering member that is turned by a driver. The steering handle 10 is fixed to the upper end of the steering shaft 11. The steering shaft 11 is provided with a steering angle sensor 13 that is a steering angle detector, and the steering angle sensor 13 detects the steering angle of the steering handle 10 that is turned by the driver. The steering angle detection unit may be configured as a rotation angle sensor that detects a rotation angle of an EPS motor described later. The steering shaft 11 is provided with a torque sensor 14 that is a torque detector, and the torque sensor 14 detects a steering torque applied to the steering handle 10.

  The vehicle steering control device 1 includes a front wheel steering unit 40 that is a front wheel side steering mechanism connected to the lower end of the steering shaft 11. The front wheel steering unit 40 is, for example, a gear unit adopting a rack and pinion type, and the rotation of the pinion gear integrally assembled to the lower end of the steering shaft 11 is transmitted to the rack bar. Further, the front wheel turning unit 40 is provided with an EPS actuator 51 for assisting the steering torque input to the steering handle 10 by the driver. The EPS actuator 51 has an EPS motor that is an electric motor, and torque (so-called assist force) generated by the EPS motor is transmitted to the rack bar.

  With this configuration, the rotational force of the steering shaft 11 is transmitted to the rack bar via the pinion gear, and the assist force of the EPS actuator 51 is transmitted to the rack bar. As a result, the rack bar is displaced in the axial direction by the rotational force from the pinion gear and the assist force of the EPS actuator 51, and the left and right front wheels FW1, FW2 connected to both ends of the rack bar are steered left and right. Yes.

  Further, the vehicle steering control device 1 can steer the left and right rear wheels RW1, RW2 in accordance with the steering of the left and right front wheels FW1, FW2. Therefore, the vehicle steering control device 1 includes a rear wheel turning unit 41 for turning the left and right rear wheels RW1 and RW2. The rear wheel turning unit 41 includes an ARS actuator 31 that generates a rotational driving force for turning the left and right rear wheels RW1 and RW2, and the ARS actuator 31 includes an ARS motor that is an electric motor. The rear wheel steering unit 41 has a well-known gear mechanism, decelerates the rotation of the ARS motor, converts the decelerated rotational motion into axial motion, and transmits it to the left and right rear wheels RW1, RW2.

  With this configuration, the ARS motor is driven to rotate in accordance with the turning operation of the steering handle 10 by the driver, that is, in accordance with the turning of the left and right front wheels FW1 and FW2, and the rotation reduced by the gear mechanism is changed to the axial movement. Converted. Then, this axial movement is transmitted to the left and right rear wheels RW1, RW2, and the left and right rear wheels RW1, RW2 are steered to the left and right.

  A rear wheel steering angle sensor 33, which is a rear wheel steering angle detector, detects the steering angles of the left and right rear wheels RW1 and RW2 to be steered. For example, the rear wheel steering angle sensor 33 may detect the rotation angle of the ARS motor corresponding to the rear wheel steering angle, or may directly detect the steering angle of the left and right rear wheels RW1 and RW2.

  The vehicle steering control device 1 includes a brake control system for controlling the brake. Each wheel FW1, FW2, RW1, RW2 is provided with a wheel speed sensor 61a, 61b, 61c, 61d (hereinafter referred to as “wheel speed sensor 61” unless otherwise specified), which is a vehicle speed detector. The wheel speed sensor 61 supplies the detected wheel speed to a BRK (brake) control device (hereinafter referred to as “BRK-ECU 60”). The BRK-ECU 60 controls a brake mechanism (not shown) according to the amount of depression of the brake pedal and the vehicle speed, and applies a necessary braking force to each wheel FW1, FW2, RW1, RW2.

  In the vehicle steering control device 1, an EPS control device (hereinafter referred to as “EPS-ECU 50”) controls the operation of the EPS actuator 51, specifically, the rotation of the EPS motor, thereby controlling the steering handle 10 of the driver. Provides assist force for steering. The EPS-ECU 50 and the EPS actuator 51 constitute an EPS system 52. In addition, an ARS control device (hereinafter referred to as “ARS-ECU 30”) controls the operation of the ARS actuator 31, specifically controls the rotation of the ARS motor, and sets the turning angle for the rear wheels RW1 and RW2. give. The ARS-ECU 30 and the ARS actuator 31 constitute an ARS system 32. Further, the BRK-ECU 60 controls a brake mechanism (not shown) to apply a braking force to the wheels FW1, FW2, RW1, and RW2.

  The EPS-ECU 50, the ARS-ECU 30, and the BRK-ECU 60 are connected to a network 2 such as a CAN (Controller Area Network) and can communicate with each other. Each ECU is configured as a microprocessor including a CPU. In addition to the CPU, each ECU includes a ROM that stores various programs, a RAM that temporarily stores data, an input / output port, a communication port, and the like.

  In the vehicle steering control device 1, the EPS system 52 performs steering assist control based on the steering torque detected by the torque sensor 14. Hereinafter, this assist control is referred to as “first steering assist control”. When any abnormality occurs in the torque sensor 14, the EPS system 52 replaces the detected value of the torque sensor 14 with a state quantity indicating that the vehicle is turning, for example, the steering angle detected by the steering angle sensor 13, the steering Steering assist control is performed based on the vehicle speed detected by the angular velocity and the wheel speed sensor 61. Hereinafter, the assist control that does not use the detection value of the torque sensor 14 is referred to as “second steering assist control”. As described above, the EPS system 52 performs the first steering assist control when the torque sensor 14 is operating normally, and performs the second steering assist control when an abnormality occurs in the operation of the torque sensor 14. It is configured.

  FIG. 2 is a functional block diagram of the vehicle steering control device 1 according to the present embodiment. Although control unit 100 is mainly configured by EPS-ECU 50, a part of the function of control unit 100 may be configured by another ECU, for example, ARS-ECU 30 or BRK-ECU 60. In the control unit 100, the assist control unit 110 has a function of generating a steering assist force. Specifically, the first control unit 112 performs the first steering assist control based on the detection value of the torque sensor 14 as the second steering assist control. The control unit 114 performs second steering assist control based on a state quantity indicating that the vehicle is turning.

<First steering assist control>
The first control unit 112 drives the EPS motor of the EPS actuator 51 based on the steering torque detected by the torque sensor 14 and the vehicle speed detected by the wheel speed sensor 61. The first control unit 112 holds an assist map that defines an assist force for the steering torque and the vehicle speed in a storage unit (not shown), and corresponds to the detected steering torque and the vehicle speed with reference to the assist map. The assist force of the EPS motor to be determined is determined, and a corresponding current is applied to the EPS motor. As a result, the EPS motor generates an assist force to reduce the operation load on the steering handle 10 by the driver. In the vehicle steering control device 1, the detection value of the wheel speed sensor 61 is output to the BRK-ECU 60, and the first control unit 112 acquires the detection value of the wheel speed sensor 61 from the BRK-ECU 60 via the network 2. To do.

  The first steering assist control by the first control unit 112 is performed on the assumption that the torque sensor 14 is operating normally. Therefore, when the torque sensor 14 fails and the torque sensor abnormality determination unit 102 determines abnormality of the torque sensor 14, the first control unit 112 stops the first steering assist control. At this time, the assist control unit 110 performs a steering assist control switching process, and specifically, the second control unit 114 starts the second steering assist control.

<Second steering assist control>
The second control unit 114 performs second steering assist control based on a state quantity indicating that the vehicle is turning. In the present embodiment, the case where the second control unit 114 uses the steering angle and the steering angular velocity as a state quantity indicating that the vehicle is turning will be described. However, for example, a yaw rate sensor or a lateral acceleration sensor is also used. Detection values such as may be used.

  The second control unit 114 adjusts the steering angle θstr detected by the steering angle sensor 13, the steering angular velocity dθstr / dt derived from the detected value θstr of the steering angle sensor 13, and the vehicle speed V detected by the wheel speed sensor 61. Based on this, the EPS motor of the EPS actuator 51 is driven. The second control unit 114 stores a first assist map that defines the assist force for the steering angle θstr and the vehicle speed V, and a second assist map that defines the assist force for the steering angular velocity dθstr / dt and the vehicle speed V (not shown). Z).

  FIG. 3A shows an example of a first assist map in which the assist force with respect to the steering angle θstr and the vehicle speed V is determined. The first assist map defines that the assist force to be applied increases as the vehicle speed increases with respect to a certain steering angle. Although FIG. 3A shows the first assist map, the second assist map that determines the assist force with respect to the steering angular velocity dθstr / dt and the vehicle speed V is given as the vehicle speed increases with respect to a certain steering angular velocity. The power assist force is reduced. The second control unit 114 refers to the first assist map to obtain the detected steering angle θstr and the first assist force for the vehicle speed V, and refers to the second assist map to detect the detected steering angular velocity dθstr / The second assist force with respect to dt and the vehicle speed V is obtained, and an added value of the first assist force and the second assist force (hereinafter referred to as “assist force Tbase”) is derived.

  According to such second steering assist control, since the assist force Tbase is derived based on the vehicle turning state amount, the assist force Tbase becomes excessive on a traveling road surface with a small road reaction force such as a low friction road. There is. Therefore, the second control unit 114 detects a decrease in the road surface reaction force based on the tire slip state amount, obtains a correction gain C of the assist force according to the tire slip state amount, and multiplies the assist force Tbase by the correction gain C. Limit the assist power with.

  The slip state amount Δθ is derived as an absolute value of the difference between the estimated steering angle θwhl obtained from the difference between the left and right wheel speeds and the steering angle θstr. The second control unit 114 uses a known function to calculate the estimated steering angle θf-whl of the front wheels based on the detected values of the wheel speed sensors 61a and 61b on the front wheels, and the wheel speed sensor 61c on the rear wheels. Based on the detected value of 61d, the estimated rear wheel steering angle θr-whl is calculated. When the second control unit 114 calculates the estimated steering angles θf-whl and θr-whl of the front and rear wheels, it calculates the absolute value Δθ of the difference between the estimated steering angle and the steering angle θstr.

  FIG. 3B shows a correspondence table between the slip state amount Δθ and the correction gain C. As shown in the correspondence table, when the slip state amount Δθ is in a predetermined range from 0, a dead zone is set to absorb sensor variations of the wheel speed sensor 61 and the like. The second control unit 114 derives a correction gain C corresponding to the slip state amount Δθ of each of the front and rear wheels, and multiplies the assist gain Tbase by the smaller correction gain C to thereby apply the assist force (Tbaes XC) is determined. The above is the description of the second steering assist control.

  The vehicle steering control device 1 of this embodiment is equipped with an ARS system 32 that can steer the vehicle rear wheels. The ARS system 32 controls the turning angles of the rear wheels RW1 and RW2. The ARS-ECU 30 has the same phase as the turning angles of the front wheels FW1 and FW2 depending on the traveling state of the vehicle, for example, the vehicle speed and the turning state. Alternatively, the steering control of the rear wheels RW1 and RW2 is performed in the opposite phase.

  When an abnormality occurs in the ARS system 32, the rear wheels RW1 and RW2 may be locked at the turning angle at the time of the abnormality depending on the type of abnormality. For example, when the ARS motor in the ARS actuator 31 fails or the current applied to the ARS motor becomes excessive, the ARS system 32 detects the occurrence of an abnormality and stops driving the ARS motor. In such a case, the rear wheels RW1 and RW2 are fixed at the turning angle when an abnormality occurs.

  FIG. 4A shows a state where the rear wheels RW1 and RW2 are fixed in a steered state. When the rudder angles of the rear wheels RW1 and RW2 are locked in the state shown in FIG. 4 (a), in order to maintain the vehicle in a straight traveling state, the driver operates the steering handle 10 to change the rear wheels RW1 and RW2. It is necessary to steer the front wheels FW1 and FW2 by the same turning angle as.

  FIG. 4B shows a state in which the vehicle is traveling straight by turning the front wheels FW1 and FW2. The driver operates the steering wheel 10 to adjust the turning angles of the front wheels FW1 and FW2 to the turning angles of the rear wheels RW1 and RW2, so that all the wheels are directed in the same direction, and the vehicle travels in the traveling direction. The vehicle travels straight while maintaining an angle with respect to the vehicle.

  In the vehicle state shown in FIG. 4B, when the second steering assist control is performed, the steering handle 10 is operated, and the steering angle sensor 13 calculates the assist force in order to detect the steering angle θstr. However, the vehicle state shown in FIG. 4B is in a state where the vehicle travels straight, and it is not preferable that the EPS actuator 51 generates an assist force.

  As described above, in the second steering assist control, the assist force Tbase is limited by the correction gain C corresponding to the slip state amount. When traveling straight ahead, the wheel speeds of the front wheels FW1 and FW2 and the wheel speeds of the rear wheels RW1 and RW2 are the same, so the estimated steering angle θf-whl of the front wheels and the estimated steering angle θr-whl of the rear wheels are both 0 and Calculated. Therefore, the slip state amount Δθ becomes equal to the steering angle θstr, and the correction gain C is derived based on the correspondence table shown in FIG. 3B. If the steering angle θstr is smaller than Δθmax, the correction gain C is greater than zero. The assist force (Tbase × C) is generated with a large value. In particular, when the steering angle θstr is in the dead zone, the correction gain C is 1, so the assist force Tbase is generated as it is. As described above, if the second steering assist control is continued when an abnormality occurs in the ARS system 32, an assist force may be generated even when the vehicle is traveling straight ahead. When an abnormality occurs in the system 32, the second steering assist control operates so as to be prohibited or restricted.

  Returning to FIG. 2, the ARS abnormality determination unit 104 determines whether the ARS system 32 is operating normally or an abnormality has occurred. The ARS-ECU 30 has a function of autonomously detecting an abnormality in the ARS system 32. When detecting an abnormality in the rear wheel steering angle sensor 33 and / or the ARS actuator 31, the ARS-ECU 30 transmits an abnormality detection signal to the control unit 100. The ARS abnormality determination unit 104 can determine the abnormality of the ARS system 32 by receiving an abnormality detection signal from the ARS-ECU 30. The ARS-ECU 30 may periodically transmit a state signal indicating whether or not the rear wheel steering angle sensor 33 and / or the ARS actuator 31 is abnormal to the control unit 100, and the ARS abnormality determination unit 104 is abnormal. An abnormality of the ARS system 32 may be determined by receiving a state signal indicating that there is an abnormality detection signal.

  When the ARS abnormality determination unit 104 determines that the ARS system 32 is abnormal, the second control unit 114 prohibits or restricts the second steering assist control. Note that prohibiting the second steering assist control means stopping the ongoing control, and restricting the second steering assist control means an assist force smaller than the calculated assist force (Tbase × C). Means to generate In this way, the second control unit 114 avoids or restricts the second steering assist control when an abnormality occurs in the ARS system 32, thereby avoiding generation of unnecessary assist force. If the ARS abnormality determination unit 104 determines that the ARS system 32 is abnormal while the first control unit 112 is performing the first steering assist control, then even if the abnormality occurs in the torque sensor 14, the second Transition to the second steering assist control by the control unit 114 is prohibited.

  The above is an example in which the ARS abnormality determination unit 104 determines the abnormality of the ARS system 32 based on the abnormality detection signal transmitted from the ARS system 32. The ARS abnormality determination unit 104 is based on the information indicating the state of the vehicle. It has a function of estimating the occurrence of an abnormality in the ARS system 32. Specifically, the ARS abnormality determination unit 104 determines an abnormality in the ARS system 32 when the difference between the detected rear wheel steering angle and the estimated rear wheel steering angle θr-whl is larger than a predetermined threshold.

  The ARS abnormality determination unit 104 receives the rear wheel steering angle detected by the rear wheel steering angle sensor 33 from the ARS-ECU 30. The difference between the received rear wheel detected steering angle and the estimated rear wheel steering angle θr-whl calculated from the left / right difference between the speeds of the two rear wheels (hereinafter referred to as “rear wheel steering angle error”) is a predetermined threshold value. When larger than this, the ARS abnormality determination unit 104 estimates that an abnormality has occurred in the ARS system 32.

  The rear wheel steering angle error tends to increase when the turning state of the vehicle is an understeer state or an oversteer state. For example, when the vehicle is in an understeer state, the vehicle's turning trajectory increases due to slipping of the tire, and the left-right difference between the two rear wheel speeds decreases. Therefore, the estimated rear wheel steering angle θr-whl is calculated to be smaller than the detected rear wheel steering angle, and therefore the rear wheel steering angle error increases. The ARS abnormality determination unit 104 distinguishes whether the cause of the large rear wheel steering angle error is that the vehicle is in an understeer state or an oversteer state or an abnormality occurs in the ARS system 32. It is preferable.

  Therefore, the ARS abnormality determination unit 104 acquires information indicating whether the turning state of the vehicle is in an understeer state or an oversteer state. The determination of the understeer state / oversteer state is performed by the BRK-ECU 60 based on a known method, and the ARS abnormality determination unit 104 receives information indicating the turning state of the vehicle from the BRK-ECU 60. The ARS abnormality determination unit 104 may determine whether the turning state of the vehicle is an understeer state or an oversteer state based on information from various sensors provided in the vehicle.

  As described above, the ARS abnormality determination unit 104 determines whether the vehicle is in an understeer state or an oversteer state by grasping the turning state of the vehicle. Thereby, the ARS abnormality determination unit 104 determines the abnormality of the ARS system 32 when the turning state of the vehicle is not an understeer state or an oversteer state and the rear wheel steering angle error is larger than a predetermined threshold value. It becomes possible. When the ARS abnormality determination unit 104 determines an abnormality in the ARS system 32, the second control unit 114 prohibits or restricts the second steering assist control to avoid generating unnecessary assist force. If the ARS abnormality determination unit 104 determines that the ARS system 32 is abnormal while the first control unit 112 is performing the first steering assist control, then even if the abnormality occurs in the torque sensor 14, the second Transition to the second steering assist control by the control unit 114 is prohibited. Note that the ARS abnormality determination unit 104 does not determine that the ARS system 32 is abnormal when the turning state of the vehicle is an understeer state or an oversteer state. Since the understeer state or the oversteer state is expected to improve depending on the operation state of the steering wheel 10 by the driver, the second control unit 114 restricts the second steering assist control when in the understeer state or the oversteer state, It is preferable to restart the second steering assist control immediately after the understeer state or the oversteer state is resolved.

  Since the wheel speed detected by the wheel speed sensor 61 includes a sensor error, there may be a difference between the detected wheel speeds even when the vehicle is traveling straight ahead. Therefore, the BRK-ECU 60 has a function of correcting the output value of the wheel speed sensor 61 so as to absorb a sensor error between the wheel speed sensors 61 when a wheel speed difference occurs during straight traveling. The BRK-ECU 60 transmits information indicating whether or not the output correction of the wheel speed sensor 61 has been performed to the control unit 100. This information may be transmitted periodically, but the BRK-ECU 60 may transmit information indicating that the output correction has been performed to the control unit 100 when the output correction of the wheel speed sensor 61 is performed. Good.

  When the correction information acquisition unit 106 acquires information indicating that the output correction of the wheel speed sensor 61 has been performed, the ARS abnormality determination unit 104 determines that the rear wheel steering is performed when the output correction of the wheel speed sensor 61 is performed. The threshold value to be compared with the angle error is made smaller than the threshold value to be compared with the rear wheel steering angle error when output correction is not performed. When the output correction of the wheel speed sensor 61 is performed, the accuracy of the detection value of the wheel speed sensor 61 is increased. Therefore, when the output correction of the wheel speed sensor 61 is performed, a threshold value to be compared with the rear wheel steering angle error is set. By making it smaller, the ARS abnormality determination unit 104 can accurately estimate the abnormal state of the ARS system 32 earlier.

  FIG. 5 shows a flowchart of the steering control in the embodiment. The torque sensor abnormality determination unit 102 determines whether or not the torque sensor 14 is operating normally (S10). If the torque sensor 14 is operating normally (Y in S10), the first control unit 112 performs the first steering assist control based on the steering torque detected by the torque sensor 14 (S12). On the other hand, if an abnormality occurs in the operation of the torque sensor 14 (N in S10), the second control unit 114 performs the second steering assist control based on the state quantity indicating that the vehicle is turning ( S14).

  When the ARS abnormality determination unit 104 receives an abnormality detection signal from the ARS-ECU 30 during execution of the second steering assist control (Y in S16), it is determined that an abnormality has occurred in the ARS system 32, and the second control unit 114 However, the second steering assist control is prohibited or restricted (S20). Even if the ARS abnormality determination unit 104 does not receive an abnormality detection signal (N in S16), if the difference between the detected rear wheel angle and the estimated rear wheel angle is larger than a predetermined threshold, the ARS system 32 is abnormal. Is estimated (Y in S18), and the second control unit 114 prohibits or restricts the second steering assist control (S20). In S18, the ARS abnormality determination unit 104 may estimate the abnormality of the ARS system 32 on the condition that the turning state of the vehicle is not the understeer state or the oversteer state. If no abnormality has occurred in the ARS system 32 (N in S18), the second steering assist control is continuously performed unless the abnormality of the torque sensor 14 is resolved (N in S10).

  In the above, this invention was demonstrated based on the Example. The embodiments are merely examples, and it will be understood by those skilled in the art that various modifications can be made to the combination of each component and each processing process, and such modifications are within the scope of the present invention.

  In the embodiment, it has been described that the ARS abnormality determination unit 104 may determine whether the turning state of the vehicle is an understeer state or an oversteer state from information of various sensors provided in the vehicle. Specifically, the following method may be used.

(1) From the difference between the ideal lateral acceleration (or yaw rate) obtained from the steering angle and vehicle speed of the vehicle and the actual lateral acceleration (or yaw rate) obtained from the output of the lateral acceleration sensor (or yaw rate sensor), A technique for estimating the turning state.
(2) An ideal lateral acceleration (or yaw rate) obtained from the steering angle and vehicle speed of the vehicle and an estimated value of the turning lateral acceleration (or yaw rate) obtained from the left / right difference between the front wheels or the rear wheels of the wheel speed sensor 61. A method of estimating the turning state of a vehicle from the difference.
(3) The estimated value of the lateral acceleration (or yaw rate) obtained from the lateral difference between the two front wheels of the wheel speed sensor 61 and the lateral acceleration (or yaw rate) obtained from the lateral difference between the two rear wheels of the wheel speed sensor 61. A method for estimating the turning state of a vehicle from the difference from the estimated value.

  In the embodiment, it has been described that the correction information acquisition unit 106 acquires information indicating that the output correction of the wheel speed sensor 61 has been performed from the BRK-ECU 60, but the correction information acquisition unit 106 receives the information from the BRK-ECU 60. It is also possible to independently correct the output of the provided wheel speed sensor 61. For example, the correction information acquisition unit 106 corrects the output values of the wheel speed sensors 61 to match if the output values of the wheel speed sensors 61 vary when the vehicle is traveling straight at a constant speed. To do. When the correction information acquisition unit 106 corrects the output value of the wheel speed sensor 61, the correction information acquisition unit 106 provides the corrected output value to the assist control unit 110, and also provides the assist control unit 110 with information indicating that the output has been corrected. To do. In order to determine whether the vehicle is traveling straight at a constant speed, the wheel acceleration is below a certain value, the lateral acceleration is below a certain value, the yaw rate is below a certain value, etc. Information may be used.

DESCRIPTION OF SYMBOLS 1 ... Vehicle steering control apparatus, 2 ... Network, 10 ... Steering handle, 11 ... Steering shaft, 13 ... Steering angle sensor, 14 ... Torque sensor, 30 ... ARS- ECU, 31 ... ARS actuator, 32 ... ARS system, 33 ... Rear wheel steering angle sensor, 40 ... Front wheel steering unit, 41 ... Rear wheel steering unit, 50 ... EPS- ECU, 51 ... EPS actuator, 52 ... EPS system, 60 ... BRK-ECU, 61 ... wheel speed sensor, 100 ... control unit, 102 ... torque sensor abnormality determination unit, 104 ... ARS abnormality determination unit, 106 ... correction information acquisition unit, 110 ... assist control unit, 112 ... first control unit, 114 ... second control unit.

Claims (4)

A torque detector for detecting a steering torque applied to the steering member;
A first control unit that performs first steering assist control based on the detected steering torque;
A first abnormality determination unit for determining abnormality of the torque detection unit;
A second control unit that performs second steering assist control based on a state quantity indicating that the vehicle is turning when an abnormality occurs in the torque detection unit;
A rear wheel steering system capable of steering the vehicle rear wheels;
A rear wheel steering angle detector for detecting a rear wheel steering angle;
A speed detector for detecting wheel speed;
When the difference between the rear wheel detection rudder angle detected by the rear wheel rudder angle detection unit and the rear wheel estimated rudder angle calculated from the rear wheel speed detected by the speed detection unit is larger than a predetermined threshold, A second abnormality determination unit for determining an abnormality of the rear wheel steering system, and a steering control device comprising:
The second control unit prohibits or restricts second steering assist control when an abnormality occurs in the rear wheel steering system.   The steering control device according to claim 1, wherein the second abnormality determination unit determines an abnormality of the rear wheel steering system when receiving an abnormality detection signal from the rear wheel steering system. A correction information acquisition unit that acquires information indicating that output correction of the speed detection unit has been performed;
The second abnormality determination unit makes a threshold value to be compared with the difference when output correction of the speed detection unit is performed smaller than a threshold value to be compared with the difference when output correction is not performed. The steering control device according to claim 1, wherein: The second abnormality determination unit is a case where the turning state of the vehicle is not an understeer state or an oversteer state, and the difference between the detected rear wheel angle and the estimated rear wheel angle is greater than a predetermined threshold value. The steering control device according to any one of claims 1 to 3, wherein an abnormality of the rear wheel steering system is determined.

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