Vehicle control device and vehicle control program

Abstract

To provide a vehicle control device and vehicle control program capable of optimizing the turning behavior.SOLUTION: A vehicle control device 100 includes: a gradient information acquisition unit 122 that acquires gradient information of a road surface on which a vehicle 10 travels; and a distribution ratio calculation unit 123 that increases a distribution ratio being the value obtained by dividing the longitudinal force to be applied to a wheel that is one of a front wheel 11F and a rear wheel 11R and is estimated that a ground load is increased on the basis of the gradient information by the required longitudinal force being the longitudinal force required for the vehicle 10.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a vehicle control device and a vehicle control program. [Background technology]

[0002] Patent Document 1 describes a driving force distribution device that distributes driving force to the four drive wheels of a vehicle during driving. The driving force distribution device adjusts the distribution of driving force applied to the inner front wheels and the inner rear wheels based on the ground load of the inner front wheels and the ground load of the inner rear wheels when the vehicle turns. In this way, the driving force distribution device aims to optimize the turning behavior of the vehicle by increasing the distribution ratio of driving force applied to the wheels with larger ground loads when the vehicle turns. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2021-181253 A Summary of the Invention [Problem to be solved by the invention]

[0004] The ground load of the four wheels also changes depending on the gradient of the road surface on which the vehicle is traveling. For this reason, there is room for improvement in the above-mentioned driving force distribution device in terms of optimizing the vehicle's turning behavior. [Means for solving the problem]

[0005] A vehicle control device that solves the above problem is a vehicle control device applied to a vehicle equipped with a first actuator that generates a longitudinal force on a first wheel and a second actuator that generates a longitudinal force on a second wheel, and includes a gradient information acquisition unit that acquires gradient information of a road surface on which the vehicle is traveling, and an allocation ratio calculation unit that increases an allocation ratio, which is a value obtained by dividing the longitudinal force applied to either the first wheel or the second wheel, which wheel is presumed to have an increased ground load based on the gradient information, by a required longitudinal force, which is the longitudinal force required of the vehicle.

[0006] A vehicle control program that solves the above problem is a vehicle control program targeted at a control device of a vehicle equipped with a first actuator that generates a longitudinal force on a first wheel and a second actuator that generates a longitudinal force on a second wheel, and causes the control device to execute a gradient information acquisition process that acquires gradient information of the road surface on which the vehicle is traveling, and an allocation ratio calculation process that increases an allocation ratio that is a value obtained by dividing the longitudinal force applied to either the first wheel or the second wheel, which wheel is presumed to have an increased ground load based on the gradient information, by a required longitudinal force, which is the longitudinal force required of the vehicle. Effect of the Invention

[0007] The above vehicle control device and vehicle control program have the effect of optimizing the turning behavior of the vehicle. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a configuration diagram of a vehicle equipped with a vehicle control device. [Diagram 2] FIG. 2 is a flowchart showing the flow of processing executed by the vehicle control device to generate longitudinal forces on the wheels. [Diagram 3] 3(a) to 3(e) are timing charts showing changes in state quantities of a vehicle when the vehicle is turning on an uphill road. [Figure 4]4(a) to 4(e) are timing charts showing changes in state quantities of a vehicle when the vehicle is turning on a downhill road. [Diagram 5] 5(a) to 5(e) are timing charts showing changes in state quantities of a vehicle when the vehicle is turning on an uphill road. [Figure 6] 6(a) to 6(e) are timing charts showing changes in state quantities of a vehicle when the vehicle is turning on a downhill road. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of a vehicle control device and a vehicle control program will be described with reference to FIGS. <Configuration of this embodiment> The vehicle 10 includes front wheels 11F and rear wheels 11R, a plurality of friction brakes 20, a braking device 30, a drive device 40, a brake operating member 51, a drive operating member 52, a steering member 53, a detection system 60, and a vehicle control device 100. The vehicle 10 of this embodiment is a four-wheeled vehicle including a left front wheel and a right front wheel as the front wheels 11F, and a left rear wheel and a right rear wheel as the rear wheels 11R.

[0010] <Friction brake> The friction brakes 20 include a front wheel friction brake 20F that generates a braking force on the front wheel 11F, and a rear wheel friction brake 20R that generates a braking force on the rear wheel 11R. The front wheel friction brake 20F may be configured to generate the same braking force on the left front wheel and the right front wheel, or may be configured to generate different braking forces on the left front wheel and the right front wheel. The same is true for the rear wheel friction brake 20R in relation to the left rear wheel and the right rear wheel.

[0011] The front wheel friction brake 20F and the rear wheel friction brake 20R each include a rotating body 21, a friction material 22, and a wheel cylinder 23. When hydraulic pressure is generated in the wheel cylinder 23, the friction material 22 is pressed against the rotating body 21 which rotates integrally with the wheel. This generates a braking force on the wheel. The higher the hydraulic pressure in the wheel cylinder 23, the greater the force pressing the friction material 22 against the rotating body 21. As a result, the braking force generated on the wheel increases. The front wheel 11F corresponds to the "first wheel" and the rear wheel 11R corresponds to the "second wheel."

[0012] <Braking and driving devices> The braking device 30 includes a braking actuator 31 that supplies brake fluid to the wheel cylinders 23 of the front wheel friction brakes 20F and the rear wheel friction brakes 20R, and a braking control unit 32 that controls the braking actuator 31. An example of the braking control unit 32 is an electronic control device. The braking control unit 32 adjusts the fluid pressure in the wheel cylinders 23 of the front wheel friction brakes 20F and the rear wheel friction brakes 20R by controlling the braking actuator 31. In other words, the braking control unit 32 adjusts the braking force applied to the vehicle 10 by adjusting the fluid pressure in the multiple wheel cylinders 23.

[0013] The drive unit 40 includes a front wheel motor generator 41 that generates a drive force on the front wheels 11F, a rear wheel motor generator 42 that generates a drive force on the rear wheels 11R, and a drive control unit 43 that controls the front wheel motor generator 41 and the rear wheel motor generator 42. An example of the drive control unit 43 is an electronic control device. The vehicle 10 travels by transmitting the power of the motor generator to the wheels. In the vehicle 10 of this embodiment, both the front wheels 11F and the rear wheels 11R are drive wheels.

[0014] Here, in the vehicle 10, at least one of the braking force and the driving force is varied to accelerate or decelerate the vehicle 10. That is, the braking force and the driving force are longitudinal forces acting in the longitudinal direction of the vehicle 10. Specifically, the braking force is a negative longitudinal force, whereas the driving force is a positive longitudinal force. Therefore, the front wheel friction brake 20F corresponds to a "first actuator" that generates a negative longitudinal force on the front wheel 11F, and the rear wheel friction brake 20R corresponds to a "second actuator" that generates a negative longitudinal force on the rear wheel 11R. In addition, the front wheel motor generator 41 corresponds to a "first actuator" that generates a positive longitudinal force on the front wheel 11F, and the rear wheel motor generator 42 corresponds to a "second actuator" that generates a positive longitudinal force on the rear wheel 11R.

[0015] <Operating parts> The brake operating member 51 is operated by the driver when applying a braking force to the vehicle 10. An example of the brake operating member 51 is a brake pedal. The drive operating member 52 is operated by the driver when applying a driving force to the vehicle 10. An example of the drive operating member 52 is an accelerator pedal. The steering member 53 is operated by the driver when turning the vehicle 10. An example of the steering member 53 is a steering wheel.

[0016] <Detection system> The detection system 60 detects the state of the vehicle 10 that changes while the vehicle 10 is traveling. The detection system 60 has a brake sensor 61, an accelerator sensor 62, a steering angle sensor 63, a wheel speed sensor 64, a longitudinal acceleration sensor 65, and a yaw rate sensor 66 as multiple sensors that detect the state of the vehicle 10.

[0017] The brake sensor 61 detects the amount of operation of the brake operating member 51 by the driver. The accelerator sensor 62 detects the amount of operation of the drive operating member 52 by the driver. The steering angle sensor 63 detects the steering angle of the steering member 53. The wheel speed sensor 64 detects the rotational speed of the wheels as the wheel speed. The longitudinal acceleration sensor 65 detects the longitudinal acceleration of the vehicle 10. The yaw rate sensor 66 detects the yaw rate of the vehicle 10. The detection system 60 outputs a signal corresponding to the detected value to the vehicle control device 100.

[0018] <Vehicle control device> As shown in Fig. 1, the vehicle control device 100 includes a processing circuit 110. For example, the processing circuit 110 is an electronic control device. In this case, the processing circuit 110 includes a CPU 111 and a memory 112. The memory 112 stores a vehicle control program executed by the CPU 111. The CPU 111 executes the vehicle control program, whereby the processing circuit 110 controls the braking device 30 and the driving device 40. The vehicle control program is a program targeted at the vehicle control device 100.

[0019] <Functional configuration of the processing circuit> The processing circuit 110 functions as a required value calculation unit 121, a gradient information acquisition unit 122, an allocation ratio calculation unit 123, and an instruction unit 124 as a result of the CPU 111 executing the vehicle control program. These will be described in detail below.

[0020] <Required value calculation section> The demand value calculation unit 121 calculates a demand longitudinal force, which is a demand value of the longitudinal force to be applied to the vehicle 10. When the driver is operating the brake operating member 51, the demand value calculation unit 121 calculates a braking force corresponding to the detection signal of the brake sensor 61 as a negative demand longitudinal force. On the other hand, when the driver is operating the drive operating member 52, the demand value calculation unit 121 calculates a drive force corresponding to the detection signal of the accelerator sensor 62 as a positive demand longitudinal force. When the vehicle 10 is traveling autonomously by automatic driving, acceleration and deceleration of the vehicle 10 may be requested from another control device. In this case, the demand value calculation unit 121 calculates a longitudinal force corresponding to the acceleration or deceleration of the vehicle 10 requested from the other control device as the demand longitudinal force.

[0021] <Gradient information acquisition section> The gradient information acquisition unit 122 acquires gradient information of the road surface on which the vehicle 10 is traveling. The gradient information is the gradient of the road surface in the front-rear direction on which the vehicle 10 is traveling. The gradient of the road surface is a positive value on an uphill road, a negative value on a downhill road, and "0" on a level road.

[0022] As an example, the gradient information acquisition unit 122 may acquire the road surface gradient as follows. The gradient information acquisition unit 122 calculates the vehicle body speed based on the detection signal of the wheel speed sensor 64, and calculates the vehicle body acceleration by time-differentiating the vehicle body speed. The gradient information acquisition unit 122 also calculates the longitudinal acceleration based on the detection signal of the longitudinal acceleration sensor 65. The gradient information acquisition unit 122 then calculates a value obtained by subtracting the vehicle body acceleration from the longitudinal acceleration as the road surface gradient. When the vehicle 10 is traveling on a level road, the vehicle body acceleration is approximately equal to the longitudinal acceleration. When the vehicle 10 is traveling on an uphill road, the vehicle body acceleration is smaller than the longitudinal acceleration, so the road surface gradient is positive. When the vehicle 10 is traveling on a downhill road, the vehicle body acceleration is larger than the longitudinal acceleration, so the road surface gradient is negative.

[0023] <Allocation Ratio Calculation Department> When the vehicle 10 is traveling on an uphill road, the ground load of the front wheel 11F is smaller and the ground load of the rear wheel 11R is larger than when the vehicle 10 is traveling on a level road. On the other hand, when the vehicle 10 is traveling on a downhill road, the ground load of the front wheel 11F is larger and the ground load of the rear wheel 11R is smaller than when the vehicle 10 is traveling on a level road. When the vehicle 10 turns, if the absolute value of the longitudinal force applied to the wheel with a small ground load is large, the wheel is likely to skid. For this reason, when the road gradient changes while the vehicle 10 is traveling, it is preferable to change the distribution ratio of the longitudinal forces applied to the front wheel 11F and the rear wheel 11R in accordance with the change in the road gradient.

[0024] Here, the value obtained by dividing the longitudinal force applied to the front wheel 11F by the required longitudinal force is called the front wheel distribution ratio Rf. Also, the value obtained by dividing the longitudinal force applied to the rear wheel 11R by the required longitudinal force is called the rear wheel distribution ratio Rr. In other words, the sum of the front wheel distribution ratio Rf and the rear wheel distribution ratio Rr is "1." Therefore, if the front wheel distribution ratio Rf increases, the rear wheel distribution ratio Rr decreases, and if the front wheel distribution ratio Rf decreases, the rear wheel distribution ratio Rr increases.

[0025] The allocation ratio calculation unit 123 determines whether the road surface on which the vehicle 10 is traveling is an uphill road or a downhill road based on the road surface gradient. Next, when the allocation ratio calculation unit 123 determines that the road surface is an uphill road, it decreases the front wheel allocation ratio Rf and increases the rear wheel allocation ratio Rr more than when it determines that the road surface is not an uphill road. On the other hand, when the allocation ratio calculation unit 123 determines that the road surface is a downhill road, it increases the front wheel allocation ratio Rf and decreases the rear wheel allocation ratio Rr more than when it determines that the road surface is not a downhill road. In this way, the allocation ratio calculation unit 123 increases the allocation ratio of the front and rear forces applied to the wheel of which the ground contact load is estimated to have increased based on the gradient information, out of the front wheels 11F and the rear wheels 11R.

[0026] When the road surface is a horizontal road, the front wheel allocation ratio Rf and the rear wheel allocation ratio Rr are set to predetermined reference values. Here, the reference value of the front wheel allocation ratio Rf may be equal to or different from the reference value of the rear wheel allocation ratio Rr. When the allocation ratio calculation unit 123 determines that the road surface is an uphill road, it decreases the front wheel allocation ratio Rf from its reference value and increases the rear wheel allocation ratio Rr from its reference value. On the other hand, when the allocation ratio calculation unit 123 determines that the road surface is a downhill road, it increases the front wheel allocation ratio Rf from its reference value and decreases the rear wheel allocation ratio Rr from its reference value.

[0027] Furthermore, when the gradient of an uphill road is steep, the ground load of the front wheels 11F is smaller and the ground load of the rear wheels 11R is larger than when the gradient of the uphill road is gentle. On the other hand, when the gradient of a downhill road is steep, the ground load of the front wheels 11F is larger and the ground load of the rear wheels 11R is smaller than when the gradient of the downhill road is gentle. In other words, the steeper the gradient of the slope on which the vehicle 10 is traveling, the greater the difference between the ground load of the front wheels 11F and the ground load of the rear wheels 11R.

[0028] Therefore, when the allocation ratio calculation unit 123 determines that the road surface is an uphill road, the larger the absolute value of the road surface gradient, the more significantly the front wheel allocation ratio Rf is decreased and the rear wheel allocation ratio Rr is increased. On the other hand, when the allocation ratio calculation unit 123 determines that the road surface is a downhill road, the larger the absolute value of the road surface gradient, the more significantly the front wheel allocation ratio Rf is increased and the rear wheel allocation ratio Rr is decreased.

[0029] Furthermore, regardless of the road surface gradient, when the vehicle 10 accelerates, the ground contact load of the front wheels 11F decreases and the ground contact load of the rear wheels 11R increases. On the other hand, when the vehicle 10 decelerates, the ground contact load of the front wheels 11F increases and the ground contact load of the rear wheels 11R decreases.

[0030] Therefore, when the required longitudinal force required of the vehicle 10 increases, the allocation ratio calculation unit 123 decreases the front wheel allocation ratio Rf and increases the rear wheel allocation ratio Rr. On the other hand, when the required longitudinal force decreases, the allocation ratio calculation unit 123 increases the front wheel allocation ratio Rf and decreases the rear wheel allocation ratio Rr. Note that cases in which the required longitudinal force increases include cases in which the required driving force increases and the required braking force decreases. Similarly, cases in which the required longitudinal force decreases include cases in which the required driving force decreases and the required braking force increases.

[0031] <Instruction section> The instruction unit 124 multiplies the required longitudinal force by the front wheel allocation ratio Rf to calculate a front wheel longitudinal force instruction value which is an instruction value of the longitudinal force to be applied to the front wheels 11F. Similarly, the instruction unit 124 multiplies the required longitudinal force by the rear wheel allocation ratio Rr to calculate a rear wheel longitudinal force instruction value which is an instruction value of the longitudinal force to be applied to the rear wheels 11R.

[0032] Next, if the front wheel longitudinal force command value is "0" or greater, the command unit 124 transmits a front wheel longitudinal force command value to the drive control unit 43, and if the rear wheel longitudinal force command value is "0" or greater, the command unit 124 transmits a rear wheel longitudinal force command value to the drive control unit 43. In this case, the drive forces generated in the front wheels 11F and the rear wheels 11R are adjusted in accordance with the command value transmitted. On the other hand, if the front wheel longitudinal force command value is "0" or less, the command unit 124 transmits a front wheel longitudinal force command value to the braking control unit 32. If the rear wheel longitudinal force command value is "0" or less, the command unit 124 transmits a rear wheel longitudinal force command value to the braking control unit 32. In this case, the braking forces generated in the front wheels 11F and the rear wheels 11R are adjusted in accordance with the command value transmitted.

[0033] <Processing contents of the processing circuit> The longitudinal force adjustment process executed by the processing circuit 110 will be described with reference to Fig. 2. This process is executed for each predetermined control cycle while the ignition switch of the vehicle 10 is on. This process is executed by the CPU 111 executing a vehicle control program stored in the memory 112.

[0034] As shown in FIG. 2, the processing circuit 110 calculates the required longitudinal force (S11). Next, the processing circuit 110 calculates the road surface gradient based on the longitudinal acceleration and the vehicle body acceleration (S12). After that, the processing circuit 110 calculates the front wheel distribution ratio Rf and the rear wheel distribution ratio Rr based on the required longitudinal force and the road surface gradient (S13). Then, the processing circuit 110 multiplies the required longitudinal force by the front wheel distribution ratio Rf and the rear wheel distribution ratio Rr to calculate the front wheel longitudinal force command value and the rear wheel longitudinal force command value, respectively (S14). After that, the processing circuit 110 transmits the front wheel longitudinal force command value and the rear wheel longitudinal force command value to the braking control unit 32 or the drive control unit 43 (S15). After that, the processing circuit 110 ends this process.

[0035] In this embodiment, step S12 corresponds to a "gradient information acquisition process", and step S13 corresponds to an "allocation ratio calculation process". The process of step S11 is a process executed by the requirement value calculation unit 121. The process of step S12 is a process executed by the gradient information acquisition unit 122. The process of step S13 is a process executed by the allocation ratio calculation unit 123. The processes of steps S14 and S15 are a process executed by the instruction unit 124.

[0036] <Actions and Effects of the Present Embodiment> The operation and effect when the vehicle 10 runs on a slope while turning will be described with reference to Figs. 3 to 6.

[0037] 3(a) to (e) show the transition of the state quantities of the vehicle 10 when the vehicle 10 is traveling on an uphill road and the driving force applied to the vehicle 10 is kept constant. As shown in Fig. 3, until the first time point t11, the steering angle of the steering member 53 is "0" and the road surface gradient is "0". In other words, until the first time point t11, the vehicle 10 travels straight on a level road. When the driver starts to operate the steering member 53 at the first time point t11, the steering angle starts to increase. In other words, the vehicle 10 starts to turn. Also, the yaw rate starts to increase.

[0038] At the second timing t12 while the vehicle 10 is turning, the road gradient becomes greater than "0". That is, the road surface on which the vehicle 10 is traveling changes from a horizontal road to an uphill road. Therefore, from the second timing t12, the front wheel allocation ratio Rf decreases and the rear wheel allocation ratio Rr increases. In detail, as the absolute value of the road gradient increases, the front wheel allocation ratio Rf gradually decreases and the rear wheel allocation ratio Rr gradually increases. In the example shown in FIG. 3, since the driving force applied to the vehicle 10 is constant, the longitudinal force applied to the front wheel 11F, which has a smaller ground load, decreases, while the longitudinal force applied to the rear wheel 11R, which has a larger ground load, increases.

[0039] At the third timing t13, when the road surface gradient of the uphill road becomes constant, the front wheel distribution ratio Rf and the rear wheel distribution ratio Rr do not change. In addition, since the steering angle gradually decreases after the third timing t13, the yaw rate starts to decrease from the third timing t13. At the fourth timing t14, when the road surface gradient starts to decrease, the front wheel distribution ratio Rf increases and the rear wheel distribution ratio Rr decreases. In detail, as the absolute value of the road surface gradient decreases, the front wheel distribution ratio Rf gradually increases and the rear wheel distribution ratio Rr gradually decreases. In the example shown in FIG. 3, since the driving force applied to the vehicle 10 is constant, the front and rear forces applied to the front wheels 11F, which have a large ground load, increase, while the front and rear forces applied to the rear wheels 11R, which have a small ground load, decrease. After that, at the fifth timing t15, when the road surface gradient becomes "0", the front wheel distribution ratio Rf and the rear wheel distribution ratio Rr return to the values ​​before the second timing t12. At the fifth timing t15, the steering angle is kept constant, that is, the yaw rate becomes "0".

[0040] Here, a comparative example will be described in which the front wheel distribution ratio Rf and the rear wheel distribution ratio Rr are not changed according to the road surface gradient. In the comparative example, even if the ground load of the front wheels 11F decreases with an increase in the road surface gradient, the front wheel distribution ratio Rf is not decreased. Therefore, when the ground load of the front wheels 11F decreases with an increase in the road surface gradient while the vehicle 10 is turning, the front wheels 11F are likely to slip sideways. For example, the turning behavior of the vehicle 10 tends to understeer. Therefore, as shown by the dashed line in FIG. 3(c), the yaw rate does not change like the steering angle.

[0041] In contrast, in this embodiment, when the vehicle 10 travels on an uphill road, the front wheel distribution ratio Rf and the rear wheel distribution ratio Rr are changed according to the road surface gradient. Therefore, even if the ground load of the front wheels 11F decreases as the road surface gradient increases while the vehicle 10 is turning, the occurrence of lateral skid at the front wheels 11F is suppressed. As a result, as shown by the solid line in FIG. 3(c), the yaw rate changes in the same way as the steering angle. Therefore, under a condition where the driving force is constant, when the vehicle 10 travels on an uphill road and turns, the stability of the turning behavior of the vehicle 10 can be optimized.

[0042] 4(a)-(e) show the transition of the state quantities of the vehicle 10 when the vehicle 10 travels downhill and the braking force applied to the vehicle 10 is kept constant. In the following explanation of Figs. 4-6, some of the explanations common to Fig. 3 will be omitted.

[0043] 4, when the driver starts to operate the steering member 53 at a first timing t21, the steering angle starts to increase. That is, the vehicle 10 starts to turn. Also, the yaw rate starts to increase.

[0044] At a second timing t22 while the vehicle 10 is turning, the road surface gradient becomes smaller than "0". That is, the road surface on which the vehicle 10 is traveling changes from a level road to a downhill road. Therefore, from the second timing t22, the front wheel distribution ratio Rf increases and the rear wheel distribution ratio Rr decreases. In the example shown in FIG. 4, since the braking force applied to the vehicle 10 is constant, the longitudinal force applied to the front wheel 11F, which has a large ground contact load, increases, while the longitudinal force applied to the rear wheel 11R, which has a small ground contact load, decreases.

[0045] At the third timing t23, when the road surface gradient of the downhill road becomes constant, the front wheel distribution ratio Rf and the rear wheel distribution ratio Rr do not change. At the fourth timing t24, when the road surface gradient starts to increase, the front wheel distribution ratio Rf decreases and the rear wheel distribution ratio Rr increases. In the example shown in FIG. 4, since the braking force applied to the vehicle 10 is constant, the longitudinal force applied to the front wheel 11F, whose ground load is decreasing, decreases, while the longitudinal force applied to the rear wheel 11R, whose ground load is increasing, increases. After that, at the fifth timing t25, when the road surface gradient becomes "0", the front wheel distribution ratio Rf and the rear wheel distribution ratio Rr return to the values ​​before the second timing t22.

[0046] Here, a comparative example will be described in which the front wheel distribution ratio Rf and the rear wheel distribution ratio Rr are not changed according to the road surface gradient. In the comparative example, even if the ground load of the rear wheel 11R decreases with a decrease in the road surface gradient, the rear wheel distribution ratio Rr is not reduced. Therefore, when the ground load of the rear wheel 11R decreases with a decrease in the road surface gradient while the vehicle 10 is turning, the rear wheel 11R is more likely to slip. For example, the turning behavior of the vehicle 10 tends to oversteer. Therefore, as shown by the dashed line in FIG. 4(c), the yaw rate does not change in the same way as the steering angle.

[0047] In contrast, in this embodiment, when the vehicle 10 travels on a downhill road, the front wheel distribution ratio Rf and the rear wheel distribution ratio Rr are changed according to the road surface gradient. Therefore, even if the ground contact load of the rear wheel 11R decreases according to a decrease in the road surface gradient while the vehicle 10 is turning, the occurrence of skid at the rear wheel 11R is suppressed. As a result, as shown by the solid line in FIG. 4(c), the yaw rate changes in the same manner as the steering angle. Therefore, under a condition where the braking force is constant, when the vehicle 10 travels on a downhill road and turns, the stability of the turning behavior of the vehicle 10 can be optimized.

[0048] 5(a) to (e) show the transition of the state quantities of the vehicle 10 when the vehicle 10 is traveling uphill and the driving force applied to the vehicle 10 is increased or decreased. 5, when the driver starts to operate the steering member 53 at a first timing t31, the steering angle starts to increase. That is, the vehicle 10 starts to turn. Also, the yaw rate starts to increase.

[0049] At the second timing t32 while the vehicle 10 is turning, the road gradient becomes greater than "0". That is, the road surface on which the vehicle 10 is traveling changes from a level road to an uphill road. For this reason, from the second timing t32, the front wheel allocation ratio Rf decreases and the rear wheel allocation ratio Rr increases. As a result, the longitudinal force applied to the front wheel 11F, which has a smaller ground contact load, decreases, while the longitudinal force applied to the rear wheel 11R, which has a larger ground contact load, increases.

[0050] Next, at the third timing t33, when the driver increases the amount of operation of the drive operating member 52, the required longitudinal force starts to increase. More specifically, the required longitudinal force gradually increases from the third timing t33 ​​to the fourth timing t34. Therefore, in conjunction with the increase in the required longitudinal force, the front wheel allocation ratio Rf decreases and the rear wheel allocation ratio Rr increases. Therefore, in the period from the third timing t33 ​​to the fourth timing t34, the decrease gradient of the front wheel allocation ratio Rf and the increase gradient of the rear wheel allocation ratio Rr become steeper than in the period from the second timing t32 to the third timing t33. At the fourth timing t34, the required longitudinal force does not change. Partly because the rate of change of the road surface gradient from the second timing t32 to the fifth timing t35 does not change, in the period after the fourth timing t34, the decrease gradient of the front wheel allocation ratio Rf and the increase gradient of the rear wheel allocation ratio Rr become equal to the gradients before the third timing t33.

[0051] At a fifth timing t35, when the road surface gradient of the uphill road becomes constant, the front wheel distribution ratio Rf and the rear wheel distribution ratio Rr do not change. In other words, the front wheel distribution ratio Rf and the rear wheel distribution ratio Rr are maintained constant. At a sixth timing t36, when the road surface gradient begins to decrease, the front wheel distribution ratio Rf increases and the rear wheel distribution ratio Rr decreases. As a result, the longitudinal force applied to the front wheel 11F, which has a large ground contact load, increases, while the longitudinal force applied to the rear wheel 11R, which has a small ground contact load, decreases.

[0052] At the seventh timing t37, when the driver reduces the amount of operation of the drive operating member 52, the required longitudinal force starts to decrease. More specifically, the required longitudinal force gradually decreases from the seventh timing t37 to the eighth timing t38. Therefore, in conjunction with the decrease in the required longitudinal force, the front wheel allocation ratio Rf increases and the rear wheel allocation ratio Rr decreases. Therefore, in the period from the seventh timing t37 to the eighth timing t38, the increase gradient of the front wheel allocation ratio Rf and the decrease gradient of the rear wheel allocation ratio Rr become steeper than in the period from the sixth timing t36 to the seventh timing t37. At the eighth timing t38, the required longitudinal force does not change. Since the rate of change of the road surface gradient from the sixth timing t36 to the ninth timing t39 does not change, in the period after the eighth timing t38, the increase gradient of the front wheel allocation ratio Rf and the decrease gradient of the rear wheel allocation ratio Rr become equal to the gradients before the seventh timing t37. After that, at the ninth timing t39, when the road surface gradient becomes "0", the front wheel distribution ratio Rf and the rear wheel distribution ratio Rr return to the values ​​before the second timing t32.

[0053] Here, a comparative example will be described in which the front wheel distribution ratio Rf and the rear wheel distribution ratio Rr are not changed according to the road gradient and the required longitudinal force. In the comparative example, even if the ground load of the front wheels 11F decreases with an increase in the road gradient and the required longitudinal force, the front wheel distribution ratio Rf is not decreased. Therefore, when the ground load of the front wheels 11F decreases with an increase in the road gradient and the required longitudinal force while the vehicle 10 is turning, the front wheels 11F are likely to slip sideways. For example, the turning behavior of the vehicle 10 tends to understeer. Therefore, as shown by the dashed line in FIG. 5(c), the yaw rate does not change like the steering angle.

[0054] In contrast, in this embodiment, when the vehicle 10 travels on an uphill road, the front wheel distribution ratio Rf and the rear wheel distribution ratio Rr are changed according to the road surface gradient and the required longitudinal force. Therefore, even if the ground load of the front wheels 11F decreases according to an increase in the road surface gradient and the required longitudinal force while the vehicle 10 is turning, the occurrence of lateral skid at the front wheels 11F is suppressed more than in the comparative example. As a result, as shown by the solid line in FIG. 5(c), the yaw rate changes in the same manner as the steering angle. Therefore, in this embodiment, when the vehicle 10 travels on an uphill road turns under a condition where the driving force is increased or decreased, the stability of the turning behavior of the vehicle 10 can be optimized.

[0055] 6(a) to (e) show the transition of the state quantities of the vehicle 10 when the vehicle 10 is traveling downhill and the braking force applied to the vehicle 10 is increased or decreased. 6, at a first timing t41, when the driver starts to operate the steering member 53, the steering angle starts to increase. That is, the vehicle 10 starts to turn. Also, the yaw rate starts to increase.

[0056] At a second timing t42 while the vehicle 10 is turning, the road surface gradient becomes smaller than "0". That is, the road surface on which the vehicle 10 is traveling changes from a level road to a downhill road. Therefore, from the second timing t42, the front wheel allocation ratio Rf increases and the rear wheel allocation ratio Rr decreases. As a result, the longitudinal force applied to the front wheel 11F, which has a larger ground contact load, increases, while the longitudinal force applied to the rear wheel 11R, which has a smaller ground contact load, decreases.

[0057] Next, at the third timing t43, when the driver increases the amount of operation of the brake operating member 51, the required longitudinal force starts to decrease. In this case, since the required longitudinal force is a negative value, the absolute value of the required longitudinal force increases. More specifically, the required longitudinal force gradually decreases from the third timing t43 to the fourth timing t44. Therefore, in conjunction with the decrease in the required longitudinal force, the front wheel allocation ratio Rf increases and the rear wheel allocation ratio Rr decreases. Therefore, from the third timing t43 to the fourth timing t44, the increase gradient of the front wheel allocation ratio Rf and the decrease gradient of the rear wheel allocation ratio Rr are steeper than those from the second timing t42 to the third timing t43. At the fourth timing t44, the required longitudinal force stops changing. Since the rate of change of the road surface gradient does not change from the second timing t42 to the fifth timing t45, in the period from the fourth timing t44 onwards, the increasing gradient of the front wheel allocation ratio Rf and the decreasing gradient of the rear wheel allocation ratio Rr become equal to the gradients before the third timing t43.

[0058] At a fifth timing t45, when the road surface gradient of the downhill road becomes constant, the front wheel distribution ratio Rf and the rear wheel distribution ratio Rr do not change. In other words, the front wheel distribution ratio Rf and the rear wheel distribution ratio Rr are maintained constant. At a sixth timing t46, when the road surface gradient begins to increase, the front wheel distribution ratio Rf decreases and the rear wheel distribution ratio Rr increases. As a result, the longitudinal force applied to the front wheel 11F, which has a smaller ground contact load, decreases, and the longitudinal force applied to the rear wheel 11R, which has a larger ground contact load, increases.

[0059] At the seventh timing t47, when the driver reduces the amount of operation of the brake operating member 51, the required longitudinal force starts to increase. That is, the required longitudinal force starts to approach "0". More specifically, the required longitudinal force increases in the period from the seventh timing t47 to the eighth timing t48. Therefore, in conjunction with the increase in the required longitudinal force, the front wheel allocation ratio Rf decreases and the rear wheel allocation ratio Rr increases. Therefore, in the period from the seventh timing t47 to the eighth timing t48, the decrease gradient of the front wheel allocation ratio Rf and the increase gradient of the rear wheel allocation ratio Rr are steeper than in the period from the sixth timing t46 to the seventh timing t47. At the eighth timing t48, the required longitudinal force does not change. Since the rate of change of the road surface gradient from the sixth timing t46 to the ninth timing t49 does not change, in the period after the eighth timing t48, the increase gradient of the front wheel allocation ratio Rf and the decrease gradient of the rear wheel allocation ratio Rr become the gradients before the seventh timing t47. After that, at the ninth timing t49, when the road surface gradient becomes "0", the front wheel distribution ratio Rf and the rear wheel distribution ratio Rr return to the values ​​before the second timing t42.

[0060] Here, a comparative example will be described in which the front wheel distribution ratio Rf and the rear wheel distribution ratio Rr are not changed according to the road gradient and the required longitudinal force. In the comparative example, even if the ground load of the rear wheel 11R decreases with the decrease in the road gradient and the required longitudinal force, the rear wheel distribution ratio Rr is not reduced. Therefore, when the ground load of the rear wheel 11R decreases with the decrease in the road gradient and the required longitudinal force while the vehicle 10 is turning, the rear wheel 11R is likely to slip sideways. For example, the turning behavior of the vehicle 10 tends to oversteer. Therefore, as shown by the dashed line in FIG. 6(c), the yaw rate does not change like the steering angle.

[0061] In contrast, in this embodiment, when the vehicle 10 travels on a downhill road, the front wheel distribution ratio Rf and the rear wheel distribution ratio Rr are changed according to the road surface gradient and the required longitudinal force. Therefore, even if the ground load of the rear wheel 11R becomes smaller according to the decrease in the road surface gradient and the required longitudinal force while the vehicle 10 is turning, the occurrence of skid at the rear wheel 11R is suppressed more than in the comparative example. As a result, as shown by the solid line in FIG. 6(c), the yaw rate changes in the same manner as the steering angle. Therefore, in this embodiment, when the vehicle 10 travels on a downhill road and turns under the condition that the braking force is increased or decreased, the stability of the turning behavior of the vehicle 10 can be optimized.

[0062] As described above, the vehicle control device 100 can suppress skidding of the wheels whose ground load becomes smaller due to changes in the road surface gradient and changes in the required longitudinal force, and can suppress the vehicle 10 from not turning as required. In other words, the vehicle control device 100 can further optimize the turning behavior of the vehicle 10.

[0063] As described above, when the vehicle 10 is traveling on an uphill road, the front wheel allocation ratio Rf is decreased. On the other hand, when the required longitudinal force decreases, the front wheel allocation ratio Rf is increased. Therefore, when the required longitudinal force decreases while the vehicle 10 is traveling on an uphill road, the front wheel allocation ratio Rf is determined by the magnitude of the slope gradient and the magnitude of the required braking force. For example, when the vehicle 10 is traveling on an uphill road, even if the slope gradient increases, if the decrease in the required longitudinal force is large, the front wheel allocation ratio Rf may be increased.

[0064] <Example of change> This embodiment can be modified as follows: This embodiment and the following modifications can be combined with each other to the extent that there is no technical contradiction.

[0065] In the above embodiment, the vehicle control device 100 adjusts the front wheel distribution ratio Rf and the rear wheel distribution ratio Rr in accordance with the road surface gradient and the required longitudinal force. In addition to adjusting the distribution of the longitudinal forces in this way, the vehicle control device 100 may adjust the distribution ratio of the longitudinal forces applied to the inner wheel and the outer wheel in accordance with the ground contact load of the inner wheel and the ground contact load of the outer wheel when the vehicle turns. In detail, the vehicle control device 100 may decrease the distribution ratio of the longitudinal force applied to the inner wheel and increase the distribution ratio of the longitudinal force applied to the outer wheel.

[0066] The vehicle 10 may be equipped with a car navigation device that stores map information that associates positions with altitudes, and a GPS device that acquires the current position of the vehicle 10. In this case, the vehicle control device 100 may calculate the road surface gradient based on the current position information of the vehicle 10 acquired by the GPS device and the map information of the car navigation device.

[0067] The vehicle 10 may be equipped with a camera, a laser device, a radar device, etc., that acquires the state of the road surface ahead of the vehicle. In this case, the vehicle control device 100 may calculate the road surface gradient according to the state of the road surface acquired by these devices.

[0068] The front wheel motor generator 41 may generate a regenerative braking force on the front wheels 11F. Similarly, the rear wheel motor generator 42 may generate a regenerative braking force on the rear wheels 11R. At least one of the front wheel motor generator 41 and the rear wheel motor generator 42 may be replaced with an internal combustion engine.

[0069] When the vehicle 10 is traveling on a road surface that is inclined laterally (hereinafter referred to as a "banked road"), a difference may occur between the ground contact load of the left wheel and the ground contact load of the right wheel. More specifically, the ground contact load of the wheel located on the lower side in the direction of gravity is likely to be greater than the ground contact load of the wheel located on the upper side. Therefore, when the vehicle 10 is traveling on a banked road, the vehicle control device 100 may increase the distribution ratio of the longitudinal force applied to the wheel with the larger ground contact load out of the left and right wheels. In this case, the distribution ratio of the longitudinal force applied to the wheel with the smaller ground contact load is decreased. In this case, one of the left and right wheels corresponds to the "first wheel" and the other corresponds to the "second wheel."

[0070] The vehicle control device 100 may perform the longitudinal force adjustment process only when the longitudinal force is a positive value. In this case, the vehicle 10 only needs to be equipped with an actuator that applies a braking force to one of the front wheels 11F and the rear wheels 11R. The vehicle control device 100 may perform the longitudinal force adjustment process only when the longitudinal force is a negative value. In this case, the vehicle 10 only needs to be equipped with an actuator that applies a driving force to one of the front wheels 11F and the rear wheels 11R.

[0071] The vehicle 10 may be a two-wheeled vehicle or a three-wheeled vehicle. The vehicle control device 100 is not limited to the processing circuit 110 that executes software processing. For example, the vehicle control device 100 may include a dedicated hardware circuit that executes at least a part of the various processes executed in the above-described embodiment. An example of the dedicated hardware circuit is an ASIC. ASIC is an abbreviation for "Application Specific Integrated Circuit." In other words, the vehicle control device 100 may have any one of the following configurations (a) to (c).

[0072] (a) A processing circuit including a processing device that executes all of the above processes according to a program, and a program storage device such as a ROM that stores the program. (b) A processing circuit having a processing device and a program storage device for executing part of the above processing in accordance with a program, and a dedicated hardware circuit for executing the remaining processing.

[0073] (c) A processing circuit having dedicated hardware circuitry for performing all of the above processes. Here, there may be a plurality of software execution devices each having a processing device and a program storage device, and a plurality of dedicated hardware circuits.

[0074] <Additional Notes> The technical ideas that can be understood from the above-described embodiment and modified examples will be described. The vehicle control method is applied to a vehicle equipped with a first actuator that generates a longitudinal force on a first wheel and a second actuator that generates a longitudinal force on a second wheel, and includes a gradient information acquisition process that acquires gradient information of a road surface on which the vehicle is traveling, and an allocation ratio calculation process that increases an allocation ratio, which is a value obtained by dividing the longitudinal force applied to either the first wheel or the second wheel, which wheel is presumed to have an increased ground load based on the gradient information, by a required longitudinal force, which is the longitudinal force required of the vehicle. [Explanation of symbols]

[0075] 10. Vehicle 11F…Front wheel (first wheel) 11R…Rear wheel (2nd wheel) 20F…Front wheel friction brake (first actuator) 20R…Rear wheel friction brake (second actuator) 41...Front wheel motor generator (first actuator) 42...Rear wheel motor generator (second actuator) 100...Vehicle control device 121...Requirement value calculation unit 122...Gradient information acquisition unit 123...Allocation ratio calculation section

Claims

1. A vehicle control device applied to a vehicle including a first actuator that generates a longitudinal force on a first wheel and a second actuator that generates a longitudinal force on a second wheel, a gradient information acquisition unit that acquires gradient information of a road surface on which the vehicle is traveling; an allocation ratio calculation unit that increases an allocation ratio that is a value obtained by dividing a longitudinal force applied to a wheel, which is one of the first wheel and the second wheel and in which a ground load is estimated to have increased based on the gradient information, by a required longitudinal force that is a longitudinal force required for the vehicle. Vehicle control device.

2. The first wheel is a front wheel and the second wheel is a rear wheel, the gradient information acquisition unit acquires, as the gradient information, a road surface gradient, which is a gradient of the road surface in a forward / rearward direction of the vehicle; The allocation ratio calculation unit is When it is determined that the road surface is an uphill road from the road surface gradient, a front wheel distribution ratio, which is a value obtained by dividing the front and rear force applied to the front wheels by the required front and rear force, is reduced compared to when it is determined that the road surface is not an uphill road. When it is determined from the road surface gradient that the road surface is a downhill road, the front wheel distribution ratio is increased compared to when it is determined that the road surface is not a downhill road. The vehicle control device according to claim 1.

3. The allocation ratio calculation unit is When it is determined that the road surface is an uphill road based on the road surface gradient, the greater the absolute value of the road surface gradient, the more significantly the front wheel distribution ratio is reduced, When it is determined from the road surface gradient that the road surface is a downhill road, the greater the absolute value of the road surface gradient, the more the front wheel distribution ratio is increased. The vehicle control device according to claim 2.

4. The allocation ratio calculation unit is When the required longitudinal force increases, the front wheel distribution ratio is decreased, When the required longitudinal force decreases, the front wheel distribution ratio is increased. The vehicle control device according to claim 2 or 3.

5. A vehicle control program for a control device of a vehicle including a first actuator that generates a longitudinal force on a first wheel and a second actuator that generates a longitudinal force on a second wheel, A gradient information acquisition process for acquiring gradient information of a road surface on which the vehicle is traveling; an allocation ratio calculation process for increasing an allocation ratio, which is a value obtained by dividing a longitudinal force applied to one of the first wheel and the second wheel, the wheel being one in which a ground load is estimated to have increased based on the gradient information, by a required longitudinal force, which is a longitudinal force required for the vehicle. Vehicle control program.

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