JP4254710B2 - Steering control device for vehicle - Google Patents

Description

  The present invention relates to a vehicle steering control device, and more specifically, to a vehicle steering control for controlling a steering transmission ratio that is a ratio of a steering wheel turning angle change amount to a steering operation change amount of a steering input means by a driver. Related to the device.

  In a vehicle such as an automobile, a steering transmission ratio variable mechanism that changes a steering transmission ratio (steering gear ratio) by turning a steering wheel relative to a steering input means such as a steering wheel by a steering drive means. A steering control device that controls the steering characteristics by controlling the steering transmission ratio variable mechanism is conventionally known.

Further, as described in, for example, the following Patent Document 1 relating to the application of the present applicant, as one of the steering control devices including a steering transmission ratio variable mechanism, the driving speed of the steering driving means is set according to the steering speed. There is already known a steering control device configured to change the steering transmission ratio by changing the steering transmission ratio.
JP-A-11-310147

  Generally, in a steering control device equipped with a transmission ratio variable mechanism, as described in Patent Document 1, the steered wheels are steered relative to a steering input means such as a steering wheel by a steered drive means. Therefore, when the steering transmission ratio is changed, the driving force necessary for turning the steered wheels becomes large especially when the vehicle speed is low and the steering speed is high. Steering drive delay is likely to occur. When a delay in the steering drive of the steered wheels by the steered drive means occurs, a deviation of the steering angle of the steered wheels with respect to the neutral position of the steering input means (deviation between the neutral position of the steer input means and the straight traveling position of the steered wheels) ) Occurs, and the driver feels strange when steering.

  Also, in this technical field, when the driving state of the vehicle becomes unstable, such as when the oversteer state or the understeer state becomes excessive, the steered driving means corrects and steers the steered wheels to stabilize It is also under consideration to ensure vehicle running stability by applying a yaw moment to the vehicle to correct the steering angle of the steering wheel relative to the neutral position of the steering input means by correcting the steering wheel. Deviation occurs.

  However, in the steering control device having the conventional steering transmission ratio variable mechanism as described in Patent Document 1, the steering angle is achieved while achieving desired steering characteristic control and desired steering wheel correction turning. Sufficient consideration has not been made on how to suppress the occurrence of the deviation and how to reduce the deviation of the generated steering angle, and further improvement is desired in this regard.

  The present invention has been made in view of the current situation as described above in a vehicle steering control device for controlling a steering transmission ratio, and the main problem of the present invention is that the occurrence of steering angle deviation is suppressed or generated. By controlling the steering transmission ratio so that the deviation of the rudder angle is reduced, the deviation of the rudder angle caused by the control of the steering characteristics and the correction turning of the steered wheels and the unnatural feeling caused by this are reduced. It is to be.

According to the present invention, the main problem described above is that the steering transmission ratio variable means for changing the steering transmission ratio that is the ratio of the steering angle change amount of the steered wheel to the steering operation amount, and the target steering according to the running state of the vehicle. Vehicle for calculating transmission ratio, means for calculating target steering angle of steering wheel based on target steering transmission ratio, and vehicle for controlling steering transmission ratio variable means so that steering angle of steering wheel becomes target steering angle in use the steering control device includes a target steering transmission ratio correcting means for correcting the target steering transmission ratio at suppressing correction amount generation of deviation of the steering angle of the steering wheel with respect to the neutral position of the steering input means, said target steering transmission ratio changing means steering control apparatus of the vehicle according to claim large to Rukoto the magnitude of the correction amount than when cut back during increased cut in the case of correcting to the target steering transmission ratio decreases ( wherein arrangement of claim 1), or Misao Steering transmission ratio variable means for changing a steering transmission ratio, which is a ratio of a steering angle change amount of the steering wheel to an operation amount, means for calculating a target steering transmission ratio according to the traveling state of the vehicle, and the steering transmission ratio is the target transmission ratio. In the vehicle steering control device that controls the steering transmission ratio variable means so as to obtain a steering transmission ratio, the target steering is performed with a correction amount that suppresses the occurrence of a deviation of the steering angle of the steering wheel with respect to the neutral position of the steering input means. And a target steering transmission ratio correction unit that corrects the transmission ratio. When the target steering transmission ratio correction unit corrects the target steering transmission ratio to be larger, the correction amount is larger at the time of switching than at the time of switching back. Or a steering transmission ratio variable means for changing a steering transmission ratio, which is a ratio of a steering angle change amount of a steering wheel to a steering operation amount. Of the vehicle Means for calculating a target steering transmission ratio in accordance with a running state; means for calculating a target steering angle of a steered wheel based on the target steering transmission ratio; and the steering transmission so that the steering angle of the steering wheel becomes the target steering angle. in the vehicle steering control apparatus for controlling the ratio varying means comprises a steering angle shift reducing means for reducing the deviation of the steering angle of the steering wheel with respect to a neutral position of the steering input means, a steering angle by the steering angle shift reducing unit The vehicle steering control device characterized in that the magnitude of the deviation reduction amount is larger when the change rate of the steering operation amount is large than when the change rate of the steering operation amount is small. To achieve this.

Further, according to the present invention, in order to effectively achieve the above main problem, in the configuration of claim 1 , the magnitude of the correction amount is controlled when the rate of change of the steering operation amount is large. The change rate of the manipulated variable is configured to be larger than when the change rate is small (configuration of claim 2 ).

Further, according to the present invention, in order to effectively achieve the above main problem, in the configuration of the above-described third aspect , the magnitude of the correction amount is adjusted when the change rate of the steering operation amount is small. It is configured to be larger than when the change rate of the manipulated variable is large (configuration of claim 4 ).

According to the present invention, in order to effectively achieve the above-mentioned main problems, in the configuration of the above-described claims 1 to 4, the magnitude of the correction amount is a steering operation when the magnitude of the steering operation amount is large. It is configured to be smaller than when the magnitude of the quantity is small (structure of claim 5 ).

According to the invention, to the aspect of the effective, in the configuration of the claims 1 to 5, wherein the target steering transmission ratio of the components and the steering wheel for controlling the steering characteristics And a component for improving the running stability of the vehicle by correcting the steering, and the target steering transmission ratio correcting means is configured so that the component for improving the running stability of the vehicle is substantially zero. It is comprised so that the said target rudder angle may be correct | amended with a correction amount (structure of Claim 6 ).

According to the present invention, in order to effectively achieve the main problem described above, in the configuration of claim 7 , the amount of reduction in the rudder angle deviation at the time of switching back is the amount of the rudder at the time of increasing. It is comprised so that it may be larger than the magnitude | size of an angular deviation reduction amount (structure of Claim 8 ).

According to the present invention, in order to effectively achieve the above main problem, in the configuration of claim 7 , the magnitude of the steering angle deviation reduction amount at the time of switching back is determined by the steering input means. Based on the relationship between the steering operation position and the steering angle of the steering wheel, the steering angle of the steering wheel is set to a value that is substantially zero when the steering operation position becomes the neutral position (configuration of claim 9 ). .

Further, according to the present invention, in order to effectively achieve the main problems described above, the target rudder angle is a component for controlling a steering characteristic and a steered wheel in the configuration according to the seventh to ninth aspects. A steering component for improving the running stability of the vehicle, and the steering angle deviation reducing means is configured to reduce the steering input when the component for improving the running stability of the vehicle is substantially zero. configured to reduce the deviation of the steering angle of the steering wheel with respect to a neutral position of the unit (the configuration of claim 1 0).

Note in the above-mentioned claims 6 and 1 0, is the "time component for improving the running stability of the vehicle is substantially 0", components for example, the control for improving the running stability of the vehicle This means that it is 0 or a value that does not deteriorate the running stability of the vehicle even if the steered wheels are not corrected and steered. In the above-mentioned claim 9 , the “value at which the steering angle of the steered wheels is substantially zero” means that the steering angle of the steered wheels is 0 or less than the reference value close to 0, for example, It means that the value is such that substantially straight running can be secured.

  In general, the self-aligning torque acts on the steered wheels when the vehicle turns, and the force required for turning the steered wheels in the turning direction is larger than that in the turning-back direction. When the cut is increased, a change in the steering transmission ratio by the steering transmission ratio variable means is more likely to be delayed than when the switch is returned.

According to the configuration of the first aspect, the target steering transmission ratio correction unit corrects the target steering transmission ratio with a correction amount that suppresses the occurrence of the deviation of the steering angle of the steering wheel with respect to the neutral position of the steering input unit, target steering transmission ratio changing means a target steering transmission than when cut back is largely be Runode, turning-increasing time the magnitude of the correction amount than when cut back during increased cut in the case of correcting to the target steering transmission ratio decreases The correction amount when correcting the target steering transmission ratio can be increased so that the ratio is reduced, and this causes a delay in the change of the steering transmission ratio by the steering transmission ratio variable means when the steering wheel is increased. it is possible to reliably reduce the possibility that excessive steering angle deviation arising in.

According to the second aspect of the present invention, the magnitude of the correction amount is larger when the change rate of the steering operation amount is large than when the change rate of the steering operation amount is small. In a situation where the rate of change of the amount is large and a delay in the change of the steering transmission ratio by the steering transmission ratio variable means is likely to occur, the correction amount of the target steering transmission ratio is surely increased at the time of switching more than at the time of switching back be able to.

According to the third aspect of the present invention, there is provided a target steering transmission ratio correcting means for correcting the target steering transmission ratio with a correction amount that suppresses the occurrence of a deviation of the steering angle of the steering wheel with respect to the neutral position of the steering input means. When the target steering transmission ratio is corrected so that the target steering transmission ratio is increased, the correction amount is made smaller at the time of switching back than at the time of switching back. The ratio correction amount can be increased, thereby reliably reducing the possibility that the change in the steering transmission ratio by the steering transmission ratio variable means becomes too fast.

According to the fourth aspect of the present invention, the magnitude of the correction amount is larger when the change rate of the steering operation amount is small than when the change rate of the steering operation amount is large. When the magnitude of the change rate of the amount is small, compared to when the magnitude of the change rate of the steering operation amount is large, in other words, when the delay of the change in the steering transmission ratio by the steering transmission ratio variable means is difficult to occur, the steering transmission ratio The amount of correction of the target steering transmission ratio can be increased compared to when the change of the steering wheel is likely to occur, so that the steering transmission ratio change by the steering transmission ratio variable means is too fast when the steering wheel is switched back. It is possible to reliably reduce the risk of becoming.

According to the fifth aspect of the present invention, since the magnitude of the correction amount is small when the magnitude of the steering operation amount is large compared to when the magnitude of the steering operation amount is small, the magnitude of the steering operation amount is large. In the situation, it is possible to reliably prevent the change amount of the steering angle of the steered wheels from becoming excessive by correcting the target steering transmission ratio.

According to the configuration of the sixth aspect, the target steering transmission ratio includes a component for controlling the steering characteristics and a component for improving the running stability of the vehicle by correcting the steered wheels, Since the angle correction means corrects the target steering transmission ratio with the correction amount when the component for improving the driving stability of the vehicle is substantially zero, the driving stability of the vehicle is improved by correcting the target steering transmission ratio. It is possible to reliably prevent the steering wheel from being effectively turned to improve the steering.

According to the configuration of the seventh aspect, the steering angle deviation reducing means for reducing the deviation of the steering angle of the steered wheels with respect to the neutral position of the steering input means is provided, and the magnitude of the steering angle deviation reduction amount by the steering angle deviation reducing means is large. Is larger when the change rate of the steering operation amount is large than when the change rate of the steering operation amount is small. Therefore, when the change rate of the steering operation amount is large, the change rate of the steering operation amount The steering angle deviation can be effectively reduced as compared with the case where the size of the steering wheel is small .

According to this configuration 9, the size of the steering angle deviation amount of reduction during cuts back is greater than the magnitude of the steering angle deviation amount of reduction during increased cut, the steering transmission by steering transmission ratio varying means during turning-increasing It is possible to effectively reduce the rudder angle deviation caused by the delay in the ratio change .

According to the configuration of claim 9 , the magnitude of the reduction amount of the steering angle deviation at the time of switching back is based on the relationship between the steering operation position of the steering input means and the steering angle of the steering wheel. Since the steering angle of the steered wheels is set to a value that is substantially zero, the steering angle deviation at the time of switching back is reduced without excess or deficiency so that the steering angle deviation is eliminated when the steering operation position becomes the neutral position. Thereby, the rudder angle deviation can be surely eliminated.

According to this configuration 1 0, the target steering angle and a component for improving the running stability of the vehicle by turning modifying the components and the steering wheel for controlling the steering characteristics, steering angle deviation The reduction means reduces the deviation of the steering angle of the steering wheel with respect to the neutral position of the steering input means when the component for improving the running stability of the vehicle is substantially zero. Thus, it is possible to reliably prevent the correction turning of the steered wheels, which is performed to improve traveling stability, from being effectively performed.

[Preferred embodiment of problem solving means]
According to one preferred embodiment of the present invention, in the configuration of the claims 1 to 1 0, the steering transmission ratio variable means by steering drive relatively steered wheels relative to the steering input means, the driver A steering driving means for steering the steering wheel independently is included (preferred aspect 1).

  According to another preferred aspect of the present invention, in the configuration of the preferred aspect 1 described above, the steered driving means can steer the first steering shaft and the steered wheels connected to the steering input means. The second steering shaft is provided between the second steering shaft and the second steering shaft relative to the first steering shaft (preferred aspect 2).

According to the aspect of the present invention, in the configuration of the claims 1 to 1 0, the steering control apparatus the target yaw moment to be applied to the vehicle to the behavior of the vehicle to the target behavior state Calculates and distributes the target yaw moment between the target yaw moment by controlling the braking / driving force of each wheel and the target yaw moment by correcting the steered wheels, and the means for calculating the target steering transmission ratio is substantially equivalent to the target yaw moment. When the value is not 0, the target transmission ratio is calculated based on at least the target yaw moment by the modified turning of the steered wheels (preferred aspect 3).

  The present invention will now be described in detail with reference to a few preferred embodiments with reference to the accompanying drawings.

  FIG. 1 shows a vehicle steering control according to the present invention configured as a part of a behavior control device that controls the steering gear ratio, controls the braking / driving force of each wheel, and controls the steering angle of the left and right front wheels. It is a schematic block diagram which shows Example 1 of an apparatus.

  In FIG. 1, 10FL and 10FR respectively indicate left and right front wheels as driven steering wheels of the vehicle 12, and 10RL and 10RR respectively indicate left and right rear wheels as drive wheels of the vehicle. The left and right front wheels 10FL and 10FR, which are steering wheels, are driven via a rack bar 18 and tie rods 20L and 20R by a rack-and-pinion type electric power steering device 16 driven in response to an operation of the steering wheel 14 by a driver. Steered.

  The steering wheel 14 is a power steering system via an upper steering shaft 22 as a first steering shaft, a turning angle varying device 24 as a steering transmission ratio varying means, a lower steering shaft 26 as a second steering shaft, and a universal joint 28. Drive connected to the pinion shaft 30 of the device 16. In the illustrated embodiment, the turning angle varying device 24 is connected to the lower end of the upper steering shaft 22 on the housing 24A side, and is connected to the upper end of the lower steering shaft 26 on the rotor 24B side. An electric motor 32 for turning driving is included.

  Thus, the turning angle varying device 24 rotationally drives the lower steering shaft 26 relative to the upper steering shaft 22 so that the left and right front wheels 10FL and 10FR are turned to the steering wheel 14 for the purpose of steering gear ratio control and behavior control. On the other hand, it functions as an automatic steering device that drives the auxiliary steering relatively, and is controlled by the steering angle control electronic control device 34.

  If an abnormality in which the lower steering shaft 26 cannot be driven to rotate relative to the upper steering shaft 22 occurs in the turning angle varying device 24, a lock device not shown in FIG. The relative rotation of the housing 24A and the rotor 24B is mechanically prevented so that the relative rotation angle of the lower steering shaft 26 with respect to 22 does not change.

  In the illustrated embodiment, the electric power steering device 16 is a rack coaxial type electric power steering device, and converts the electric motor 36 and the rotational torque of the electric motor 36 into a force in the reciprocating direction of the rack bar 18. For example, it has a ball screw type conversion mechanism 38. The electric power steering device 16 is controlled by an electric power steering device (EPS) control electronic control device 40, and generates an auxiliary steering force that drives the rack bar 18 relative to the housing 42, so that the driver's It functions as an auxiliary steering force generator that reduces the steering burden. The auxiliary steering force generator may be of any configuration known in the art.

  The braking force of each wheel is controlled by controlling the pressure Pi (i = fl, fr, rl, rr) in the wheel cylinders 46FL, 46FR, 46RL, 46RR, that is, the braking pressure, by the hydraulic circuit 44 of the braking device 43. It has become so. Although not shown in the drawing, the hydraulic circuit 44 includes an oil reservoir, an oil pump, various valve devices, and the like, and the braking pressure of each wheel cylinder is normally driven according to the depression operation of the brake pedal 48 by the driver. It is controlled by the master cylinder 50 and individually controlled by the behavior control electronic control device 52 as will be described in detail later.

  In the illustrated embodiment, the upper steering shaft 22 is provided with a steering angle sensor 60 for detecting the rotation angle of the upper steering shaft as a steering angle θ. As shown in FIG. A signal indicating θ is input to the steering angle control electronic control unit 34 and the behavior control electronic control unit 52 via the CAN 62. The turning angle varying device 24 is provided with a rotation angle sensor 64 that detects the relative rotation angle of the housing 24A and the rotor 24B as the relative rotation angle θre of the lower steering shaft 26 with respect to the upper steering shaft 22, and the relative rotation angle θre. Is input to the steering angle control electronic control unit 34. The rotation angle sensor 64 may be replaced with a sensor that detects the rotation angle θs of the lower steering shaft 26, and the relative rotation angle θre may be obtained as a steering angle difference θs−θ.

  The steering angle control electronic control device 34 and the behavior control electronic control device 52 include a signal indicating the vehicle lateral acceleration Gy detected by the lateral acceleration sensor 66 and a signal indicating the vehicle yaw rate γ detected by the yaw rate sensor 68. A signal indicating the vehicle speed V detected by the vehicle speed sensor 70 is input via the CAN 62, a signal indicating the master cylinder pressure Pm detected by the pressure sensor 72, and the braking pressure Pi of each wheel detected by the pressure sensors 74FL to 74RR. Is input to the behavior control electronic control unit 52.

  The steering angle control electronic control device 34, the EPS control electronic control device 40, and the behavior control electronic control device 52 each have a CPU, a ROM, a RAM, and an input / output port device, which are connected by a bidirectional common bus. It may include microcomputers connected to each other. Further, the steering angle sensor 60, the rotation angle sensor 64, the lateral acceleration sensor 66, and the yaw rate sensor 68 are respectively set to the steering angle θ, the relative rotation angle θre, and the lateral acceleration when the vehicle is steered, steered, or turned in the left turn direction. Gy and yaw rate γ are detected.

  The electronic controller 52 for behavior control indicates the degree of spin (oversteer state) of the vehicle based on the driving operation amount such as the steering angle θ and the vehicle state amount such as the lateral acceleration Gy of the vehicle that change as the vehicle travels. The vehicle target yaw for calculating the state quantity SS and the drift-out state quantity DS indicating the degree of vehicle drift-out (understeer state) and stabilizing the vehicle behavior based on the spin state quantity SS and the drift-out state quantity DS. The moment Mt and the target deceleration Gxbt of the vehicle are calculated.

  Then, the behavior control electronic control unit 52 distributes the target yaw moment Mt at a predetermined ratio to the target yaw moment Mts by the steering angle control of the left and right front wheels and the target yaw moment Mtb by the control of the braking force of each wheel. The target turning angle Δδac of the active steering (corrected turning) of the left and right front wheels by the turning angle varying device 24 for improving the running stability of the vehicle based on the yaw moment Mts and the target speed increasing ratio by the turning angle varying device 24 Kac is calculated and a signal indicating the target turning angle Δδac and the target speed increase ratio Kac is output to the steering angle control electronic control unit 34 via the CAN 62.

  In particular, as is well known in the art, the behavior control electronic control unit 52 is designed to decelerate the vehicle and to apply a yaw moment in a turning suppression direction to the vehicle so as to decelerate the vehicle. Mt and the target deceleration Gxbt of the vehicle are calculated. Therefore, the turning direction of the target turning angle Δδac in this case is the direction opposite to the turning direction, that is, the switchback direction, and the behavior of the vehicle is stabilized by the behavior control. In the process, the left and right front wheels are steered relatively in the turning direction, that is, in the direction of additional turning.

  Also, as is well known in the art, the behavior control electronic control unit 52 decelerates the vehicle and applies the yaw moment in the turning assist direction to the vehicle when the vehicle is in a drift-out state. The moment Mt and the target deceleration Gxbt of the vehicle are calculated. In this case, the lateral force of the front wheels is saturated, and the lateral force cannot be increased even if the front wheels are turned and steered, so the target yaw moment Mt Are allotted to the target yaw moment Mtb by controlling the braking force of each wheel, and the target turning angle Δδac is calculated to zero.

  The behavior control electronic control unit 52 calculates the target braking pressure Pti of each wheel based on the target deceleration Gxbt and the target yaw moment Mtb, and the hydraulic circuit so that the braking pressure Pi of each wheel becomes the corresponding target braking pressure Pti. 44 is controlled.

  The steering angle control electronic control device 34 calculates a target speed increase ratio Kvt by the turning angle varying device 24 for achieving a desired steering characteristic based on the vehicle speed V according to a flowchart shown in FIG. When active steering of the left and right front wheels for improving the running stability of the vehicle is not necessary, the target steering angle δt of the left and right front wheels is calculated as the product of the steering angle θ indicating the steering operation amount of the driver and the target speed increase ratio Kvt. Is calculated.

  The steering angle control electronic control unit 34 corrects the steering angle of the left and right front wheels in order to reduce the deviation of the steering angle of the left and right front wheels, that is, the deviation between the neutral position of the steering wheel 14 and the vehicle straight position of the left and right front wheels. Δδs is calculated, and the target steering angle δt is corrected with the corrected turning angle Δδs. The steering angle control electronic control unit 34 controls the turning angle varying device 24 so that the steering angle δ of the left and right front wheels becomes the target steering angle δt.

  In particular, the magnitude of the corrected turning angle Δδs is increased so that the steering operation direction and the steering angular velocity θd are increased so that the steering angle and the steering angular velocity θd are larger when the steering is steered and larger when the steering angular velocity θd is larger. It is variably set accordingly.

  Therefore, when the behavior of the vehicle is stable or when the vehicle is in a drift-out state, the steering angle control electronic control unit 34 has a target turning angle Δδac of 0, so that the steering angle of the left and right front wheels is the target steering angle. The steered angle varying device 24 is controlled so as to have an angle δt, thereby achieving desired steering characteristics and reducing the deviation of the steered angles of the left and right front wheels.

  Further, the steering angle control electronic control unit 34, when the vehicle is in a spin state, achieves a desired steering characteristic with an amount corresponding to the target steering angle Δδac and the target speed increase ratio Kac for active steering. The steering angle variable device 24 is controlled so that the steering angle of the left and right front wheels becomes the corrected target steering angle δt by adjusting the angle, thereby achieving the desired steering characteristics and improving the running stability of the vehicle. Secure.

  Further, the EPS control electronic control unit 40 indicates a signal indicating the steering torque Ts from a steering torque sensor not shown in FIG. 1, a signal indicating the steering angle θ from the steering angle sensor 60, and a vehicle speed V from the vehicle speed sensor 70. The electric power steering device 16 receives the signal, and the electronic control device 40 for EPS control generates a steering assist force that reduces the driver's steering burden in a manner known in the art based on the information. The electronic power steering device 16 is controlled so as to assist the control of the steering angle of the left and right front wheels by the steering angle control electronic control device 34 and to reduce the fluctuation of the steering reaction force due to the control of the steering angle of the left and right front wheels. To do.

  Next, a steering control routine for the left and right front wheels in the illustrated embodiment 1 will be described with reference to the flowchart shown in FIG. The control according to the flowchart shown in FIG. 2 is started by closing an ignition switch not shown in the figure, and is repeatedly executed at predetermined time intervals.

  First, at step 10, a signal indicating the vehicle speed V is read, and at step 20, the basic target speed increase ratio Kvt is calculated from the map corresponding to the graph shown in FIG. The In this case, the basic target speed increase ratio Kvt is calculated as a positive value when the vehicle speed V is low, and is calculated as a negative value when the vehicle speed V is high.

  In step 30, it is determined whether or not active steering of the left and right front wheels to correct the steering angle of the left and right front wheels to improve the running stability of the vehicle, that is, not shown in the figure. The behavior control routine determines whether or not at least the target steering angle Δδac of active steering is calculated to a value greater than the control dead zone reference value. If an affirmative determination is made, the process proceeds to step 140. When a negative determination is made, the routine proceeds to step 40.

  In step 40, for example, the steering angular velocity θd is calculated as a time differential value of the steering angle θ, and the basic limit turning speed δdmaxb is calculated from the map corresponding to the graph shown in FIG. 4 based on the absolute value of the steering angular velocity θd. Then, the gain Kg is calculated from the map corresponding to the graph shown in FIG. 5 based on the vehicle speed V, and the limited turning speed δdmax is calculated as the product of the basic limited turning speed δdmaxb and the gain Kg.

  In step 50, it is determined whether or not the absolute value of the product of the steering angular velocity θd and the basic target speed increase ratio Kvt, that is, the absolute value of the target turning speed of the left and right front wheels exceeds the limit turning speed δdmax. If a negative determination is made, the process proceeds to step 70. If an affirmative determination is made, the process proceeds to step 60.

In step 60, assuming that the previous value of the target steering angle δt of the left and right front wheels is δtf and the cycle time of the flowchart shown in FIG. 2 is ΔT, the target steering angle δt of the left and right front wheels is calculated according to the following equation 1. Thereafter, the process proceeds to step 300.
δt = δtf + δdmaxΔT (1)

  In step 70, for example, it is determined whether or not the steering operation by the driver is increased based on the sign of the product of the steering angle θ and the steering angular velocity θd. Then, based on the absolute value of the steering angular velocity θd, the corrected turning angle Δδs of the left and right front wheels for reducing the neutral position deviation is calculated from the map corresponding to the graph shown by the solid line in FIG. When a negative determination is made, in step 90, the right and left front wheels are corrected to reduce the neutral position deviation from the map corresponding to the graph shown by the broken line in FIG. 6 based on the absolute value of the steering angular velocity θd. After the angle Δδs is calculated, the process proceeds to step 120.

  In step 120, the target steering angle δt of the left and right front wheels is calculated as the product θKvt of the steering angle θ and the basic target speed increase ratio Kvt. In step 130, when the target steering angle δt is a positive value, the target The steering angle δt is corrected by subtracting the correction steering angle Δδs, and when the target steering angle δt is a negative value, the target steering angle δt is corrected by adding the correction steering angle Δδs, and then step 300 is performed. Proceed to

In step 140, the previous value of the steering angle Δδack of the left and right front wheels based on the target speed increase ratio Kac of active steering is Δδackf, the previous value of the steering angle θ is θf, and the target increase of active steering according to the following equation 2 The turning angle Δδack of the left and right front wheels based on the speed ratio Kac is calculated, and the neutral position deviation that remains without being reduced by the neutral position deviation reduction during inactive steering is assumed to be δoff. Accordingly, the target rudder angle δt of the left and right front wheels is calculated. Note that Δδac in Equation 3 is the target turning angle of active steering as described above.
Δδack = Δδackf + (θ−θf) Kac (2)
δt = θKvt + δoff + Δδac + Δδack (3)

  In step 150, it is determined whether or not the target speed increase ratio Kac for active steering is 0. If a negative determination is made, the process proceeds to step 300, and if an affirmative determination is made, the process proceeds to step 160. .

  In step 160, based on the absolute value of the steering angular velocity θd, the steering angle Δδack for the left and right front wheels based on the target speed increase ratio Kac for active steering is gradually reduced to 0 from the map corresponding to the graph shown in FIG. A basic correction amount Δδacka is calculated, a gain Ka is calculated from a map corresponding to the graph shown in FIG. 8 based on the vehicle speed V, and based on a vehicle steering state calculated by a behavior control routine not shown in the figure. The gain Kb is calculated from the map corresponding to the graph shown in FIG. 9, and the product of the basic correction amount Δδacka, the gain Ka, and the gain Kb with respect to the steering angle Δδack of the left and right front wheels based on the target steering speed ratio Kac of active steering. A correction amount Δδacka is calculated.

  In step 170, when the turning angle Δδack of the left and right front wheels based on the target speed increase ratio Kac of active steering is a positive value, the turning angle Δδack is corrected by subtracting the correction amount Δδacka, and the target of active steering is corrected. When the turning angle Δδack of the left and right front wheels based on the speed increase ratio Kac is a negative value, the turning angle Δδack is corrected by adding a correction amount Δδacka.

  In step 180, the target steering angle δt of the left and right front wheels is calculated according to the above equation 3 using the corrected steering angle Δδack of the left and right front wheels based on the target speed increase ratio Kac of active steering. The target rudder angle δt is corrected.

  In step 300, the steering angle varying device 24 is controlled so that the steering angle δ of the left and right front wheels becomes the target steering angle δt, whereby the steering control of the left and right front wheels is executed.

  Thus, according to the illustrated first embodiment, when active steering is not being performed, the corrected turning angle Δδs of the left and right front wheels for reducing the neutral position deviation of the left and right front wheels with respect to the neutral position of the steering wheel 14 is calculated. Since the target steering angle δt of the front wheels is corrected with the corrected steering angle Δδs, the neutral position shift of the left and right front wheels can be effectively reduced while achieving the desired steering characteristics as much as possible.

  In particular, according to the illustrated embodiment 1, when active steering is not performed, the basic limit turning speed δdmaxb is calculated based on the absolute value of the steering angular speed θd in step 40, and the gain Kg is calculated based on the vehicle speed V. Then, the limited turning speed δdmax is calculated as the product of the basic limited turning speed δdmaxb and the gain Kg, and in step 50, the absolute value of the product of the steering angular speed θd and the basic target speed increasing ratio Kvt, that is, the left and right front wheels When it is determined that the absolute value of the target turning speed exceeds the limit turning speed δdmax, the amount of change in the target steering angle δt of the left and right front wheels is limited to the limit turning speed δdmax in step 60. Therefore, it is possible to reliably prevent the steering angle of the left and right front wheels from changing at an excessively high speed. This also applies to Example 2 described later.

  FIG. 10 shows a vehicle steering control according to the present invention configured as a part of a behavior control device that controls the steering gear ratio, controls the braking / driving force of each wheel, and controls the steering angle of the left and right front wheels. It is a flowchart which shows the steering control routine of the left-right front wheel in Example 2 of an apparatus. In FIG. 10, the same steps as those shown in FIG. 2 are assigned the same step numbers as those shown in FIG.

  In this second embodiment, steps 10 to 80, 120, 130, and 140 to 300 are executed in the same manner as in the first embodiment, but when a negative determination is made in step 70, In other words, when it is determined that the steering operation by the driver is switchback, the routine proceeds to step 100.

In step 100, the steering angle θ is set so that the steering angle δ of the left and right front wheels becomes zero when the steering wheel is turned back to the neutral position based on the relationship between the steering angle θ and the steering angle δ of the left and right front wheels. The correction coefficient Ks is calculated as the ratio δ / θ of the change amount of the steering angle δ of the left and right front wheels with respect to the change amount. In step 110, the previous value of the steering angle θ is θf, and the corrected turning angle Δδs according to the following equation 4. Is calculated, and then the routine proceeds to step 120.
Δδs = Ks (θ−θf) (4)

  Thus, according to the second embodiment shown in the drawing, when the steering wheel 14 is steered back to the neutral position based on the relationship between the steering angle θ and the steering angle δ of the left and right front wheels in step 100, the steering angle δ of the left and right front wheels. The correction coefficient Ks is calculated as the ratio δ / θ of the change amount of the steering angle δ of the left and right front wheels with respect to the change amount of the steering angle θ so that the steering angle θ becomes 0. In step 110, the previous value of the steering angle θ is calculated. As θf, the corrected steering angle Δδs is calculated according to the above equation 4, and the target steering angle δt of the left and right front wheels is corrected with the corrected steering angle Δδs, so that neutral position deviation of the left and right front wheels can be reduced without excess or deficiency at the time of switchback steering. Thus, the neutral position shift of the left and right front wheels can be reliably eliminated when the steering wheel 14 is steered back to the neutral position.

  For example, as shown in FIG. 13, in a situation where the neutral position shift occurs due to the drive delay of the turning angle varying device 24, the steering angle θ is θ1, and the steering angle δ of the left and right front wheels is δ1. Assume that switchback steering is started. When the control of the illustrated embodiment 2 is not performed, the steering angle θ and the steering angle δ of the left and right front wheels change as indicated by the two-dot chain line arrow in FIG. Thus, the neutral position deviation remains when the steering angle θ becomes zero.

  On the other hand, according to the illustrated second embodiment, the correction coefficient Ks is calculated as the slope of the straight line L connecting the point A and the origin in step 100, so that the steering angle θ is changed from θ1 to θ2 by switchback steering. When changed, the steering angle δ of the left and right front wheels changes by Ks (θ2−θ1), whereby the point determined by the steering angle θ and the steering angle δ of the left and right front wheels moves from A to the point B along the straight line L. To do. Accordingly, since the point determined by the steering angle θ and the steering angle δ of the left and right front wheels is surely close to the origin at the time of back-turn steering, the neutral position deviation of the left and right front wheels can be reliably reduced without excess or deficiency, and reliably when the steering angle is zero. In addition, the steering angle of the left and right front wheels can be set to the straight position of the vehicle.

  FIG. 11 shows a vehicle steering control according to the present invention configured as a part of a behavior control device that controls the steering gear ratio, controls the braking / driving force of each wheel, and controls the steering angle of the left and right front wheels. FIG. 12 is a flowchart showing a subroutine for calculating a target rudder angle δt for the left and right front wheels in step 200 of the flowchart shown in FIG. 11. . In FIG. 11, the same steps as those shown in FIG. 2 are assigned the same step numbers as those shown in FIG.

In the third embodiment, steps 10 to 30, 160 to 180, and 300 are executed in the same manner as in the first embodiment, but when an affirmative determination is made in step 30, that is, active. When it is determined that steering is in progress, in step 145, the target rudder angle δt of the left and right front wheels is calculated according to the following equation 5 corresponding to the above equation 3. In Formula 5, the remaining neutral position shift amount δoff in Formula 3 is not included. In this embodiment, the speed increase ratio Kvt is set so that neutral position shift does not occur during inactive steering. It is because it is controlled.
δt = θKvt + Δδac + Δδack (5)

  Further, when a negative determination is made in step 30, that is, when it is determined that the active steering is not being performed, in step 210, the driver performs the same procedure as in step 70 of the first embodiment. A determination is made as to whether or not the steering operation is increased. If an affirmative determination is made, a map corresponding to the graph shown by the solid line in FIG. 12 based on the absolute value of the steering angular velocity θd in step 220. After the speed increasing ratio gradual change amount Δα is calculated, the routine proceeds to step 240, and when a negative determination is made, it corresponds to the graph shown by the broken line in FIG. 12 based on the absolute value of the steering angular velocity θd at step 230. After the speed increase ratio gradual change amount Δα is calculated from the map, the routine proceeds to step 240.

In step 240, the previous value of the basic target speed increase ratio Kvt is set to Kvtf, and the target speed increase ratio correction amount ΔKvt for reducing the target speed increase ratio is corrected according to the following formula 6 so that the neutral position shift does not occur. Then, the process proceeds to step 250.
ΔKvt = ΔKvtf + Δα (6)

  In step 250, it is determined whether or not the target acceleration ratio correction amount ΔKvt is a positive value. If a negative determination is made, in step 260, the target acceleration ratio correction amount ΔKvt is determined. After setting to 0, the process proceeds to step 270, and when an affirmative determination is made, the process proceeds to step 270 as it is.

In step 270, the target rudder angle δt of the left and right front wheels is calculated according to the following formula 7, and then the process proceeds to step 300.
δt = θ (Kvt−ΔKvt) (7)

  Thus, according to the illustrated third embodiment, when the active steering is not performed, the correction amount ΔKvt of the target speed increase ratio as the correction amount for suppressing the occurrence of the neutral position shift of the left and right front wheels with respect to the neutral position of the steering wheel 14 is Calculated, the basic target acceleration ratio Kvt is corrected by the correction amount ΔKvt, and the target steering angle δt of the left and right front wheels is calculated based on the corrected basic target acceleration ratio Kvt, so that the desired steering characteristics are achieved as much as possible. In addition, the occurrence of the neutral position shift of the left and right front wheels can be effectively suppressed.

  According to the illustrated third embodiment, when it is determined in step 250 that the target acceleration ratio correction amount ΔKvt is not a positive value, the target acceleration ratio correction amount ΔKvt is zero in step 260. However, when the correction amount ΔKvt of the target acceleration ratio is not a positive value, the correction amount ΔKvt of the target acceleration ratio is set to Kam with a correction coefficient greater than 0 and smaller than 1. You may correct | amend so that it may correct | amend by 2 times.

  Further, according to the above-described first to third embodiments, when an affirmative determination is made at step 30, that is, when it is determined that active steering is being performed, the target acceleration ratio Kac for active steering is determined at step 150. Is determined to be 0, and when it is determined that the target speed increase ratio Kac for active steering is 0, changes in the target rudder angle δt of the left and right front wheels are suppressed in steps 160 to 180. Therefore, it is possible to effectively reduce the possibility of the neutral position shift of the left and right front wheels due to the active steering while improving the running stability of the vehicle as effectively as possible by the active steering as effective as possible. it can.

  Although the present invention has been described in detail with reference to specific embodiments, the present invention is not limited to the above-described embodiments, and various other embodiments are possible within the scope of the present invention. It will be apparent to those skilled in the art.

  For example, in the above-described first embodiment, in step 40, the basic limit turning speed δdmaxb is calculated from the map corresponding to the graph shown in FIG. 4 based on the absolute value of the steering angular speed θd. However, even if the basic limit turning speed δdmaxb is modified to be variably set according to the magnitude of the deviation from the yaw rate so that the magnitude of the deviation between the target yaw rate of the vehicle and the actual yaw rate increases. Good.

  In the first embodiment described above, the corrected turning angle Δδs with respect to the target steering angle δt of the left and right front wheels is obtained from maps corresponding to the graphs indicated by the solid line and the broken line in FIG. Although it is calculated, the corrected turning angle Δδs may be modified so as to be variably set according to the magnitude of the deviation from the yaw rate so that the magnitude of the yaw rate deviation becomes smaller.

In the third embodiment, the speed increasing ratio gradual change amount Δα is variably set in accordance with the absolute value of the steering angular velocity θd in step 220 or 230. For example, as shown in FIG. As shown, the speed change ratio gradual change amount Δα is variably set according to the absolute value of the steering angular velocity θd and the absolute value of the steering angle θ so that the magnitude decreases as the absolute value of the steering angle θ increases. May be. In this case, the larger the absolute value of the steering angle θ, the smaller the amount of change in the target acceleration ratio correction amount ΔKvt. Therefore, when the steering angle θ is large, the right and left front wheels are corrected by correcting the target acceleration ratio Kvt. It is possible to reliably prevent the amount of change in the steering angle from becoming excessive.

  Further, in each of the above-described embodiments, the target turning angle Δδac and the target speed increase ratio Kac for the left and right front wheels for improving the running stability of the vehicle are calculated, and the target steering angle δt for the left and right front wheels is calculated by the active steering. When necessary, the vehicle is calculated based on the target turning angle Δδac and the target speed increase ratio Kac, but the steering control device of the present invention does not perform behavior control by steering wheel steering control. May be applied.

  Further, in each of the above-described embodiments, the turning angle varying device 24 rotates the lower steering shaft 26 relative to the upper steering shaft 22 by the electric motor 32 so as not to depend on the steering operation of the driver. The front wheel 10FL and 10FR are automatically steered, but as long as the left and right front wheels can be steered relative to the steering wheel 14 by controlling the steering transmission ratio, Any configuration known in the art may be used.

  In each of the above-described embodiments, the vehicle target yaw moment Mt and the vehicle target deceleration Gxbt for stabilizing the vehicle behavior are calculated, and the target yaw moment Mt is a predetermined ratio between the left and right front wheels. The target yaw moment Mts by the steering angle control and the target yaw moment Mtb by the braking force control of each wheel are distributed to the target turning angle Δδac of the left and right front wheels for improving the running stability of the vehicle based on the target yaw moment Mts. And the target speed increase ratio Kac are calculated, but the target turning angle Δδac and the target speed increase ratio Kac for stabilizing the behavior of the vehicle are in any manner known in the art. May be calculated.

  In each of the above-described embodiments, the behavior control by controlling the braking / driving force controls the behavior of the vehicle by controlling the braking force of each wheel and applying the required yaw moment to the vehicle. However, the behavior control by controlling the braking / driving force may be performed by controlling the braking force and driving force of each wheel, and the behavior control by controlling the braking / driving force may be omitted. .

Implementation of a vehicle steering control device according to the present invention configured as part of a behavior control device that controls the steering gear ratio and controls the braking / driving force of each wheel and the steering angle of the left and right front wheels to control the behavior of the vehicle 1 is a schematic configuration diagram illustrating Example 1. FIG. 4 is a flowchart showing a steering control routine for left and right front wheels in the first embodiment. It is a graph which shows the relationship between the vehicle speed V and the basic target speed increase ratio Kvt of a turning angle variable apparatus. 6 is a graph showing a relationship between an absolute value of a steering angular velocity θd and a basic limit turning speed Δdmaxb. It is a graph which shows the relationship between the vehicle speed V and the gain Kg. 6 is a graph showing a relationship between an absolute value of a steering angular velocity θd and a corrected turning angle Δδs. 6 is a graph showing a relationship between an absolute value of a steering angular velocity θd and a basic correction amount Δδacka. It is a graph which shows the relationship between the vehicle speed V and the gain Ka. It is a graph which shows the relationship between the vehicle speed V and the gain Kb. Implementation of a vehicle steering control device according to the present invention configured as part of a behavior control device that controls the steering gear ratio and controls the braking / driving force of each wheel and the steering angle of the left and right front wheels to control the behavior of the vehicle 7 is a flowchart showing a steering control routine for left and right front wheels in Example 2; Implementation of a vehicle steering control device according to the present invention configured as part of a behavior control device that controls the steering gear ratio and controls the braking / driving force of each wheel and the steering angle of the left and right front wheels to control the behavior of the vehicle 10 is a flowchart showing a steering control routine for left and right front wheels in Example 3. It is a graph which shows the relationship between the absolute value of steering angular velocity (theta) d, and speed increase ratio gradual change amount (DELTA) (alpha). It is explanatory drawing which shows reduction of the neutral position shift of the right-and-left front wheel in the case of carrying out switchback steering in Example 2. 6 is a graph showing a relationship between an absolute value of a steering angular velocity θd, an absolute value of a steering angle θ, and a speed increase ratio gradual change amount Δα.

Explanation of symbols

DESCRIPTION OF SYMBOLS 14 Steering wheel 16 Electric power steering device 24 Steering angle variable device 34 Steering angle control electronic control device 40 Electric power steering device (EPS) control electronic control device 43 Braking device 52 Behavior control electronic control device 60 Steering angle Sensor 62 CAN
64 Rotation angle sensor 66 Lateral acceleration sensor 68 Yaw rate sensor 70 Vehicle speed sensor 72 Pressure sensor 74FL to 74RR Pressure sensor

Claims (10)

Steering transmission ratio variable means for changing a steering transmission ratio that is a ratio of a steering angle change amount of a steered wheel to a steering operation amount, means for calculating a target steering transmission ratio according to a running state of the vehicle, In the vehicle steering control device that controls the steering transmission ratio variable means so as to achieve a target steering transmission ratio, the target is set with a correction amount that suppresses the occurrence of a deviation in the steering angle of the steering wheel with respect to the neutral position of the steering input means. A target steering transmission ratio correcting means for correcting a steering transmission ratio, and the target steering transmission ratio changing means corrects the correction amount at the time of switching more than at the time of switching back when the target steering transmission ratio is corrected to be small. steering control apparatus of the vehicle according to claim large to Rukoto size. The vehicle steering according to claim 1 , wherein the magnitude of the correction amount is larger when the change rate of the steering operation amount is large than when the change rate of the steering operation amount is small. Control device. Steering transmission ratio variable means for changing a steering transmission ratio that is a ratio of a steering angle change amount of a steered wheel to a steering operation amount, means for calculating a target steering transmission ratio according to a running state of the vehicle, In the vehicle steering control device that controls the steering transmission ratio variable means so as to achieve a target steering transmission ratio, the target is set with a correction amount that suppresses the occurrence of a deviation in the steering angle of the steering wheel with respect to the neutral position of the steering input means. And a target steering transmission ratio correcting means for correcting the steering transmission ratio. When the target steering transmission ratio correcting means corrects the target steering transmission ratio to be large, the correction amount of the correction amount is larger at the time of switching than at the time of switching back. car輌用steering control apparatus characterized in that to reduce the size. 4. The vehicle steering system according to claim 3 , wherein the magnitude of the correction amount is larger when the change rate of the steering operation amount is small than when the change rate of the steering operation amount is large. Control device.   5. The vehicle steering control device according to claim 1, wherein the magnitude of the correction amount is smaller when the magnitude of the steering operation amount is large than when the magnitude of the steering operation amount is small. The target steering transmission ratio includes a component for controlling steering characteristics and a component for improving steering stability of the vehicle by correcting and steering the steered wheels. vehicle steering control device according to claim 1, wherein said correcting the target steering transmission ratio by the correction amount when component for improving the stability is substantially zero. Steering transmission ratio variable means for changing a steering transmission ratio that is a ratio of a steering angle change amount of a steered wheel to a steering operation amount, means for calculating a target steering transmission ratio according to a running state of the vehicle, and the target steering transmission ratio And a vehicle steering control device for controlling the steering transmission ratio variable means so that the steering angle of the steering wheel becomes the target steering angle. Steering angle deviation reduction means for reducing the deviation of the steering angle of the steered wheel with respect to the position, and the magnitude of the steering angle deviation reduction amount by the steering angle deviation reduction means is steered when the rate of change of the steering operation amount is large. A steering control device for a vehicle, characterized in that the change rate of the manipulated variable is large compared to a small amount of change . 8. The vehicle steering control device according to claim 7 , wherein a magnitude of the steering angle deviation reduction amount at the time of switching back is larger than a magnitude of the steering angle deviation reduction amount at the time of addition . The amount of reduction in the steering angle deviation at the time of switching back is based on the relationship between the steering operation position of the steering input means and the steering angle of the steering wheel. When the steering operation position becomes a neutral position, the steering angle of the steering wheel is substantially reduced. The vehicle steering control device according to claim 7 , wherein the vehicle steering control device is set to a value that becomes zero. The target rudder angle includes a component for controlling the steering characteristics and a component for correcting and steering the steered wheels to improve the running stability of the vehicle, and the rudder angle deviation reducing means includes the running stability of the vehicle. The vehicle steering control according to any one of claims 7 to 9 , wherein a deviation of a steering angle of a steered wheel with respect to a neutral position of the steering input means is reduced when a component for improving the vehicle is substantially zero. apparatus.

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