JP2008167640A - Vehicle control device and driving system for electric vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vehicle control device and a driving system for an electric vehicle capable of controlling the optimum driving force, according to the operating conditions for each vehicle, in the electric vehicle that drives each wheel by a separate and independent electric motor. <P>SOLUTION: The vehicle control device 100 has a driving force calculating unit 129 that calculates a forward and backward control forth F<SB>Xi</SB>', (driving force of each wheel) that should be controlled with respect to each wheel; and an electric motor controller 131 that controls a current value i, supplied to in-wheel motors 30FL, 30FR, 30RL and 30RR, based on a calculated backward and forward control force F<SB>Xi</SB>', of each wheel (driving force), by using a difference F<SB>ex</SB>in the actual backward and forward force F<SP>Λ</SP><SB>X</SB>and a target backward and forward force F<SP>*</SP><SB>X</SB>of the electric vehicle; a lateral force difference F<SB>eY</SB>in an actual lateral force F<SP>Λ</SP><SB>Y</SB>and a target vehicle lateral force F<SP>*</SP><SB>Y</SB>; a difference M<SB>eZ</SB>in an actual yaw moment M<SP>Λ</SP><SB>Z</SB>and a target yaw moment M<SP>*</SP><SB>Z</SB>; and a tire operation availability η<SB>i</SB>in each wheel, determined on the basis of a grounding load in each wheel, with respect to the actual backward and forward force F<SP>Λ</SP><SB>X</SB>and the actual lateral force F<SP>Λ</SP><SB>Y</SB>of the wheel. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a vehicle control device and a drive system for controlling the behavior of an electric vehicle, and more particularly to a vehicle control device for an electric vehicle in which each wheel is driven by an independent electric motor, and a drive system for an electric vehicle.

2. Description of the Related Art Conventionally, so-called direct yaw moment control (DYC) that directly generates a yaw moment using a difference in driving force or braking force between left and right wheels has been known (for example, Patent Document 1). In general DYC, when the driving force of each wheel is controlled, the output of the internal combustion engine that generates the driving force is controlled according to the ground load (F _zi ) of each wheel.
Japanese Patent Laying-Open No. 2003-159966 (page 4-9)

In recent years, research and development have been conducted on electric vehicles in which each wheel is driven by an independent electric motor. When the above-described conventional DYC is applied to such an electric vehicle, there are the following problems. That is, in the conventional DYC, the output of the internal combustion engine that generates the driving force is controlled according to the ground contact load (F _zi ) of each wheel. I can't.

  In other words, since the operating state of each wheel, specifically, the pneumatic tire, differs depending on the road surface state (for example, split road surface), etc., it is possible to control the optimum driving force according to the operating state of each wheel. There is a problem that can not be.

  Therefore, the present invention has been made in view of such a situation, and in an electric vehicle in which each wheel is driven by an independent electric motor, the optimum driving force according to the operating state of each wheel is controlled. An object of the present invention is to provide a vehicle control device for an electric vehicle and a drive system for the electric vehicle.

In order to solve the above-described problems, the present invention has the following features. First, the first feature of the present invention is that an electric vehicle (electric automobile 4) that drives each wheel (wheels 20FL, 20FR, 20RL, 20RR) by an independent electric motor (in-wheel motors 30FL, 30FR, 30RL, 30RR). A wheel control device (vehicle control device 100) for the wheel 10), the slip ratio of the wheels (the slip ratio K _{i of} each wheel), and the longitudinal force generated in the wheels (the longitudinal force F _{xi of} each wheel); Based on the tire data (tire data TD) indicating the relationship with the lateral force (lateral force F _{yi of} each wheel), the actual longitudinal force (F _Xi ) generated on each wheel and the sum (F ^{^} _X ) Based on the tire data, the actual lateral force (F _Yi ) generated on each wheel and the sum (F ^{^} _Y ) are calculated based on the tire data. The actual yaw moment (actual yaw moment M generated in the electric vehicle) from the calculation results of the actual lateral force calculation unit (driving force calculation unit 129), the actual longitudinal force calculation unit and the actual lateral force calculation unit. ^{^} _Z ) is calculated based on the yaw moment calculation unit (yaw moment calculation unit 125), the steering angle (steering angle δ) of the electric vehicle, and the vehicle speed. Based on the target longitudinal force calculation unit (driving force calculation unit 129) for calculating the target vehicle longitudinal force (F ^* _X ) and the steering angle and vehicle speed of the electric vehicle, the electric vehicle has the desired steering characteristics. From the calculation results of the target lateral force calculation unit (driving force calculation unit 129) that calculates the target vehicle lateral force (F ^* _Y ) of the electric vehicle, the target longitudinal force calculation unit, and the target lateral force calculation unit, Automatic Target yaw moment calculation unit for calculating a target yaw moment (the target yaw moment M ^{* _Z)} and (target yaw moment calculation unit 123), wherein the sum of the actual longitudinal force calculated by the actual longitudinal force computing unit the target longitudinal The difference (F _eX ) from the target vehicle longitudinal force calculated by the force calculation unit, the total of the actual lateral force calculated by the actual lateral force calculation unit, and the target vehicle calculated by the target lateral force calculation unit The difference from the lateral force (F _eY ), the difference between the actual yaw moment calculated by the yaw moment calculator and the target yaw moment calculated by the target yaw moment calculator (M _eZ ), and Tire gain determined based on the ground contact load (ground contact load F _Zi ) of each wheel against the actual longitudinal force (F _Xi ) and actual lateral force (F _Yi ) being generated. Control front / rear force calculation unit (driving force calculation) that calculates the control front / rear force to be controlled for each wheel (control front / rear force F _Xi ′ of each wheel) using the duty factor (tire operation rate η _{i of} each wheel) 129) and an electric motor control unit (electric motor control unit 131) for controlling a current value (current value i) supplied to the electric motor based on the control longitudinal force calculated by the control longitudinal force calculation unit. It is a summary to provide.

  According to such a vehicle control apparatus for an electric vehicle, the difference between the total sum of the actual longitudinal forces and the target vehicle longitudinal force, the difference between the sum of the actual lateral forces and the target both side forces, the actual yaw moment and the target yaw moment The control longitudinal force to be controlled for each wheel is calculated using the tire operating rate determined based on the difference between the actual front / rear force generated on each wheel and the ground contact load of each wheel against the actual lateral force. Is done.

  The tire operating rate is determined based on a friction circle that can be obtained by the resultant force of the actual longitudinal force and the actual lateral force. That is, according to such a vehicle control device for an electric vehicle, realistic vehicle control in consideration of the grip force of the wheels (pneumatic tire) can be realized. In the conventional vehicle control device, the control longitudinal force to be controlled is determined without considering the tire operation rate, so the longitudinal force that is actually outside the friction circle is determined, and effective vehicle control is performed. There was a problem that it could not be executed.

  That is, according to such a vehicle control device for an electric vehicle, in an electric vehicle in which each wheel is driven by an independent electric motor, it is possible to control the optimum driving force according to the operating state of each wheel.

  A second feature of the present invention relates to the first feature of the present invention, wherein the tire operating rate is a ratio of a total of actual longitudinal force and actual lateral force of each wheel and a ground load of each wheel. It is a summary.

であることを要旨とする。 The third feature of the present invention relates to the first feature of the present invention, wherein the tire operating rate η _i of each wheel is the actual longitudinal force of each wheel F _xi and the actual lateral force of each wheel is F _yi , when the ground contact load of each wheel is F _zi , and the friction coefficient of the road surface on which each wheel rolls is μ _i ,

It is a summary.

  A fourth feature of the present invention is an electric vehicle drive system for driving an electric vehicle, comprising: an electric motor that individually drives each wheel; and a vehicle control device that controls the behavior of the electric vehicle, The vehicle control device calculates an actual longitudinal force generated on each wheel based on tire slip data indicating a slip ratio of the wheel and a relationship between a longitudinal force and a lateral force generated on the wheel. From the calculation results of the calculation unit, the actual lateral force calculation unit that calculates the actual lateral force generated in each wheel based on the tire data, the actual longitudinal force calculation unit, and the actual lateral force calculation unit A target yaw moment calculation unit for calculating an actual yaw moment generated in the electric vehicle, and a target vehicle of the electric vehicle having a desired steering characteristic based on a steering angle and a vehicle speed of the electric vehicle. A target lateral force calculation unit that calculates a target vehicle lateral force of the electric vehicle that has the desired steering characteristics based on a steering angle and a vehicle speed of the electric vehicle, and a target longitudinal force calculation unit that calculates a longitudinal force A target yaw moment calculator that calculates a target yaw moment of the electric vehicle, and the actual longitudinal force calculator that calculates the target yaw moment from the calculation results of the target longitudinal force calculator and the target lateral force calculator. The difference between the actual longitudinal force and the target vehicle longitudinal force calculated by the target longitudinal force calculator, the actual yaw moment calculated by the yaw moment calculator and the target yaw moment calculated by the target yaw moment calculator Tire operating rate determined on the basis of the contact load of each wheel with respect to the difference between the actual front / rear force and actual lateral force generated on each wheel. A control longitudinal force calculation unit for calculating a control longitudinal force to be controlled for each wheel, and a current value supplied to the electric motor based on the control longitudinal force calculated by the control longitudinal force calculation unit And an electric motor control unit for controlling the operation.

  A fifth feature of the present invention relates to the fourth feature of the present invention, wherein the tire operating rate is a ratio of a total of the actual longitudinal force and actual lateral force of each wheel and a ground load of each wheel. It is a summary.

であることを要旨とする。 A sixth feature of the present invention relates to the fourth feature of the present invention, wherein the tire operating rate η _i of each wheel is the actual longitudinal force of each wheel F _xi and the actual lateral force of each wheel is F _yi , when the ground contact load of each wheel is F _zi , and the friction coefficient of the road surface on which each wheel rolls is μ _i ,

It is a summary.

  According to the features of the present invention, in an electric vehicle in which each wheel is driven by an independent electric motor, the vehicle control device for the electric vehicle capable of controlling the optimum driving force according to the operating state of each wheel, and the electric An automobile drive system can be provided.

  Next, an embodiment of an electric vehicle drive system according to the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic and ratios of dimensions are different from actual ones.

  Accordingly, specific dimensions and the like should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

(Overall schematic configuration of electric automobile)
FIG. 1 is a schematic perspective view of an electric automobile 10 according to the present embodiment. The electric automobile 10 includes electric motors, so-called in-wheel motors, inside the wheels 20FL, 20FR, 20RL, and 20RR. In other words, the electric automobile 10 drives each wheel (wheels 20FL, 20FR, 20RL, 20RR) by the independent in-wheel motors 30FL, 30FR, 30RL, 30RR.

  In addition, the electric automobile 10 includes a vehicle control device 100. The vehicle control device 100 uses the difference between the driving force or braking force of the left and right wheels (hereinafter, the driving force and the braking force may be collectively referred to as “braking / driving force” or “front / rear force”). The behavior of the electric automobile 4 is controlled by so-called direct yaw moment control (DYC) that generates a direct yaw moment. A sensor unit 110 that detects various states (for example, steering angle) of the electric automobile 10 is connected to the vehicle control device 100.

  In the present embodiment, the vehicle control device 100 and the in-wheel motors 30FL, 30FR, 30RL, 30RR provided inside each wheel constitute a drive system for an electric automobile.

(Functional block configuration of electric automobile drive system)
FIG. 2 is a functional block configuration diagram of the drive system for the electric automobile according to the present embodiment. As described above, the vehicle control apparatus 100 and the in-wheel motors 30FL, 30FR, 30RL, and 30RR provided inside each wheel constitute a drive system for an electric automobile.

  The vehicle control device 100 includes a feedforward moment calculator 121, a target yaw moment calculator 123, a yaw moment calculator 125, a PID controller 127, a driving force calculator 129, and an electric motor controller 131.

  In the present embodiment, the target yaw moment calculator 123 uses a two-wheel model as the target model. Further, in the calculation of the driving force in the driving force calculation unit 129, so-called “optimal control” is adopted.

Specifically, the driving force computing unit 129 determines the correction amount [delta] _K to minimize a predetermined evaluation function. In the present embodiment, distribution errors of the vehicle yaw moment (M), the vehicle lateral force (F _Y ), the vehicle longitudinal force (F _X ), the tire slip rate (K), and the tire operation rate (η) are used. The details of the driving force control by the vehicle control device 100 will be described later.

  The sensor unit 110 includes a steering angle sensor 111, a vehicle speed sensor 113, a yaw rate sensor 115, and an acceleration sensor 117.

  The steering angle sensor 111 detects the steering angles of the front wheels of the electric four-wheeled vehicle 10, specifically, the wheels 20FL and 20FR. This steering angle can also be detected by calculating the steering angle by dividing the steering angle by the steering gear ratio. The vehicle speed sensor 113 detects the vehicle speed of the electric automobile 4.

The yaw rate sensor 115 detects the yaw rate in the electric automobile 10 (see FIG. 3). The acceleration sensor 117 measures the acceleration (acceleration a _X ) in the front-rear direction (x direction in FIG. 3) and the acceleration (acceleration a _Y ) in the lateral direction (y direction in FIG. 3) occurring in the electric automobile 10. To detect.

  Next, each functional block which comprises the vehicle control apparatus 100 is demonstrated with reference to FIGS.

(1) Feed forward moment calculation unit 121
Feedforward moment calculation unit 121 calculates the feedforward compensation yaw moment _{M FF.} Specifically, the feedforward moment calculation unit 121, based on the steering angle δ and the vehicle speed V outputted from the sensor unit 110, calculates a feed-forward compensation yaw moment M _FF.

First, the yaw rate γ of the electric automobile 10 will be described prior to the description of a specific calculation method in the feedforward moment calculation unit 121. In the electric automobile 10, the yaw rate γ can be expressed as (Expression 1).

  FIG. 3 schematically shows the electric automobile 10 as a four-wheel model having degrees of freedom in three directions (x direction, y direction, and rotation direction) (that is, rolling is not considered). ). As shown in FIG. 3, δ in (Expression 1) is an actual steering angle. In the present embodiment, the steering angle is detected, and this is divided by the steering gear ratio, and the actual steering angle detected by calculation is used. Further, l (lf + lr) is a wheel base, m is a vehicle mass, kf is a cornering power of a front wheel, and kr is a cornering power of a rear wheel.

In the present embodiment, the vehicle control device 100 uses DYC to control the braking / driving force (front / rear force) of each wheel so that the steering characteristic of the electric four-wheeled vehicle 10 is neutral steer. From (Equation 1), the yaw rate γ _NS during neutral steering can be expressed as (Equation 2).

Here, Δγ is an increase / decrease amount of the yaw rate necessary for setting the steering characteristic of the electric automobile 10 to neutral steer. Next, the stability factor K of the electric automobile 10 and the yaw rate γ (0) with respect to the input to the vehicle control device 100 (DYC) can be expressed as (Expression 3).

ここで、Ｇ_ｆｆ（Ｖ）は、フィードフォワードゲインである。 Further, from (Expression 2) and (Expression 3), the feedforward compensation yaw moment M _FF necessary for setting the steering characteristic of the electric automobile 10 to neutral steering can be expressed as (Expression 4). it can.

Here, G _ff (V) is a feed forward gain.

(2) Target yaw moment calculation unit 123
Target yaw moment calculation unit 123 calculates a target yaw moment _{M d.} Specifically, the target yaw moment calculation unit 123, based on the steering angle δ and the vehicle speed V outputted from the sensor unit 110 computes a target yaw moment M _d. Target yaw moment M _d may be expressed as (equation 5) and (5 'type).

Here, the lateral force Yf is a lateral force (cornering force) generated on the front wheels (wheels 20FL and 20FR). Further, the lateral force Yr is a lateral force (cornering force) generated in the rear wheels (wheel 20RL and wheel 20RR). Further, the relationship among the yaw rate γ _NS , the slip angle β _NS at the time of neutral steering, and the steering angle δ can be expressed as (Expression 6).

Therefore, (5 ′ equation) can be transformed into (7 equation).

  Here, Gd (V) is a target yaw moment gain. Furthermore, in this embodiment, kf = lr / lf · kr is substituted.

(3) Yaw moment calculation unit 125 and PID controller 127
The yaw moment calculator 125 calculates the yaw moment of the electric automobile 10 used for controlling the behavior of the electric automobile 10. Specifically, the yaw moment calculating unit 125 calculates the yaw moment of the electric automobile 4 based on the steering angle δ, the vehicle speed V, the yaw rate γ, the acceleration a _X, and the acceleration a _Y output from the sensor unit 110. Calculate.

Also, PID controller 127 is a controller for feedback yaw moment calculated by the target yaw moment M _d and the yaw moment calculating section 125 calculated by the target yaw moment calculation unit 123.

The PID controller 127 (feedback compensator) feeds back the yaw moment so that there is no error with the target model used in the target yaw moment calculator 123. Specifically, the PID controller 127 operates based on (Equation 8).

Here, M _FB is a feedback yaw moment, and M is a yaw moment generated in the electric automobile 10 to be controlled. Also, _{K P} is a proportional gain, _{K I} is an integral gain, _{K D} is the derivative gain. Furthermore, (Equation 9) is established.

M _E is the yaw moment error. In this embodiment, the yaw moment error M _E, electric four-wheeled vehicle 10 is a yaw moment M _DYC should be controlled in order to become a neutral steering.

As shown in FIG. 3, when the electric automobile 10 is a four-wheel model having degrees of freedom in three directions (x direction, y direction, and rotation direction), (Equation 10) is established.

F _xfl , F _xfr , F _xrl and F _xrr are front and rear forces (front and rear forces F _xi ) of the respective wheels. F _yfl , F _yfr , F _yrl and F _yrr are lateral forces (lateral forces F _yi ) of each wheel. I is the moment of inertia of the electric automobile 10 in the yaw direction. d is the tread width of the electric automobile 10. U and ν are velocity components in the x and y directions (see FIG. 3).

Next, the friction circles of the pneumatic tires constituting the wheels 20FL, 20FR, 20RL, and 20RR can be expressed as (Expression 11).

Here, if r (friction circle radius) or a and b (width and height of the friction ellipse) are known, the longitudinal force F _xi and lateral force F _yi of each wheel can be calculated. Further, the vertical direction is taken into consideration, the ground contact load F _Z can be expressed as (Expression 12).

From (Expression 11) and (Expression 12), (1) r or a, b of each wheel, (2) longitudinal force initial value F _XOi , lateral force initial value F _{YOi of} each wheel, (3) inclination of each wheel If the coefficient α (coefficient determined according to the slope of the curve indicating the friction coefficient μ vs. the slip ratio λ characteristic) is known, the longitudinal force F _xi and lateral force F _yi of the wheels 20FL, 20FR, 20RL, 20RR can be calculated. .

In the present embodiment, data based on the magic formula (MF) is used as the tire data TD in order to obtain the longitudinal force _Fxi and the lateral force _Fyi of each wheel described above.

  Next, a change in the vertical load (Wx, Wy) accompanying the traveling of the electric automobile 10 will be considered. FIG. 4 is an explanatory diagram for explaining a change in the vertical load in the vehicle front-rear direction accompanying the acceleration / deceleration of the electric automobile 10. FIG. 5 is an explanatory diagram for explaining a change in the vertical load in the vehicle width direction accompanying cornering of the electric automobile 10.

The change in the vertical load during acceleration / deceleration of the electric automobile 10 can be expressed as (13).

Further, the change in vertical load during cornering of the electric automobile 10 can be expressed as (14).

Here, H is the height from the road surface to the center of gravity point CG. Thus, by measuring the acceleration a _Y of the acceleration a _X and transverse the longitudinal direction, by (14 'equation), the vertical load of each wheel, i.e., it is possible to determine the vertical load F _Z.

Here, _FZ0i is the vertical load in the 1G (static) state of each wheel. Next, considering the longitudinal force F _xi , since the electric automobile 10 uses an electric motor (in-wheel motor), the longitudinal force F _xi can be expressed as a general expression (Expression 15). .

Here, K _M is the torque constant, i is a current value. If the electric motor is a first-order lag system in consideration of dynamic characteristics, it can be expressed as (15 ′ equation).

Here, τ is a time constant, and F _x0 is a static torque.

Note that the friction coefficient μ of the road surface on which the wheels 20FL, 20FR, 20RL, 20RR (specifically, pneumatic tires) roll is estimated based on (Expression 17). Further, the front-rear direction component of the friction coefficient μ, that is, the front-rear direction friction coefficient μ _x, and the lateral direction component of the friction coefficient μ, that is, the lateral friction coefficient μ _y are expressed by (17 ′), (17 ″) (Equation) and (17 ′ ″ equation).

Here, Fμ is the frictional force between the road surface and the pneumatic tire. As shown in (Equation 17), if the longitudinal force F _x and the ground contact load F _Z are known, the longitudinal friction coefficient μ _x can be estimated. The lateral friction coefficient μ _y can be calculated from (17 ″) using the actual lateral force F _yi of each wheel calculated from the tire data. Therefore, the friction coefficient μ can be estimated from (Expression 17 ′ ″). That is, acceleration can be detected using the torque of an electric motor (in-wheel motor). Further, the deceleration can be detected using the deceleration torque calculated based on the hydraulic pressure of the braking device of the electric automobile 10. In the present embodiment, the friction coefficient μ is a fixed value.

(4) Driving force calculation unit 129
The driving force calculator 129 calculates the braking / driving force (front / rear force) by the in-wheel motors 30FL, 30FR, 30RL, 30RR. Specifically, the driving force calculation unit 129 calculates the braking / driving force by optimally controlling a predetermined evaluation function.

In the present embodiment, the driving force calculation unit 129 uses the evaluation function L for optimal control as described above. The evaluation function L can be expressed as (18).

Further, the tire operation rate η _i of each wheel can be expressed as (Equation 19).

In this embodiment, the tire operation rate η is averaged between the left and right front and rear wheels. Therefore, in the control, the tire operating rates η _fl , η _fr , η _rl , and η _rr of the left and right front and rear wheels are calculated, respectively, and the average value of the tire operating rates of the front two wheels and the rear two wheels and the wheels From the tire operation rates η _fl , η _fr , η _rl , and η _rr , tire operation rate errors η _efl , η _efr , η _erl , and η _err of each wheel were defined as shown in (19 ′).

Here, it is considered that the evaluation function L is minimized. Here, E on the right-hand side of the evaluation function L (Equation 18) is the target vehicle longitudinal / lateral force, yaw moment, and tire operating rate, and the actual longitudinal / lateral force, yaw generated from the tire of each allocated wheel. This is a distribution error between the moment and the tire operating rate. Compared to the conventional control, the actual vehicle longitudinal and lateral forces follow the target vehicle longitudinal and lateral forces in addition to the yaw moment, and the tire operating rate The characteristic is that the control is performed so as to average the two wheels. This distribution error E can be expressed as (Equation 20).

Here, in (Expression 20), F ^* _X is the target vehicle longitudinal force, F ^* _Y is the target vehicle lateral force, and M ^* _Z is the target yaw moment. Further, F ^{^} _X is the total actual longitudinal force F _Xi distributed and distributed to each wheel, and F ^{^} _Y is the total actual lateral force _FYi generated on each wheel. An actual lateral force M ^{^} _Z of a vehicle is an actual yaw moment of the vehicle. Further, F _eX is a vehicle front-rear force distribution error, F _eY is a vehicle lateral force distribution error, and M _eZ is a vehicle yaw moment distribution error. Incidentally, the correction amount of the correction amount [delta] _K is the slip ratio K in (18 type). The correction amount [delta] _K, each wheel slip ratio correction amount _{δ Kfl, δ Kfr, δ Krl} , the floor function of [delta] _Krr, can be expressed as (21 type).

_{Further, W} E, W _.delta.K is a weight function for the distribution error E and the slip ratio correction amount [delta] _K, respectively (22 type), it can be expressed as (23 type).

Further, the tire operation rate η _i (η _fl , η _fr , η _rl , η _rr ), the vehicle longitudinal force F _X , the lateral force F _Y, and the yaw moment M _Z allocated to each wheel are generated in each wheel. The actual longitudinal force F _Xi (F _Xfl , F _Xfr , F _Xrl , F _Xrr ), the actual lateral force F _Yi (F _Yfl , F _Yfr , F _Yrl , F _Yrr ), the actual yaw moment M ^{^} _Z , and the actual tire The availability factor η ^{^} _i (η ^{^} _fl , η ^{^} _fr , η ^{^} _rl , η ^{^} _rr ) and the Jacobian J shown in (24) can be expressed as (25).

Here, M _dyc is a yaw moment by vehicle control. From the above, the slip ratio correction amount δ _K for minimizing the evaluation function L is given by satisfying (Equation 26).

Accordingly, the slip ratio correction amount [delta] _K can be expressed as (27 type).

Here, _ΔE in (Equation 27) is the distribution error η _efl , η _efr , η _erl , η _err of the tire operating rate of each wheel, the distribution error F _{eX of} the vehicle longitudinal force, and the lateral force of the vehicle By a floor function of the distribution error F _eY and the distribution error M _eZ of the yaw moment of the vehicle, it can be expressed as (Equation 28).

The driving force calculation unit 129 determines the braking / driving force to be distributed to the wheels 20FL, 20FR, 20RL, and 20RR based on the calculation results using (Expression 27) and (Expression 28). Specifically, the driving force calculation unit 129 calculates from the correction amount δ _K of the slip ratio K _i calculated by (Expression 27) and (Expression 28) to minimize the evaluation function L for each wheel. Based on the tire data TD of each wheel, a control longitudinal force F _xi ′ (driving force) to be controlled by each wheel is calculated and output as a torque command value. Note that F ^* _Y and F _Ye may not be used.

That is, the driving force calculation unit 129 generates each wheel based on the slip ratio K _i of each wheel and the tire data TD indicating the relationship between the longitudinal force F _xi and the lateral force F _yi generated on each wheel. calculating real and longitudinal force F ^{^} _X of the vehicle is the sum of the actual longitudinal force F _Xi, the actual lateral force F ^{^} _Y of the vehicle is the sum of the actual lateral force F _Yi are inflicting on each wheel. The driving force calculation unit 129 calculates the slip ratio K _i of each wheel based on the rotational speed of the wheel and the vehicle speed V of the electric four-wheeled vehicle 10. In the present embodiment, the driving force calculation unit 129 constitutes an actual longitudinal force calculation unit.

Further, the driving force calculation unit 129, based on the steering angle δ and the vehicle speed V of the electric four-wheeled vehicle 10, the target vehicle longitudinal force F ^{* of the} electric four-wheeled vehicle 10 in which the electric four-wheeled vehicle 10 becomes neutral steer ^. _X and the target vehicle lateral force F ^* _Y are calculated. In the present embodiment, the driving force calculation unit 129 constitutes a target longitudinal force calculation unit.

The driving force calculation unit 129 also calculates the longitudinal force error F _eX between the calculated actual vehicle longitudinal force F ^{^} _X and the target vehicle longitudinal force F ^* _X , the calculated vehicle actual lateral force F ^{^} _Y, and the target vehicle lateral force. F ^* _Y lateral force error F _eY , vehicle actual yaw moment M ^{^} _Z and target yaw moment M ^* _Z error M _eZ , and actual longitudinal force F ^{^} _X and actual lateral force generated on each wheel Using the tire operating rate η _i of each wheel determined based on the ground contact load F _Zi of F ^{^} _{Y, the} control longitudinal force F _Xi ′ (driving force of each wheel) to be controlled for each wheel is calculated. Calculate. In the present embodiment, the driving force calculation unit 129 constitutes a control longitudinal force calculation unit.

The electric motor control unit 131 calculates the current value i supplied to the in-wheel motors 30FL, 30FR, 30RL, 30RR based on the control longitudinal force F _Xi ′ (driving force) of each wheel calculated by the driving force calculation unit 129. Control.

(Overview of operation of the drive system for electric automobiles)
Next, an outline of the operation of the vehicle control device 100 described above will be described. FIG. 6 is a control operation flow of braking / driving force (front / rear force) by the vehicle control device 100.

As shown in FIG. 6, in step S10, the vehicle control device 100 determines that the vehicle actual longitudinal force F ^{^} is the sum of the actual longitudinal forces F _Xi generated in the wheels (wheels 20FL, 20FR, 20RL, 20RR). _X and the actual lateral force F ^{^} _Y of the vehicle, which is the sum of the actual lateral forces _FYi generated on each wheel, are calculated. Specifically, the vehicle control device 100 is generated at each wheel based on the slip ratio K _i of each wheel and the tire data TD indicating the relationship between the longitudinal force F _xi and the lateral force F _yi generated at each wheel. and the actual longitudinal force F ^{^} _X of the vehicle is the actual longitudinal force F _Xi and the sum is made to, the actual lateral force F ^{^} _Y of the vehicle is the actual lateral force F _Yi and the sum is causing the wheels Calculate.

In step S20, the vehicle control apparatus 100 calculates the target vehicle longitudinal force F ^* _X and the target vehicle lateral force F ^* _Y of the electric four-wheel vehicle 10 in which the electric four-wheel vehicle 10 becomes neutral steer. Specifically, the vehicle control apparatus 100 uses the above-described (10 formula), (27 formula), and (28 formula) to calculate the target vehicle longitudinal force F ^* _{X at} which the electric four-wheel vehicle 10 becomes neutral steer. The target vehicle lateral force F ^* _Y is calculated.

In step S30, the vehicle control device 100 performs the actual longitudinal force F ^{^} _X and actual lateral force F ^{^} _Y calculated in step S10, and the target vehicle longitudinal force F ^* _X and target vehicle lateral force F calculated in step S20. ^{* Using} _Y and the tire operation rate η _{i of} each wheel, a control longitudinal force F _xi ′ (driving force of each wheel) to be controlled for each wheel is calculated.

Specifically, the vehicle control apparatus 100 includes the actual longitudinal force F ^{^} _X , the actual lateral force F ^{^} _Y , the actual yaw moment M ^{^} _Z , the target vehicle longitudinal force F ^* _X , and the target vehicle lateral force F ^* _Y. , Distribution errors F _eXi , F _eY , M _eZ with target yaw moment M ^* _Z , and tire operation rate η _i of each wheel, and using the above-described (Expression 27) and (Expression 28), etc. A correction amount δ _K of the slip ratio K _i for minimizing the evaluation function L for the wheel is obtained. Further, based on the obtained correction amount δ _K of the slip ratio K _i and the tire data TD of each wheel, a control longitudinal force F _xi ′ (driving force) to be controlled by each wheel is calculated.

In step S40, the vehicle control device 100, based on the calculated each wheel controlled longitudinal force _{F xi} to be controlled of the '(driving force), in-wheel motor 30FL, 30FR, 30RL, controls the current i supplied to 30RR To do.

(Comparison evaluation)
Next, a comparative evaluation method and results of the vehicle control device 100 according to this embodiment will be described with reference to FIGS.

(1) Evaluation Method Here, an electric automobile (hereinafter referred to as an example) equipped with the vehicle control device 100 according to the present embodiment, an electric automobile (hereinafter referred to as an automobile) equipped with a vehicle control device according to a comparative example A comparative evaluation was carried out on a comparative example) and an electric four-wheeled vehicle (hereinafter, a conventional example) not equipped with a vehicle control device. In addition, the content of the parameter used as the basis of the evaluation function L used for vehicle control differs in an Example and a comparative example as follows.

Example: Yaw moment M, longitudinal force F _xi , lateral force F _yi , slip rate K _i and tire operating rate η _i
Comparative example: Yaw moment M, longitudinal force F _xi , lateral force F _yi , slip ratio K _i
Various conditions for comparative evaluation are as follows.

・ Friction coefficient of road surface (μ): 0.25 (low μ road)
・ Driving pattern: Slalom running (ISO1999 compliant), vehicle speed 60km / h
Tire data: Magic formula (MF) used

(2) Results of Comparative Evaluation FIG. 7 shows the state of the steering angle δ in the slalom running of the electric automobile according to the example, the comparative example, and the conventional example. As shown in FIG. 7, in the comparative example and the conventional example, the steerable angle is used up. In other words, the electric automobiles according to the comparative example and the conventional example fail because the behavior of the electric automobile according to the slalom running cannot be controlled.

  FIG. 8 shows the state of the slip angle β in the slalom running of the electric automobile according to the example, the comparative example, and the conventional example. FIG. 9 shows the state of the yaw rate γ in the slalom running of the electric automobile according to the example, the comparative example, and the conventional example.

  As shown in FIGS. 8 and 9, the electric automobile according to the embodiment has the smallest change amount of the slip angle β and the yaw rate γ, and the behavior is stable.

(Action / Effect)
According to the vehicle control apparatus 100 according to the present embodiment described above, the vehicle is the sum of the actual longitudinal force F ^{^} _X of the vehicle, which is the sum of the actual longitudinal forces F _Xi of each wheel, and the actual lateral force F _Yi of each wheel. Error F _eXi , F _eY , M _eZ of actual lateral force F ^{^} _Y , actual yaw moment M ^{^} _Z , and target vehicle longitudinal force F ^* _X , target vehicle lateral force F ^* _Y , target yaw moment M ^* _Z And each wheel should be controlled using the tire operating rate η _i of each wheel determined based on the ground contact load F _Zi of each wheel with respect to the actual longitudinal force F _Xi and actual lateral force F _Yi of each wheel. A control longitudinal force F _Xi ′ (driving force of each wheel) is calculated.

The tire operation rate η _i of each wheel is determined based on a friction circle that can be obtained by the resultant force of the actual longitudinal force F _Xi of each wheel and the actual lateral force F _Yi of each wheel. That is, according to such a vehicle control apparatus 100, realistic vehicle control in consideration of the grip force of the wheels (pneumatic tire) can be realized. In the conventional vehicle control device, the tire operating rate eta _i is controlled longitudinal force F _Xi to be controlled in any way without being considered _'to be determined, the actual control longitudinal force such that the outside of the friction circle in F _Xi' There is a problem that effective vehicle control cannot be executed.

  That is, according to such a vehicle control device 100, in the electric four-wheeled vehicle 10 in which each wheel is driven by the independent in-wheel motors 30FL, 30FR, 30RL, and 30RR, the optimum according to the operating state of each wheel. The driving force can be controlled.

Further, according to the vehicle control device 100, it is possible to extend the life to the wear limit of the pneumatic tire while sufficiently extracting the performance such as the gripping force possessed by the wheel (pneumatic tire). That is, according to the vehicle control device 100, since the control longitudinal force F _Xi ′ that is outside the friction circle is not determined, the slip amount of the wheel (pneumatic tire) is suppressed.

(Other embodiments)
Although the contents of the present invention have been disclosed through the embodiments of the present invention as described above, it should not be understood that the descriptions and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

For example, the tire operation rate η _i used in the above-described embodiment may be a ratio between the total of the longitudinal force F _xi and the lateral force F _yi of each wheel and the ground load of each wheel.

  In the embodiment described above, the tire data TD based on the magic formula is used. However, the tire data TD may be based on a tire model (for example, a brush model). Alternatively, the tire data TD may be based on experimental values.

  As described above, the present invention naturally includes various embodiments that are not described herein. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description. For example, in the present embodiment, a four-wheel electric vehicle has been described as an example, but the present invention is also applicable to a vehicle having wheels other than four wheels, such as six wheels.

1 is a schematic perspective view of an electric automobile according to an embodiment of the present invention. It is a functional block block diagram of the drive system of the electric four-wheeled vehicle which concerns on embodiment of this invention. It is the figure which showed typically the electric motor vehicle which concerns on embodiment of this invention as a four-wheel model which has a freedom degree in three directions (x direction, y direction, and a rotation direction). It is explanatory drawing explaining a mode that the vertical load of the vehicle front-back direction accompanying the acceleration / deceleration of the electric four-wheeled vehicle which concerns on embodiment of this invention changes. It is explanatory drawing explaining a mode that the vertical load of the vehicle width direction accompanying the cornering of the electric motor vehicle which concerns on embodiment of this invention changes. It is a control operation | movement flow of the braking / driving force (front-rear force) by the vehicle control apparatus which concerns on embodiment of this invention. It is a graph which shows the comparative evaluation result (steering angle) of the vehicle control apparatus which concerns on embodiment of this invention, a comparative example, and a prior art example. It is a graph which shows the vehicle control apparatus which concerns on embodiment of this invention, the comparative evaluation result (slip angle) of a comparative example, and a prior art example. It is a graph which shows the comparative evaluation result (yaw rate) of the vehicle control apparatus which concerns on embodiment of this invention, a comparative example, and a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Electric four-wheeled vehicle, 20FL, 20FR, 20RL, 20RR ... Wheel, 30FL, 30FR, 30RL, 30RR ... In-wheel motor, 100 ... Vehicle control apparatus, 110 ... Sensor part, 111 ... Steering angle sensor, 113 ... Vehicle speed Sensor: 115 ... Yaw rate sensor, 117 ... Acceleration sensor, 121 ... Feed forward moment calculator, 123 ... Target yaw moment calculator, 125 ... Yaw moment calculator, 127 ... PID controller, 129 ... Driving force calculator, 131 ... Electricity Motor control unit, CG: center of gravity, d: tread width, a _X , a _Y : acceleration, F _xi ... longitudinal force of electric automobile, F _yi ... lateral force of electric automobile, TD ... tire data , Β ... Slip angle, γ ... Yaw rate, δ ... Steering angle

Claims (6)

A vehicle control device for an electric vehicle in which each wheel is driven by an independent electric motor,
Based on tire slip data indicating the relationship between the slip ratio of the wheel and the longitudinal force and lateral force generated in the wheel, an actual longitudinal force calculating unit that calculates the actual longitudinal force generated in each wheel and the sum thereof; ,
Based on the tire data, an actual lateral force calculating unit that calculates the actual lateral force generated in each wheel and the sum thereof, and
From each calculation result of the actual longitudinal force calculation unit and the actual lateral force calculation unit, a yaw moment calculation unit that calculates an actual yaw moment generated in the electric vehicle;
A target longitudinal force calculator that calculates a target vehicle longitudinal force of the electric vehicle based on a steering angle and a vehicle speed of the electric vehicle, the electric vehicle having a desired steering characteristic;
A target lateral force calculator that calculates a target vehicle lateral force of the electric vehicle based on a steering angle and a vehicle speed of the electric vehicle, the electric vehicle having the desired steering characteristics;
From each calculation result of the target longitudinal force calculation unit and the target lateral force calculation unit, a target yaw moment calculation unit that calculates a target yaw moment of the electric vehicle;
The difference between the total of the actual longitudinal force calculated by the actual longitudinal force calculation unit and the target vehicle longitudinal force calculated by the target longitudinal force calculation unit, the actual lateral force calculated by the actual lateral force calculation unit Of the target vehicle lateral force calculated by the target lateral force calculator, the actual yaw moment calculated by the yaw moment calculator and the target yaw moment calculated by the target yaw moment calculator The control longitudinal force to be controlled for each wheel using the difference and the tire operating rate determined based on the ground contact load of each wheel with respect to the actual longitudinal force and the actual lateral force generated on each wheel. Control longitudinal force calculation unit for calculating
An electric motor vehicle control device comprising: an electric motor control unit that controls a current value supplied to the electric motor based on the control front / rear force calculated by the control front / rear force calculation unit.   The vehicle control device for an electric vehicle according to claim 1, wherein the tire operation rate is a ratio of a sum of an actual longitudinal force and an actual lateral force of each wheel and a ground load of each wheel. When the actual longitudinal force of each wheel is F _xi , the actual lateral force of each wheel is F _yi , the ground load of each wheel is F _zi , and the friction coefficient of the road surface on which each wheel rolls is μ _i The tire operating rate η _i of each wheel is

The vehicle control apparatus for an electric vehicle according to claim 1. An electric vehicle drive system for driving an electric vehicle,
An electric motor that drives each wheel independently;
A vehicle control device for controlling the behavior of the electric vehicle,
The vehicle control device includes:
Based on the tire slip data indicating the relationship between the slip ratio of the wheel and the longitudinal force and lateral force generated in the wheel, an actual longitudinal force calculation unit that calculates the actual longitudinal force generated in each wheel;
Based on the tire data, an actual lateral force calculation unit that calculates an actual lateral force generated in each wheel;
From each calculation result of the actual longitudinal force calculation unit and the actual lateral force calculation unit, a yaw moment calculation unit that calculates an actual yaw moment generated in the electric vehicle;
A target longitudinal force calculator that calculates a target vehicle longitudinal force of the electric vehicle based on a steering angle and a vehicle speed of the electric vehicle, the electric vehicle having a desired steering characteristic;
A target lateral force calculator that calculates a target vehicle lateral force of the electric vehicle based on a steering angle and a vehicle speed of the electric vehicle, the electric vehicle having the desired steering characteristics;
From each calculation result of the target longitudinal force calculation unit and the target lateral force calculation unit, a target yaw moment calculation unit that calculates a target yaw moment of the electric vehicle;
The difference between the actual longitudinal force calculated by the actual longitudinal force calculation unit and the target vehicle longitudinal force calculated by the target longitudinal force calculation unit, the actual yaw moment calculated by the yaw moment calculation unit, and the target yaw Using the tire operation rate determined based on the difference between the target yaw moment calculated by the moment calculation unit and the ground contact load of each wheel with respect to the actual longitudinal force and actual lateral force generated in each wheel, A control front / rear force calculator for calculating a control front / rear force to be controlled for each wheel;
An electric vehicle drive system comprising: an electric motor control unit that controls a current value supplied to the electric motor based on the control longitudinal force calculated by the control longitudinal force calculation unit.   5. The electric vehicle drive system according to claim 4, wherein the tire operation rate is a ratio of a total of an actual longitudinal force and an actual lateral force of each wheel and a ground load of each wheel. When the actual longitudinal force of each wheel is F _xi , the actual lateral force of each wheel is F _yi , the ground load of each wheel is F _zi , and the friction coefficient of the road surface on which each wheel rolls is μ _i The tire operating rate η _i of each wheel is

The drive system for an electric vehicle according to claim 4.

Images