JP4423934B2 - Electric vehicle behavior control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a behavior controller of electric vehicle in which the revolution amount (e.g. yaw rate) of a vehicle and the revolution attitude of the body can be realized in desired characteristics simultaneously by suppressing disturbance in the revolution amount even in a situation where a driving wheel cannot receive a sufficient pavement reaction because of a small frictional coefficient of the pavement. <P>SOLUTION: The behavior controller of an electric vehicle capable of independent control of driving wheel comprises a steering mechanism for steering wheels depending on the steering operation, means (S14, S15) for calculating a target revolution amount and a target slip angle basic value of the vehicle based on the vehicle speed and the steering operation amount, a means (S17) for calculating a driving force difference command value based on the target revolution amount and the target slip angle basic value, a means (S18) for controlling the driving wheels based on the driving force difference command value, means (S19, S20) for calculating a target slip angle by correcting the target slip angle basic value based on the deviation amount of the difference of actual driving force of the driving wheels from the driving force difference command value, and means (S21, S22) for correcting the steering angle of the steering mechanism based on the target steering angle and the target revolution amount. <P>COPYRIGHT: (C)2005,JPO&amp;NCIPI

Description

  The present invention relates to a behavior control device for an electric vehicle capable of controlling left and right driving forces by independently controlling driving wheels with an electric motor.

  Conventionally, for engine vehicles, four-wheel steering (4WS) that enables smooth and stable turning, lane change, and the like has been developed. The electric vehicle includes a left and right drive wheel independent drive type electric vehicle in which a plurality of motors are arranged so that the left and right drive wheels can be independently rotated. In such an electric vehicle, the left and right drive wheels are By generating torques different from each other, the same effect as 4WS in a gasoline vehicle can be achieved without using a large-scale and complicated mechanism and control system. Therefore, in an electric vehicle, the front wheel or the rear wheel is steered with respect to an operation amount of the steering wheel (hereinafter referred to as “steering operation amount”), and a driving force difference is generated between the left and right driving wheels, thereby There has been proposed a vehicle behavior control device that improves performance during turning.

  For example, transfer characteristics from two manipulated variables (difference in driving force between front wheel steering angle and left and right wheels) to yaw rate and sliding angle (transfer function from front wheel steering angle to yaw rate, transfer function from front wheel steering angle to sliding angle, left and right 4) transfer function from wheel driving force difference to yaw rate, right and left wheel driving force difference to slip angle), and two transmissions that define the desired response from steering operation amount to yaw rate and slip angle There is a vehicle behavior control device that calculates a front wheel steering angle target value and a left and right wheel driving force difference target value according to a steering operation amount using a function. However, in this device, since the difference in driving force between the left and right wheels is used as the operation amount, for example, in a case where the driving wheel cannot receive sufficient road reaction force due to a small road friction coefficient, a sufficient driving force difference between the left and right wheels. May not be realized. In such a case, the front wheel rudder angle (or rear wheel rudder angle) may be achieved according to the command value, but the driving force difference between the left and right wheels is not achieved according to the command value. Both corners cannot match the target value. In particular, the turning amount (for example, the yaw rate) is a value that is directly connected to the turning radius of the vehicle. If the turning amount is disturbed, the turning radius of the vehicle is disturbed, so that there is a possibility that the vehicle trajectory desired by the driver cannot be drawn.

Therefore, for example, in Patent Document 1, a driving motor is provided on each of the left and right wheels of the vehicle, a yaw moment is generated in the vehicle by making a difference in the driving force between the two when turning the vehicle, and the yaw rate of the vehicle is detected. There has been proposed a vehicle behavior control device that feeds back a left / right driving force difference or adjusts a steering angle of a front wheel or a rear wheel so that a detected yaw rate matches a target yaw rate.
JP-A-10-271613

  However, since the conventional vehicle behavior control apparatus described above determines the operation amount by feeding back the yaw rate, the control functions after the behavior of the vehicle appears as a yaw rate change. Therefore, when a sufficient driving force difference cannot be achieved, such as when the road friction coefficient is small, the control action is taken only after the change in the vehicle's behavior appears, so the control timing is likely to be delayed, and the change in the vehicle's behavior is sufficient. It cannot be suppressed.

  The present invention has been made paying attention to such conventional problems, and suppresses the disturbance of the turning amount even in a situation where the driving wheel cannot receive sufficient road surface reaction force because the road surface friction coefficient is small. An object of the present invention is to provide a behavior control device for an electric vehicle that can simultaneously achieve the desired characteristics of the turning amount of the vehicle (for example, the yaw rate) and the turning posture of the vehicle body.

  The present invention solves the above problems by the following means. In addition, in order to make an understanding easy, although the code | symbol corresponding to embodiment of this invention is attached | subjected, it is not limited to this.

  The present invention relates to a behavior control device for an electric vehicle capable of controlling left and right driving forces by independently controlling driving wheels by an electric motor, and a steering mechanism that steers at least front wheels or rear wheels in accordance with a steering operation. And a target turning amount calculation means (step S14) for calculating a target turning amount of the vehicle based on the vehicle speed and the steering operation amount, and a target slip angle for calculating a basic target slip angle value of the vehicle based on the vehicle speed and the steering operation amount. A basic value calculating means (step S15), and a driving force difference command value calculating means (step S17) for calculating a driving force difference command value for the driving wheels based on the target turning amount and the target slip angle basic value; Based on the driving force difference command value, the driving wheel control means (step S18) for controlling the driving wheel and the actual driving force of the driving wheel controlled by the driving wheel control means However, when there is a deviation from the driving force difference command value, a slip angle correction value is calculated based on the deviation amount, and the target slip angle basic value is corrected by the slip angle correction value to obtain a target slip. Target slip angle calculating means (steps S19, S20) for calculating an angle, and steering angle correcting means (steps S21, S22) for correcting the steering angle of the steering mechanism based on the target slip angle and the target turning amount. It is characterized by having.

  According to the present invention, the driving force difference command value for the driving wheel is calculated based on the target turning amount and the target slip angle basic value, and the driving wheel is controlled based on the driving force difference command value. When the actual driving force difference between the driving wheels deviates from the driving force difference command value, a slip angle correction value is calculated based on the deviation amount, and the target value is calculated based on the slip angle correction value. The target slip angle is calculated by correcting the slip angle basic value, and the steering angle of the steering mechanism is corrected based on the target slip angle and the target turning amount. Since it did in this way, the behavior of a vehicle can be controlled, without feeding back the actual behavior of a vehicle. Therefore, even when the road surface friction coefficient is low and the road surface reaction force is small, it is possible to calculate the rudder angle command value according to the road surface condition even when the difference in driving force between the left and right wheels cannot be generated. The target turning amount can be continuously realized. In addition, the vehicle behavior is detected using a yaw rate sensor or a lateral acceleration sensor of the vehicle, and compared to a method in which the driving force difference command value and steering angle command value of the left and right wheels are feedback controlled so as to suppress the behavior. The amount of disturbance is suppressed, and the vehicle can be turned stably.

Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings.
(First embodiment)
FIG. 1 is a configuration diagram of an electric vehicle in which four wheels are driven by separate electric motors and front wheels are steered. The model used for the following equation of motion is generally used for vehicle motion analysis as described in, for example, “Automotive Motion and Control” (Sankaido).

  The electric vehicle includes electric motors 3FL, 3FR, 3RL, 3RR as driving force generation sources, and the rotation shafts of the respective motors are wheels 2FL of the electric vehicle via speed reducers 4FL, 4FR, 4RL, 4RR. , 2FR, 2RL, 2RR. The output characteristics of the four motors, the reduction ratios of the four reduction gears, and the radii of the four wheels are all the same.

  Motors 3FL, 3FR, 3RL, and 3RR are all three-phase synchronous motors in which permanent magnets are embedded in a rotor. Torque command values tTFL (front left wheel), tTFR (right) that drive circuits 5FL, 5FR, 5RL, and 5RR that control power exchange with the lithium ion battery 6 receive the power running and regenerative torque of these motors from the integrated controller 30 Adjust so that it matches the front wheels, tTRL (left rear wheel), and tTRR (right rear wheel). However, in a situation where the wheels run idle when output according to the torque command value, the torque is limited and outputted for each wheel so that the wheels corresponding to the drive circuit do not run idle. The drive circuits 5FL, 5FR, 5RL, and 5RR detect the output torque of each motor, the motor rotation speed detected by a rotation position sensor (not shown) attached to the motor rotation shaft, and a thermistor (not shown). The upper limit value of the absolute value of the torque corresponding to the drive circuit temperature and the motor temperature (the maximum value of the torque absolute value set in advance to suppress the temperature rise) is transmitted to the integrated controller 30.

  Here, as a method of limiting and outputting the motor torque of each wheel so that the wheel does not run idle, for example, as disclosed in JP-A-6-98418, the reaction force that the wheel receives from the road surface is estimated, As disclosed in the method of adjusting the motor torque of each wheel based on the estimated value and the literature “Lateral Motion Stabilization with Feedback Controlled Wheels” (Sakai et al., 6th International Symposium on Advanced Vehicle Control, 2002). There is a method that uses a model that expresses the wheel rotation speed characteristics and adjusts the motor torque independently for each wheel according to the difference between the wheel rotation speed output by the model and the actual rotation speed. The description is omitted here.

  The front wheels 2FL and 2FR are mechanically steered mechanically through the steering gear 14 by the rotational movement of the steering wheel 11 operated by the driver, and the steering gear 14 is entirely moved in the vehicle width direction by the auxiliary steering motor 12. Auxiliary steering is performed by moving to. That is, the steering angles of the front wheels 2FL and 2FR are the sum of the main steering angle by the steering wheel 11 and the auxiliary steering angle by the auxiliary steering motor 12. The auxiliary steering angle is controlled to match the target auxiliary steering angle tDF transmitted by the integrated controller 30 by the control circuit 13 adjusting the output of the auxiliary steering motor 12.

  The integrated controller 30 includes an accelerator opening signal detected by the accelerator pedal sensor 23, a brake pedaling force signal detected by the brake pedal sensor 22, and a steering angle sensor 21 attached to the rotating shaft of the steer wheel 11. A rotation angle signal of the link wheel and a vehicle body lateral acceleration (acceleration in the vehicle width direction) signal detected by the acceleration sensor 24 attached to the center of gravity of the vehicle are input. Further, the maximum value of the electric power that can be extracted from the battery is received from the controller 7 that monitors the storage state and temperature of the battery 6. Then, the integrated controller 30 calculates torque command values tTFL, tTFR, tTRL, tTRR for each motor based on these signals, transmits them to the drive circuit of each motor, and auxiliary steering angle command value tDF for the front wheel steering angle. Is also calculated and transmitted to the control circuit 13.

  Next, the integrated controller 30 will be described in detail. The integrated controller 30 includes peripheral components such as a RAM / ROM in addition to the microcomputer, and executes the flowchart of FIG. 2 at regular intervals, for example, every 5 ms.

  First, in step S11, sensor signals and received signals from the controller 7 and the drive circuits 5FL, 5FR, 5RL, and 5RR are stored in RAM variables. Specifically, the accelerator opening signal is stored in variable APS (unit:%, but when fully opened, 100%), the brake pedal force signal is stored in variable BRK (unit: Pa), and the steering wheel rotation The angle signal is stored in a variable STR (unit is rad, counterclockwise is positive), and the vehicle body lateral acceleration signal is stored in a variable YG (leftward in FIG. 1 is positive). Further, the value received from the controller 7, that is, the maximum value of the power that can be extracted from the battery is stored in the variable Pbat (unit: kW). Further, for the signals received from the drive circuits 5FL, 5FR, 5RL, and 5RR, the output torques of the motors 3FL, 3FR, 3RL, and 3RR are variable TFL, TFR, TRL, and TRR, respectively (the unit is Nm, and the vehicle is accelerated) The rotation direction of each motor is stored in the variables NFL, NFR, NRL, and NRR (all units are rad / s, and the direction in which the vehicle moves forward is positive). Then, the absolute upper limit value of each motor torque is stored in variables LTFL, LTFR, LTRL, and LTRR (all units are Nm).

  In step S12, the vehicle speed V (the unit is m / s and the forward direction of the vehicle is positive) is calculated by the following equation.

V = (NFL / GG * R + NFR / GG * R + NRL / GG * R + NRR / GG * R) / 4
Where R is the wheel radius and GG is the reduction gear ratio.

  In step S13, the target driving force tTD of the vehicle is calculated. This calculation is performed by referring to a map MAP_tTD (V, APS) stored in advance in the ROM. The map MAP_tTD (V, APS) is characteristic data centered on the vehicle speed and the accelerator opening, and is set as shown in FIG. 3, for example.

  In step S14, the target lateral force tY of the vehicle is calculated. This calculation is performed by referring to a map MAP_tY (V, STR) stored in advance in the ROM. Here, the target lateral force tY is a target value of the total force generated by the four wheels in the vehicle width direction, and is the positive direction of the force generated during the left steady turn (in FIG. 1, left The direction of The map MAP_tY (V, STR) is characteristic data with the vehicle speed and the steering rotation angle as axes, and is set as shown in FIG. 4, for example.

  In step S15, a target slip angle basic value tβ0 of the vehicle gravity center position is calculated. This calculation is performed by referring to a map MAP_tβ0 (V, STR) stored in advance in the ROM. Here, the target slip angle basic value tβ0 is an angle formed by the direction in which the center of gravity of the vehicle body advances and the direction of the vehicle body. The unit is rad, and the direction in which the position of the center of gravity of the vehicle body advances is positive in the counterclockwise direction with respect to the vehicle body direction. The map MAP_tβ0 (V, STR) is characteristic data with the vehicle speed and the steering rotation angle as axes, and is set as shown in FIG. 5, for example.

  In step S16, an upper limit value and a lower limit value of the target slip angle that can be realized are calculated, and the target slip angle basic value tβ0 is limited therebetween. This calculation is realized according to the flowchart of FIG.

  First, in step S161, an upper limit value tUU and a lower limit value of the left and right wheel driving force difference that can be realized based on the absolute value upper limit values LTFL, LTFR, LTRL, LTRR of the motor torque from the drive circuits 5FL, 5FR, 5RL, 5RR. Calculate tUL. Here, the absolute value upper limit values LTFL, LTFR, LTRL, and LTRR of the motor torque are upper limit values of the absolute value of the torque according to the drive circuit temperature and the motor temperature. FIG. 7 shows the left front wheel as an example. Thus, the torque value corresponds to the actual rotational speed NFL of the motor. The higher the drive circuit temperature and the motor temperature, the smaller the value. Based on these values, an upper limit value tUU and a lower limit value tUL of the left and right wheel driving force difference are calculated by the following equations. The upper limit value tUU and the lower limit value tUL respectively correspond to the minimum value and the maximum value of the driving force difference that can be applied to the left and right wheels under the constraint that the target driving force tTD is realized with four wheels.

tUU = min ((LTFR + LTRR) * GG / R * 2-tTD, (LTFL + LTRL) * GG / R * 2 + tTD)
tUL = -min ((LTFR + LTRR) * GG / R * 2 + tTD, (LTFL + LTRL) * GG / R * 2-tTD)
Subsequently, in step S162, a steady value tβ0a of the slip angle that can be realized by the difference between the left and right wheel driving force of the upper limit value tUU and the front wheel steering angle value that realizes the target lateral force tY is calculated. This calculation is performed by referring to the map MAP_tβS (V, tY, U) stored in advance in the ROM. The map MAP_tβS (V, tY, U) is a map having three axes: vehicle speed, target lateral force, and left / right driving force difference. For example, the steady-state characteristic of the slip angle with respect to the left-right driving force difference at a target lateral force value that is a certain vehicle speed value is stored as shown by a solid line in FIG. In the map MAP_tβS (V, tY, U), the steady value tβ0a of the slip angle is calculated by table-up as U = tUU.

  Subsequently, in step S163, a steady value tβ0b of the slip angle that can be realized by the difference between the left and right wheel driving force of the lower limit value tUL and the front wheel steering angle value that realizes the target lateral force tY is calculated. This calculation is performed by referring to a map MAP_tβS (V, tY, U) stored in advance in the ROM, as in step S162. In the map MAP_tβS (V, tY, U), the steady value tβ0b of the slip angle is calculated by table-up as U = tUL.

  Subsequently, in steps S164 to S166, tβ0a and tβ0b are corrected according to the state of the battery. In step S164, it is determined whether the maximum value Pbat of power that can be extracted from the battery is smaller than a predetermined value (for example, 10 kW). The case where it is small is a case where it is not possible to sufficiently supply electric power that gives a difference between left and right driving forces. At this time, the process proceeds to S165. If not, the process proceeds to S167. It should be noted that the failure determination of the motor, the drive circuit, or the battery is always performed, and the process may be shifted to S165 when it is determined that any of the failure has occurred.

  Subsequently, in step S165, a steady value tβ0c of the slip angle that can be realized with the front wheel steering angle value that realizes the target lateral force tY when the left and right wheel driving force difference is zero is calculated. This calculation is performed by referring to a map MAP_tβS (V, tY, U) stored in advance in the ROM, as in step S162. In the map MAP_tβS (V, tY, U), the steady value tβ0c of the slip angle is calculated by table-up as U = 0.

  In step S166, tβ0c is substituted for tβ0a and tβ0b.

  Subsequently, in step S167, the target slip angle basic value tβ0 is limited and output between tβ0a and tβ0b, and this routine is terminated.

  Returning again to FIG. In step S17, a target left / right driving force difference tU is calculated from the target lateral force tY and the target slip angle basic value tβ0. This calculation principle and implementation method will be described in detail later.

  In step S18, torque command values tTFL, tTFR, tTRL, tTRR for the four wheels are calculated from the target driving force tTD and the target left / right driving force difference tU and transmitted to the drive circuits 5FL, 5FR, 5RL, 5RR for the respective motors. . Torque command values tTFL, tTFR, tTRL, tTRR for the four wheels are calculated by the following equations.

tTFL = tTD * R / GG / 4-tU * R / GG / 4
tTFR = tTD * R / GG / 4 + tU * R / GG / 4
tTRL = tTD * R / GG / 4-tU * R / GG / 4
tTRR = tTD * R / GG / 4 + tU * R / GG / 4
However, if the absolute values of tTFL, tTFR, tTRL, tTRR exceed the upper limit values LTFL, LTFR, LTRL, LTRR of the respective motor torques from the drive circuits 5FL, 5FR, 5RL, 5RR, Not exceeding the value
tTFL + tTFR + tTRL + tTRR = tTD * R / GG
-tTFL + tTFR-tTRL + tTRR = tU * R / GG
The command value is recalculated to satisfy For example, if tTFL> LTFL (> 0), tTFL-LTFL is added to tTRL, and tTFL = LTFL.

  In step S19, the target slip angle correction value tβ1 is calculated based on the torque command values tTFL, tTFR, tTRL, tTRR to each motor and the output torques TFL, TFR, TRL, TRR of each motor. This calculation is realized according to the flowchart of FIG.

  First, in step S191, based on the torque command values tTFL, tTFR, tTRL, tTRR to each motor, the estimated torque values pTFL, pTFR, pTRL, pTRR when the road surface reaction force received by the wheels is assumed to be sufficient are set to tTFL. , tTFR, tTRL, tTRR are calculated so that the time constants are primary response waveforms corresponding to the motor current response speed (for example, 5 ms).

In step S192, a steady value pβ of the slip angle that is achieved when the planned torque values pTFL, pTFR, pTRL, and pTRR are steadily realized is calculated. This calculation is performed by referring to the map MAP_tβS (V, tY, U) stored in advance in the ROM as in step S162. In the map MAP_tβS (V, tY, U)
U =-pTFL * GG / R + pTFR * GG / R-pTRL * GG / R + pTRR * GG / R
To calculate the steady value pβ of the slip angle.

In step S193, a steady value rβ of the slip angle that is achieved when the actual torque detection values are constantly TFL, TFR, TRL, and TRR is calculated. This calculation is performed by referring to the map MAP_tβS (V, tY, U) stored in advance in the ROM as in step S162. In the map MAP_tβS (V, tY, U)
U =-TFL * GG / R + TFR * GG / R-TRL * GG / R + TRR * GG / R
To calculate the steady value rβ of the slip angle.

  In step S194, the target slip angle correction value tβ1 is calculated by the following equation.

tβ1 = pβ-rβ
Step S194 is executed to end this routine.

  Returning again to FIG. In step S20, the target slip angle tβ is calculated by the following equation.

tβ = tβ0-tβ1
In step S21, a front wheel steering angle tDFS corresponding to the target lateral force tY and the target slip angle tβ is calculated. This calculation principle and implementation method will be described in detail later.

  Finally, in step S22, an auxiliary steering angle command value tDF for the front wheel steering angle is calculated and transmitted to the drive circuit 13. The auxiliary steering angle command value tDF for the front wheel steering angle is calculated based on the front wheel steering angle tDFS and the steering rotation angle STR. The characteristic of the steering angle amount that is mechanically steered corresponding to the steering rotation angle STR is stored in the ROM in advance as a table TBL_DFS (STR) as shown in FIG. Using the reference value of this table, the auxiliary steering angle command value tDF for the front wheel steering angle is calculated as follows.

tDF = tDFS-TBL_DFS (STR)
That is, using the fact that the steering angle of the front wheels is the sum of the main steering angle by the steering wheel 11 and the auxiliary steering angle by the auxiliary steering motor 12, the main steering angle TBL_DFS ( The steering angle tDF to be assisted is calculated by subtracting (STR).

  As described above, in step S17, the target left / right driving force difference tU is calculated from the target lateral force tY and the target slip angle basic value tβ0. In step S21, the front wheel steering angle corresponding to the target lateral force tY and the target slip angle tβ is calculated. Calculate tDFS. These are calculated so that the response of the lateral force Y and the slip angle β with respect to the steering rotation angle STR has desirable transfer characteristics (normative model).

  Then, the calculation principle and the realization method will be described next.

  The equations of motion of the vehicle behavior for steering the front and rear wheels are: front wheel rudder angle δf [rad], rear wheel rudder angle δr [rad], right wheel driving force u / 2 [N], left wheel driving force -u / 2 [ N] is an operation amount, and the yaw rate γ [rad / s] and slip angle β [rad] of the vehicle are state amounts, which can be expressed as follows. However, the vehicle speed V [m / s] is constant (dV / dt = 0), V ≠ 0, and the slip angle (β [rad]) is very small (| β | << 1, sinβ ≒ β, cosβ ≒ 1) And

Here, Lf is the front wheel axle center point distance [m], Lr is the rear axle center point distance [m], Lt is the tread base distance / 2 (same front and rear wheels) [m], L is Lf + Lr [m], m is the vehicle weight [kg], and Iγ is the yaw moment of inertia [Nmss]. Kf is the front tire cornering stiffness [N / rad], and Kr is the rear tire cornering stiffness [N / rad], taking into account the decrease in cornering power with respect to the steering angle due to the effects of front and rear wheel steering stiffness. It is.

  Further, the lateral force Y [N], the yaw rate γ [rad / s], and the slip angle β [rad] are expressed by the following relational expressions.

Y = mV (dβ / dt + γ)
These equations of motion can be rewritten into the following form using the differential calculator s.

T11, T12, T13, T21, T22, T23, T21, T22, T23, and Td are all functions of the vehicle speed and are expressed by the following equations.

Further, the front wheel steering angle command is set so that the response of the lateral force Y and the slip angle β has desirable transmission characteristics (reference model) by steering the front wheel and the driving force difference between the left and right driving wheels without steering the rear wheel. In order to calculate and realize the value δ _f ^* and the command value u ^{* for} the driving force difference between the left and right wheels, the following may be performed.

That is, in order to set the desired transmission characteristic of the lateral force Y to the steering operation amount δ to G _Y δ and the desirable transmission characteristic of the slip angle β to the steering operation amount δ to Gβδ, the front wheel steering angle command value δ _f ^* , The command value for the driving force difference between the left and right wheels may be realized by calculating u ^* as follows. However, for T11, T13, T31, T33 (when using T12, T21, T22, T23, T32 other than the present embodiment, T12, T21, T22, T23, T32 are also the same), the vehicle motion differential equation The steady gain is corrected according to the vehicle speed V, the steering operation amount δ, and the lateral force Y, respectively, in consideration of the non-linearity. For example, the correction of T11 is performed so that the steady-state gain of the actual vehicle from the front wheel rudder angle to the slip angle matches T11 (0) / Td (0).

The transfer characteristics G _Y δ and Gβδ are set to the following equations so that, for example, the denominator pole is the double root of -wn. Here, wn and b1 are functions of the vehicle speed, and values that characterize a transient response. G0 _Y δ and G0βδ are steady gains from the steering operation amount δ to the lateral force Y and the slip angle β, respectively.

When the above formulas A and B are summarized, the relational expression between the steering operation amount δ, the front wheel steering angle command value δ _f ^*, and the left and right wheel driving force difference command value u ^* is considered by taking into account the order of each function. Can be written as:

Here, A3, A2, A1, A0, B13, B12, B11, B10, B23, B22, B21, B20, B33, B32, B31, B30, B43, B42, B41, B40 are vehicle speed V, steering operation amount G0 _Y δ and G0βδ are steady gains from the steering operation amount δ to the lateral force Y, and steady gains from the steering operation amount δ to the slip angle β, respectively. It is a function of quantity. With this equation, it is possible to calculate the front wheel steering angle command value δ _f ^* and the driving force difference command value u ^* for the left and right wheels that realize a desired lateral force and slip angle including transient response.

  Next, a method for realizing these calculations will be described using the following equation as an example.

Here, “′” represents a one-time differential value, and “″” ”represents a four-time differential value. This equation can be written as shown in FIG. 11 using an integrator (1 / s). Therefore, even if AA3, AA2, AA1, AA0, BB4, BB3, BB2, BB1, BB0, etc. change according to time or state, update their values at regular intervals and calculate the integral. From the left, for example, Euler approximation is performed to obtain X3, X2, X1, and X0, and from these values, the response of the output y to the input u can be calculated momentarily.

  Based on the above, step S17 will be described in detail.

  In step S17, a target left / right driving force difference tU corresponding to the target lateral force tY and the target slip angle basic value tβ0 is calculated. The calculation will be described with reference to the flowchart of FIG.

  First, in step S171, coefficients A3, A2, A1, A0, B33, B32, B31, B30, B43, B42, B41, and B40 of Expression D are calculated from the vehicle speed V, the steering operation amount STR, and the target lateral force tY.

In step S172, the steady target value G0 _Y δ from the steering operation amount δ (= STR) to the lateral force Y and the steady target value G0βδ from the steering operation amount δ (= STR) to the slip angle β are respectively set to G0 _Y Let δ = tY and G0βδ = tβ0.

In step S173, the front wheel steering angle command value δ _f ^* (= tDFS) is calculated by the above-described calculation method described with reference to FIG. Specifically, the coefficients A3, A2, A1, A0, B33, B32, B31, B30, B43, B42, B41, B40, G0 _Y δ, G0 βδ obtained in S171 and S172 are used as the coefficients AA0, AA1, in FIG. AA2, AA3, BB0, BB1, BB2, BB3, BB4 are calculated, and then the integral calculation of FIG. 11 is performed by Euler approximation from the left using X3, X2, X1, X0 at the time of previous execution of S172, and X3 , X2, X1, X0 are updated. Then, according to these values, the output y is calculated from the relational expression shown in FIG. 11 and substituted into the driving force difference command value u ^* (= tU) for the left and right wheels.

  After execution of step S173, this routine is terminated.

  Next, step S21 will be described in detail.

  In step S21, a front wheel steering angle tDFS corresponding to the target lateral force tY and the target slip angle tβ is calculated. The calculation will be described with reference to the flowchart of FIG.

  First, in step S211, coefficients A3, A2, A1, A0, B13, B12, B11, B10, B23, B22, B21, and B20 of Expression C are calculated from the vehicle speed V, the steering operation amount STR, and the target lateral force tY.

In step S212, the steady target value G0 _Y δ from the steering operation amount δ (= STR) to the lateral force Y and the steady target value G0βδ from the steering operation amount δ (= STR) to the slip angle β are respectively expressed as G0 _Y Let δ = tY, G0βδ = tβ. In step S172, G0βδ = tβ0 (tβ0 is a target slip angle basic value), whereas in this step, G0βδ = tβ (tβ is a target slip angle).

In step S213, the front wheel steering angle command value δ _f ^* (= tDFS) is calculated by the above-described calculation method described with reference to FIG. From A3, A2, A1, A0, B13, B12, B11, B10, B23, B22, B21, B20, G0 _Y δ, G0βδ obtained in S211 and S212, the coefficients AA0, AA1, AA2, AA3, BB0 in FIG. , BB1, BB2, BB3, BB4, and then the integral calculation of FIG. 11 is performed by Euler approximation from the left using X3, X2, X1, X0 at the previous execution of S212, and X3, X2, X1, Update X0. Then, according to these values, the output y is calculated from the relational expression shown in FIG. 11 and substituted into the front wheel steering angle command value δ _f ^* (= tDFS).

  After execution of step S213, this routine is terminated.

In addition, when calculating the target lateral force tY in step S14 of FIG. 2, only (G _Y δδ−m * YG) may be added. Here, as described above, each variable is δ (= STR) is the steering operation amount, G _Y δ The desired transmission characteristic of the lateral force Y with respect to the steering operation amount δ, m is the vehicle weight, and YG is the detected vehicle body lateral acceleration. is there. By doing so, the target lateral force is corrected so that the lateral force of the vehicle body coincides with the lateral force G _Y δδ including the transient characteristics, and the front wheel steering angle and the left and right wheel driving forces are calculated in accordance with the calculations S17 and S21 of FIG. The difference is adjusted.

According to this embodiment, the following functions can be realized.
(1) The front wheel steering angle and the left / right wheel driving force difference can be adjusted so that a predetermined lateral force can be realized with a predetermined transient response according to the vehicle speed and the steering operation amount.
(2) When the road surface friction coefficient that can be realized by the motor is sufficiently high and sufficient road surface reaction force is obtained, a slip angle that is predetermined according to the vehicle speed and the steering operation amount can be realized with a predetermined transient response. The front wheel steering angle and the left / right wheel driving force difference can be adjusted.
(3) When it is not possible to apply torque to the drive amount motor according to the command value, such as when the road surface friction coefficient that can be realized by the motor is low, the front wheel steering angle is calculated according to the difference between the torque command value and the actual torque. Correct the target slip angle to be used. Since the front wheel steering angle is adjusted based on the target lateral force and the corrected target slip angle, at least the vehicle body lateral force can be matched with the target lateral force. In particular, since the difference between the torque command value and the actual torque is detected and the detected value is used to reflect the situation before the vehicle behavior (lateral force or yaw rate) is disturbed, it is possible to use a method such as yaw rate feedback. In addition, the behavior disturbance of the vehicle body can be suppressed.
(4) Further, the torque range that can be adjusted by the motor is detected according to the state of the motor or battery, and the target slip angle is limited in advance so that it can be realized within the torque range. The target slip angle and the target lateral force corresponding to the situation are calculated even when the temperature is high or when the battery fails. Since the difference between the front wheel rudder angle and the left and right wheel driving force is adjusted based on the lateral force and the slip angle that can be realized in advance, the disturbance of the lateral force can be further suppressed.
(5) Furthermore, since the detection value from the lateral force sensor is ford-backed, it has become possible to reduce the influence of crosswinds and road surface disturbances regardless of the operation of the driver. As a result, the driving load on the driver can be reduced.

(Second embodiment; another form of drive system)
In each embodiment shown below, the same code | symbol is attached | subjected to the part which fulfill | performs the same function as 1st Embodiment mentioned above, and the overlapping description is abbreviate | omitted suitably.

  The drive system is not limited to the embodiment shown in FIG. For example, a drive form as shown in FIG. 14 may be used. 14A and 14B show a configuration in which only the rear wheels are driven by independent left and right motors, FIGS. 14C and 14D show an embodiment in which only the front wheels are driven by independent left and right motors, and FIG. 14E shows a rear configuration. Clutch motor (both the inner and outer motors are rotatably supported, and this is a motor that can apply reverse torque to the left and right wheels by generating torque in the motor. In other words, the driving force difference is applied to the left and right rear wheels.

  In any case, any form may be used as long as a driving force difference is generated between the left and right wheels by the electric motor. Accordingly, the front wheels in FIG. 14 (a) and the rear wheels in FIG. 14 (d) may be configured such that the left and right wheels are driven via a gear ratio using the engine as a power source. These forms can be similarly realized by changing the above-described embodiment according to the form.

For example, FIG. 15 is a form of FIG. It has an engine 43 as a drive source, and the engine output transmits the same torque to the left and right wheels via the continuously variable transmission 42 and the differential gear 41. The engine 43 and the continuously variable transmission 42 realize a front wheel driving force corresponding to the accelerator opening of the driver by the controller 44 and transmit the driving force eTD to the integrated controller 30. The rest of the configuration is the same as in FIG. Even in such a form, the present invention can be applied by changing the calculation in the integrated controller 30 as follows after removing the processing related to the front wheel motor and the drive circuit in the above embodiment.
(1) In step S12, the vehicle speed V is calculated by the following equation.

V = (NRL / GG * R + NRR / GG * R) / 2
(2) In step S161, the upper limit value tUU and the lower limit value tUL of the left and right wheel driving force difference are calculated by the following equations.

tUU = min ((LTRR) * GG / R * 2- (tTD-eTD), (LTRL) * GG / R * 2 + (tTD-eTD))
tUL = -min ((LTRR) * GG / R * 2 + (tTD-eTD), (LTRL) * GG / R * 2- (tTD-eTD))
(3) In step S18, torque command values tTRL and tTRR are calculated by the following equations.

tTRL = (tTD-eTD) * R / GG / 2-tU * R / GG / 2
tTRR = (tTD-eTD) * R / GG / 2 + tU * R / GG / 2
(4) In step S192, U is calculated by the following equation.

U = -pTRL * GG / R + pTRR * GG / R
(5) In step S193, U is calculated by the following equation.

U = -TRL * GG / R + TRR * GG / R
It can implement | achieve also with the form of FIG. 15 by changing as mentioned above.

(Third embodiment; another form of steering system)
The steering system is not limited to the above-described embodiment. For example, as shown in Japanese Patent Application Laid-Open No. 2003-19975 and the like, by electronically connecting a steering handle and a steering mechanism, a system that can freely associate an operation amount of the steering handle and a front wheel steering amount. Is also possible (FIG. 16A). In that case, it can be similarly realized by using the front wheel steering angle command value tDFS in the above-described embodiments as the steering amount command value.

  Further, as disclosed in JP-A-11-91608 and the like, front wheel steering is mechanically connected to the steering wheel, and rear wheel steering can be freely associated according to the operation amount of the steering wheel. The rear wheel steering system can be similarly realized (FIG. 16B). In that case, the rear wheel rudder angle command value and the left and right wheel driving force difference command value are calculated using the following relational expression instead of the above formula A, and the rear wheel rudder angle and left and right wheel drive are matched with these values. It can be realized similarly by adjusting the force difference.

In addition, as shown in FIGS. 16C and 16D, the present invention can be similarly applied to a combination of these.

(Fourth embodiment)
In each of the embodiments described above, the turning amount is a lateral force applied to the vehicle, but it may be a lateral acceleration or a turning radius value. When the lateral acceleration is used, it can be similarly realized by using a relational expression of lateral acceleration = lateral force ÷ vehicle weight. Further, when the turning radius value is used, it can be similarly realized by using a relational expression of turning radius value = vehicle weight × vehicle speed × vehicle speed ÷ lateral force. However, as the value when the lateral force is 0, the turning radius is defined as a sufficiently large value.

  The turning amount may be the yaw rate. When using the yaw rate, it can be similarly realized by using the following relational expression instead of the expressions A and B. Here, wn, b1, and b2 are functions of the vehicle speed, and values that characterize a transient response. G0γδ and G0βδ are steady gains from the steering operation amount δ to the yaw rate γ and the slip angle β, respectively, and are functions of the vehicle speed and the steering operation amount.

Note that a yaw rate sensor may be attached to the vehicle, and the target lateral force tY may be added by (Gγδδ−YY) in step S14 of FIG. 2 using the output value YY. Here, as described above, each variable is a desirable transfer characteristic of yaw rate γ with respect to steering operation amount δ and δδ = STR, and Gγδ to steering operation amount δ. By performing this correction, the target lateral force is corrected so that the vehicle body lateral force matches Gγδδ including transient characteristics, and the difference between the front wheel steering angle and the driving force between the left and right wheels is adjusted in S19 in FIG.

  The present invention is not limited to the embodiment described above, and various modifications and changes can be made within the scope of the technical idea, and it is obvious that these are equivalent to the present invention.

It is a block diagram of the electric vehicle which drives four wheels with a separate electric motor and steers a front wheel. It is a flowchart which shows the main routine of 1st Embodiment of this invention. It is a figure which shows map MAP_tTD (V, APS) of the characteristic data centering on vehicle speed and accelerator opening. It is a figure which shows map MAP_tY (V, STR) of the characteristic data centering on a vehicle speed and a steering rotation angle. FIG. 6 is a diagram showing a map MAP_tβ0 (V, STR) of characteristic data with the vehicle speed and the steering rotation angle as axes. It is a flowchart which shows the routine which restrict | limits a target slip angle basic value. It is a figure which shows the upper limit characteristic of the absolute value of the torque according to drive circuit temperature and motor temperature. It is a figure which shows the steady value characteristic of the slip angle with respect to the left-right driving force difference at the time of the target lateral force value which is a certain vehicle speed value. It is a flowchart which shows the routine which calculates a target slip angle correction value. FIG. 10 is a diagram showing a table TBL_DFS (STR) of characteristics of a steering angle amount that is mechanically main-steered corresponding to a steering rotation angle STR. It is a figure which shows the calculation method of a differential equation using an integrator. It is a flowchart which shows the routine which calculates a target right-and-left driving force difference. It is a flowchart which shows the routine which calculates a front-wheel steering angle. It is a figure which shows 2nd Embodiment (another form of drive system) of this invention. It is detail drawing of 2nd Embodiment. It is a figure which shows 3rd Embodiment (another form of a steering system) of this invention.

Explanation of symbols

2FL, 2FR, 2RL, 2RR Wheel 3FL, 3FR, 3RL, 3RR Electric motor 4FL, 4FR, 4RL, 4RR Reducer 5FL, 5FR, 5RL, 5RR Drive circuit 11 Steering wheel 12 Auxiliary steering motor 21 Steering angle sensor 22 Brake pedal Sensor 23 Accelerator pedal sensor 24 Acceleration sensor 30 Integrated controller Step S14 Target turning amount calculation means Step S15 Target slip angle basic value calculation means Step S17 Driving force difference command value calculation means Step S18 Drive wheel control means Steps S19 and S20 Target slip angle calculation Means Steps S21, S22 Steering angle correction means

Claims (3)

An electric vehicle behavior control device capable of controlling the driving force on the left and right by independently controlling the driving wheels with an electric motor,
A steering mechanism that steers at least the front wheels or the rear wheels according to a steering operation;
Target turning amount calculation means for calculating a target turning amount of the vehicle based on the vehicle speed and the steering operation amount;
Target slip angle basic value calculating means for calculating a target slip angle basic value of the vehicle based on the vehicle speed and the steering operation amount;
Driving force difference command value calculating means for calculating a driving force difference command value for the driving wheel based on the target turning amount and the target slip angle basic value;
Driving wheel control means for controlling the driving wheel based on the driving force difference command value;
When the actual driving force difference of the driving wheels controlled by the driving wheel control means deviates from the driving force difference command value, a slip angle correction value is calculated based on the deviation amount, and A target slip angle calculating means for correcting the target slip angle basic value with a slip angle correction value to calculate a target slip angle;
Steering angle correction means for correcting the steering angle of the steering mechanism based on the target slip angle and the target turning amount;
A behavior control apparatus for an electric vehicle characterized by comprising: A slip angle range calculating means for detecting a possible range of the difference between the left and right driving force and calculating a range of a slip angle that can be realized in the range;
The target slip angle basic value calculation means limits the calculated target slip angle basic value to the possible range and outputs it.
The behavior control apparatus for an electric vehicle according to claim 1. A turning amount detecting means for detecting an actual turning amount;
Correction calculation means for correcting and calculating at least a steering angle command value or a driving force difference command value so that the actual turning amount matches the target turning amount;
Behavior control device for an electric vehicle according to claim 1 or claim 2, characterized in that it comprises a.