JP2009023561A - Steering control device, steering angle control unit - Google Patents

Abstract

In a steering control device capable of independently controlling the steering angle of each wheel, it is possible to provide a steering control device and a steering angle control unit capable of preventing the steering from being disabled even if an abnormality is detected.
In a steering control device capable of controlling the steering angles θa to θd independently for each wheel FL, RL, FR, RR, the steering angle A of the wheel A in which an abnormality of the wheel steering angle sensor 19a is detected is It has the control part 14 controlled using the detected value of the wheel steering angle sensor 19b-19d which detects the steering angle B nearest to the steering angle A of the wheel A before abnormality detection, It is characterized by the above-mentioned.
[Selection] Figure 1

Description

  The present invention relates to a steering control device and the like that can independently control the steering angles of four wheels, and more particularly to a steering control device and a steering angle control unit that perform fail-safe control when an abnormality occurs.

  Many vehicle steering devices connect a steering wheel to a tie rod via a gearbox to physically convert a driver's steering angle into a steering angle. Steering according to the steering angle of the driver A steering-by-wire is known in which a target steering angle is calculated so as to be an angle, and a wheel is driven by an actuator. By using such a steering method, it becomes possible to control the steering angle more flexibly. For example, an actuator is provided independently for each of the four wheels, and the steering angle of each wheel can be controlled independently (hereinafter referred to as four). This is called wheel independent steering).

  In four-wheel independent steering, a wheel rudder angle sensor, an actuator, and the like are arranged on a square wheel, and therefore, a fail-safe technique at the time of abnormality has been proposed (see, for example, Patent Documents 1 and 2). Patent Document 1 describes a four-wheel independent steering device that can travel by providing a plurality of actuators on each wheel so long as all the actuators of the wheels do not become abnormal.

Further, in Patent Document 2, each wheel is provided with a wheel steering angle sensor that detects a steering angle. When an abnormality is detected in any of the wheel steering angle sensors, a wheel steering angle sensor in which no abnormality is detected is used. Based on this, there is described a four-wheel independent steering device that estimates and controls the steering angle of a wheel in which a wheel steering angle sensor in which an abnormality is detected is arranged.
JP 2006-0669456 A JP 2001-322557 A

  However, when the actuators for the respective wheels are multiplexed like the four-wheel independent steering device of Patent Document 1, there is a problem that the cost and the weight are increased. In addition, as in the four-wheel independent steering device of Patent Document 2, it is often difficult to appropriately control the steering angle of a wheel in which an abnormality is detected from the steering angle of a wheel in which no abnormality is detected.

  In view of the above problems, the present invention provides a steering control device and a steering angle control unit capable of preventing the steering from being disabled even if an abnormality is detected in a steering control device capable of independently controlling the steering angle of each wheel. For the purpose.

  In view of the above problems, the present invention provides a steering control device capable of controlling the steering angle independently for each wheel, and determines the steering angle A of the wheel A in which the abnormality of the wheel steering angle sensor is detected. And a control unit that controls using a detected value of a wheel steering angle sensor that detects a steering angle B closest to the steering angle A.

  According to the present invention, when there is a symmetric relationship between the four wheels, such as on-the-spot turning, crab running, etc., it is difficult to determine which of the other three wheels the steering angle should be used, but the difference is minimized. Thus, the steering angle of the wheel having an abnormality can be controlled.

  Further, the present invention provides a steering control device that controls a steering angle of at least one wheel to turn on the spot using a value detected by a sensor of another wheel. And a control unit that controls the steering angle of the abnormal wheel so that the physical quantity to be detected is detected.

  According to the present invention, it is possible to appropriately set the steering angle of a wheel having an abnormality by comparing several physical quantities by utilizing the state of steady turning without slipping.

  In one embodiment of the present invention, the control unit controls the steering angle of the wheel A so that the wheel speed A of the abnormal wheel A substantially coincides with the wheel speed B of any other wheel during turning. It is characterized by.

  According to the present invention, even if the wheel speed is low, an abnormal wheel steering angle shift can be corrected.

  In a steering control device capable of independently controlling the steering angle of each wheel, it is possible to provide a steering control device and a steering angle control unit that can prevent the steering from being disabled even if an abnormality is detected.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a schematic configuration diagram of the steering control device 100. When an abnormality is detected in any of the steering devices 50a to 50d provided in each of the four wheels, the steering control device 100 according to the present embodiment detects the steering angle detected by the steering devices 50a to 50d in which no abnormality is detected. Is used to control the steering angle of the failed steering devices 50a to 50d. As a result, even if an abnormality is detected in any of the steering devices 50a to 50d, it is possible to control the steering devices 50a to 50d while preventing the vehicle from immediately becoming unable to travel.

  The steering control device 100 includes steering devices 50a to 50d for each of the wheels FL, RL, FR, and RR, and the steering devices 50a to 50d are independently controlled by a steering angle control ECU (Electronic Control Unit) 14. First, the steering devices 50a to 50d will be described.

  The knuckles 15a and 15c disposed on the front wheels FL and FR are connected at their rear ends to the tie rods 17a and 17c so as to be rotatable in the vertical direction. The knuckles 15b and 15d disposed on the rear wheels RL and RR are connected at one end in front of the vehicle to the tie rods 17b and 17d so as to be rotatable in the vertical direction.

  The other ends of the tie rods 17a to 17d are connected to the steering actuators 18a to 18d, and are driven in the vehicle width direction by the steering actuators 18a to 18d. The steering actuators 18a to 18d respectively accommodate an electric motor and a conversion mechanism that converts rotation of the motor into linear motion to drive the arms 21a to 21d in the vehicle width direction.

  The tie rods 17a to 17d are connected to the arms 21a to 21d on the inner side in the vehicle width direction and the knuckles 15a to 15d on the outer side in the vehicle width direction so as to be rotatable about their respective axes. Absorbs fluctuations in the horizontal plane against displacement. Accordingly, the wheels FL, RL, FR, and RR are independently steered through the tie rods 17a to 17d and the knuckles 15a to 15d.

  The steering actuators 18a to 18d integrally have wheel steering angle sensors 19a to 19d that detect the steering angles θa to θd of the wheels FL, RL, FR, and RR. The wheel steering angle sensors 19a to 19d are displacement sensors that detect displacement amounts of the arms 21a to 21d in the vehicle width direction, for example. The steering angles θa to θd represent a neutral position where the vehicle goes straight ahead as zero degrees, and represents a left-hand steering as positive and a right-hand steering angle as negative.

  Further, the steering devices 50a to 50d have wheel speed sensors 16a to 16d for controlling the steering angle according to the traveling speed of the vehicle. For example, the cycle according to the wheel speed of each wheel FL, RL, FR, RR. The wheel speeds of the wheels FL, RL, FR, RR are detected by counting the pulses generated in step.

  The steering angle of the steering wheel 11 by the driver is detected by a steering angle sensor 12. The steering wheel steering angle sensor 12 is a non-contact rotary encoder that outputs a pulse corresponding to the steering wheel operation angle based on, for example, a neutral position where the vehicle travels straight.

  A reaction force actuator 13 is disposed on the steering wheel 11 coaxially with the steering shaft. The reaction force actuator 13 includes, for example, an electric motor for rotationally driving the steering wheel 11 and the steering shaft around the axis, and causes the reaction force torque corresponding to the steering angles θa and θc to be generated in the steering wheel 11.

  Note that an elastic body such as a torsion bar is interposed on the steering shaft, and the elastic body causes a slight rotational angle shift above and below the elastic body when the steering wheel 11 is operated. . Further, a steering torque sensor for detecting a steering torque applied by the driver to the steering wheel 11 is arranged on the steering shaft coaxially with the steering shaft.

  The steering control device 100 includes a biaxial G sensor 22 that detects acceleration in the front-rear direction and the vehicle width direction, for example, in order to detect vehicle behavior. The G sensor 22 is, for example, a capacitance type or piezoresistive type sensor formed by micromachining.

  The steering angle control ECU 14 is a CPU for executing a program, a RAM for storing data temporarily, a RAM for temporarily storing data, a ROM for storing a boot program and BIOS, an OS, a program, a nonvolatile memory for storing files, and data. An input / output unit for inputting and outputting is a computer connected by an internal bus.

  When the CPU executes a program, it detects abnormalities in the target steering angle calculation means 31 and the steering devices 50a to 50d that calculate the target steering angle of each wheel FL, RL, FR, RR according to the steering wheel operation angle and the wheel speed. An abnormality detecting means 32 for performing an operation, a steering angle estimating means 33 for estimating a steering angle of a wheel in which an abnormality has been detected, and a steering angle interpolation means 34 for interpolating an angle difference between the estimated steering angle θa_est and the steering angle θa when an abnormality occurs. Is done.

  Next, calculation of the target steering angle will be described. The steering angle control ECU 14 stores a target steering angle map in which the relationship between the steering wheel operation angle and the target steering angle is stored in a ROM or the like. FIG. 2A shows an example of the target steering angle map, and FIG. 2B shows the relationship between the turning center O and the distances between the wheels FL, RL, FR, and RR.

  When the traveling speed is high, if the steering angle is large, the lateral G also increases and the riding comfort decreases. Therefore, the target steering angle is determined to be smaller as the traveling speed increases. The relationship between the steering wheel operation angle and the target steering angle is stored for each wheel FL, RL, FR, RR.

  There are various methods for calculating the target steering angle. Here, the target steering angle on the inner ring side is extracted from the target steering angle map, the distance between the turning center O and the inner wheel is calculated, and then the steering angle of the outer wheel is set as the turning center. Calculated from the positional relationship with O. Therefore, the target steering angle of the inner wheel is extracted from the target steering angle map, and the target steering angle of the outer wheel is calculated so as to be consistent with the target steering angle of the inner wheel (for example, the slip amount is minimized).

  When the steering wheel 11 is operated in the right direction and the steering wheel operation angle is negative, the sign of the target steering angle θC extracted from the target steering angle map is reversed (negative) and the right front wheel corresponding to the front wheel inside the turn The target steering angle -θC of FR is set, and the target steering angle θD extracted from the target steering angle map is set as the target steering angle θD of the right rear wheel RR corresponding to the rear wheel inside the turn as it is.

  Next, distances L1 and L4 from the turning center O of the vehicle to the centers of the right front wheel FR and the right rear wheel RR are calculated. In this case, the line connecting the turning center O and the rotation surfaces of the right front wheel FR and the right rear wheel RR is set to form a right angle.

  Therefore, the following equations (1) and (2) are established, and the distances L1 and L4 can be calculated by solving the equations. In Expression (2), K is a vehicle wheel base.

L1 · cos | θC | = L4 · cos | θD | (1)
L1 · sin | θC | + L4 · sin | θD | = K (2)

  Next, target rudder angles θA and θB of the left front wheel FL and the left rear wheel RL that are front and rear wheels on the outside of the turn are calculated. As shown in FIG. 2B, since the steering directions of the left and right front wheels FL and FR are substantially the same, the signs of the target rudder angles θA and θC of the left and right front wheels FL and FR are the same, and the left and right rear wheels RL. , RR also have substantially the same steering direction, so that the signs of the target steering angles θB, θD of the left and right rear wheels RL, RL are the same.

  Similarly, a line connecting the turning center O and the rotation surfaces of the left front wheel FL and the left rear wheel RL is set to form a right angle. Therefore, when the distances from the turning center O to the centers of the left front wheel FL and the left rear wheel RL are L2 and L3, the following expressions (3) to (6) are established.

L1 · sin | θC | = L2 · sin | θA | (3)
L4 · sin | θD | = L3 · sin | θB | (4)
L2 · cos | θA | = L3 · cos | θB | (5)
L2 · sin | θA | + L3 · sin | θB | = K (6)
Since L1 and L4 are obtained from the equations (1) and (2), the target steering angles θA and θB of the left front wheel FL and the left rear wheel RL can be calculated from the equations (3) to (6).

  FIG. 3 shows an example of the steering angle of each wheel FL, RL, FR, RR in a rotation mode in which the vehicle body rotates on the spot around a predetermined portion of the vehicle. The rotation mode can be switched, for example, by operating a predetermined switching button while parking or stopping, or by operating the steering wheel operating angle to the maximum amount.

  As in the case of left turn traveling, the target steering angle is set so that the straight line connecting the turning center O and the rotation surfaces of the wheels FL, RL, FR, and RR is vertical. Therefore, in the rotation mode, the target steering angle of the left front wheel FL and the right front wheel FR and the target steering angle of the left rear wheel RL and the right rear wheel RR are linear with respect to a straight line parallel to the vehicle front-rear direction passing through the turning center O. It becomes symmetric. In the rotation mode, the target steering angle of the left front wheel FL and the left rear wheel RL and the target steering angle of the right front wheel FR and the right rear wheel RR are axisymmetric with respect to a straight line parallel to the axle and passing through the turning center O. (Hereafter, it is simply called a symmetrical relationship). Considering the sign, it can be expressed as follows. If there is a symmetric relationship, the straight line connecting the turning center O and the rotating surfaces of the wheels FL, RL, FR, RR does not necessarily have to be perpendicular to the rotating surface.

Target steering angle of left front wheel FL = −θA
Target steering angle of left rear wheel RL = θB
Target steering angle of the right front wheel FR = θC
Target steering angle of the right rear wheel RR = −θD
| −θA | = θC, | −θA | = θB, θB = | −θD |, θC = | −θD | (7)

  Next, abnormality detection of the steering devices 50a to 50d in the rotation mode as shown in FIG. 3 will be described. The abnormality of the present embodiment means that the steering devices 50a to 50d cannot be normally controlled, for example, sensor abnormality of the wheel steering angle sensors 19a to 19d, disconnection of the wheel steering angle sensors 19a to 19d, and the like. The sensor abnormality is detected because the steering angles θa to θd detected with respect to the target steering angle change suddenly, or the detected steering angles θa to θd show a fixed value despite the change of the target steering angle. it can. The disconnection can be detected because there is no response from the wheel steering angle sensors 19a to 19d. The abnormality detection means 32 detects that an abnormality has occurred in the steering devices 50a to 50d when such a situation continues for a predetermined time.

  Next, the fail-safe control of the steering angle when an abnormality is detected will be described. For example, when an abnormality occurs in any of the wheel steering angle sensors 19a to 19d, the steering angles θa to θd cannot be accurately detected, and the steering angles θa to θd are set to appropriate angles by the steering actuators 18a to 18d. I can't control it.

  In this embodiment, the steering angles θa to θd detected by the wheel steering angle sensors 19a to 19d detected by the wheel steering angle sensors 19a to 19d detected by the wheel steering angle sensors 19a to 19d in which no abnormality is detected are substituted. By doing so, it becomes possible to continue the control of the failed steering devices 50a to 50d.

  FIG. 4A shows an example of the relationship between the steering angle of each wheel FL, RL, FR, RR and time in the rotation mode. In FIG. 4A, it is assumed that an abnormality has occurred in the wheel steering angle sensor 19a. When the abnormality detection means 32 detects an abnormality of the wheel steering angle sensor 19a, the steering angle estimation means 33 estimates the left front wheel FL from the steering angles θb to θd detected by the wheel steering angle sensors 19b to 19d in which no abnormality is detected. Estimate the steering angle θa_est.

  FIG. 4B is an explanatory diagram for estimating the steering angle θa of the wheel steering angle sensor 19a in which an abnormality has been detected. Since the steering angle θa and the steering angle θc are symmetrical, it may be considered that the steering angle is similar to the steering angle θa if the sign of the steering angle θc is reversed. Assuming that the wheel FL, RL, FR, and RR are in a neutral state and the button for switching to the rotation mode is operated, the steering angles θa and θc increase at almost the same speed as time passes. That is, the steering angle estimation means 33 estimates the estimated steering angle θa_est by inverting the steering angle θc detected by the wheel steering angle sensor 19c every predetermined cycle time.

  The steering angle control ECU 14 controls the steering angle θa of the left front wheel FL so as to be the estimated steering angle θa_est by feedback control, for example. Therefore, even if an abnormality occurs in the wheel steering angle sensor 19a, the life of the steering device 50a can be extended. In FIG. 4B, the steering angle θc is reversed, but the steering angle θb may be reversed, or the steering angle θd may be substituted without changing the sign of the steering angle θd.

  By the way, since the time from when the abnormality occurs until the abnormality detecting means 32 confirms the abnormality and the time until the steering angle θc is reversed occurs, the steering angle θa of the left front wheel FL is controlled after the abnormality occurs. There is a delay before it resumes.

  FIG. 5 is an explanatory diagram for explaining the delay. Regarding the delay time from the occurrence of abnormality to the resumption of control, the steering angle θa of the left front wheel FL is not controlled, so the steering angle θa shows a constant value. For this reason, when the control is switched to the estimated steering angle θa_est when the control is resumed, the steering angle θa changes abruptly to the estimated steering angle θa_est, which may reduce the steering feeling and riding comfort of the occupant. Therefore, it is more preferable to interpolate this angle difference and perform the fail safe control on the steering angle θa.

  Therefore, the steering angle interpolation means 34 interpolates the angle difference up to the estimated steering angle θa_est with the angular velocity of the steering angle θa in the process of transitioning to the rotation mode, which is calculated by monitoring the steering angle θa before the abnormality occurs. . If the angular velocity is obtained, the inclination of the line segment connecting the estimated steering angle θa_est immediately before the occurrence of the abnormality shown in FIG. 5 and the estimated steering angle θa_est can be known. The steering actuator 18a is controlled while adding a small amount of the corresponding interpolation steering angle θa_h. By repeating this until the angle difference with the estimated steering angle θa_est disappears, it is possible to prevent the steering feeling and the like from being lowered due to a sudden angle difference in the steering angle.

  A procedure in which the steering angle control ECU 14 performs fail-safe control when an abnormality is detected using the above configuration will be described with reference to the flowchart of FIG. The flowchart in FIG. 6 starts when, for example, a rotation mode switching button is operated.

  The abnormality detection unit 32 repeats the determination of whether or not an abnormality has been detected in any one or more of the steering devices 50a to 50d (S10).

  If an abnormality has occurred (Yes in S10), the steering angle estimating means 33 estimates the estimated steering angle of the wheel in which the abnormality has occurred from the steering angle of the wheel in which no abnormality is detected (S20). In FIG. 6, an abnormality occurs in the left front wheel FL, and the estimated steering angle θa_est is estimated from the steering angle θc of the right front wheel FR. Further, it is assumed that the angular velocity of the left front wheel FL until an abnormality occurs is calculated before the abnormality occurs.

  Next, the steering angle interpolation means 34 interpolates the angle difference between the estimated steering angle θa_est and the steering angle θa immediately before the abnormality detection based on the angular velocity (S30). That is, the angle difference between the steering angle θa at the time of abnormality detection and the estimated steering angle θa_est is interpolated by the interpolation steering angle θa_h.

  Then, the steering angle control ECU 14 controls the steering angle of the left front wheel FL with the interpolation steering angle θa_h as a target until the estimated steering angle θa_est is reached (S40).

  According to the present embodiment, even if an abnormality occurs in the wheel steering angle sensor 19a, the steering angle θa of the left front wheel FL is determined using the steering angles θb to θd detected by the wheel steering angle sensors 19b to 19d that are not abnormal. Can be controlled. In this embodiment, an abnormality occurs in any one of the wheel rudder angle sensors 19a to 19d. However, as long as no abnormality occurs in all the wheel rudder angle sensors 19a to 19d, the same fail-safe control is performed. Can do.

  Further, in this embodiment, it is used that the steering angles θa to θd of the wheels FL, RL, FR, and RR are symmetrical, but not limited to the rotation mode, but symmetrical to the steering angles of four wheels such as crab running. If there is a serious relationship, this embodiment can be preferably applied.

  The deviation of the actual steering angles θa to θd with respect to the target steering angles θA to θD is different for each wheel FL, RL, FR, RR depending on the vehicle weight distribution applied to the wheels FL, RL, FR, RR and the road surface condition. For this reason, the steering angles θb to θd detected by the wheel steering angle sensors 19b to 19d in which no abnormality has occurred also have deviations from the target steering angles θB to θD. Therefore, it is preferable that the steering angles θb to θd of the wheel steering angle sensors 19b to 19d that detect values closest to the steering angle θa detected by the wheel steering angle sensor 19a in which an abnormality is detected be the estimated steering angle θa_est. Therefore, in this embodiment, among the steering angles θb to θd detected by the wheel steering angle sensors 19b to 19d in which no abnormality is detected, the steering angle closest to the steering angle θa detected by the wheel steering angle sensor 19a in which the abnormality is detected is selected. The estimated steering angle is θa_est.

  FIG. 7A is a diagram showing an example of the relationship between the steering angle of each wheel FL, RL, FR, RR and time. If an abnormality occurs in the steering device 50a at time t1, the steering angle estimation means 33 reverses the signs of the steering angle θb and the steering angle θc, and reverses the steering angles θb and θc and the steering angle θd. Compare Then, one of the steering angles θb to θd that minimizes the difference between | θa | − | θb |, | θa | − | θc |, and | θa | − | θd | is selected as the estimated steering angle θa_est.

  In FIG. 7A, the steering angle θc of the right front wheel FR is adopted. By selecting the steering angle for obtaining the estimated steering angle in this way, it is possible to minimize the influence of vehicle weight distribution and road surface conditions.

  By the way, in the case of the present embodiment, even when the steering angle having the smallest difference is used, not only a delay but also an angle difference due to deviation occurs. Therefore, in order to avoid the deterioration of feeling caused by suddenly setting the angle difference to zero, the interpolation steering angle θa_h having the angle difference is set.

  On the other hand, in order to avoid a state in which an angle difference remains between the estimated steering angle θa_est and the actual steering angle θa, a correction value corresponding to the magnitude of the angle difference is obtained and gradually increased to the estimated steering angle θa_est. The steering actuator 18a is controlled so as to approach.

  Therefore, in this embodiment, as shown in FIG. 7B, the interpolation steering angle θa_h is determined such that the angular velocity of the steering angle θa changes from the time of abnormality detection, and the angle difference from the estimated steering angle θa_est gradually disappears. The steering angle θa is controlled.

  8A shows the correction map 1 showing the relationship between the angle difference and the correction amount, FIG. 8B shows the correction map 2 showing the relationship between the time and the correction gain, and FIG. 8C shows the correction maps 1 and 2. Each control example in which the angle difference gradually approaches zero with time by controlling the steering angle θa is shown. The larger the angle difference, the larger the correction amount, and the smaller the angle difference, the smaller the correction amount (FIG. 8 (a)) and the larger the correction gain with time (FIG. 8 (b)). It becomes possible to control without deteriorating the feeling from a large state to a state in which the angle difference becomes zero (FIG. 8C). That is, as shown in FIG. 8C, the angle difference is large at the beginning of the correction, but the angle difference gradually decreases, and the angle difference reduction speed is eventually increased. As the angle decreases, the reduction rate of the angle difference becomes moderate.

  A correction map 3 that further adjusts the correction gain according to the wheel speed may be used. FIG. 8D shows an example of the correction map 3 showing the relationship between the wheel speed and the correction gain. The correction gain in FIG. 8 (d) gradually decreases when the vehicle speed is high. When the wheel speeds of the wheels FL, RL, FR, and RR are high, the correction amount is small and the wheel speed is high. In this case, the correction can be relaxed to reduce the sense of incongruity.

  With reference to the flowchart shown in FIG. 9, the procedure for the fail-safe control when the steering angle control ECU 14 detects an abnormality will be described. The flowchart of FIG. 9 starts when, for example, a rotation mode switching button is operated.

  The abnormality detection unit 32 repeats the determination of whether or not an abnormality has been detected in any one or more of the steering devices 50a to 50d (S10).

  When an abnormality has occurred (Yes in S10), the steering angle estimating means 33 selects the steering angle closest to the steering angle θa immediately after the abnormality detection from the steering angles θb to θd of the wheels RL, FR, RR (S21). Here, it is assumed that the steering angle θc of the right front wheel FR is selected. Therefore, the steering angle θc becomes the estimated steering angle θa_est, and thereafter, the steering angle θa is controlled using the steering angle θc detected by the wheel steering angle sensor 19c.

  Next, the steering angle interpolation means 34 determines an interpolation steering angle θa_h for interpolating the angle difference between the estimated steering angle θa_est and the steering angle θa immediately before the abnormality detection based on the correction maps 1 and 2 (S31). As a result, as shown in FIG. 8C, the angular velocity can be smoothly asymptotically approached to the estimated steering angle θa_est while the angular velocity is variably controlled.

  Then, the steering angle control ECU 14 controls the steering angle of the left front wheel FL with the interpolation steering angle θa_h as a target until the estimated steering angle θa_est is reached (S40).

  According to the present embodiment, even if an abnormality occurs in the wheel steering angle sensor 19a, the steering angle θa of the left front wheel FL is determined using the steering angles θb to θd detected by the wheel steering angle sensors 19b to 19d that are not abnormal. Can be controlled. In addition, the appropriate wheel steering angle sensors 19b to 19d are selected in consideration of the influence of vehicle weight distribution and road surface conditions, and the steering angle θa is gradually controlled, so that steering can be performed without deteriorating the feeling.

  In the present embodiment, the steering angles θa to θd of the wheel rudder angle sensors 19a to 19d in which an abnormality has been detected are fail-safe controlled using physical quantities that can be detected by the vehicle. In this embodiment, it is assumed that an abnormality has occurred in the wheel steering angle sensor 19a of the left front wheel FL.

[Fail safe using wheel speed]
In the rotation mode, the wheel speeds of the wheels FL, RL, FR, and RR should be approximately the same, but if the steering angle rotates in an inappropriate state, the wheel speed of the wheel (the abnormal left front wheel FL) decreases. This is used to control the steering angle θa of the left front wheel FL.

  FIG. 10A shows a block diagram of the steering control device 100 of the present embodiment. In FIG. 10A, the same parts as those in FIG. As shown in FIG. 10A, the steering control device 100 includes a steering angle setting unit 36 and a determination unit 35 that are realized by a CPU executing a program. The steering angle setting means 36 sets the steering angle at which the steering angle θa detected by the wheel steering angle sensor 19a in which abnormality is detected gradually increases or decreases, so the steering actuator 18a gently controls the steering angle of the left front wheel FL. be able to.

  The determination means 35 monitors the wheel speed of each wheel FL, RL, FR, RR, and the wheel speed of the left front wheel FL where the abnormality of the wheel steering angle sensor 19a is detected is about the same as the other wheels RL, FR, RR. It is determined whether or not. If the vehicle rotates with an inappropriate steering angle, the wheel speed decreases. However, if the rotation is similar, the steering angle θa of the left front wheel FL can be appropriately controlled.

  FIG. 11 shows an example of a flowchart in which the steering control device 100 controls the steering angle θa based on the wheel speed.

  a1. First, for example, a driving force control ECU that controls the driving force of each wheel FL, RL, FR, RR makes the wheel driving force of the left front wheel FL in which an abnormality is detected free. Then, the wheels RL, FR, RR in which no abnormality is detected are rotated with a predetermined driving force, and whether the wheel speed of the left front wheel FL and the wheel speed of the wheels RL, FR, RR coincide (the difference is predetermined). Within the range). The wheel speeds of the wheels RL, FR, and RR are known in advance according to the relationship between the driving force of the wheels and the steering angles θb to θd.

  a2. Next, the steering angle setting means 36 gradually increases or decreases the steering angle of the left front wheel FL so that the steering actuator 18a steers the steering angle of the left front wheel FL to either the left or right.

  a3. The judging means 35 judges whether or not the wheel speed of the left front wheel FL becomes smaller than the wheel speeds of the normal wheels RL, FR and RR. If it becomes smaller, the steering actuator 18a is stopped and the wheel driving of the left front wheel FL is carried out. To resume.

  a4. The steering angle setting means 36 gradually decreases or gradually increases the steering angle of the left front wheel FL in reverse to step a2, so that the steering actuator 18a steers the steering angle of the left front wheel FL in reverse to a2. Then, returning to step a3, when the wheel speed of the left front wheel FL decreases, the steering actuator 18a is stopped and the wheel driving of the left front wheel FL is resumed.

  That is, by controlling the steering angle of the left front wheel FL in which an abnormality has been detected so that the wheel speed of the normal wheel becomes normal, the steering angle of the left front wheel FL can be controlled to a steering angle suitable for the rotation mode, and the wheel steering angle Even if an abnormality occurs in the sensor 19a, fail-safe control can be performed. Further, the deviation of the steering angle θa can be corrected even when the wheel speed or the vehicle speed is low.

[Fail safe using horizontal G]
If the steering angle θa is not properly controlled while traveling on a curve, the wheel speed of the left front wheel FL decreases, so the lateral G acting on the vehicle also decreases. The wheel speed (vehicle speed) of each wheel is detected, and the curvature radius of the curve correlates with the steering angle of the steering wheel. Therefore, if there is no abnormality in the left front wheel FL, the steering wheel operating angle, the vehicle speed, and the lateral G applied to the vehicle have a predetermined value. There is a relationship. By storing this relationship in advance, if the steering wheel operating angle and the wheel speed are known, the steering angle of the left front wheel FL is adjusted so that the lateral G becomes a predetermined value. Even in such a case, the steering angle θa can be fail-safe controlled.

  FIG. 10B shows a block diagram of the steering control device 100. FIG. 10B uses a G sensor 22 instead of the wheel speed sensors 16a to 16d. If the steering angle θa deviates from the steering angle suitable for the steering wheel operation angle, the wheel speed of the left front wheel FL decreases and as a result, the lateral G also decreases. Since the relationship between the steering wheel operating angle, the wheel speed, and the lateral G in the normal state is known, the lateral G detected by the determination unit 35 is compared with the lateral G in the normal state, and the steering angle setting unit 36 By setting the steering angle θa so that G can be obtained, the steering angle θa can be appropriately controlled.

  FIG. 12 shows an example of a flowchart in which the steering control device 100 controls the steering angle θa based on the lateral G. Note that the abnormality of the left front wheel FL has already been confirmed.

  b1. First, the steering angle setting means 36 gradually increases or decreases the steering angle of the left front wheel FL so that the steering actuator 18a steers the left front wheel FL so that the steering angle of the left front wheel FL increases to either the left or right.

  b2. Then, the determination unit 35 determines whether or not the lateral G increases to a normal value. When it increases to the normal value, the steering actuator 18a is stopped, and the steering angle θa at the time of stopping becomes the steering angle θa suitable for the rotation mode.

  b3. If the steering angle does not increase to the normal value, the steering angle setting means 36 gradually decreases or gradually increases the steering angle θa in the opposite direction to b1, so that the steering actuator 18a steers the steering angle of the left front wheel FL opposite to b1. Conversely, when the lateral G increases to a normal value by driving, the steering actuator 18a is stopped.

  That is, by controlling the steering angle θa of the left front wheel FL in which an abnormality is detected so as to be normal lateral G, the steering angle θa of the left front wheel FL can be controlled to a steering angle suitable for curve traveling, and the wheel steering angle Even if an abnormality occurs in the sensor 19a, the steering angle θa can be fail-safe controlled.

  Here, the description has been given by taking a curve as an example, but the steering angle θa of the left front wheel FL can be controlled to a steering angle suitable for the rotation mode so that the lateral G becomes a normal value in the rotation mode as well. In the rotation mode, the wheels FL, RL, FR, and RR are controlled to the predetermined steering angles θa to θd as described above, so there is no need to detect the steering wheel operation angle. From this relationship, the steering angle θa may be controlled so that the lateral G becomes a normal value.

[Fail safe using reaction force actuator 13]
The fail safe during straight running will be described. FIG. 13A shows a plan view of the vehicle when an abnormality occurs in the steering angle. In FIG. 13A, an abnormality is detected in the steering device 50a for the left front wheel FL, and the steering angle θa is not properly controlled.

  Incidentally, a reaction force actuator 13 is disposed on the steering wheel 11 and generates a reaction force according to the actual steering angles θa and θc. Thereby, the road surface reaction force that the road surface acts on the front wheels FL and FR can be transmitted to the driver. Since the steering angles θa and θc may depend on the steering angle by the driver, there is a predetermined relationship between the steering angle and the reaction force by the reaction force actuator 13.

  Therefore, when a predetermined deviation or more occurs in the relationship between the steering wheel operating angle and the reaction force for a predetermined time or more, it is considered that the steering angle θa or θc is not an appropriate angle, that is, the wheel steering angle sensor 19a is abnormal. The abnormality detection means 32 can detect an abnormality.

  FIG. 13B shows a block diagram of the steering control device 100. The steering control device 100 includes a steering angle correction unit 37 that is realized by a CPU executing a program. The steering angle correction means 37 detects the amount of deviation of the steering angle θa from the reaction force detected by the reaction force actuator 13 and the steering wheel operation angle.

  When the vehicle is traveling straight ahead, the steering wheel operating angle is neutral, and no reaction force should be generated. Therefore, detection of the amount of deviation is preferable during straight traveling. Since it may be considered that the state in which the steering wheel operation angle is zero continues for a predetermined time during straight traveling, it is easy to detect a deviation amount of the steering angle θa.

  During straight traveling, the steering angle correction means 37 corrects the steering angle θa so that the reaction force (deviation amount) becomes zero, and controls the steering actuator 18a. By this correction, when the reaction force becomes zero, the steering angle θa becomes zero, and it can be estimated that the steering can be performed to the neutral position.

  In addition, since a feeling will deteriorate if it correct | amends suddenly when the deviation | shift amount of a reaction force and a steering wheel operating angle is large, it is suitable to adjust a correction amount according to deviation | shift amount (reaction force at the time of a straight drive). FIG. 13C shows an example of the relationship between the deviation amount and the correction amount of the steering angle θa. When the deviation amount is small as shown in FIG. 13C, the steering angle θa can be gradually corrected by reducing the correction amount.

  According to the present embodiment, when turning without slipping as in the rotation mode, the steering angle of the steering device 50a having an abnormality can be appropriately steered by comparing several physical quantities.

  As described above, the steering control device 100 according to the present embodiment prevents the vehicle from immediately running even if an abnormality is detected in any of the wheel rudder angle sensors 19a to 19d, thereby preventing the wheels FL, RL, The steering angle of FR and RR can be controlled.

It is a schematic block diagram of a steering control apparatus. It is a figure which shows an example of a target steering angle map. It is a figure which shows an example of the steering angle of each wheel FL, RL, FR, RR in the rotation mode in which a vehicle body rotates on the spot centering | focusing on the predetermined part of a vehicle. It is a figure which shows an example of the relationship between the steering angle of each wheel FL, RL, FR, RR in rotation mode, and time. It is explanatory drawing explaining a delay. It is a flowchart figure which shows the procedure which steering angle control ECU performs fail safe control at the time of abnormality detection. (Example 2) which is a figure which shows an example of the relationship of the steering angle of each wheel FL, RL, FR, RR and time. It is a figure which shows the correction map etc. which show the relationship between an angle difference and a correction amount. (Example 2) which is a flowchart which shows the procedure which steering angle control ECU performs fail safe control at the time of abnormality detection. It is an example of the block diagram of a steering angle control apparatus (Example 3). It is an example of the flowchart figure in which a steering angle control apparatus controls steering angle (theta) a based on wheel speed. It is an example of a flowchart diagram in which the steering angle control device controls the steering angle θa based on the lateral G. FIG. 2 is a plan view of a vehicle when an abnormality occurs in a steering angle.

Explanation of symbols

11 Steering wheel 12 Steering wheel steering angle sensor 13 Reaction force actuator 14 Steering angle control ECU
15a to 15d Knuckles 16a to 16d Wheel speed sensors 17a to 17d Tie rods 18a to 18d Steering actuators 19a to 19d Wheel steering angle sensors 22 G sensors 50a to 50d Steering devices 31 Target steering angle calculation means 32 Abnormality detection means 33 Steering angle estimation means 34 Steering angle interpolation means 35 Determination means 36 Steering angle setting means 37 Steering angle correction means 100 Steering control device

Claims (7)

In the steering control device that can control the steering angle independently for each wheel,
The steering angle A of the wheel A in which the abnormality of the wheel steering angle sensor is detected is controlled using the detection value of the wheel steering angle sensor that detects the steering angle B closest to the steering angle A of the wheel A before the abnormality detection. Having a control unit,
A steering control device characterized by that. In a steering control device for controlling a steering angle of at least one wheel to turn on the spot using a value detected by a sensor of another wheel,
A control unit that controls the steering angle of the wheel having an abnormality so as to detect a physical quantity detected at the time of turning on the spot,
A steering control device characterized by that. The control unit controls the steering angle of the wheel A so that the wheel speed A of the abnormal wheel A substantially coincides with the wheel speed B of any other wheel during the turning.
The steering control device according to claim 2. In the steering control device that controls the steering angle according to the steering wheel operation angle,
A control unit that controls the steering angle of the abnormal wheel so that the wheel speed and lateral G of the wheel satisfy a predetermined relationship;
A steering control device characterized by that. In the steering control device that controls the steering angle according to the steering wheel operation angle,
An actuator that generates a reaction torque on the steering wheel according to the steering angle;
A control unit for controlling the steering angle of the abnormal wheel so that a steering wheel operating angle and the reaction force torque satisfy a predetermined relationship;
A steering control device comprising: In the steering angle control unit that controls the steering actuator independently for each wheel,
Steering angle interpolation means for correcting the steering angle A of the wheel A in which an abnormality has been detected by a detection value of a wheel steering angle sensor that detects the steering angle B closest to the steering angle A of the wheel A before the abnormality detection;
A steering angle control unit comprising: In a steering angle control unit for controlling the steering angle of at least one wheel to turn on the spot using a value detected by a sensor of another wheel,
Steering angle setting means for controlling the steering angle of the wheel having an abnormality so as to detect a physical quantity detected at the time of turning on the spot,
A steering angle control unit comprising:

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