JP2006347286A - Steering device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steering device for a vehicle capable of inhibiting fluctuations of steering reaction during corrective control of automatic behaviors. <P>SOLUTION: This steering device for a vehicle includes: a steering controller 13 capable of turning steered wheels independent of a steering wheel 1 steered by a driver; a brake controller 17 capable of assigning a braking/driving force to the wheels independent of braking/driving operations by the driver; an automatic behavior correction controller for correcting vehicle behaviors so as to reduce understeering or oversteering by at least either the steering controller 13 or the brake controller 17 during understeering or oversteering; and a steering reaction controller for assigning steering reaction at least in accordance with the amount of steering state of front wheels 5, 5 to the steering wheel 1. While the automatic behavior correction controller is being executed, the steering reaction controller decreases steering reaction corresponding to the amount of a steering state and increases steering reaction in accordance with the amount of turning state. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention belongs to the technical field of vehicle steering devices.

In a conventional vehicle steering apparatus, the steering reaction force according to the steered state of the front wheels is simulated by feeding back the tire turning angle and the steering actuator load to the steering reaction force (see, for example, Patent Document 1).
JP 2002-2474 A

  However, in the above prior art, when the front wheels are steered separately from the driver's steering operation by automatic behavior modification control that corrects understeer and oversteer, the amount of steered state (tire turning angle and steering actuator load) ), The steering reaction force fluctuates, causing a problem that the steering wheel is taken off.

  The present invention has been made paying attention to the above problems, and an object of the present invention is to provide a vehicle steering apparatus that can suppress fluctuations in steering reaction force during automatic behavior correction control.

In order to achieve the above object, the present invention provides:
Steering control means capable of steering the steered wheels independently of the steering wheel steered by the driver;
Braking / driving force control means capable of imparting braking / driving force to the wheels independently of the driver's braking / driving operation;
Automatic behavior correction control means for correcting vehicle behavior so as to reduce understeer or oversteer at least one of the steering control means and the braking / driving force control means at the time of understeer or oversteer;
Steering reaction force control means for applying a steering reaction force corresponding to at least the steering state amount of the steering wheel to the steering wheel;
In a vehicle steering apparatus comprising:
The steering reaction force control means reduces the steering reaction force in accordance with the steered state quantity and the vehicle behavior state quantity and the steering state quantity when the automatic behavior modification control by the automatic behavior modification control means is being executed. The steering reaction force according to at least one of the above is increased.

  In the present invention, when the automatic behavior correction control is being executed, the steering reaction force corresponding to the steered state amount is reduced, so that fluctuations in the steering reaction force during the automatic behavior correction control can be suppressed.

  Hereinafter, the best mode for carrying out the present invention will be described based on Examples 1 and 2.

First, the configuration will be described.
FIG. 1 is a configuration diagram of a vehicle steering apparatus according to a first embodiment. The vehicle steering apparatus according to the first embodiment is configured to control the operation of the steering actuators 2 and 2 that are driven according to the rotation of the steering wheel 1. Steering is achieved without mechanically connecting the steering wheel 1 and the steering mechanism 3 by converting the steering wheel 4 and 4 into the steering motion of the front wheels (steering wheels) 5 and 5. The pinion shafts 6, 6 of the steering gears 4, 4 are provided with torque sensors 7, 7 for detecting the turning torque and a turning angle sensor 8 for detecting the turning angle of the front wheels 5, 5. In the vehicle steering system of the first embodiment, the steering actuator 2, the steering gear 4, the pinion shaft 6, the torque sensor 7, and the turning angle sensor 8 are provided on the left and right sides, respectively, and the front wheels 5 and 5 are steered independently on the left and right sides. Although it is a possible configuration, the following description will be made assuming that it is one for simplicity.

  The handle 1 is connected to a rotating shaft 9 that is rotatably supported with respect to the vehicle body. The rotating shaft 9 is provided with a reaction force actuator 10 for applying a steering reaction force to the handle 1. The rotation shaft 9 is provided with a steering angle sensor 11 that detects a steering angle θ corresponding to the rotation angle of the rotation shaft 9 in order to detect an operation input value of the handle 1. The rotating shaft 9 is provided with a torque sensor 12 that detects a steering torque T applied to the handle 1.

  The output signal of each sensor is connected to a steering controller (steering control means) 13. The steering controller 13 controls the steering actuator 2 and the reaction force actuator 10 via a drive circuit. The steering controller 13 is further connected to a lateral acceleration sensor 14 that detects the lateral acceleration Gy of the vehicle, a yaw rate sensor 15 that detects the yaw rate y of the vehicle, and a vehicle speed sensor 16 that detects the vehicle speed.

  On the other hand, the steering controller 13 communicates with a brake controller (braking / driving force control means) 17 for controlling braking of the vehicle via a communication circuit 18 to exchange data. Data representing the lateral acceleration Gy, yaw rate y, and vehicle speed detected by the lateral acceleration sensor 14, the yaw rate sensor 15, and the vehicle speed sensor 16 is used in the steering controller 13 and also via the communication circuit 18 to the brake controller 17. Also transmitted.

  A backup means comprising a cable column 19 and a clutch 20 is interposed between the rotary shaft 9 and the pinion shaft 6, and if the steering actuator 2 or the reaction force actuator 10 fails, the clutch 20 And the steering wheel 1 and the steering mechanism 3 are mechanically coupled.

  The braking pressure corresponding to the depressing force of the brake pedal is generated by the master cylinder. This braking pressure is amplified by a braking pressure control unit (not shown) and distributed to the brake devices for the front and rear wheels. Applies a braking force to each wheel.

  The braking pressure control unit is controlled by the brake controller 17 so that the braking pressure of each wheel is individually controlled. The brake controller 17 is connected to a braking force sensor that individually detects the braking force of each wheel and a wheel speed sensor that individually detects each rotational speed of each wheel (not shown).

  The brake controller 17 controls the braking pressure control unit so that the braking pressure can be amplified and distributed according to the rotational speed of each wheel detected by the wheel speed sensor and the feedback value from the braking force sensor. Thereby, it is possible to individually control the braking force of each wheel. Note that the braking pressure control unit can generate the braking pressure by the built-in gear pump even when the brake pedal is not operated.

  The steering controller 13 and the brake controller 17 each perform automatic behavior correction control for stabilizing the vehicle behavior. That is, the steering controller 13 controls the steering actuator 2 to stabilize the vehicle behavior. Specifically, the turning angle δ of the front wheels 5 and 5 and the target yaw rate yI are calculated based on the steering angle θh of the handle 1, and the vehicle yaw rate y detected by the yaw rate sensor 15 is a threshold value (± Δyth). ), The front wheels 5 and 5 are subjected to correction steering control so that the actual yaw rate yR converges to the target yaw rate yI.

  On the other hand, the brake controller 17 controls the magnitude of the braking pressure in the turning inner wheel or turning outer wheel of the vehicle, thereby converging the vehicle yaw rate y to the target yaw rate yI and realizing vehicle attitude control. When the vehicle is understeered, the braking force of the inner turning wheel is greater than the braking force of the outer turning wheel, and when the vehicle is oversteered, the braking force of the outer turning wheel is greater than the braking force of the inner turning wheel. Thus, the braking force of the left and right wheels is individually controlled.

  When the brake command is input by determining the operation of the brake pedal by a brake pedal switch (not shown) or by determining the generated braking force by the braking force sensor, the brake controller 17 is connected to the steering controller via the communication circuit 18. By obtaining the information from 13, it is determined whether or not the automatic behavior correction control by the steering controller 13 is in operation.

  FIG. 2 is a control block diagram of the steering controller 13 of the first embodiment. The steering controller 13 includes a basic turning calculation unit 13a, a turning control unit 13b, a turning state determination unit 13c, an automatic behavior correction amount calculation unit 13d, a basic reaction force calculation unit 13e, and a reaction force control unit 13f. And an automatic behavior correction reaction force calculation unit 13g.

  The basic turning calculation unit 13a generates a target yaw rate yI of the vehicle based on the vehicle speed signal, the yaw rate signal, the lateral acceleration signal, the steering angle signal, the steering torque signal, the turning angle signal, and the turning torque signal. A turning angle command value δI for the front wheels 5 and 5 to obtain the yaw rate yI is calculated. The turning control unit 13b drives and controls the turning actuator 2 based on the calculated turning angle command value δI.

  The turning state determination unit 13c determines the turning state based on each sensor signal. The automatic behavior correction amount calculation unit 13d determines the automatic behavior correction amount according to the automatically corrected turning amount according to the difference Δy between the turning state, the target yaw rate yI and the actual yaw rate yR, and the automatic correction braking amount by the brake controller 17. To correct the turning angle command value δI.

  The basic reaction force calculation unit 13e generates a target steering reaction force to be applied to the steering wheel 1 based on each sensor signal, and calculates a reaction force command value Th of the reaction force actuator 10 that obtains this target steering reaction force. The reaction force control unit 13f drives and controls the reaction force actuator 10 based on the calculated reaction force command value Th. The automatic behavior correction reaction force calculator 13g calculates a reaction force command value Th during automatic behavior correction control according to the automatic behavior correction amount (automatic correction braking amount + automatic correction turning amount).

Next, the operation will be described.
[Automatic correction steering control processing]
FIG. 3 is a flowchart (corresponding to automatic behavior correction control means) showing the flow of the automatic correction turning control process executed by the steering controller 13 of the first embodiment. Each step will be described below.

  In step S1, each sensor signal is read, and the process proceeds to step S2.

  In step S2, a target yaw rate yI is calculated based on each sensor signal read in step S1, and the process proceeds to step S3.

  In step S3, when the actual yaw rate yR is less than or equal to zero and the deviation Δy between the absolute value of the target yaw rate | yI | and the absolute value of the actual yaw rate | yR | is less than the negative threshold value −Δyth The process proceeds to step S4, and otherwise, the process proceeds to step S5.

  In step S4, automatic behavior correction control for correcting understeer is performed, and the process proceeds to return.

  In step S5, if the actual yaw rate yR is greater than or equal to zero and the deviation Δy between the absolute value of the target yaw rate | yI | and the absolute value of the actual yaw rate | yR | is greater than or equal to the positive threshold value Δyth, The process proceeds to step S4. Otherwise, the process proceeds to step S6.

  In step S6, if the actual yaw rate yR is greater than or equal to zero and the deviation Δy between the absolute value of the target yaw rate | yI | and the absolute value of the actual yaw rate | yR | is less than the negative threshold value −Δyth The process proceeds to step S7, and otherwise, the process proceeds to step S8.

  In step S7, automatic behavior correction control for correcting oversteer is performed, and the process proceeds to return.

  In step S8, when the actual yaw rate yR is equal to or less than zero and the deviation Δy between the absolute value of the target yaw rate | yI | and the absolute value of the actual yaw rate | yR | is greater than or equal to the positive threshold value Δyth, The process proceeds to step S7, and otherwise, the process proceeds to step S9.

In step S9, normal steering control is performed, and the process proceeds to return.
[Automatic braking control process]
FIG. 4 is a flowchart (corresponding to automatic behavior correction control means) showing the flow of the automatic correction braking control process in the understeer state executed by the brake controller 17 of the first embodiment. Each step will be described below.

  In step S11, each sensor signal is read, and the process proceeds to step S12.

  In step S12, it is determined whether to perform understeer correction based on each sensor signal read in step S11. If YES, the process proceeds to step S13, and if NO, the process proceeds to return.

  In step S13, the braking pressure of the inner turning wheel is increased and the braking pressure of the outer turning wheel is decreased based on the automatically corrected braking amount corresponding to the deviation Δy, and the process proceeds to return.

  FIG. 5 is a flowchart (corresponding to automatic behavior correction control means) showing the flow of the automatic correction braking control process in the oversteer state executed by the brake controller 17 of the first embodiment. Each step will be described below.

  In step S21, each sensor signal is read, and the process proceeds to step S22.

  In step S22, based on each sensor signal read in step S21, it is determined whether oversteer correction is performed or application. If YES, the process proceeds to step S23, and if NO, the process proceeds to return.

  In step S23, based on the automatically corrected braking amount corresponding to the deviation Δy, in addition to increasing the braking pressure of the outer turning wheel and decreasing the braking pressure of the inner turning wheel, the automatic correction turning amount is increased, and the process proceeds to return.

[Reaction force command value calculation control processing during automatic behavior correction control]
FIG. 6 is a flowchart (steering reaction force) showing the flow of reaction force command value calculation control processing executed by the automatic behavior correction reaction force calculation unit 13g during automatic behavior correction control (automatic correction turning control or automatic correction braking control). In the following, each step will be described.

  In step S31, each sensor signal is read, and the process proceeds to step S32.

  In step S32, coefficients a to h for calculating the basic reaction force command value are calculated based on the sensor signals read in step S31, and the basic reaction force command value is calculated based on the calculated coefficients a to h. Is calculated and the process proceeds to step S33. The calculation method of the basic reaction force command value and the calculation methods of the coefficients a to h will be described later.

  In step S33, the automatic behavior correction calculation result is read from the automatic behavior correction amount calculation unit 13d, and the process proceeds to step S34.

  In step S34, coefficients A, B, and C for calculating the reaction force command value Th are calculated based on the automatic behavior correction calculation result read in step S34, and the process proceeds to step S35. A method for calculating the coefficients A, B, and C will be described later.

  In step S35, the reaction force command value Th is calculated based on the coefficients A, B, and C calculated in step S34, and the process proceeds to return. A method for calculating the reaction force command value Th will be described later.

[Automatic behavior correction control logic]
For example, the right side of the vehicle traveling direction is a high μ road surface such as a dry asphalt road surface, and the left road surface of the vehicle traveling direction is a low μ road surface such as an ice surface. When the brake pedal is depressed with the right wheel on the high μ road surface and the left wheel on the low μ road surface, a yaw moment is generated in the vehicle due to the difference between the left and right driving forces. In order to cancel this yaw moment, the steering controller 13 and the brake controller 17 each perform an automatic behavior correction control operation.

  If the maximum braking pressure is applied to the wheels in a state where the automatic behavior correction control (automatic correction turning) is not performed by the steering controller 13, the vehicle is easily oversteered on the μ split road surface. Conventionally, when the steering controller 13 does not perform automatic behavior correction control, the brake controller 17 performs vehicle braking while performing automatic behavior correction control (automatic correction braking). Accordingly, since the behavior of the vehicle does not become unstable, the vehicle does not fall into an uncontrollable state, but the brake controller 17 gives a control command for braking while stabilizing the vehicle behavior. In order to give to the braking pressure control unit, the maximum braking force is not always generated in this case, and the braking distance may be increased.

  Therefore, by performing automatic behavior correction control (automatic correction turning) by the steering controller 13 in addition to the above automatic correction braking, the brake controller 17 can be applied to the vehicle even if a command signal for increasing pressure is input until the wheel shows a lock sign. Will not fall out of control. As a result, automatic behavior correction control (automatic correction steering) by the control of the steering mechanism 3 is performed, and control that provides the maximum braking force can be performed. Therefore, even when the braking operation is performed on the μ-split road surface, the vehicle is not over-steered, and the vehicle can be stopped at a short distance, so that the safety of the vehicle is improved.

[Steering state judgment logic]
The determination of the steering state can be made by comparing the target yaw rate yI calculated from the vehicle speed V and the steering angle θh with the actual yaw rate yR measured by the yaw rate sensor 15. In the first embodiment, the counterclockwise yaw rate y is negative, and the clockwise yaw rate y is positive.

  In the turning state determination unit 13c of the steering controller 13, a deviation Δy (= | yI | − | yR |) between the magnitude | yR | of the actual yaw rate yR and the magnitude | yI | of the target yaw rate yI indicates the turning state. As a parameter, if this deviation Δy is a positive value (a value greater than the positive threshold value Δyth) greater than or equal to a predetermined value that makes it difficult to maintain the lane, it is determined that the vehicle is in an understeer state, and lane maintenance is If it is a negative value less than a predetermined value that makes it difficult (negative threshold value-a value smaller than Δyth), it is determined that the state is an oversteer state.

  Of course, if it is neither, it can be determined that the vehicle is in the neutral steer state. The target yaw rate yI can be obtained from calculation by a known method based on the vehicle speed V and the steering angle θh.

  Further, since the strength of understeer and oversteer corresponds to the difference Δy between the target yaw rate yI and the actual yaw rate yR, in the automatic behavior correction control, in the case of an oversteer state, the automatic correction turning amount corresponding to this difference Will be added.

  As described above, when it is determined that the vehicle is in the oversteer state, the brake controller 17 individually controls the braking forces of the left and right wheels so that the braking force of the outer turning wheel is larger than the braking force of the inner turning wheel. And the steering controller 13 performs automatic correction steering control according to the map of FIG. In the map of FIG. 7, when the deviation Δy is between the negative threshold value Δyth and the positive threshold value Δyth, the automatic correction turning amount is set to zero, and when the deviation Δy is exceeded, the deviation is large. The automatic correction turning amount is set to increase accordingly.

  Because the friction between the road surface and the tires is limited, if the vehicle reaches the friction limit and becomes excessively understeered, the vehicle's yaw motion must be maintained in order to maintain the intended turning radius. That is, it is necessary not only to control the vehicle posture on the vehicle running surface but also to decelerate the vehicle.

  When it is determined that the vehicle is in the understeer state, the brake controller 17 increases the braking force of the turning inner wheel to be larger than the braking force of the turning outer wheel according to the deviation Δy. At this time, the steering controller 13 does not perform automatic correction turning.

[Reaction force command value generation logic during automatic behavior correction control]
The reaction force command value Th during automatic behavior correction control is calculated by the following calculation.
Reaction force command value Th = A × steering state feedback + B × steering state feedback
+ C × vehicle behavior feedback amount Here, A, B, and C are coefficients.

The amount of steering state feedback (steering reaction force according to the amount of steering state) is calculated as follows.
Steering state feedback = a × steering angle + b × steering angular velocity + c × steering angular acceleration
+ D × steering torque The amount of steering state feedback (steering reaction force according to the amount of steering state) is calculated as follows.
Steering state feedback = e × steering angle + f × steering angular velocity + g × steering angular acceleration
+ H × steering torque The amount of vehicle behavior feedback (steering reaction force corresponding to the amount of vehicle behavior state) is calculated as follows.
Vehicle behavior feedback = yaw rate or lateral acceleration Gy

  Here, as shown in FIG. 8, the coefficients a to h are calculated from a map corresponding to the vehicle speed V and each detected value. a to h are set to be larger as the detection value is larger and as the speed is lower.

The coefficients B and C are determined according to the maps of FIGS.
As shown in FIGS. 9 and 10, the coefficient B is set to decrease and the coefficient C is set to increase as (automatic correction turning amount + automatic correction braking amount) increases. In other words, since automatic correction steering is not performed in daily driving where strong yaw rate behavior does not occur, in this case, the vehicle behavior feedback generated with a delay with respect to steering is reduced, and By increasing the rudder state feedback, the vehicle behavior pre-detection is improved, so that the driver can easily perform a feed-forward steering operation, and the drivability is improved.

  On the other hand, when a strong oversteer behavior such as a snowy road is likely to occur and automatic correction turning is performed, the amount of turning state feedback changed by turning is reduced and the amount of vehicle behavior feedback is increased. As a result, a change in the steering torque due to the automatic correction turning can be reduced, and therefore, the feeling that the driver can take the steering wheel 1 can be reduced. Further, by increasing the vehicle behavior feedback, the driver can sense the current vehicle behavior state through the steering torque T.

The coefficients B and C are changed in size according to the automatic behavior correction amount. For example, in the method of canceling the steering state feedback at the time of automatic correction turning and switching to the vehicle behavior feedback, a sudden change of the steering torque T occurs at the time of the switching, which makes it strange. The steering torque change at the time can be made smooth.
In the first embodiment, the coefficient A is a constant that adds springiness and damping properties, for example, 0.2.

  The coefficient B is set so as to be a constant gain of 0.1 or more which does not become zero even when the automatic behavior correction amount is very large. By doing so, when the driver performs the correction steering during the automatic correction steering, the driver can sense the steering state, and thus feed-forward steering wheel correction steering can be performed. It becomes easier to perform corrective steering.

  FIG. 11 shows temporal changes in the steering angle θh, the yaw rate y, and the lateral acceleration Gy when automatic correction braking control and automatic correction turning control are performed during steady turning. FIG. 12B shows a control example in which the steering state feedback is switched to the lateral acceleration feedback at the time of automatic correction turning. As shown in FIG. 12 (b), in the control for switching from the steering state feedback to the lateral acceleration feedback during the automatic correction steering control, a sudden change of the steering torque T occurs at the time of switching, and the driver feels uncomfortable.

  On the other hand, in the first embodiment, the coefficients B and C are changed according to the automatic behavior correction amount, and the weight is changed for the turning state feedback and the vehicle behavior feedback with respect to the reaction force command value Th. The torque change can be smoothed (FIG. 12 (c)). In the first embodiment, the fluctuation range of the steering reaction force is reduced by about 24% as compared with the case without the conventional control (FIG. 12A).

  FIG. 13 shows an example in which the yaw rate y is used in place of the lateral acceleration Gy, and in this case as well, the steering torque change during the automatic correction turning can be smoothed (FIG. 13 (c)). In addition, the fluctuation range of the steering reaction force is reduced by about 30% compared to the case without the conventional control (FIG. 13A).

  In Example 1, the smaller the front wheel side slip angle (steering angle) βf is, the higher the tire cornering power is, and the larger the steering torque change for the steering state feedback per unit correction turning amount is. When the vehicle is running, the road surface feedback reduction amount of the steering torque T is increased and the increase amount of the vehicle behavior feedback is reduced as the absolute value of the front wheel side slip angle βf is smaller.

By measuring the longitudinal speed Vb and lateral speed Vy of the vehicle, the side slip angle β of the vehicle body is
β = tan ^-1 (Vy / Vb)
Can be calculated. From this, the front wheel side slip angle βf is assumed to be yaw rate y, front-rear speed Vb, turning angle δ, front axis to rear axis lf.
βf ≒ β + lf × y / Vb−δ
Is required.

[Conventional technology]
In the vehicle steering apparatus described in Japanese Patent Laid-Open No. 2002-2474, a reaction force command value is calculated by using a steering actuator load sensor, a wheel slip angle sensor, a steering angle sensor, a yaw rate sensor, a lateral acceleration Gy sensor, and a vehicle speed sensor. Used to generate steering reaction torque.

  Here, in order to realize a good braking operation on the split μ road, when the vehicle behavior stabilization control is performed by the steering controller, the steering controller performs the steering operation separately from the driver's steering operation. For this reason, the conventional technique has a problem that the steering actuator load sensor value changes, the steering torque is changed, and the steering wheel is removed (FIG. 15 (a)). In addition, since the steered position cannot be detected, there is a problem that when the variable gear control or the like is performed, the steering system is not properly attenuated and the steering wheel restoring property (convergence) is deteriorated.

  For example, when the counter steer (FIG. 14 (b)) is applied during a circular turn (FIG. 14 (b)) and the vehicle is decelerated, the lateral acceleration Gy decreases (FIG. 14 (c)), and the vehicle behavior Can be stabilized. However, since the sudden increase of the self-aligning torque at the start of the counter steering (FIG. 14 (d)) is fed back to the steering reaction force, the steering wheel is removed.

[Reaction force command value correction action during automatic behavior correction control]
On the other hand, in the vehicle steering apparatus of the first embodiment, when the steering controller 13 performs automatic correction turning, the road surface feedback amount to the steering torque T is reduced and the other feedback amounts are increased. As a result, it is possible to reduce steering wheel pulling when control is performed to perform automatic correction steering that corrects understeer, oversteer, and the like that make lane maintenance difficult (FIG. 15 (c)).

  In the first embodiment, the road surface feedback reduction amount to the steering torque T is increased in accordance with the magnitude of the automatic behavior correction amount, and the vehicle behavior feedback increase amount is increased. Thereby, the fluctuation | variation of the steering torque at the time of the start of automatic correction turning according to the magnitude | size of automatic behavior correction amount is reduced, and discomfort is reduced. For example, in the method of canceling the steering state feedback at the time of automatic correction turning and switching to the vehicle behavior feedback (lateral acceleration feedback), a sudden change in the steering torque T occurs at the time of the switching, resulting in an uncomfortable feeling (FIG. 15 ( b)).

  Therefore, by increasing the road surface feedback reduction amount to the steering torque T according to the magnitude of the automatic behavior correction amount and increasing the vehicle behavior feedback increase amount, a sudden change in the steering torque change is reduced and smoothed.

  Further, in the first embodiment, when automatic correction turning is applied, the road surface feedback reduction amount of the steering torque T is increased and the vehicle behavior feedback increase amount is increased as the front wheel side slip angle βf is smaller. As a result, the smaller the front wheel side slip angle βf is, the higher the tire cornering power is, and the steering wheel feedback can be increased by the turning state feedback per unit correction turning amount.

  In the first embodiment, the steering torque T is generated using the detected values of the turning angle δ and the turning angular velocity. As a result, even when the relationship between the steering angle θh and the turning angle δ is variable, such as a variable gear, an appropriate steering system damping characteristic can be set and an appropriate steering wheel restoring property can be obtained.

Next, the effect will be described.
In the vehicle steering apparatus according to the first embodiment, the following effects can be obtained.

  (1) A steering controller 13 capable of steering the steered wheels independently of the steering wheel 1 steered by the driver, a brake controller 17 capable of applying braking / driving force to the wheels independently of the driver's braking / driving operation, and understeer Alternatively, at the time of oversteering, at least one of the steering controller 13 and the brake controller 17 automatically behavior correction control means (FIGS. 3, 4 and 5) for correcting the vehicle behavior so as to reduce understeer or oversteer, and at least the front wheel on the steering wheel 1 In the vehicle steering apparatus provided with the steering reaction force control means (FIG. 6) for applying the steering reaction force according to the steering state amounts of 5 and 5, the steering reaction force control means executes the automatic behavior correction control. When this is done, the steering reaction force according to the steered state quantity is reduced and the steering reaction force according to the vehicle behavior state quantity is increased. Therefore, fluctuations in the steering reaction force during automatic behavior correction control can be suppressed.

  (2) The steering reaction force control means reduces the steering reaction force according to the turning state amount as the vehicle behavior correction amount of the automatic behavior correction control is larger, and at least one of the vehicle behavior state amount and the steering state amount. The steering reaction force corresponding to is increased. Therefore, the steering torque change during the automatic behavior correction control can be made smooth, and the uncomfortable feeling given to the driver can be suppressed.

  (3) The steering reaction force control means decreases the steering reaction force according to the steered state amount and increases the steering reaction force according to the vehicle behavior state amount as the front wheel side slip angle βf decreases. Therefore, the road surface feedback portion of the steering torque T that varies according to the front wheel side slip angle βf can be effectively suppressed.

  In the second embodiment, the vehicle behavior feedback for determining the reaction force command value Th is varied. That is, the vehicle behavior feedback for the reaction force command value Th is calculated by the sum of the reaction force due to the lateral acceleration Gy and the reaction force due to the yaw rate y. As a result, the yaw rate gain reaction force is large and the lateral acceleration gain reaction force is small at low speeds, so that a reaction force corresponding to the yaw rate y can be generated. On the other hand, a steering reaction force corresponding to the lateral acceleration Gy is reversed at high speeds. The ratio between the yaw rate y and the lateral acceleration Gy in the steering reaction force can be automatically changed according to the vehicle speed V.

Next, the operation will be described.
[Method for calculating vehicle behavior feedback for reaction force command value]
In the second embodiment, the vehicle behavior feedback for the reaction force command value Th is set as follows.
Vehicle behavior feedback = i x yaw rate y + j x lateral acceleration Gy

  The coefficient i is calculated using the map of FIG. As shown in FIG. 16, the coefficient i is set to increase as the yaw rate y increases. Furthermore, it is set so that the oversteer reduction control amount (the amount of automatic behavior correction during oversteer) is large or the vehicle speed V is high.

  The coefficient j is calculated using the map of FIG. As shown in FIG. 17, the coefficient j is set so as to increase as the lateral acceleration Gy increases. Furthermore, it is set so that the oversteer reduction control amount (the amount of automatic behavior correction during oversteering) is larger or the vehicle speed V is higher.

[Vehicle behavior feedback variable action according to vehicle speed]
The yaw rate y generates a large value during low speed traveling, but a small value during high speed traveling. On the other hand, the lateral acceleration Gy generates a large value during high-speed traveling, but a small value during low-speed traveling.

  FIG. 18 shows (a) the yaw rate y and (b) the lateral acceleration Gy with respect to the steering angle θ when traveling at 40 km / h. FIG. 19 shows (a) yaw rate y and (b) lateral acceleration Gy with respect to the steering angle θ when traveling at 120 km / h. As shown in FIGS. 18 and 19, when the vehicle is traveling at 40 km / h and the vehicle is traveling at 120 km / h, the steering necessary for generating the lateral acceleration Gy used on a daily basis is shown. The generation range of yaw rate y in the angular range (150 degrees at 40 km / h, 40 degrees at 120 km / h) is larger at low speed.

  In the second embodiment, as the vehicle speed V increases, the yaw rate y and the lateral acceleration Gy of the vehicle behavior feedback amount are reduced, and the lateral acceleration is increased. That is, since the resolution of the yaw rate detection value in the high vehicle speed range is reduced, it is necessary to increase the gain at a high vehicle speed V, but the noise component also increases, so that the steering torque T becomes oscillatory. Therefore, the noise component can be reduced and the vibration of the steering torque T can be suppressed by using the detected value of the lateral acceleration Gy with high resolution in the high speed range.

[Vehicle behavior feedback variable action according to automatic behavior correction control direction]
In the second embodiment, when the steering controller 13 and the brake controller 17 control the ratio of the yaw rate y and the lateral acceleration Gy of the vehicle behavior feedback amount in the oversteer reducing direction, the yaw rate is reduced and the lateral acceleration component is reduced. Increase. When control is applied in the direction of understeer reduction, the yaw rate is increased and the lateral acceleration is reduced.

  The yaw rate y at the time of oversteer is in an increasing direction, and the lateral acceleration Gy is in a decreasing direction because the vehicle body slip angle exceeds the angle at which the tire cornering force MAX (maximum value) is taken. In this state, when the steering controller 13 and the brake controller 17 control the oversteer reduction, the yaw rate y decreases, and the vehicle body slip angle becomes close to the angle at which the tire cornering force MAX is obtained due to the oversteer reduction. Will increase. In such a case, if the yaw rate gain reaction force is large, the steering reaction force decreases as the oversteer is reduced.

  On the other hand, in the second embodiment, the yaw rate gain reaction force is reduced and the lateral acceleration gain reaction force is increased, so that the steering reaction force increases as the oversteer reduction and the lateral acceleration increase, and the tire grip is felt to be restored. Will be able to.

Next, the effect will be described.
In the vehicle steering apparatus of the second embodiment, the effects listed below are obtained in addition to the effects (1) to (3) of the first embodiment.

  (4) When the automatic behavior correction control corrects the oversteer, the steering reaction force control means calculates the steering reaction force corresponding to the lateral acceleration Gy out of the steering reaction force corresponding to the vehicle behavior state quantity. To be larger than the steering reaction force corresponding to. Therefore, the grip feeling of the tire at the time of oversteer reduction can be provided to the steering reaction force.

  (5) When the automatic behavior correction control corrects the understeer, the steering reaction force control means converts the steering reaction force corresponding to the yaw rate y out of the steering reaction force corresponding to the vehicle behavior state quantity into the lateral acceleration Gy. It is made larger than the corresponding steering reaction force. Therefore, the grip feeling of the tire at the time of understeer reduction can be imparted to the steering reaction force.

  (6) The steering reaction force control means reduces the steering reaction force corresponding to the yaw rate y out of the steering reaction force corresponding to the vehicle behavior state quantity as the vehicle speed V is higher, and responds to the lateral acceleration Gy. Increase the steering reaction force. Therefore, by using the detection value of the lateral acceleration sensor 14 with high resolution in a high speed region, the noise component can be reduced and the vibration of the steering reaction force can be suppressed.

(Other examples)
The best mode for carrying out the present invention has been described based on the embodiments. However, the specific configuration of the present invention is not limited to the first and second embodiments, and departs from the gist of the invention. Even if there is a design change or the like within a range not to be included, it is included in the present invention.

  In the embodiment, an example is shown in which an auxiliary yaw moment is applied to the vehicle by applying a braking force left / right difference to the vehicle, and the actual yaw rate is brought close to the target yaw rate. It may be configured to correct the steer.

In the embodiment, the coefficient A for the steering state feedback of the reaction force command value is set to a constant value (0.2), but may be variable according to the steering state amount.
Instead of the torque sensor that detects the steering torque, an axial force sensor that detects the rack axial force input to the rack shaft of the steering mechanism may be provided.

  In the embodiment, the example in which the present invention is applied to the steer-by-wire system in which the handle and the front wheel are mechanically separated has been described. However, the present invention is a steering device in which the handle and the front wheel are mechanically coupled. Thus, the present invention can also be applied to a steering apparatus having a steering mechanism (for example, a variable gear ratio mechanism) that can be steered independently of the steering operation.

1 is a configuration diagram of a vehicle steering apparatus according to Embodiment 1. FIG. FIG. 3 is a control block diagram of the steering controller 13 according to the first embodiment. 4 is a flowchart showing a flow of automatic correction turning control processing executed by the steering controller 13 of the first embodiment. 6 is a flowchart showing a flow of an automatic correction braking control process in an understeer state executed by the brake controller 17 of the first embodiment. 6 is a flowchart illustrating a flow of an automatic correction braking control process in an oversteer state executed by the brake controller 17 according to the first embodiment. It is a flowchart which shows the flow of the reaction force command value calculation control processing performed in the reaction force calculating part 13g at the time of automatic behavior correction at the time of automatic behavior correction control (automatic correction steering control or automatic correction braking control). It is an automatic correction turning amount setting map. It is a setting map of the coefficients ah according to the vehicle speed V and the detection value of each sensor. It is a setting map of the coefficient B according to the automatic behavior correction amount. It is a setting map of the coefficient C according to the automatic behavior correction amount. It is a figure which shows the time change of a steering angle, a yaw rate, and a lateral acceleration at the time of performing automatic correction braking control and automatic correction turning control during steady turning. It is a figure which shows the reaction force command value correction effect | action according to the automatic behavior correction amount of Example 1. FIG. It is a figure which shows the reaction force command value correction effect | action according to the automatic behavior correction amount of Example 1. FIG. It is a figure which shows the vehicle locus | trajectory during circular turning, the motor angle of a steering actuator, a lateral acceleration, and a self-aligning torque. It is a figure which shows the reaction force command value correction effect | action at the time of the automatic behavior correction control of Example 1. FIG. 7 is a setting map of a coefficient i according to an oversteer reduction control amount, a vehicle speed V, and a yaw rate y according to the second embodiment. FIG. 10 is a setting map of a coefficient j according to the oversteer reduction control amount, the vehicle speed V, and the lateral acceleration Gy of the second embodiment. It is a figure which shows the yaw rate y and the lateral acceleration Gy with respect to the steering angle (theta) at the time of low speed driving | running | working. It is a figure which shows the yaw rate y and the lateral acceleration Gy with respect to steering angle (theta) at the time of high speed driving | running | working.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Handle 2 Steering actuator 3 Steering mechanism 4 Steering gear 5 Front wheel 6 Pinion shaft 7 Torque sensor 8 Steering angle sensor 9 Rotating shaft 10 Reaction force actuator 11 Steering angle sensor 12 Torque sensor 13 Steering controller 13a Basic steering calculating part 13b Rudder control unit 13c Turning state determination unit 13d Automatic behavior correction amount calculation unit 13e Basic reaction force calculation unit 13f Reaction force control unit 13g Reaction behavior calculation unit 14 during automatic behavior correction Lateral acceleration sensor 15 Yaw rate sensor 16 Vehicle speed sensor 17 Brake controller 18 Communication Circuit 19 Cable type column 20 Clutch

Claims (7)

Steering control means capable of steering the steered wheels independently of the steering wheel steered by the driver;
Braking / driving force control means capable of imparting braking / driving force to the wheels independently of the driver's braking / driving operation;
Automatic behavior correction control means for correcting vehicle behavior so as to reduce understeer or oversteer at least one of the steering control means and the braking / driving force control means at the time of understeer or oversteer;
Steering reaction force control means for applying a steering reaction force corresponding to at least the steering state amount of the steering wheel to the steering wheel;
In a vehicle steering apparatus comprising:
The steering reaction force control means reduces the steering reaction force in accordance with the steered state quantity and the vehicle behavior state quantity and the steering state quantity when the automatic behavior modification control by the automatic behavior modification control means is being executed. A steering apparatus for a vehicle, wherein a steering reaction force corresponding to at least one of the two is increased. The vehicle steering apparatus according to claim 1,
The steering reaction force control means reduces the steering reaction force in accordance with the steered state amount as the vehicle behavior correction amount of the automatic behavior correction control is larger, and sets the vehicle behavior state amount and the steering state amount. A steering apparatus for a vehicle, wherein a steering reaction force corresponding to at least one is further increased. The vehicle steering apparatus according to claim 1 or 2,
When the automatic behavior correction control corrects oversteer, the steering reaction force control means determines a steering reaction force corresponding to a lateral acceleration out of a steering reaction force corresponding to the vehicle behavior state quantity according to a yaw rate. A steering apparatus for a vehicle, wherein the steering reaction force is larger than the steering reaction force. The vehicle steering apparatus according to any one of claims 1 to 3,
When the automatic behavior correction control corrects the understeer, the steering reaction force control means determines the steering reaction force corresponding to the yaw rate out of the steering reaction force corresponding to the vehicle behavior state quantity according to the lateral acceleration. A steering apparatus for a vehicle, characterized by being larger than a steering reaction force component. The vehicle steering apparatus according to any one of claims 1 to 4, wherein:
The steering reaction force control means reduces the steering reaction force according to the steered state amount as the side slip angle of the steered wheel is smaller, and at least one of the vehicle behavior state amount and the steering state amount. A vehicle steering apparatus characterized by further increasing the corresponding steering reaction force. The vehicle steering apparatus according to any one of claims 1 to 5,
The steering reaction force control means reduces the steering reaction force corresponding to the yaw rate out of the steering reaction force corresponding to the vehicle behavior state quantity as the vehicle speed is higher, and the steering reaction force component corresponding to the lateral acceleration. A steering apparatus for a vehicle, characterized in that the vehicle is made larger. In a vehicle steering apparatus that performs a yaw moment control that gives an auxiliary yaw moment to a vehicle and a steering reaction force control that gives a steering reaction force according to a steering state amount of a steered wheel to a steering wheel,
When an auxiliary yaw moment is applied to the vehicle, the steering reaction force component corresponding to the steered state amount is reduced and the steering reaction force component corresponding to at least one of the vehicle behavior state amount and the steering state amount is increased. A vehicle steering apparatus characterized by the above.

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