Vehicle control method and vehicle control device

Abstract

To realize drive force control that balances acceleration performance on high-μ roads and line-traceability on low-μ roads.SOLUTION: A vehicle control method comprises: detecting, by an acceleration sensor, longitudinal acceleration and lateral acceleration of a vehicle (S1); estimating a ground load acting on wheels of the vehicle (S3); estimating a maximum friction circle of the wheels on the basis of the ground load, the longitudinal acceleration, and the lateral acceleration (S6); estimating a tire lateral force (S4); calculating a target tire longitudinal force being a target value of the tire longitudinal force to be generated by the wheels on the basis of the maximum friction circle and the tire lateral force (S7); limiting a drive force of the vehicle on the basis of the target tire longitudinal force (S11); calculating the estimated longitudinal acceleration on the basis of an accelerator opening degree of the vehicle (S2); calculating the estimated lateral acceleration on the basis of a steering angle of the vehicle (S2); and suppressing the limitation of the drive force of the vehicle based on the target tire longitudinal force on the basis of the longitudinal acceleration, the lateral acceleration, the estimated longitudinal acceleration and the estimated lateral acceleration (S10, S11).SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a vehicle control method and a vehicle control device.

Background Art

[0002] The vehicle control device of Patent Document 1 below calculates the allowable driving force of each wheel from the road surface friction coefficient, the ground contact load of each wheel, and the lateral force of each wheel, calculates the allowable engine torque based on the allowable driving force of each wheel, limits the engine output, and calculates the transfer clutch torque in the front-rear driving force distribution control, the rear wheel torque movement amount in the left-right driving force distribution control, and the steering angle correction amount in the steering angle control.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the control device according to Patent Document 1 above, since the engine output exceeding the maximum friction circle of the tire is restricted, it is not possible to allow the slip of the tire on a high-μ road and give priority to acceleration performance. On the other hand, if the restriction of the engine output is suppressed in order to give priority to acceleration performance, there is a problem that the line tracing performance is impaired on a low-μ road. An object of the present invention is to realize driving force control that achieves both acceleration performance on a high-μ road and line tracing performance on a low-μ road.

Means for Solving the Problems

[0005] In a vehicle control method according to one aspect of the present invention, the longitudinal acceleration and lateral acceleration of the vehicle are detected by an acceleration sensor, the ground load acting on the wheels of the vehicle is estimated, the maximum friction circle of the wheels is estimated based on the ground load, the longitudinal acceleration, and the lateral acceleration, the tire lateral force acting on the wheels is estimated, a target tire longitudinal force, which is a target value of the tire longitudinal force to be generated on the wheels, is calculated based on the maximum friction circle and the tire lateral force, and the driving force of the vehicle is limited based on the target tire longitudinal force. In the vehicle control method, an estimated longitudinal acceleration is calculated based on the accelerator opening of the vehicle, an estimated lateral acceleration is calculated based on the steering angle of the vehicle, and the limitation of the driving force of the vehicle based on the target tire longitudinal force is suppressed based on the longitudinal acceleration, the lateral acceleration, the estimated longitudinal acceleration, and the estimated lateral acceleration.

Advantages of the Invention

[0006] According to the present invention, it is possible to realize driving force control that achieves both acceleration performance on a high-μ road and line tracing performance on a low-μ road.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0008] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that each drawing is schematic and may differ from the actual one. Further, the embodiments of the present invention shown below illustrate devices and methods for embodying the technical idea of the present invention, and the technical idea of the present invention does not specify the structure, arrangement, etc. of the components as follows. The technical idea of the present invention can be variously modified within the technical scope defined by the claims described in the claims.

[0009] (Configuration) Referring to FIG. 1. The vehicle control device 10 of the embodiment is mounted on the vehicle 1 and controls the respective driving forces generated on the right front wheel 2FR, left front wheel 2FL, right rear wheel 2RR, and left rear wheel 2RL of the vehicle 1. In the following description, the right front wheel 2FR and the left front wheel 2FL may be collectively referred to as the "front wheels 2F", and the right rear wheel 2RR and the left rear wheel 2RL may be collectively referred to as the "rear wheels 2R". Also, the wheel on the inner side of the turning of the right front wheel 2FR and the left front wheel 2FL may be referred to as the front turning inner wheel 2FI, and the wheel on the inner side of the turning of the right rear wheel 2RR and the left rear wheel 2RL may be referred to as the rear turning inner wheel 2RI.

[0010] The vehicle control device 10 includes a steering angle sensor 11, a vehicle speed sensor 12, an acceleration sensor 13, an accelerator opening sensor 15, a chassis controller 16, a power train controller 17, and a drive source 18. The steering angle sensor 11 detects the steering angle θ of the steering wheel. The vehicle speed sensor 12 detects the vehicle speed Vh of the vehicle 1. The acceleration sensor 13 detects the longitudinal acceleration Gax and the lateral acceleration Gay acting on the vehicle 1. The accelerator opening sensor 15 detects the accelerator opening Ac corresponding to the operation amount of the accelerator pedal by the driver.

[0011] The chassis controller 16 is an electronic control unit (ECU: Electronic Control Unit) that calculates the operation amounts necessary for chassis control of the vehicle 1. The chassis controller 16 includes a processor 16a and peripheral components such as a storage device 16b. The functions of the chassis controller 16 described below are realized, for example, when the processor 16a executes a computer program stored in the storage device 16b.

[0012] The chassis controller 16 may be formed of dedicated hardware for executing each of the information processes described below. For example, the chassis controller 16 may include a functional logic circuit set in a general-purpose semiconductor integrated circuit. For example, the chassis controller 16 may have a programmable logic device (PLD) such as a field-programmable gate array (FPGA). The same applies to the power train controller 17.

[0013] The power train controller 17 is an electronic control unit that calculates the driving forces FxF and FxR to be generated on the front wheels 2F and the rear wheels 2R, respectively, based on the accelerator opening Ac from the accelerator opening sensor 15 and the control signal from the chassis controller 16, and causes the driving force to be generated by the drive source 18. The power train controller 17 includes a processor 17a and peripheral components such as a storage device 17b. The functions of the power train controller 17 are realized, for example, when the processor 17a executes a computer program stored in the storage device 17b.

[0014] The drive source 18 is a power source that generates independent driving forces for the front wheels 2F and the rear wheels 2R, respectively. For example, the drive source 18 may include electric motors (such as in-wheel motors) provided independently for the front wheels 2F and the rear wheels 2R, respectively. Also, for example, the drive source 18 may include a common power source (engine or motor) and a differential mechanism that can variably control the distribution ratio of the driving force generated by this power source to the front wheels 2F and the rear wheels 2R.

[0015] FIG. 2 is a block diagram of a functional configuration example of the power train controller 17. The power train controller 17 includes a required driving force calculation unit 30 and an actual driving force calculation unit 31. Based on the accelerator opening Ac from the accelerator opening sensor 15, the required driving force calculation unit 30 calculates a driver required torque Td according to the driver's acceleration intention. The required driving force calculation unit 30 outputs the driver required torque Td to the actual driving force calculation unit 31 and the chassis controller 16.

[0016] FIG. 3 is a block diagram of a functional configuration example of the chassis controller 16. The chassis controller 16 includes a driving force calculation unit 40, an estimated lateral acceleration calculation unit 41, an estimated longitudinal acceleration calculation unit 42, a wheel load estimation unit 43, a root mean square calculation unit 44, a lateral force calculation unit 45, a friction circle estimation unit 46, a target driving force calculation unit 47, a slip ratio calculation unit 48, and a target driving force correction value calculation unit 49. Based on a predetermined distribution method, the driving force calculation unit 40 distributes the driver required torque Td to the front wheels 2F and the rear wheels 2R, and divides the distributed torque by the tire radii of the front wheels 2F and the rear wheels 2R to calculate a front wheel required driving force FxdF and a rear wheel required driving force FxdR.

[0017] Based on the steering angle θ and the vehicle speed Vh, the estimated lateral acceleration calculation unit 41 calculates an estimated lateral acceleration Gey, which is the lateral acceleration estimated to occur in the vehicle 1 according to the steering angle θ and the vehicle speed Vh. The longitudinal and lateral acceleration calculation unit 42 calculates an estimated longitudinal and lateral acceleration Gex, which is estimated to occur in the vehicle 1 when a driving force corresponding to the driver demand torque Td is generated, based on the driver demand torque Td and the vehicle speed Vh.

[0018] The wheel load estimation unit 43 estimates the wheel loads WFR, WFL, WRR, and WRL of the right front wheel 2FR, the left front wheel 2FL, the right rear wheel 2RR, and the left rear wheel 2RL based on the estimated lateral acceleration Gey and the estimated longitudinal and lateral acceleration Gex. For example, assuming the mass of the vehicle 1 is m, the wheelbase is L, the tread is T, the center of gravity height is H, the static front wheel load is WFS, and the static rear wheel load is WRS, the wheel loads WFR, WFL, WRR, and WRL may be estimated based on the following equations (1) to (4).

[0019] WFR = WFS + m × (-Gex × H / L + Gey × H / T) / 2 …(1) WFL = WFS + m × (-Gex × H / L - Gey × H / T) / 2 …(2) WRR = WRS + m × (Gex × H / L + Gey × H / T) / 2 …(3) WRL = WRS + m × (Gex × H / L - Gey × H / T) / 2 …(4)

[0020] The square root of the sum of squares calculation unit 44 calculates the square root of the sum of squares Gxy = (Gax 2 + Gay 2 ) 1 / 2 of the longitudinal acceleration Gax and the lateral acceleration Gay detected by the acceleration sensor 13. The lateral force calculation unit 45 calculates the tire lateral forces FyF and FyR acting on the front inner wheel 2FI and the rear inner wheel 2RI based on the estimated lateral acceleration Gey calculated by the estimated lateral acceleration calculation unit 41 and the wheel loads WFR, WFL, WRR, and WRL calculated by the wheel load estimation unit 43.

[0021] For example, assuming that the distances from the vehicle center of gravity to the front wheel axle and the rear wheel axle are Lf and Lr respectively, the lateral force calculation unit 45 may calculate the target lateral forces FxtFR, FxtFL, FxtRR, and FxtRL for each of the right front wheel 2FR, left front wheel 2FL, right rear wheel 2RR, and left rear wheel 2RL based on the following equations (5) to (8). FxtFR = m × Gey × (Lr / L) × (1 / 2)…(5) FxtFL = m × Gey × (Lr / L) × (1 / 2)…(6) FxtRR = m × Gey × (Lf / L) × (1 / 2)…(7) FxtRL = m × Gey × (Lf / L) × (1 / 2)…(8)

[0022] The lateral force calculation unit 45 may calculate the tire lateral forces FyF and FyR acting on the front turning inner wheel 2FI and the rear turning inner wheel 2RI based on the following equations (9) and (10). FyF = (FxtFR + FxtFL) × min(WFR, WFL) / (WFR + WFL)…(9) FyR = (FxtRR + FxtRL) × min(WRR, WRL) / (WRR + WRL)…(10)

[0023] The friction circle estimation unit 46 uses the square root of the sum of squares Gxy calculated by the square root of the sum of squares calculation unit 44 as an approximation of the road surface friction coefficient μ, and multiplies the square root of the sum of squares Gxy by the wheel loads of the front turning inner wheel 2FI and the rear turning inner wheel 2RI based on the following equations (11) and (12) to estimate the maximum friction circles FyFL and FyRL of the front turning inner wheel 2FI and the rear turning inner wheel 2RI. FyFL = Gxy × min(WFR, WFL)…(11) FyRL = Gxy × min(WRR, WRL)…(12)

[0024] The target driving force calculation unit 47 calculates the front wheel target tire longitudinal force FxtF and the rear wheel target tire longitudinal force FxtR based on the front wheel required driving force FxdF and the rear wheel required driving force FxdR calculated by the driving force calculation unit 40, the tire lateral forces FyF and FyR acting on the front turning inner wheel 2FI and the rear turning inner wheel 2RI calculated by the lateral force calculation unit 45, and the maximum friction circles FyFL and FyRL of the front turning inner wheel 2FI and the rear turning inner wheel 2RI calculated by the friction circle estimation unit 46. Also, the front wheel target tire longitudinal force FxtF and the rear wheel target tire longitudinal force FxtR may be simply calculated by multiplying the current values of the front wheel tire longitudinal force and the rear wheel tire longitudinal force by (the maximum friction circle FyFL) / (the current value of the sum of the longitudinal force and the lateral force of the front wheel tire). The front wheel target tire longitudinal force FxtF is the target value of the total value of the tire longitudinal forces generated in the right front wheel 2FR and the left front wheel 2FL, and the rear wheel target tire longitudinal force FxtR is the target value of the total value of the tire longitudinal forces generated in the right rear wheel 2RR and the left rear wheel 2RL.

[0025] The target driving force calculation unit 47 calculates the front wheel target tire longitudinal force FxtF and the rear wheel target tire longitudinal force FxtR by restricting the front wheel required driving force FxdF and the rear wheel required driving force FxdR based on the maximum friction circles FyFL and FyRL and the tire lateral forces FyF and FyR. For example, the target driving force calculation unit 47 calculates the required driving forces FxdFI and FxdRI of the front turning inner wheel 2FI and the rear turning inner wheel 2RI based on the front wheel required driving force FxdF and the rear wheel required driving force FxdR.

[0026] For example, the target driving force calculation unit 47 may set 1 / 2 of the front wheel required driving force FxdF and the rear wheel required driving force FxdR as the required driving force FxdFI = FxdF / 2 and the required driving force FxdRI = FxdR / 2. For example, the target driving force calculation unit 47 may calculate the front wheel target tire longitudinal force FxtF and the rear wheel target tire longitudinal force FxtR based on the following equations (13) and (14).

[0027]

Equation

[0028] The target driving force calculation unit 47 calculates the sum of the front wheel target tire longitudinal force FxtF and the rear wheel target tire longitudinal force FxtR as the target driving force Fxt = FxtF + FxtR. The slip ratio calculation unit 48 calculates the slip ratio λ based on the estimated value of the acceleration of the vehicle 1 estimated by the estimated lateral acceleration calculation unit 41 and the estimated longitudinal and lateral acceleration calculation unit 42 from the steering angle θ and the accelerator opening Ac, and the actual acceleration of the vehicle 1 detected by the acceleration sensor 13. The slip ratio λ is an index value indicating the degree to which the tires of the vehicle 1 are slipping on the road surface. The larger the slip ratio λ, the better the tires are gripped by the road surface, and the smaller the slip ratio λ, the more the tires are slipping on the road surface.

[0029] For example, the slip ratio calculation unit 48 may calculate the longitudinal slip ratio λ1 = Gax / Gex as the division result of dividing the longitudinal acceleration Gax detected by the acceleration sensor 13 by the estimated longitudinal acceleration Gex. Also, the slip ratio calculation unit 48 may calculate the lateral slip ratio λ2 = Gay / Gey as the division result of dividing the lateral acceleration Gay detected by the acceleration sensor 13 by the estimated lateral acceleration Gey. The longitudinal slip ratio λ1 and the lateral slip ratio λ2 are examples of the "first slip ratio" and the "second slip ratio" described in the claims.

[0030] For example, the slip ratio calculation unit 48 may determine the slip ratio λ based on both the longitudinal slip ratio λ1 and the lateral slip ratio λ2. For example, the higher one of the longitudinal slip ratio λ1 and the lateral slip ratio λ2 may be selected, and the slip ratio λ may be determined to be the selected value. Also, for example, the lower one of the longitudinal slip ratio λ1 and the lateral slip ratio λ2 may be selected, and the slip ratio λ may be determined to be the selected value. Also, the average value or the weighted average value of the longitudinal slip ratio λ1 and the lateral slip ratio λ2 may be calculated as the slip ratio λ. Also, for example, the slip ratio calculation unit 48 may determine the slip ratio λ based on only one of the longitudinal slip ratio λ1 and the lateral slip ratio λ2.

[0031] For example, the slip ratio calculation unit 48 may include a delay element that delays the signals of the estimated longitudinal acceleration Gex and the estimated lateral acceleration Gey input from the estimated lateral acceleration calculation unit 41 and the estimated longitudinal and lateral acceleration calculation unit 42. The slip ratio calculation unit 48 may calculate the longitudinal slip ratio λ1 using the delayed estimated longitudinal acceleration Gex, and may calculate the lateral slip ratio λ2 using the delayed estimated lateral acceleration Gey. For example, the longitudinal slip ratio λ1 may be calculated by dividing the longitudinal acceleration Gax by the delayed estimated longitudinal acceleration Gex, and the longitudinal slip ratio λ1 and the lateral slip ratio λ2 may be calculated by dividing the lateral acceleration Gay by the delayed estimated lateral acceleration Gey.

[0032] The target driving force correction value calculation unit 49 calculates a target driving force correction value Fxc by correcting the target driving force Fxt calculated by the target driving force calculation unit 47 based on the slip ratio λ and the square root of the sum of squares Gxy. FIG. 4 is a block diagram of a functional configuration example of the target driving force correction value calculation unit 49. The target driving force correction value calculation unit 49 includes a conversion unit 50, subtractors 51 and 54, a gain setting unit 52, and a multiplier 53. The conversion unit 50 converts the driver required torque Td into a driving force Fxd generated on the wheel by dividing it by the tire radius. This driving force Fxd is equivalent to the sum of the front wheel required driving force FxdF and the rear wheel required driving force FxdR calculated by the driving force calculation unit 40.

[0033] The subtractor 51 calculates a difference (Fxd - Fxt) obtained by subtracting the target driving force Fxt from the driving force Fxd. The gain setting unit 52 sets an operation limit gain K, which is a gain for suppressing the limitation of the front wheel required driving force FxdF and the rear wheel required driving force FxdR by the target driving force calculation unit 47 based on the slip ratio λ and the square root of the sum of squares Gxy.

[0034] For example, the gain setting unit 52 may set a smaller operation limit gain K as the slip ratio λ is larger. Also, for example, the gain setting unit 52 may set a smaller operation limit gain K as the square root of the sum of squares Gxy is larger. FIG. 5 is a characteristic diagram of an example of the operation limit gain K. The operation limit gain K may be set to a value greater than or equal to a constant K0 of "0" or more and less than or equal to a constant K1 of "1" or less. The constants K0 and K1 may be, for example, "0" and "1", respectively.

[0035] Refer to FIG. 4. The multiplier 53 calculates the product K×(Fxd - Fxt) obtained by multiplying the difference (Fxd - Fxt) by the operation limit gain K. The subtractor 54 calculates the target driving force correction value Fxc = Fxd - K×(Fxd - Fxt) which is the difference obtained by subtracting the product K×(Fxd - Fxt) from the driving force Fxd. Therefore, the closer the operation limit gain K is to "0", the closer the target driving force correction value Fxc is to the driving force Fxd. That is, it approaches the sum of the front wheel required driving force FxdF and the rear wheel required driving force FxdR before being restricted by the target driving force calculation unit 47.

[0036] In other words, the closer the operation limit gain K is to "0", the more the target driving force Fxt is corrected so as to suppress the restriction by the target driving force calculation unit 47, and the target driving force correction value Fxc is output.

[0037] Therefore, the higher the slip ratio λ (the higher the road surface friction coefficient μ and the tire grips the road surface), the more the restriction by the target driving force calculation unit 47 is suppressed. Or, the higher the root mean square Gxy (that is, the higher the acceleration of the vehicle 1), the more the restriction by the target driving force calculation unit 47 is suppressed. For example, when the slip ratio λ is less than a predetermined value, the operation limit gain K may be set to "1", and when the slip ratio λ is greater than or equal to the predetermined value, it may be set to a value smaller than "1". Thereby, when the slip ratio λ is greater than or equal to the predetermined value, the restriction by the target driving force calculation unit 47 can be suppressed. For example, when selecting the higher one of the longitudinal slip ratio λ1 and the lateral slip ratio λ2 as the slip ratio λ, when either the longitudinal slip ratio λ1 or the lateral slip ratio λ2 is greater than or equal to the predetermined value, the restriction by the target driving force calculation unit 47 is suppressed.

[0038] Further, for example, when the lower one of the longitudinal slip ratio λ1 and the lateral slip ratio λ2 is selected as the slip ratio λ, the restriction by the target driving force calculation unit 47 is suppressed when both the longitudinal slip ratio λ1 and the lateral slip ratio λ2 are equal to or greater than a predetermined value. Note that as described above, the slip ratio λ is set based on the longitudinal acceleration Gax, the estimated longitudinal acceleration Gex, the lateral acceleration Gay, and the estimated lateral acceleration Gey. Therefore, based on the longitudinal acceleration Gax, the estimated longitudinal acceleration Gex, the lateral acceleration Gay, and the estimated lateral acceleration Gey, the restriction by the target driving force calculation unit 47 is suppressed.

[0039] On the other hand, the closer the operation restriction gain K is to "1", the closer the target driving force correction value Fxc is to the target driving force Fxt after the restriction by the target driving force calculation unit 47. That is, the closer the operation restriction gain K is to "1", the more effective the restriction by the target driving force calculation unit 47 becomes.

[0040] Therefore, the lower the slip ratio λ (the lower the road surface friction coefficient μ and the more the tire slips on the road surface), the more the target driving force correction value Fxc that reflects the suppression by the target driving force calculation unit 47 is output. Or, the higher the square root of the sum of squares Gxy (that is, the higher the acceleration of the vehicle 1), the more the target driving force correction value Fxc that reflects the suppression by the target driving force calculation unit 47 is output.

[0041] Referring to FIG. 2, the execution driving force calculation unit 31 of the power train controller 17 and the required driving force calculation unit 30 convert the driver required torque Td into a driving force generated on the wheels by dividing it by the tire radius. The execution driving force calculation unit 31 mediates the converted driving force and the target driving force correction value Fxc calculated by the target driving force correction value calculation unit 49, and sets the mediated target driving force Fxarb.

[0042] For example, the execution driving force calculation unit 31 may set the lower driving force among the driving force converted from the driver required torque Td and the target driving force correction value Fxc as the mediated target driving force Fxarb. The execution driving force calculation unit 31 calculates a target front-wheel driving force FxF and a target rear-wheel driving force FxR by distributing the arbitration target driving force Fxarb to the front wheels 2F and the rear wheels 2R based on a predetermined distribution method. The execution driving force calculation unit 31 drives and controls the drive source 18 so that the front wheels 2F and the rear wheels 2R generate the target front-wheel driving force FxF and the target rear-wheel driving force FxR.

[0043] (Operation) FIG. 6 is a flowchart of an example of the vehicle control method according to the embodiment. In step S1, the chassis controller 16 captures various parameters such as the steering angle θ, the vehicle speed Vh, the driver required torque Td, the longitudinal acceleration Gax, and the lateral acceleration Gay. In step S2, the estimated lateral acceleration calculation unit 41 calculates the estimated lateral acceleration Gey. The estimated longitudinal acceleration calculation unit 42 calculates the estimated longitudinal acceleration Gex.

[0044] In step S3, the wheel load estimation unit 43 estimates the wheel loads WFR, WFL, WRR, and WRL. In step S4, the lateral force calculation unit 45 calculates the tire lateral forces FyF and FyR acting on the front inner turning wheel 2FI and the rear inner turning wheel 2RI. The driving force calculation unit 40 calculates the front-wheel required driving force FxdF and the rear-wheel required driving force FxdR. In step S5, the square root of sum of squares calculation unit 44 calculates the square root of sum of squares Gxy.

[0045] In step S6, the friction circle estimation unit 46 estimates the maximum friction circles FyFL and FyRL of the front inner turning wheel 2FI and the rear inner turning wheel 2RI. In step S7, the target driving force calculation unit 47 calculates the target driving force Fxt by limiting the front-wheel required driving force FxdF and the rear-wheel required driving force FxdR based on the maximum friction circles FyFL and FyRL and the tire lateral forces FyF and FyR. In step S8, the slip ratio calculation unit 48 calculates the slip ratio λ.

[0046] In step S9, the gain setting unit 52 of the target driving force correction value calculation unit 49 sets the operation limit gain K. In step S10, the target driving force correction value calculation unit 49 corrects the target driving force Fxt so that the limitation by the target driving force calculation unit 47 is suppressed by the operation limit gain K, and calculates the target driving force correction value Fxc. In step S11, the execution driving force calculation unit 31 performs drive control on the drive source 18 so that the front wheels 2F and the rear wheels 2R generate the arbitration target driving force Fxarb obtained by arbitrating the driver required torque Td and the target driving force correction value Fxc.

[0047] (Effect of Embodiment) (1) In the vehicle control method, the longitudinal and lateral accelerations of the vehicle are detected by an acceleration sensor, the ground contact load acting on the wheels of the vehicle is estimated, the maximum friction circle of the wheels is estimated based on the ground contact load, the longitudinal and lateral accelerations, the tire lateral force acting on the wheels is estimated, and based on the maximum friction circle and the tire lateral force, the target tire longitudinal force, which is the target value of the tire longitudinal force generated in the wheels, is calculated, and the driving force of the vehicle is limited based on the target tire longitudinal force.

[0048] In this vehicle control method, the estimated longitudinal acceleration is calculated based on the accelerator opening of the vehicle, the estimated lateral acceleration is calculated based on the steering angle of the vehicle, and based on the longitudinal and lateral accelerations, the estimated longitudinal acceleration, and the estimated lateral acceleration, the limitation of the driving force of the vehicle based on the target tire longitudinal force is suppressed. As a result, it is possible to limit or suppress the limitation of the driving force of the vehicle according to the grip state of the tire. As a result, it is possible to realize driving force control that achieves both acceleration performance on a high μ road and line tracing performance on a low μ road.

[0049] (2) Based on the longitudinal acceleration and the estimated longitudinal acceleration, calculate a first slip ratio which is the slip ratio of the vehicle in the longitudinal direction, and based on the lateral acceleration and the estimated lateral acceleration, calculate a second slip ratio which is the slip ratio of the vehicle in the lateral direction. Based on the first slip ratio and the second slip ratio, it is possible to suppress the limitation of the driving force of the vehicle based on the target tire longitudinal force. Thereby, it is possible to limit or suppress the limitation of the driving force of the vehicle based on the slip ratio of the vehicle in the longitudinal direction and the slip ratio of the vehicle in the lateral direction.

[0050] (3) When one of the first slip ratio or the second slip ratio is equal to or greater than a predetermined value, it is possible to suppress the limitation of the driving force of the vehicle based on the target tire longitudinal force. Also, when both the first slip ratio and the second slip ratio are equal to or greater than a predetermined value, it is possible to suppress the limitation of the driving force of the vehicle based on the target tire longitudinal force. Thereby, when the road surface friction coefficient is high and the tire is in a gripping state, the limitation of the driving force of the vehicle can be suppressed and the acceleration performance can be prioritized.

[0051] (4) The first slip ratio may be calculated based on the estimated longitudinal acceleration subjected to delay processing. Also, the second slip ratio may be calculated based on the estimated lateral acceleration subjected to delay processing. Thereby, it is possible to suppress the error caused by the delay of the estimated longitudinal acceleration and the estimated lateral acceleration detected by the sensor with respect to the longitudinal acceleration and the lateral acceleration calculated based on the accelerator opening and the steering angle.

[0052] (5) Based on the sum of the squares of the longitudinal acceleration and the lateral acceleration, it is possible to suppress the limitation of the driving force of the vehicle based on the target tire longitudinal force. For example, when the sum of the squares is equal to or greater than a predetermined value, it is possible to suppress the limitation of the driving force of the vehicle based on the target tire longitudinal force. Thereby, it is possible to estimate the gripping state of the tire based on the estimated longitudinal acceleration and the estimated lateral acceleration detected by the sensor, and limit or suppress the limitation of the driving force of the vehicle.

Explanation of Signs

[0053] 1…Vehicle, 2F…Front wheels, 2FL…Left front wheel, 2FR…Right front wheel, 2R…Rear wheels, 2RL…Left rear wheel, 2RR…Right rear wheel, 10…Vehicle control device, 11…Steering angle sensor, 12…Vehicle speed sensor, 13…Acceleration sensor, 15…Accelerator opening sensor, 16…Chassis controller, 16a, 17a…Processor, 16b, 17b…Memory device, 17…Power train controller, 18…Drive source, 30…Required driving force calculation unit, 31…Execution driving force calculation unit, 40…Driving force calculation unit, 41…Estimated lateral acceleration calculation unit, 42…Estimated longitudinal acceleration calculation unit, 43…Wheel load estimation unit, 44…Square root of sum of squares calculation unit, 45…Lateral force calculation unit, 46…Friction circle estimation unit, 47…Target driving force calculation unit, 48…Slip ratio calculation unit, 49…Target driving force correction value calculation unit, 50…Converter, 51, 54…Subtractor, 52…Gain setting unit, 53…Multiplier

Claims

1. Detecting the longitudinal acceleration and lateral acceleration of a vehicle using an acceleration sensor, estimating the ground load acting on the wheels of the vehicle, estimating the maximum friction circle of the wheel based on the ground load, the longitudinal acceleration, and the lateral acceleration, estimating the tire lateral force acting on the wheel, calculating a target tire longitudinal force, which is a target value of the tire longitudinal force to be generated on the wheel, based on the maximum friction circle and the tire lateral force, A vehicle control method for limiting the driving force of the vehicle based on the target tire longitudinal force, calculating an estimated longitudinal acceleration based on the accelerator opening of the vehicle, calculating an estimated lateral acceleration based on the steering angle of the vehicle, suppressing the limitation of the driving force of the vehicle based on the target tire longitudinal force based on the longitudinal acceleration, the lateral acceleration, the estimated longitudinal acceleration, and the estimated lateral acceleration, The vehicle control method is characterized by the above.

2. Calculating a first slip ratio, which is the slip ratio of the vehicle in the longitudinal direction, based on the longitudinal acceleration and the estimated longitudinal acceleration, Calculating a second slip ratio, which is the slip ratio of the vehicle in the lateral direction, based on the lateral acceleration and the estimated lateral acceleration, Suppressing the limitation of the driving force of the vehicle based on the target tire longitudinal force based on the first slip ratio and the second slip ratio, The vehicle control method according to claim 1, characterized by the above.

3. The vehicle control method according to claim 2, characterized in that when one of the first slip ratio or the second slip ratio is equal to or greater than a predetermined value, the limitation of the driving force of the vehicle based on the target tire longitudinal force is suppressed.

4. The vehicle control method according to claim 2, characterized in that when both the first slip ratio and the second slip ratio are equal to or greater than a predetermined value, the limitation of the driving force of the vehicle based on the target tire longitudinal force is suppressed.

5. The vehicle control method according to claim 2, characterized in that the first slip ratio is calculated based on the estimated longitudinal acceleration subjected to delay processing.

6. The vehicle control method according to claim 2, characterized in that the second slip ratio is calculated based on the estimated lateral acceleration subjected to delay processing.

7. The vehicle control method according to claim 2, characterized in that the limitation of the driving force of the vehicle based on the target tire longitudinal force is suppressed based on the sum of the squares of the longitudinal acceleration and the lateral acceleration.

8. The vehicle control method according to claim 7, characterized in that when the sum of the squares is equal to or greater than a predetermined value, the limitation of the driving force of the vehicle based on the target tire longitudinal force is suppressed.

9. An acceleration sensor that detects the longitudinal acceleration and lateral acceleration of a vehicle, a process of estimating the ground load acting on the wheels of the vehicle, a process of estimating the maximum friction circle of the wheels based on the ground load, the longitudinal acceleration, and the lateral acceleration, a process of estimating the tire lateral force acting on the wheels, and a process of calculating a target tire longitudinal force, which is a target value of the tire longitudinal force to be generated in the wheels, based on the maximum friction circle and the tire lateral force, and a process of limiting the driving force of the vehicle based on the target tire longitudinal force, and a vehicle control device comprising: the controller calculates an estimated longitudinal acceleration based on the accelerator opening of the vehicle, calculates an estimated lateral acceleration based on the steering angle of the vehicle, and suppresses the limitation of the driving force of the vehicle based on the target tire longitudinal force based on the longitudinal acceleration, the lateral acceleration, the estimated longitudinal acceleration, and the estimated lateral acceleration. A vehicle control device characterized by that.

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