JP4353011B2 - Vehicle steering control device - Google Patents

Description

  The present invention relates to a vehicle steering control device, and more specifically, a steering means for applying a yaw moment to a vehicle by steering a steering wheel, and a yaw moment to a vehicle by giving a difference between braking / driving forces of left and right wheels. The present invention relates to a steering control device having braking / driving force difference applying means for applying

  As one of the steering control devices for vehicles such as automobiles, for example, as described in Patent Document 1 below, the braking / driving force difference that gives a difference between the steering means for steering the steering wheel and the braking / driving force of the left and right wheels There is already known a steering control device that includes an imparting unit and is configured to turn the vehicle by a difference in braking / driving force between the left and right wheels when the vehicle speed is equal to or less than a predetermined value.

According to this steering control device, for example, when the vehicle is automatically driven to follow the preceding vehicle, the vehicle is automatically driven only by controlling the braking / driving force of the left and right wheels without driving the steering means. be able to.
JP-A-6-227283

  In general, when the driver operates the steering wheel to turn the vehicle from a straight traveling state, it is preferable that the vehicle starts to turn slowly. However, in the conventional steering control device as described above, a braking / driving force difference is not given to the left and right wheels so that the turning response characteristic is achieved, and there is room for improvement in this respect.

  The present invention has been made in view of the above-described problems in the conventional steering control device configured to turn the vehicle by the difference in braking / driving force between the left and right wheels in addition to the steering of the steered wheels by the steering means. The main problem of the present invention is to correct the yaw moment applied to the vehicle due to the yaw moment caused by the braking / driving force difference between the left and right wheels in a situation where the yaw moment is applied to the vehicle by steering the steering wheel. The above-mentioned preferable turning response characteristic is achieved.

According to the present invention, the main problem described above is that the configuration of claim 1, that is, the steering means that gives the vehicle a yaw moment by steering the steering wheel, and the braking / driving force of the left and right wheels are given a difference. A braking / driving force difference imparting means for imparting a yaw moment to the vehicle, and when the steering wheel is steered between a straight traveling position and a turning position by the steering means, the braking / driving force difference is imparted during non-braking. The steering by the yaw moment in the reverse direction due to the driving force difference between the left and right wheels given by the means, and the yaw moment in the reverse direction due to the braking force difference between the left and right wheels given by the braking / driving force difference giving means during braking at least partially offset the yaw moment by means, the degree of offset of the yaw moment is the steering wheel turning position when the steering wheel is steered to the turning position from the straight position Straight steering control instrumentation of the vehicle, characterized in that larger than the degree of offset of the yaw moment when steered to the location, or the second aspect, i.e. the yaw moment to the vehicle by steering the steering wheel Steering means for imparting a braking force and a braking / driving force difference imparting means for imparting a yaw moment to the vehicle by giving a difference between the braking / driving forces of the left and right wheels, and the steered wheels are moved straight and turned by the steering means. When the steering wheel is steered between, the yaw moment by the steering means is at least partially offset by the yaw moment in the reverse direction by the braking / driving force difference applying means, and the steered wheel is steered from the straight traveling position to the turning position. The degree of cancellation of the yaw moment at the time of the vehicle is larger than the degree of cancellation of the yaw moment when the steered wheel is steered from the turning position to the straight traveling position. It is accomplished by rudder controller.

According to the present invention, in order to effectively achieve the above-mentioned main problem, in the configuration of the above-described claim 1 or 2 , the yaw moment is canceled by a predetermined steering operation in which the steered wheel includes the rectilinear position. It is comprised so that it may be performed when it exists in an angle range (structure of Claim 3 ).

According to the invention, to the aspect of the effective, in the configuration of the claims 1 to 3, the degree of offset of the yaw moment is the magnitude of the steering angle of the steering wheel configured smaller than that when the magnitude of the steering angle of the steering wheel is smaller when a large (the fourth aspect).

According to the invention, to the aspect of the effective, in the configuration of the claims 1 to 4, the degree of offset of the yaw moment than when the vehicle speed is low when the vehicle speed is high It is comprised so that it may be large (structure of Claim 5 ).

According to the present invention, in order to effectively achieve the main problems described above, in the configuration of the above-described claims 1 to 5 , the yaw moment cancellation is such that the vehicle speed is higher than a reference value for determining the middle and high vehicle speed range. It is comprised so that it may be performed from time to time (structure of Claim 6 ).

Further, according to the present invention, in order to effectively achieve the main problems described above, in the configuration of the first to sixth aspects, when the vehicle speed is equal to or less than the reference value for the low vehicle speed range determination, the yaw by the steering means is obtained. It is comprised so that the yaw moment by the said braking / driving force difference provision means may be generated in the same direction as a moment (structure of Claim 7 ).

According to the present invention, in order to effectively achieve the main problem described above, in the configuration of claim 7 , the magnitude of the yaw moment by the braking / driving force difference applying means is such that the vehicle speed is low when the vehicle speed is low. It is configured to be larger than when it is high (structure of claim 8 ).

According to the first and second aspects of the present invention, when the steered wheel is steered between the straight travel position and the turning position by the steering means, the yaw moment by the steering means is the reverse yaw moment by the braking / driving force difference providing means. Therefore, the vehicle turns more slowly when it is steered by the driver than when the yaw moment by the steering means is not canceled by the reverse yaw moment by the braking / driving force difference applying means. Can be started.
According to the first aspect of the present invention, the yaw moment in the reverse direction is generated by the driving force difference between the left and right wheels given by the braking / driving force difference applying means during non-braking, and given by the braking / driving force difference applying means during braking. As a result, the yaw moment in the opposite direction is generated by the difference in braking force between the left and right wheels or the difference in braking force between the left and right wheels. Regardless of the situation, the turning response of the vehicle can be controlled to a preferable response.
According to the first and second aspects of the present invention, the degree of yaw moment cancellation when the steered wheel is steered from the straight drive position to the turning position is the yaw moment when the steered wheel is steered from the turn position to the straight drive position. Therefore, when the vehicle starts turning from the straight traveling state, the vehicle slowly starts turning, and when the vehicle returns from the turning state to the straight traveling state, the vehicle starts turning from the straight traveling state. The turning response of the vehicle can be made higher than the case.

According to the third aspect of the present invention, since the yaw moment is canceled when the steered wheel is within a predetermined steered angle range including the straight traveling position, the steering operation amount by the driver is large, and the steered wheel steer angle. It is possible to reliably start the turning of the vehicle slowly and reliably in the region where the steering angle of the steering wheel is small, while reliably preventing the turning response of the vehicle from deteriorating in the region where the steering wheel is large.

According to the fourth aspect of the present invention, the degree of cancellation of the yaw moment is smaller when the steering angle of the steering wheel is large than when the steering angle of the steering wheel is small. The vehicle starts turning slowly and surely in a region where the steering angle is small, and the turning response of the vehicle does not cancel the yaw moment as the steering angle of the steering wheel increases. Thus, it is possible to reduce the change in turn response due to the change in the steering angle of the steered wheels.

Further, according to the configuration of claim 5 , the degree of yaw moment cancellation is greater when the vehicle speed is higher than when the vehicle speed is low, so without sacrificing the turning response of the vehicle when the vehicle speed is low, As the vehicle speed increases, the turning response of the vehicle is lowered, and thereby the turning feeling of the vehicle can be improved regardless of the vehicle speed.

Further, according to the configuration of the sixth aspect , the yaw moment is canceled when the vehicle speed is higher than the reference value for the determination of the middle / high vehicle speed range, so that the turning responsiveness of the vehicle deteriorates in the low vehicle speed range. It can be surely prevented.

According to the seventh aspect of the present invention, when the vehicle speed is equal to or lower than the reference value for the low vehicle speed range determination, the yaw moment by the braking / driving force difference applying means is generated in the same direction as the yaw moment by the steering means. When the yaw moment by the braking / driving force difference applying means is generated in the opposite direction to the yaw moment by the steering means even when the vehicle speed is below the reference value for the low vehicle speed range determination, or the braking / driving force difference in the same direction as the yaw moment by the steering means Compared to the case where the yaw moment is not generated by the applying means, the turning response of the vehicle when the vehicle speed is lower than the reference value for the low vehicle speed range determination can be increased, and thereby the vehicle can be stationary and widened. It can be done easily.

Further, according to the configuration of the eighth aspect , the magnitude of the yaw moment by the braking / driving force difference applying means is larger when the vehicle speed is low than when the vehicle speed is high. Therefore, the lower the vehicle speed, the higher the turning response of the vehicle. However, the vehicle can be easily turned.

[Preferred embodiment of problem solving means]
According to one preferred aspect of the present invention, in the configuration of the first to eighth aspects, the braking / driving force difference applying means controls the braking / driving force difference between the left and right front wheels by controlling at least the braking / driving force between the left and right front wheels. It is comprised so that it may provide (the preferable aspect 1).

According to another preferred aspect of the present invention, the basic target braking / driving force of each wheel is calculated based on the braking / driving operation of the driver in the configuration of the above-described claims 1 to 8 , and the braking / driving force difference is calculated. Calculate the target yaw moment in the reverse direction by the applying means, calculate the braking / driving force correction value of each wheel to achieve the target yaw moment, and correct the basic target braking / driving force with the braking / driving force correction value Accordingly, the target braking / driving force of each wheel is calculated, and control is performed so that the braking / driving force of each wheel becomes the target braking / driving force (preferred aspect 2).

  According to another preferable aspect of the present invention, in the configuration of the preferable aspect 2, the target yaw moment in the reverse direction by the braking / driving force difference applying means is calculated based on at least the steering angle ( Preferred embodiment 3).

  According to another preferable aspect of the present invention, in the configuration of the preferable aspect 3, the reverse target yaw moment is calculated by the braking / driving force difference applying means based on the steering angle and the vehicle speed. (Preferred embodiment 4).

According to the aspect of the present invention, independent of the claims In the structure of claim 1 to 8, longitudinal force difference providing means corresponding wheel the other wheel provided corresponding to each wheel (Embodiment 5).

According to the aspect of the present invention, independent of the claims In the structure of claim 1 to 8, longitudinal force difference providing means corresponding wheel the other wheel provided corresponding to each wheel Thus, it is configured to include a braking device for braking (preferred aspect 6).

  According to another preferred aspect of the present invention, in the configuration of the preferred aspect 5, each electric motor is configured to function as a regenerative braking device that regeneratively brakes the corresponding wheel independently of the other wheels. (Preferred embodiment 7)

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

  FIG. 1 is a schematic diagram showing one embodiment of a steering control device according to the present invention applied to a wheel-in-motor four-wheel drive vehicle.

  In FIG. 1, 10FL and 10FR represent the left and right front wheels of the vehicle 12, respectively, and 10RL and 10RR represent the left and right rear wheels, respectively. The left and right front wheels 10FL and 10FR, which are steered wheels, are steered via tie rods 18L and 18R by a rack and pinion type power steering device 16 that is driven in response to turning of the steering wheel 14 by the driver.

  Motor generators 22FL and 22FR, which are wheel-in motors, are incorporated in the left and right front wheels 10FL and 10FR, respectively. The left and right front wheels 10FL and 10FR are driven by the motor generators 22FL and 22FR, and the motor generators 22FL and 22FR are It is controlled by the driving force control electronic control unit 24. The motor generators 22FL and 22FR also function as left and right front wheel generators, respectively, and the function as a regenerative generator (regenerative drive) is also controlled by the driving force control electronic control unit 24.

  Similarly, motor generators 22RL and 22RR, which are wheel-in motors, are incorporated in the left and right rear wheels 10RL and 10RR, respectively. The left and right front wheels 10RL and 10RR are driven by the motor generators 22RL and 22RR, and the motor generator 22RL and 22RR are also controlled by the driving force control electronic control unit 24. The motor generators 22RL and 22RR also function as left and right rear wheel generators, respectively, and the function as a regenerative generator is also controlled by the driving force control electronic control unit 24.

  Although not shown in detail in FIG. 1, the driving force control electronic control unit 24 includes a microcomputer and a drive circuit. The microcomputer includes, for example, a central processing unit (CPU), a read only memory (ROM), and the like. It may have a general configuration including a random access memory (RAM) and an input / output port device, which are connected to each other by a bidirectional common bus. Further, during normal traveling, electric power charged in a battery (not shown in FIG. 1) is supplied to each motor generator 22FL to 22RR through a drive circuit. During deceleration braking of the vehicle, regenerative braking is performed by each motor generator 22FL to 22RR. The generated power is charged to the battery via the drive circuit.

  The friction braking force of the left and right front wheels 10FL, 10FR and the left and right rear wheels 10RL, 10RR is also controlled by controlling the braking pressure of the corresponding wheel cylinders 30FL, 30FR, 30RL, 30RR by the hydraulic circuit 28 of the friction braking device 26. Is done. Although not shown in the drawing, the hydraulic circuit 28 includes a reservoir, an oil pump, various valve devices, and the like, and the braking pressure of each wheel cylinder is set to the pressure of the master cylinder 34 that is driven in response to depression of the brake pedal 32. Accordingly, the oil pump and various valve devices are controlled by being controlled by the braking force control electronic control device 36.

  Although not shown in detail in FIG. 1, the braking force control electronic control unit 36 also includes a microcomputer and a drive circuit. The microcomputer includes, for example, a central processing unit (CPU), a read-only memory (ROM), and the like. It may have a general configuration including a random access memory (RAM) and an input / output port device, which are connected to each other by a bidirectional common bus.

  The driving force control electronic control device 24 includes a signal indicating the vehicle speed V from the vehicle speed sensor 38, and an accelerator opening as an accelerator pedal depression amount not shown in the figure operated by the driver from the accelerator opening sensor 40. A signal indicating φ and a signal indicating the steering angle θ are input from the steering angle sensor 42.

  A signal indicating the master cylinder pressure Pm is input from the pressure sensor 44 to the braking force control electronic control device 36, and the corresponding wheel braking pressure (wheel cylinder pressure) Pi (i = fl, fr, rl, rr) are input. As shown in the figure, the driving force control electronic control device 24 and the braking force control electronic control device 36 exchange signals with each other as necessary.

  The driving force control electronic control unit 24 controls the driving torque of each wheel by the motor generators 12FL to 12RR when the vehicle is driven according to the flowcharts shown in FIGS. 3 to 5, and the motor generators 12FL to 12FL when the vehicle is braked. The regenerative braking torque of each wheel by 12RR or the braking force of each wheel by the friction braking device 26 is controlled, and thereby the yaw moment by the steering of the left and right front wheels 10FL and 10FR of the driver performed via the power steering device 16 is changed to the left and right front wheels. At least partially offset by the yaw moment in the reverse direction due to the braking / driving force difference.

  The steering angle sensor 42 detects the steering angle θ with the direction of the vehicle turning left as positive, and the vehicle yaw moment is assumed to be positive in the vehicle left turn direction.

  Next, the braking / driving torque control by the steering control in the embodiment will be described with reference to the flowchart shown in FIG. The control according to the flowchart shown in FIG. 2 is started when an ignition switch (not shown) is closed, and is repeatedly executed every predetermined time until the ignition switch is opened.

  First, at step 10, a signal indicating the vehicle speed V detected by the vehicle speed sensor 38 is read. At step 20, it is determined whether the vehicle is in a braking state based on, for example, the master cylinder pressure Pm. When a positive determination is made, the process proceeds to step 90. When a negative determination is made, the process proceeds to step 30.

  In step 30, for example, the drive torque distribution conversion coefficient for each wheel is Kdi (i = fl, fr, rl, rr), and the basic drive torque Tdbi (i = fl, fr) of each wheel based on the accelerator opening φ. , Rl, and rr) are respectively calculated as products of the distribution conversion coefficient Kdi and the accelerator opening φ, and are applied to the vehicle by the driving force difference between the left and right front wheels in step 40 according to the flowchart shown in FIG. The power yaw moment Yd is calculated.

In step 60, for example, corrected driving torques Tdafl and Tdafr for the left front wheel and the right front wheel for achieving the yaw moment Yd according to the following equations 1 and 2 are calculated using Tr as the vehicle tread.
Tdafl = -2Yd / Tr (1)
Tdafr = 2Yd / Tr (2)

  In step 70, the target drive torque Tdti (i = fl, fr, rl, rr) of each wheel is calculated according to the following equations 3 to 6, and in step 80, the drive torque Tdi (i = The motor generators 12FL to 12RR are controlled so that fl, fr, rl, and rr) become the target drive torque Tdti. When Tdafl or Tdafr is larger than Tdbfl or Tdbfr, Tdtfl or Tdtfr becomes a negative value, that is, braking torque. In this case, the motor generators 12FL to 12RR are configured to perform regenerative braking. Be controlled.

Tdtfl = Tdbfl + Tdafl (3)
Tdtfr = Tdbfr + Tdafr (4)
Tdtrl = Tdbrl (5)
Tdtrr = Tdbrr (6)

  In step 90, for example, the distribution conversion coefficient of braking torque for each wheel is set to Kbi (i = fl, fr, rl, rr), and the basic braking torque Tbbi (i = fl, fr) of each wheel based on the master cylinder pressure Pm. , Rl, rr) are respectively calculated as products of the distribution conversion coefficient Kbi and the master cylinder pressure Pm, and are applied to the vehicle by the difference in braking force between the left and right rear wheels in step 100 in accordance with the flowchart shown in FIG. The yaw moment Yb to be calculated is calculated.

In step 120, for example, corrected braking torques Tbafl and Tbafr of the left front wheel and the right front wheel for achieving the yaw moment Yb are calculated according to the following equations 7 and 8.
Tbafl = 2Yb / Tr (7)
Tbafr = -2Yb / Tr (8)

In step 130, the target braking torque Tbti (i = fl, fr, rl, rr) of each wheel is calculated according to the following formulas 9 to 10, and in step 140, the braking torque Tbi (i = The motor generators 12FL to 12RR or the friction braking device 26 are controlled according to a flowchart shown in FIG. 5 described later so that fl, fr, rl, and rr) become the target braking torque Tbti. When Tbafl or Tbafr is larger than Tbbfl or Tbbfr, Tbtfl or Tbtfr becomes a negative value, that is, driving torque. In this case, the motor generators 12FL to 12RR generate driving torque. It is controlled as follows.
Tbtfl = Tbbfl + Tbafl ...... (9)
Tbtfr = Tbbfr + Tbafr (10)
Tbtrl = Tbbrl (11)
Tbtrr = Tbbrr (12)

  Next, the driving force difference yaw moment Yd calculation routine in step 40 will be described with reference to the flowchart shown in FIG.

  In step 42, it is determined whether or not the vehicle speed V is equal to or less than a reference value Vdo (positive constant) for determining a low vehicle speed during acceleration. If a negative determination is made, the process proceeds to step 46, where an affirmative determination is made. In step 44, the yaw moment Yd to be applied to the vehicle is calculated from the map corresponding to the graph shown in FIG. 6 on the basis of the steering angle θ and the vehicle speed V based on the driving force difference between the left and right front wheels. Proceed to step 60.

  In step 46, for example, by determining whether or not the sign of the steering angle θ and the sign of the rate of change θd of the steering angle θ are the same, it is determined whether or not the steering direction by the driver is the cutting direction. If the determination is affirmative, the yaw moment Yd to be applied to the vehicle due to the difference in driving force between the left and right front wheels from the map corresponding to the graph shown in FIG. 7 based on the steering angle θ and the vehicle speed V in step 48. When a negative determination is made in step 50, the yaw moment to be applied to the vehicle due to the difference in driving force between the left and right front wheels from the map corresponding to the graph shown in FIG. 8 based on the steering angle θ and the vehicle speed V in step 50. When Yd is calculated and step 48 or 50 is completed, the routine proceeds to step 60.

  Next, the braking force difference yaw moment Yb calculation routine in step 100 will be described with reference to the flowchart shown in FIG.

  In step 102, it is determined whether or not the vehicle speed V is equal to or less than a reference value Vbo (positive constant) for determining the low vehicle speed during braking. If a negative determination is made, the process proceeds to step 106, where an affirmative determination is made. In step 104, the yaw moment Yb to be applied to the vehicle is calculated from the map corresponding to the graph shown in FIG. 9 based on the steering angle θ and the vehicle speed V, based on the braking force difference between the left and right front wheels. Proceed to step 120.

  In step 106, it is determined whether or not the steering direction by the driver is the cutting direction in the same manner as in step 46. If an affirmative determination is made, steering is performed in step 108. Based on the angle θ and the vehicle speed V, the yaw moment Yb to be applied to the vehicle is calculated from the map corresponding to the graph shown in FIG. Based on the steering angle θ and the vehicle speed V, the yaw moment Yb to be applied to the vehicle is calculated from the map corresponding to the graph shown in FIG. 11 based on the braking force difference between the left and right front wheels, and when step 108 or 110 is completed, the routine proceeds to step 120. .

  Next, the braking / driving torque control routine in step 140 will be described with reference to the flowchart shown in FIG.

  In step 122, it is necessary to determine whether the target braking torque Tbtfl of the left front wheel is larger than the maximum regenerative braking torque Tfmax of the motor generator 12FL of the left front wheel, that is, the left front wheel must be braked by the friction braking device 26. If a positive determination is made, the process proceeds to step 126. If a negative determination is made, the target braking pressure Pbtfl of the left front wheel is set to 0 in step 124, and then the process proceeds to step 132. move on.

  In step 126, the target regenerative braking torque Trtfl for the left front wheel is set to the maximum regenerative braking torque Tfmax. In step 128, the braking torque-braking pressure conversion coefficient for the left front wheel is set to Kpfl, and the target braking pressure Pbtfl for the left front wheel. Is set to Kpfl (Tbtfl−Tfmax), then the routine proceeds to step 132.

  In step 132, it is necessary to determine whether the target braking torque Tbtfr for the right front wheel is larger than the maximum regenerative braking torque Tfmax of the motor generator 12FR for the right front wheel, that is, the right front wheel must be braked by the friction braking device 26. If the determination is affirmative, the process proceeds to step 136. If the determination is negative, the target braking pressure Pbtfr of the right front wheel is set to 0 in step 134 and then the process proceeds to step 142. move on.

  In step 136, the target regenerative braking torque Trtfr for the right front wheel is set to the maximum regenerative braking torque Tfmax. In step 138, the braking torque-braking pressure conversion coefficient for the right front wheel is set to Kpfr, and the target braking pressure Pbtfr for the right front wheel. Is set to Kpfr (Tbtfr-Tfmax), then the routine proceeds to step 142.

  In step 142, it is determined whether the left rear wheel target braking torque Tbtrl is larger than the maximum regenerative braking torque Trmax of the left rear wheel motor generator 12RL, that is, the left rear wheel is also braked by the friction braking device 26. Whether or not it is necessary is determined. When an affirmative determination is made, the process proceeds to step 146. When a negative determination is made, the target braking pressure Pbtrl of the left rear wheel is set to 0 in step 144. Proceed to step 152.

  In step 146, the target regenerative braking torque Trtrl for the left rear wheel is set to the maximum regenerative braking torque Trmax, and in step 148, the left rear wheel braking torque-braking pressure conversion coefficient is set to Kprl. After the braking pressure Pbtrl is set to Kprl (Tbtrl−Trmax), the routine proceeds to step 152.

  In step 152, it is determined whether or not the target braking torque Tbtrr for the right rear wheel is larger than the maximum regenerative braking torque Trmax of the motor generator 12RR for the right rear wheel, that is, the right rear wheel is also braked by the friction braking device 26. If the determination is affirmative, the process proceeds to step 156. If the determination is negative, the target braking pressure Pbtrr for the right rear wheel is set to 0 in step 154. Proceed to step 160.

  In step 156, the target regenerative braking torque Trtrr for the right rear wheel is set to the maximum regenerative braking torque Trmax. In step 158, the braking torque-braking pressure conversion coefficient for the right rear wheel is set to Kprr and the target for the right rear wheel is set. After the braking pressure Pbtrr is set to Kprr (Tbtrr-Trmax), the routine proceeds to step 160.

  In step 160, the motor generators 12FL to 12RR are controlled so that the regenerative braking torque Tri (i = fl, fr, rl, rr) of each wheel becomes the target regenerative braking torque Trti. The friction braking device 26 is controlled so that the braking pressure Pi (i = fl, fr, rl, rr) of each wheel becomes the target braking pressure Pbti.

  Next, the operation of the steering control device of the embodiment configured as described above will be described for each of various traveling states of the vehicle.

(1) At the time of cutting steering during non-braking traveling at medium and high vehicle speeds When the driver performs cutting steering at a vehicle speed that is not braking at a vehicle speed higher than the reference vehicle speed Vo, a step is performed. In step 30, a negative determination is made. In step 30, the basic driving torque Tdbi of each wheel is calculated based on the accelerator opening .phi., A negative determination is made in step 42, and an affirmative determination is made in step 46. Therefore, in step 48, the yaw moment Yd to be applied to the vehicle is calculated from the map corresponding to the graph shown in FIG.

  In step 60, the corrected driving torques Tdafl and Tdafr for the left front wheel and the right front wheel for achieving the yaw moment Yd are calculated. In step 70, the sum of the basic driving torque Tdbi and the corrected driving torques Tdafl and Tdafr is calculated. The target drive torque Tdti of each wheel is calculated, and in step 80, the motor generators 12FL to 12RR are controlled so that the drive torque Tdi of each wheel becomes the target drive torque Tdti.

  Therefore, the smaller the magnitude of the steering angle θ and the higher the vehicle speed V, the larger the difference in driving force between the left and right front wheels in the turning suppression direction, and thereby the yaw moment in the direction opposite to the steering direction can be increased. The smaller the size of the vehicle and the higher the vehicle speed V, the slower the vehicle can start when the vehicle moves from the straight traveling state to the turning state, improving the turning response feeling of the vehicle and at the time of medium speed traveling of the vehicle The running stability of the vehicle can be improved.

  For example, FIG. 12A shows the driving force of each of the wheels 10FL to 10RR when the driver performs cutting steering while the vehicle 12 is running without braking at a vehicle speed higher than the reference vehicle speed Vo. The yaw moment Ys due to the steering of the left and right front wheels acting on the vehicle and the yaw moment Yd due to the difference in driving force between the left and right front wheels are shown. From FIG. 12A, it can be seen that the yaw moment Yd acts in the opposite direction to the yaw moment Ys.

(2) At the time of switchback steering at the time of non-braking driving at medium and high vehicle speeds When the driver performs the switchback steering at the time of vehicle non-braking driving at a vehicle speed higher than the reference vehicle speed Vo. As in the case of (1) above, a negative determination is made in step 20, the basic drive torque Tdbi of each wheel is calculated based on the accelerator opening φ in step 30, and a negative determination is made in step 42. However, since a negative determination is also made in step 46, the yaw moment Yd to be applied to the vehicle due to the difference in driving force between the left and right front wheels is determined in step 50 from the map corresponding to the graph shown in FIG. The motor generators 12FL to 12RR are controlled by steps 60 to 80 as in the case of (1) above.

  Therefore, the smaller the magnitude of the steering angle θ and the higher the vehicle speed V, the larger the difference in driving force between the left and right front wheels in the turning suppression direction, and thereby the yaw moment in the direction opposite to the steering direction can be increased. The smaller the size of the vehicle and the higher the vehicle speed V, the slower the vehicle can start when the vehicle changes from the turning state to the straight-ahead state. The running stability of the vehicle can be improved, and the turning response of the vehicle can be made slightly higher than when the vehicle is cut.

  For example, FIG. 12 (B) shows the driving of the wheels 10FL to 10RR when the driver performs switching back steering in a situation where the vehicle 12 is running without braking at a vehicle speed higher than the reference vehicle speed Vo. A yaw moment Ys due to the steering of the left and right front wheels acting on the vehicle and a yaw moment Yd due to a difference in driving force between the left and right front wheels are shown together with the magnitude relationship of the forces. As understood from the comparison between FIG. 12A and FIG. 12B, the driving force difference and the yaw moment Yd between the left and right front wheels are smaller than those in FIG.

(3) Steering during non-braking travel at low vehicle speed When steering is performed by the driver in a situation where the vehicle is traveling without braking at a vehicle speed equal to or lower than the reference vehicle speed Vo, (1) As in the case of, a negative determination is made at step 20, and the basic drive torque Tdbi of each wheel is calculated based on the accelerator opening φ at step 30, but an affirmative determination is made at step 42. In step 44, the yaw moment Yd to be applied to the vehicle is calculated from the map corresponding to the graph shown in FIG. 6 based on the driving force difference between the left and right front wheels, and in the same manner as in the case (1), the steps 60 to 80 are performed. Motor generators 12FL to 12RR are controlled.

  Therefore, the smaller the magnitude of the steering angle θ and the lower the vehicle speed V, the larger the difference in driving force between the left and right front wheels in the direction of turning assistance, thereby increasing the yaw moment in the same direction as the steering direction. The smaller the size and the lower the vehicle speed V, the easier the vehicle can turn when the vehicle moves between the straight traveling state and the turning state, improving the turning response feeling of the vehicle, It is possible to reduce the driver's steering burden during the width adjustment.

  For example, FIG. 12C shows the driving force of each of the wheels 10FL to 10RR when the vehicle 12 is not braked at a vehicle speed equal to or lower than the reference vehicle speed Vo and the driver performs the turning steering. Along with the magnitude relationship, the yaw moment Ys due to the steering of the left and right front wheels acting on the vehicle and the yaw moment Yd due to the difference in driving force between the left and right front wheels are shown. From FIG. 12C, it can be seen that the yaw moment Yd acts in the same direction as the yaw moment Ys.

(4) At the time of cutting steering during braking at medium and high vehicle speeds When the vehicle is braking at a vehicle speed higher than the reference vehicle speed Vo and the steering is performed by the driver, step 20 is executed. In step 90, the basic braking torque Tbbi of each wheel is calculated based on the master cylinder pressure Pm. In step 102, a negative determination is made. In step 106, an affirmative determination is made. Therefore, in step 108, the yaw moment Yb to be applied to the vehicle is calculated from the map corresponding to the graph shown in FIG.

  In step 120, corrected braking torques Tbafl and Tbafr for the left front wheel and right front wheel for achieving the yaw moment Yd are calculated. In step 130, the sum of the basic braking torque Tbbi and the corrected braking torques Tbafl and Tbafr is calculated. The target braking torque Tbti for each wheel is calculated, and in step 140, the motor generators 12FL to 12RR or the friction braking device 26 are controlled so that the braking torque Tbi for each wheel becomes the target braking torque Tbti.

  Accordingly, the smaller the steering angle θ is and the higher the vehicle speed V is, the larger the braking force difference between the left and right front wheels in the turning restraining direction can be increased, so that the yaw moment in the direction opposite to the steering direction can be increased. As in the case of), the smaller the steering angle θ is and the higher the vehicle speed V is, the more slowly the vehicle can start turning when the vehicle moves from the straight traveling state to the turning state. It is possible to improve the running stability during medium and high speed running of the vehicle.

  For example, FIG. 12D shows the braking force of each of the wheels 10FL to 10RR when the vehicle 12 is braked at a vehicle speed higher than the reference vehicle speed Vo and the driver performs the turning steering. Along with the magnitude relationship, the yaw moment Ys due to the steering of the left and right front wheels acting on the vehicle and the yaw moment Yd due to the braking force difference between the left and right front wheels are shown. From FIG. 12D, it can be seen that the yaw moment Yd acts in the opposite direction to the yaw moment Ys.

(5) At the time of switchback steering at the time of braking driving at medium and high vehicle speeds When the vehicle is braking at a vehicle speed higher than the reference vehicle speed Vo and the driver performs switchback steering, As in the case of (4), an affirmative determination is made at step 20, a basic braking torque Tbbi for each wheel is calculated based on the master cylinder pressure Pm at step 90, and a negative determination is made at step 102. However, since a negative determination is made at step 106, the yaw moment Yb to be applied to the vehicle is calculated at step 110 from the map corresponding to the graph shown in FIG. The motor generators 12FL to 12RR or the friction braking device 26 are controlled by steps 120 to 140 as in the case of (4) above.

  Accordingly, the smaller the steering angle θ is and the higher the vehicle speed V is, the larger the difference in braking force between the left and right front wheels in the turning restraining direction is, so that the yaw moment in the direction opposite to the steering direction can be increased. As in the case of), the smaller the steering angle θ is and the higher the vehicle speed V is, the more slowly the vehicle can be started when the vehicle moves from the turning state to the straight traveling state, and the turning response feeling of the vehicle is improved. As well as improving the running stability of the vehicle at medium and high speeds, the turning response of the vehicle can be made slightly higher than when the vehicle is cut.

  For example, FIG. 12E shows the braking force of each of the wheels 10FL to 10RR when the driver performs switching back steering in a situation where the vehicle 12 is braking at a vehicle speed higher than the reference vehicle speed Vo. The yaw moment Ys due to the steering of the left and right front wheels acting on the vehicle and the yaw moment Yd due to the difference in braking force between the left and right front wheels are shown. As understood from the comparison between FIG. 12D and FIG. 12E, the braking force difference and the yaw moment Yd between the left and right front wheels are smaller than those in FIG.

(6) At the time of steering at the time of braking at a low vehicle speed When steering is performed by the driver in a situation where the vehicle is braking at a vehicle speed below the reference vehicle speed Vo, As in step S20, an affirmative determination is made in step 20, and in step 90 the basic braking torque Tbbi of each wheel is calculated based on the master cylinder pressure Pm, but in step 102 an affirmative determination is made. In 104, the yaw moment Yb to be applied to the vehicle is calculated based on the braking force difference between the left and right front wheels from the map corresponding to the graph shown in FIG. 9, and the motor generation is performed in steps 120 to 140 as in the case of (4) above. The machines 12FL to 12RR or the friction braking device 26 are controlled.

  Therefore, the smaller the steering angle θ is and the lower the vehicle speed V is, the larger the braking force difference between the left and right front wheels in the direction of turning assistance is, which can increase the yaw moment in the same direction as the steering direction. The smaller the size and the lower the vehicle speed V, the easier the vehicle can turn when the vehicle moves between the straight traveling state and the turning state, improving the turning response feeling of the vehicle, It is possible to reduce the driver's steering burden during the width adjustment.

  For example, FIG. 12 (F) shows the magnitude of the braking force of each of the wheels 10FL to 10RR when the driver performs cutting steering in a situation where the vehicle 12 is braked at a vehicle speed equal to or lower than the reference vehicle speed Vo. The yaw moment Ys due to the steering of the left and right front wheels acting on the vehicle and the yaw moment Yd due to the difference in braking force between the left and right front wheels are shown. From FIG. 12F, it can be seen that the yaw moment Yd acts in the same direction as the yaw moment Ys.

  As can be seen from the above description, when the vehicle travels at medium and high speeds, the turning response of the vehicle in a region where the steering angle θ is small is moderated, and when the vehicle travels at low speed, the steering angle It is possible to increase the turning response of the vehicle in the region where the magnitude of θ is small, thereby improving the feeling of the turning response of the vehicle in various traveling states of the vehicle.

  For example, FIG. 13 shows a case where the vehicle travels at medium and high speed (thick solid line) and a case where the vehicle travels at low speed (thick broken line) compared to the case where the conventional vehicle travels at medium and high speed (thin solid line). It is a graph which shows the turning response characteristic of a vehicle. As shown in FIG. 13, according to the illustrated embodiment, the initial turning response of the vehicle is moderated and the vehicle is driven at a low speed when the vehicle is traveling at a medium to high speed as compared with the conventional vehicle. It can be seen that the initial turning response of the vehicle in the situation can be improved.

  Further, according to the illustrated embodiment, the yaw moment Yd acting in the turning restraining direction when the vehicle travels at medium and high speed and acting in the turning assist direction when the vehicle travels at low speed is Yaw moment Yd is generated only by the driving force difference between the left and right wheels or the braking force difference between the left and right wheels because the braking force is generated by the driving force difference between the left and right front wheels. Compared to the case, the turning response of the vehicle can be controlled to a preferable response regardless of the braking / driving state of the vehicle.

  Further, according to the illustrated embodiment, when the braking force necessary for generating the yaw moment Yd is high, the friction braking force by the friction braking device 26 is also generated in addition to the regenerative braking force. -12RR need not be a high output capable of generating a high regenerative braking force, and the necessary yaw moment Yd can be reliably generated even during braking of the vehicle.

  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 embodiment, the corrected braking / driving torque for achieving the yaw moment Yd is calculated only for the left and right front wheels, but the corrected braking / driving torque for achieving the yaw moment Yd is It may be calculated for the left and right rear wheels, or may be calculated for the left and right front wheels and the left and right rear wheels.

  In the above-described embodiment, the yaw moment Yd due to the braking / driving force difference between the left and right wheels is calculated to control the driving force or braking force of the left and right wheels, both when the vehicle is not braking and when braking. However, the yaw moment Yd due to the braking / driving force difference between the left and right wheels is calculated only when the vehicle is unbraking or braking, and is corrected so that the driving force or braking force of the left and right wheels is controlled. Also good.

  Further, in the above-described embodiment, the wheels 10FL to 10RR are directly driven by the motor generators 12FL to 12RR, respectively, but the wheels 10FL to 10RR are respectively connected via a speed reduction mechanism such as a gear speed reduction mechanism. The motor generators 12FL to 12RR may be directly driven.

  In the above-described embodiments, the motor generator is a wheel-in motor incorporated in each wheel, but the motor generator may be a motor generator supported on the vehicle body as long as it can drive each wheel. The motor generator in the above embodiment is a motor generator that performs regenerative braking when the vehicle is braked, but the motor generator does not perform regenerative braking, and the braking force is generated only by the friction braking device. It may be modified as follows.

It is a schematic block diagram which shows one Example of the steering control apparatus by this invention applied to the wheel-in-motor type four-wheel drive vehicle. It is a flowchart which shows the main routine of the braking / driving torque control by the steering control in an Example. 4 is a flowchart showing a driving force difference yaw moment Yd calculation routine in step 40 of FIG. 3 is a flowchart showing a braking force difference yaw moment Yb calculation routine in step 100 of FIG. 2. 3 is a flowchart showing a braking / driving torque control routine in step 140 of FIG. 2. 5 is a graph showing a relationship between a steering angle θ and a vehicle speed V when a vehicle is accelerated at a low vehicle speed and a yaw moment Yd to be applied to the vehicle due to a driving force difference between left and right front wheels. 4 is a graph showing a relationship between a steering angle θ and a vehicle speed V when a vehicle is accelerated at medium and high speeds and a cutting steering is performed, and a yaw moment Yd to be applied to the vehicle due to a driving force difference between left and right front wheels. 4 is a graph showing a relationship between a steering angle θ and a vehicle speed V when a vehicle is accelerated at medium and high speeds and a return steering is performed, and a yaw moment Yd to be applied to the vehicle due to a driving force difference between left and right front wheels. 6 is a graph showing a relationship between a steering angle θ and a vehicle speed V when a vehicle is braked at a low vehicle speed and a yaw moment Yb to be applied to the vehicle due to a difference in braking force between left and right front wheels. 5 is a graph showing a relationship between a steering angle θ and a vehicle speed V when a vehicle is braked at medium and high speeds and a cutting steering is performed, and a yaw moment Yb to be applied to the vehicle due to a braking force difference between left and right front wheels. 6 is a graph showing a relationship between a steering angle θ and a vehicle speed V when a vehicle is driven at a medium and high speed and a return steering is performed, and a yaw moment Yb to be applied to the vehicle due to a braking force difference between left and right front wheels. Depending on the magnitude of the braking / driving force of each wheel when the driver is steering in various driving situations of the vehicle, the yaw moment Ys due to the steering of the left and right front wheels acting on the vehicle and the braking / driving force difference between the left and right front wheels It is explanatory drawing which shows the yaw moment Yd. When the vehicle travels at medium to high speed (thick solid line) and when the vehicle travels at low speed (thick broken line), the vehicle turns compared to the conventional vehicle traveling at medium to high speed (thin solid line) It is a graph which shows a response characteristic.

Explanation of symbols

DESCRIPTION OF SYMBOLS 14 Steering wheel 16 Power steering apparatus 22FL-22RR Motor generator 24 Electronic controller for driving force control 26 Friction brake device 32 Brake pedal 36 Electronic controller for braking force control 38 Vehicle speed sensor 40 Accelerator opening sensor 42, 44FL-44RR Pressure Sensor

Claims (8)

Steering means for applying a yaw moment to the vehicle by steering a steered wheel; and a braking / driving force difference providing unit for providing a yaw moment to the vehicle by giving a difference to the braking / driving force of the left and right wheels. When the wheel is steered between the straight driving position and the turning position by the steering means, the yaw moment in the reverse direction due to the driving force difference between the left and right wheels given by the braking / driving force difference applying means at the time of non-braking, During braking, the yaw moment in the reverse direction due to the difference in braking force between the left and right wheels given by the braking / driving force difference applying means at least partially cancels the yaw moment by the steering means , and the steering wheel turns from a straight traveling position. The degree of cancellation of the yaw moment when steered to a position is the degree of cancellation of the yaw moment when the steered wheel is steered from a turning position to a straight position. Steering control apparatus of the vehicle, characterized in that larger than.   Steering means for applying a yaw moment to the vehicle by steering a steered wheel; and a braking / driving force difference providing unit for providing a yaw moment to the vehicle by giving a difference to the braking / driving force of the left and right wheels. When the wheel is steered between the straight traveling position and the turning position by the steering means, the yaw moment by the steering means is at least partially offset by the yaw moment in the reverse direction by the braking / driving force difference providing means, and the steering The degree of cancellation of the yaw moment when the wheel is steered from the straight position to the turning position is greater than the degree of cancellation of the yaw moment when the steering wheel is steered from the turning position to the straight position. A vehicle steering control device.   The vehicle steering control device according to claim 1 or 2, wherein the canceling of the yaw moment is performed when the steering wheel is within a predetermined steering angle range including the rectilinear position.   The degree of cancellation of the yaw moment is smaller when the steering angle of the steering wheel is large than when the steering angle of the steering wheel is small. Vehicle steering control device. Vehicle steering control apparatus according to any one of claims 1 to 4 degree of offset of the yaw moment being greater than when the vehicle speed is low when the vehicle speed is high. Vehicle steering control apparatus according to any one of claims 1 to 5 offset of the yaw moment is characterized to be performed when the vehicle speed is higher than the reference value of the determination medium and high speed range. The vehicle according to any one of claims 1 to 6 , wherein a yaw moment is generated by the braking / driving force difference applying means in the same direction as a yaw moment by the steering means when the vehicle speed is equal to or less than a reference value for low vehicle speed range determination. Steering control device.   8. The vehicle steering control device according to claim 7, wherein the magnitude of the yaw moment by the braking / driving force difference applying means is larger when the vehicle speed is low than when the vehicle speed is high.

Images