JP4470481B2 - Electric vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric-driven vehicle in which a driver accustomed to a regular car can make a turn with less sense of incongruity, and can perform the high-speed travel as the car and the turning operation at the vehicle speed though the configuration thereof is simple and has no turning mechanism of a tire on a front wheel. <P>SOLUTION: The electric-driven vehicle has rear wheels 2RL and 2RR to generate the braking and driving force and the differential braking and driving force in right and left wheels by electric motors 3RL and 3RR, front wheels 42FL and 42FR which generate only a small force in the lateral direction of a vehicle body in comparison with the rear wheels 2RL and 2RR, and are rotated following the direction of the vehicle body with the position of the center of gravity of the vehicle body being close to the rear wheels, and an integrated controller 30 to operate the output of the electric motors 3RL and 3RR according to the turning command value, the acceleration/deceleration command value and the vehicle speed. <P>COPYRIGHT: (C)2005,JPO&amp;NCIPI

Description

  The present invention belongs to the technical field of an electric vehicle having a simple configuration that uses an electric motor as a drive source and does not have a tire steering mechanism.

As a vehicle configuration with a simple configuration that does not have a tire steering mechanism, it is known that the rear wheel of the vehicle is a caster type and the front wheels are motor-driven independently from each other. In this electric vehicle, the motor output of the front wheels is known. Is adjusted independently on the left and right sides to realize a turning operation with a small turning radius (see, for example, Patent Document 1).
JP-A 48-44914

  However, since the conventional electric vehicle is configured to turn with a difference in the left and right driving force applied to the front wheels, the behavior when the vehicle turns is a behavior in which the rear end of the vehicle turns largely. On the other hand, the vehicle behavior of a normal front-wheel-steered automobile is a behavior in which the front end of the vehicle turns largely. Therefore, there is a problem that a driver who is used to a normal front-wheel-steered vehicle has a sense of discomfort when operating a conventional electric vehicle.

  Moreover, in the conventional electric vehicle, it is not considered that the turning characteristic of the vehicle changes greatly according to the vehicle speed (for the change of the turning characteristic of the vehicle depending on the vehicle speed, “ Movement and control ”(see, for example, published by Sankaido on May 31, 1994). Therefore, it is suitable for a vehicle that always travels at a low speed (for example, the upper limit of the vehicle speed is 10 km / h), and therefore the turning characteristics of the vehicle can be regarded as almost unchanged within the range of the vehicle speed. However, when applied to vehicles such as automobiles where the vehicle speed changes from 0 km / h to 100 km / h or more, the left and right motor outputs are adjusted in consideration of the fact that the turning characteristics of the vehicle change greatly depending on the vehicle speed. The problem of having to do arises.

  The present invention has been made paying attention to the above-mentioned problems, and while having a simple configuration without a tire steering mechanism on the front wheels, a driver accustomed to a normal automobile can turn with less discomfort and can operate at a high speed as an automobile. An object of the present invention is to provide an electric vehicle capable of running and turning at the vehicle speed.

In order to achieve the above object, in the electric vehicle of the present invention, a rear wheel that generates a braking / driving force and a braking / driving force difference between the left and right wheels by an electric motor, a center of gravity position of the vehicle body is closer to the rear wheel, and the rear wheel Compared with the front wheel that generates only a small force in the lateral direction of the vehicle and rotates following the direction of the vehicle, the output of the electric motor is calculated according to the turn command value, the acceleration / deceleration command value, and the vehicle speed detection value. Motor output calculation means , wherein the motor output calculation means outputs the outputs of the left and right wheel electric motors according to the turning command value and the detected vehicle speed so that the turning characteristic of the vehicle becomes a desired turning characteristic. Adjust .

Therefore, in the electric vehicle according to the present invention, when a braking / driving force difference is generated between the left and right rear wheels by the electric motor, the front wheel that generates only a small lateral force in the lateral direction of the vehicle compared to the rear wheel is directed toward the vehicle body. Since it follows and rotates, it becomes possible to turn in a vehicle posture in which the front end of the vehicle makes a large turn when turning the front wheel. Also, in the motor output calculation means, the difference between the rear wheel left and right driving force is adjusted according to not only the turn command value but also the vehicle speed detection value, so that the vehicle speed changes greatly and the turning characteristics of the vehicle change accordingly. Even in this case, it is possible to realize a turning characteristic that keeps the behavior of the vehicle stable in accordance with the change. As a result, while having a simple configuration without a tire steering mechanism on the front wheels, a driver accustomed to a normal car can turn with less discomfort, and can run at high speed as a car and turn at that speed. it can.

  Hereinafter, the best mode for carrying out an electric vehicle of the present invention will be described based on Example 1 shown in the drawings.

First, the configuration will be described.
FIG. 1 is an overall system diagram illustrating an electric vehicle according to a first embodiment. As shown in FIG. 1, the electric vehicle according to the first embodiment includes electric motors 3RL and 3RR as driving force generation sources, and the rotation shafts of the electric motors 3RL and 3RR are connected to the reduction gears 4RL and 4RR. And connected to the rear wheels 2RL and 2RR of the electric vehicle. Here, the output characteristics of the two electric motors 3RL and 3RR, the reduction ratios of the two reduction gears 4RL and 4RR, and the radii of the two left and right rear wheels 2RL and 2RR are all the same.

  Each of the electric motors 3RL and 3RR is a three-phase synchronous motor in which a permanent magnet is embedded in a rotor. Torque command values tTRL (left rear wheel), tTRR () in which the drive circuits 5RL and 5RR that control power transfer with the lithium ion battery 6 receive the power running and regenerative torque of the electric motors 3RL and 3RR from the integrated controller 30. Adjust to match the right rear wheel). However, in the situation where the rear wheels 2RL and 2RR run idle if output according to the torque command value, the torque is limited for each rear wheel 2RL and 2RR so that the rear wheels 2RL and 2RR corresponding to the drive circuits 5RL and 5RR do not run idle. And output. The drive circuits 5RL and 5RR transmit the motor rotation speed detected by a rotation position sensor (not shown) attached to each motor rotation shaft to the integrated controller 30 (motor output calculation means).

  Here, as a method for limiting and outputting the motor torque of each wheel so that the rear wheels 2RL and 2RR do not slip, for example, as disclosed in JP-A-6-98418, the wheels receive from the road surface. A method of estimating the reaction force and adjusting the motor torque of each wheel based on the estimated value, as disclosed in the document “Lateral Motion Stabilization with Feedback Controlled Wheels” (Sakai et al. 6th International Symposium on Advanced Vehicle Control, 2002) In addition, using a model that represents the wheel rotation speed characteristics with respect to the motor torque, and adjusting 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, There is a method of adjusting the torque of the motor independently so that the slip ratio is within a predetermined range, but any method can be used, so the description is omitted here. To do.

  The front wheels 42FL and 42FR are provided on the turning shafts 41FL and 41FR of the front wheels 42FL and 42FR. FIG. 2 shows one front wheel 42 out of the left and right front wheels 42FL and 42FR having a caster structure. The turning rotation shaft 41 of the front wheel 42 is inside the hollow support portion 45 of the front wheel 42 and rotates with respect to 45 through a bearing. The elements 44 and 43 and the front wheel 42 are all supported so as to rotate integrally around the turning shaft 41. Here, the intersection point P with the ground surface when the center of the rotation shaft 41 is extended and the point Q directly below the rotation center point 43 of the tire are configured such that the distance is ζ (> 0). A so-called caster structure in which the tire naturally steers so that the traveling direction of the turning rotation shaft 41 of the front wheel 42 coincides with the tire orientation A by traveling resistance during traveling is employed. The hollow support portion 45 of the front wheel 42 has a support shaft (not shown) in the vehicle longitudinal direction and the vehicle lateral direction so that the hollow support portion 45 is not easily deformed in the vehicle longitudinal and lateral directions. Further, the hollow support portion 45 is provided with a spring and a damper (not shown) in the vertical direction so that the vertical force received by the front wheel 42 from the road surface is hardly transmitted to the vehicle body.

  In addition, the front wheel 42 is provided with a friction brake by a hydraulic system (not shown) at a part 44, and the brake system hydraulic pressure rises in response to the driver's depression of the brake pedal 22, and the part according to the hydraulic pressure increase. A brake pad fixed to 44 brakes the front wheel 42 by sandwiching a disk that rotates together with the front wheel 42.

  The rear wheels 2RL and 2RR are also provided with friction brakes (not shown), and the rear wheels 2RL and 2RR are braked in response to the driver's depression of the brake pedal 22, as with the front wheels 42. Furthermore, the rear wheels 2RL and 2RR are connected to a link 51 for turning the left and right wheels with the same size. By moving the link 51 in the vehicle left-right direction by the steering motor 52, the rear wheels Steer (rear wheel steering means). A motor drive circuit 53 is connected to the steering motor 52, and the motor drive circuit 53 is based on the detected steering angle value from the actual steering angle sensor and the rear wheel steering angle target value tδr received from the integrated controller 30. Thus, the torque of the steering motor 52 is adjusted so that the actual rear wheel steering angle matches the rear wheel steering angle target value tδr. As such a steering device, there is one disclosed in Japanese Patent Application Laid-Open No. 2003-19975.

  In addition, electric motors 3RL, 3RR, a battery, etc. are arrange | positioned in the front-back position of rear-wheel 2RL, 2RR so that the front-back center-of-gravity position of the electric vehicle of FIG. For example, the front-rear center of gravity position is designed so that the wheel load ratio between the front wheels 45FL and 45FR and the rear wheels 2RL and 2RR is 2: 8.

  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 steering wheel 11. The rotation angle signal of the wheel 11, the vehicle body lateral acceleration (acceleration in the vehicle width direction) and the longitudinal acceleration signal detected by the acceleration sensor 24 attached to the center of gravity of the vehicle, the yaw rate signal detected by the yaw rate sensor 8, and the driver A state signal of the operated shift lever 25 and front wheel rotation speed signals detected by the front wheel rotation sensors 49 and 50 respectively attached to the turning rotation shafts 43FL and 43FR of the left and right front wheels 42FL and 42FR are input.

  The shift position of the shift lever 25 can be selected only when the vehicle is stopped, is a position “P” used when parking, a position “D” used during normal forward travel, a position “R” used during normal reverse travel, and mode A. There are a position “A” that is used during forward traveling in mode A, a position “AR” that is used during backward traveling in mode A, and a position “B” that is used during turning in mode B. Here, the mode A is an operation mode in which the vehicle is rotated with the vicinity of the rear wheel of the turning inner wheel as the turning center, and the mode B is an operation in which the vehicle is rotated with the point between the left and right rear wheels as the turning center. Mode.

  These shift positions are selected by the driver by operating the shift lever 25. Based on these signals, the integrated controller 30 calculates a torque command value tTRL for the rear left wheel motor 3RL, a torque command value tTRR for the rear right wheel motor 3RR, and a rear wheel steering angle target value tδr to obtain each motor 3RL, Transmit to 3RR drive circuits 5RL and 5RR. Here, the torque command value tTRL to the rear left wheel motor 3RL and the torque command value tTRR to the rear right wheel motor 3RR are both in units of Nm, and the direction in which the vehicle is accelerated forward is positive. The rear wheel rudder angle target value tδr has a unit of rad, and the direction to turn left is positive.

  Next, the operation will be described.

[Mode selection control processing]
FIG. 3 is a flowchart showing the flow of the mode selection control process executed by the integrated controller 30 according to the first embodiment. Each step will be described below. The integrated controller 30 includes peripheral components such as a RAM / ROM in addition to the microcomputer, and executes the flowchart of FIG. 3 at regular intervals, for example, every 5 ms.

  In step S401, each sensor signal and the received signals from the drive circuits 5RL and 5RR are stored in the RAM variable, and the process proceeds to step S402. Specifically, the accelerator opening signal is stored in a variable APS (unit is% and fully opened is 100%), the brake pedal force signal is stored in a variable BRK (unit is Pa), and the steering wheel 11 The rotation angle signal is stored in a variable δ (unit is rad, counterclockwise is positive), the vehicle body lateral acceleration signal is stored in a variable YG (the direction when turning left in FIG. 1 is positive), The vehicle yaw rate signal is stored in the variable γ (the direction when turning left is positive in FIG. 1), and the vehicle body lateral acceleration signal is stored in the variable YG (the direction when turning left is positive in FIG. 1). Store the lever signal in the variable SFT. The rotation speed signal from the left front wheel rotation sensor 49 is a variable NFL, and the rotation speed signal from the right front wheel rotation sensor 50 is a variable NFR (both units are rad / s, and the direction in which the vehicle moves forward is positive). ). Further, for the signals received from the drive circuits 5RL and 5RR, the rotational speeds of the respective motors are stored in variables NRL and NRR (both units are rad / s, and the direction in which the vehicle advances is positive).

In step S402, the vehicle speed V (unit is m / s, and the direction in which the vehicle moves forward is positive) is calculated by the following equation, and the process proceeds to step S403 (vehicle speed detecting means).
V = (NFL * Rf + NFR * Rf + NRL / GG * Rr + NRR / GG * Rr) * R / 4
Here, Rf is the radius of the front wheel, Rr is the radius of the rear wheel, and GG is the reduction ratio of the reduction gear of the rear wheel.

  In step S403, it is determined whether or not the shift lever position is the position “P” used during parking. If “P”, the process proceeds to step S404, and this routine is terminated with tTRL = tTRR = tδr = 0. . Otherwise, the process proceeds to step S410.

  In step S410, it is determined whether or not the shift lever position is “D”, “A”, or “B”. If the shift lever position is “D”, “A”, or “B”, the process proceeds to step S411. If not, the process proceeds to step S420.

  In step S411, it is determined whether or not the shift lever position is “B” and the vehicle speed V is less than a second vehicle speed threshold value Vb (for example, 1 m / s). If yes, step S412 is performed. , The calculation routine in mode B described later is executed, and this routine is terminated. Otherwise, the process proceeds to step S413.

  In step S413, it is determined whether or not the shift lever position is “A” and the vehicle speed V is less than a first vehicle speed threshold value Va (for example, 3 m / s). If yes, the process proceeds to step S414. Then, the calculation routine in mode A, which will be described later, is executed, and this routine ends. If not, the process proceeds to step S415, an arithmetic routine in mode D described later is executed, and this routine is terminated.

  When the process proceeds from step S410 to step S420, in step S420, the shift lever position is “AR” and the absolute value | V | of the vehicle speed V is less than a predetermined value Var (for example, 2 m / s). If YES in step S421, the flow advances to step S421 to execute a calculation routine in mode AR described later, and this routine ends. If not, the process proceeds to step S422, an arithmetic routine for mode R described later is executed, and this routine is terminated.

[Mode selection control action]
When the shift position of the shift lever 25 can be selected only when the vehicle is stopped and the “P” position used for parking is selected, the flow proceeds from step S401 to step S402 to step S403 to step S404 in the flowchart of FIG. In step S404, the torque command value tTRL for the rear left wheel motor 3RL, the torque command value tTRR for the rear right wheel motor 3RR, and the rear wheel steering angle target value tδr are set to tTRL = tTRR = tδr = 0, and this routine is terminated. To do.

  When “D” or “A” or “B” is selected as the shift position of the shift lever 25, and neither the “A” position selection condition nor the “B” position selection condition is satisfied. In the flowchart of FIG. 3, the process proceeds from step S401 to step S402, step S403, step S410, step S411, step S413, and step S415. In step S415, the calculation routine for mode D used during normal forward travel is performed. Execute and end this routine.

When the position of “D”, “A”, or “B” is selected as the shift position of the shift lever 25, the “A” position is selected and the A position selection condition of V <Va is satisfied. In the flowchart of FIG. 3, the flow proceeds from step S401 to step S402, step S403, step S410, step S411, step S413, and step S414. In step S414, the mode A is used for extremely low speed forward travel. Execute the calculation routine and end this routine.
That is, even when the “A” position is selected, when the vehicle speed V is equal to or higher than the first set threshold value Va, the process proceeds to step S415, and the calculation routine for mode D is executed. migration Ru is prohibited. For this reason, it is possible to suppress instability of vehicle behavior due to abrupt transition to driving mode A while the vehicle is traveling.

When the position of “D”, “A”, or “B” is selected as the shift position of the shift lever 25, the “B” position selection and the B position selection condition of V <Vb are satisfied. In the flowchart of FIG. 3, the process proceeds from step S401 to step S402, step S403, step S410, step S411, and step S412. In step S412, the calculation routine for mode B used during extremely low speed turning is executed. Then, this routine ends.
That is, even in the “B” position selection, when the vehicle speed V is equal to or higher than the second set threshold value Vb, the process proceeds from step S413 to step S415 and the calculation routine in mode D is executed. the transition to B is Ru is prohibited. For this reason, it is possible to suppress instability of vehicle behavior due to abrupt transition to driving mode B while the vehicle is traveling.

When the “AR” position used during reverse travel in mode A is selected as the shift position of the shift lever 25, and the AR position selection condition that the vehicle speed absolute value | V | is less than the predetermined value Var is satisfied In the flowchart of FIG. 3, the flow proceeds from step S401 to step S402, step S403, step S410, step S420, and step S421. In step S421, an arithmetic routine for the mode AR used during reverse running is executed. End the routine.
That is, even in the “AR” position selection, if the vehicle speed absolute value | V | is equal to or greater than the predetermined value Var, the process proceeds from step S420 to step S422, and the calculation routine in mode R is executed. Transition to AR is prohibited. For this reason, the vehicle behavior instability caused by suddenly shifting to the driving mode AR when traveling backward can be suppressed.

  When the “R” position used during normal reverse travel is selected as the shift position of the shift lever 25, the process proceeds from step S401 to step S402 to step S403 to step S410 to step S420 to step S422 in the flowchart of FIG. In step S422, the calculation routine for the mode R used during normal reverse running is executed, and this routine ends.

[About the design principle and operation form of the controller that realizes the reference model response]
Next, the calculation routine in step S415 in mode D (FIG. 5), the calculation routine in step S414 in mode A (FIG. 8), the calculation routine in step S412 in mode B (FIG. 10), and the mode R in step S422 In the time calculation routine (FIG. 12) and the calculation routine in the mode AR of step S421 (FIG. 14), the torque command value tTRL to the rear left wheel motor 3RL, the torque command value tTRR to the rear right wheel motor 3RR, and the rear wheel steering The method for calculating the target angle value tδr will be described in order. Before describing the calculation processing in each calculation routine, the calculation principle and the implementation method will be described first.

  “Motor motion and control” (Sankaido) shows the equation of motion of the vehicle behavior for steering the front and rear wheels. For example, for p194, the front wheel rudder angle δf [rad] and the rear wheel rudder angle δr [rad] are the manipulated variables, and the vehicle yaw rate γ [rad / s] and the vehicle slip angle β [rad] at the vehicle body center of gravity are the state variables. The equation of motion is shown. This equation of motion shows that the vehicle speed V [m / s] is constant (dV = 0), V ≠ 0, and the slip angle (β [rad]) is very small (| β | << 1, sinβ? Β, cosβ? 1). Derived on the premise of.

ここで、Lrは後輪軸と重心との距離[m]、Ltは後輪のトレッドベース距離/2[m]、mは車重[kg]、Iγはヨー慣性モーメント[Nmss]である。また、Krは後輪タイヤコーナリングスティッフネス[N/rad] であり、後輪ステアリング剛性の影響によるステアリング角に対するコーナリングパワーの低下分も加味した値である。Ｖは車速[m/s]であり、γはヨーレート[rad/s]、βは車体重心位置の車体すべり角[rad]である。
「自動車の運動と制御」（山海堂）p52に記されているように横力Ｙ[N]とヨーレートγ[rad/s]と滑り角β[rad]は次の関係にある。
Ｙ＝mＶ(dβ/dt＋γ) …(A2) The concept of the equation of motion can be applied to the electric vehicle according to the first embodiment of the present invention. That is, by adding the operation amount that the driving force of the right wheel is u [N] and the driving force of the left wheel is -u [N], and the front wheel is the caster type of FIG. Assuming that the force is almost zero, the equation of motion can be derived as follows.

Here, Lr is the distance [m] between the rear wheel shaft and the center of gravity, Lt is the tread base distance / 2 [m] of the rear wheel, m is the vehicle weight [kg], and Iγ is the yaw moment of inertia [Nmss]. Kr is the rear wheel tire cornering stiffness [N / rad], which takes into account the decrease in cornering power with respect to the steering angle due to the influence of the rear wheel steering stiffness. V is the vehicle speed [m / s], γ is the yaw rate [rad / s], and β is the vehicle slip angle [rad] at the center of gravity of the vehicle.
As described in “Vehicle Movement and Control” (Sankaido) p52, the lateral force Y [N], the yaw rate γ [rad / s], and the slip angle β [rad] have the following relationship.
Y = mV (dβ / dt + γ) (A2)

These equations of motion can be rewritten into the following form using the differential operator s.
β = {Q ₁₂ (s) / Qden (s)} · δr + {Q ₁₃ (s) / Qden (s)} · u
γ = {Q ₂₂ (s) / Qden (s)} · δr + {Q ₂₃ (s) / Qden (s)} · u
Y = {Q ₃₂ (s) / Qden (s)} · δr + {Q ₃₃ (s) / Qden (s)} · u (A3)
Q ₁₂ (s), Q ₁₃ (s), Q ₂₂ (s), Q ₂₃ (s), Q ₃₂ (s), Q ₃₃ (s), and Qden (s) are all functions of the vehicle speed V. It is expressed by the following formula.
Q ₁₂ (s) = 2VKr (I _γ s + mVLr)
Q ₁₃ (s) = -2Lt (mV ² -2LrKr)
Q ₂₂ (s) = -2mV ² KrLrs
Q ₂₃ (s) = 2VLt (mVs + 2Kr)
Q ₃₂ (s) = 2mV ² KrI _γ s ²
Q ₃₃ (s) = 4mVLtKr (Lrs + V)
^{Qden (s) = mV 2 I} γ s 2 + 2VKr (mLr 2 + I γ) s + 2mV 2 LrKr ... (A4)

“Automotive motion and control” (Sankaido) p203-p207, the front wheel rudder angle is adjusted so that the response of the vehicle yaw rate γ and slip angle β to the steering operation amount δ is a desirable transfer characteristic (reference model). A controller derivation method for generating the command value δf ^* and the rear wheel steering angle command value δr ^* is also shown. According to this method, in the first embodiment of the present invention, the command value u of the driving force difference between the left and right wheels is set so that the response of the yaw rate γ and the slip angle β to the steering operation amount δ is a desirable transmission characteristic (reference model). A controller (P1 (s) and P2 (s) in FIG. 4 (a)) for calculating * and the rear wheel steering angle command value δf ^* can be derived as follows.

Now, _let G _{γδ be} the desired transfer characteristic (normative model) of yaw rate γ with respect to the steering operation amount δ, and G _{βδ be} the desired transfer characteristic (normative model) of the slip angle β with respect to the steering operation amount δ.
G _γδ = m2 / (s ² + 2wns + wn ² )
G _βδ = 0 (A5)

That is, desired response smooth second order response of the yaw rate γ for steering operation amount [delta] (e.g., wn = 4π, m2 = wn 2/4) and then, is always slip angle β is 0 regardless of the amount of steering operation [delta] Set as follows.
In FIG. 4A, the relationship between the steering operation amount δ and the yaw rate γ and the relationship between the steering operation amount δ and the slip angle β are as follows. Here, 1 / Td (s) is the servo delay of the rear wheel steering system.
_{β = ({Q 13 (s} ) / Qden (s)} p1 (s) + {Q 12 (s) / Qden (s)} · {p2 (s) / Td (s)}) δ
_{γ = ({Q 23 (s} ) / Qden (s)} p1 (s) + {Q 22 (s) / Qden (s)} · {p2 (s) / Td (s)}) δ ... (A6)
Therefore, the equation (A7) is derived from the condition that these transfer characteristics are made to coincide with the desired transfer characteristics G _βδ and G _γδ , respectively.
_{G βδ = 0 = {Q 13} (s) / Qden (s)} p1 (s) + {Q 12 (s) / Qden (s)} · {p2 (s) / Td (s)}
G _γδ = m2 / (s ² + 2wns + wn ² )

_{= {Q 23 (s) /} Qden (s)} p1 (s) + {Q 22 (s) / Qden (s)} · {p2 (s) / Td (s)} ... (A7)
By solving this simultaneous equation and using the relational expression of equation (A4), controllers P1 (s) and P2 (s) can be derived as in equation (A8). Here, the servo delay of the rear wheel steering is a first-order delay of a time constant τ (for example, τ = 0.1 [s]), that is, Td = τs + 1.
p1 (s) = {m2 / 2Lt} {(I _γ s + mVLr) / (s ² + 2wns + wn ² )}
p2 (s) = {m2 (mV ² −2LrKr) / 2VKr} {(τs + 1) / (s ² + 2wns + wn ² )}… (A8)

As described above, in the first embodiment of the present invention, the command value u * for the driving force difference between the left and right wheels is set so that the response of the yaw rate γ and the slip angle β to the steering operation amount δ is a desirable transmission characteristic (reference model). A controller (P1 (s) and P2 (s) in FIG. 4 (a)) for calculating the rear wheel steering angle command value δf ^* can be derived.

Next, a method for realizing the controllers P1 (s) and P2 (s) in the equation (A8) will be described. Since P1 (s) and P2 (s) can be rewritten by the following equation (A9), a method for realizing the equation (A9) will be described. b0 and b1 are functions of the vehicle speed V.
yx = (b1s + b0) / (s ² + 2wns + wn ² )… (A9)
Equation (A9) can be rewritten as shown in FIG. Therefore, at predetermined time intervals (for example, every 5 ms), first, X2 and X1 are updated by performing the integration operation in FIG. 4B by Euler approximation, for example, and then b0 and b1 are set to the vehicle speed V. This is realized by sequentially updating the output yx from X2, X1, b0, and b1 from time to time.

[Calculation routine in mode D]
In the calculation routine in mode D of step S415 in FIG. 3, the flowchart of FIG. 5 is executed.

  In step S501, the target driving force tTD of the vehicle is calculated. The 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 with the vehicle speed V and the accelerator opening APS as axes, and is set as shown in FIG. 6, for example.

  In steps S503 to S506, the target torque tU [Nm] and the rear wheel steering command value δtr of the driving force difference generated in the rear wheel left and right motors are calculated according to the steering wheel rotation angle δ and the vehicle speed V. Based on the above design principle, the calculation is performed so that the response of the yaw rate to the steering wheel rotation angle δ matches the reference model response, and the response of the vehicle slip angle to the steering wheel rotation angle δ also matches the reference model response. The reference model response of the yaw rate with respect to the steering wheel rotation angle δ is assumed to be the secondary transfer characteristic shown in the equation (A5), and the reference model response of the vehicle body slip angle with respect to the steering wheel rotation angle δ is always assumed to be zero.

In step S503, the vehicle speed V calculated in step S420 is used to calculate the values corresponding to b0 and b1 in equation (A9) for the first equation in equation (A8) as follows.
b1 = m2 * Ir / 2 / Lt
b0 = m2 * m * V * Lr / 2 / Lt (B1)
Here, m2 is such that the steady value of the yaw rate with respect to the steering wheel rotation angle δ is, for example, δ / 4.
m2 = wn ^2/4 (wn is set to, for example, 4 [pi])
Keep it as Vehicle design values are used for m, Ir, Lr, and Lt.

  In step S504, X2 and X1 at the time when the previous step S504 was executed are used, and X2 and X1 are updated by Euler approximation of the integral calculation of FIG. 4B. In FIG. 4B, ux is the steering wheel rotation angle δ, and the output yx is the driving force difference command value tU for the left and right wheels. When calculating, variables X2a and X1a are used as variables used in step S504 as X2 and X1 in FIG. After updating X2 and X1 in FIG. 4 (b), the left and right wheels are calculated by calculating the output yx from the relational expression shown in FIG. 4 (b) according to the values and b0 and b1 obtained in step S503. The driving force difference command value tU is calculated.

In step S505, the vehicle speed V calculated in step S420 is used to calculate the values corresponding to b0 and b1 in equation (A9) for the equation in the second stage of equation (A8) as follows. In order to prevent 0%, the vehicle speed V is calculated by limiting the minimum value to Vmin (for example, 1 m / s).
b1 = m2 * (m * V * V-2 * Lr * Kr) / 2 / V / Kr * τ
b0 = m2 * (m * V * V-2 * Lr * Kr) / 2 / V / Kr (B2)
Here, m, Ir, Lr, Lt, and Kr use vehicle design values. Also, τ is set to, for example, about 0.1 in accordance with the servo delay of the rear wheel steering system.

  In step S506, X2 and X1 at the time when the previous step S506 was executed are used, and X2 and X1 are updated by Euler approximation of the integral calculation in FIG. 4B. In FIG. 4B, ux is the steering wheel rotation angle δ, and the output yx is the rear wheel steering command value tδr. When calculating, variables X2b and X1b are used as variables used in step S504 as X2 and X1 in FIG. After updating X2 and X1 in FIG. 4 (b), the rear wheel is calculated by calculating the output yx from the relational expression shown in FIG. 4 (b) according to these values and b0 and b1 obtained in step S505. A steering command value tδr is calculated.

In step S507, torque command values tTRL and tTRR to the rear wheels are calculated from the target driving force tTD and the target left / right driving force difference tU by the following equation.
TTRL = tTD * Rr / GG / 2-tU * Rr / GG
TTRR = tTD * Rr / GG / 2 + tU * Rr / GG… (B3)
After the calculation in step S507, this routine ends.

  An example of the above vehicle behavior simulation is shown in FIG. The vehicle weight is 1670kg. The reduction ratio of the reduction gear is set to 4. This is an example of the result when the steering wheel is steered stepwise at time 0 while traveling at a vehicle speed of 100 km / h. FIG. 7A is a time series waveform, and FIG. 7B is a vehicle trajectory (viewed from above). It can be confirmed that the turning operation is performed while the vehicle body slip angle is almost always kept near 0, and the desired operation can be realized.

[Calculation routine in mode A]
In the calculation routine in mode A of step S414 in FIG. 3, the flowchart of FIG. 8 is executed.

  In step S801, a target speed tV at the center position of the rear wheel shaft is calculated. For example, when the accelerator calculation APS is 0, tV = 0, and when the APS is 100%, tV = 3 [m / s] is assigned proportionally.

In step S802, a target value tρ that is an inverse value of the turning radius of the center position of the rear wheel shaft is calculated. The target value tρ is a positive value when turning left, that is, when the vehicle's turning center is on the left, and negative when turning right, that is, when the vehicle's turning center is on the right. For example, the characteristics shown in FIG. 9 are set according to δ. Here, when the length of half of the tire width is Wt and the length of half of the tread base distance of the rear wheel is Lt, the target value tρ is -1 / (Lt + Wt) and 1 / (Lt + Set to be in the range between (Wt) .

In step S803, the target rotational speeds tNRL and tNRR of the left rear wheel motor and the right rear wheel motor are calculated from the target speed tV of the center position of the rear wheel shaft and the target value tρ of the reciprocal value of the turning radius of the center position of the rear wheel shaft by the following equations: Calculate with.
tNRL = tV * (1-Lt * tρ) / Rr * GG
tNRR ＝ tV * (1 + Lt * tρ) / Rr * GG… (C1)

In step S804, feedback control is performed so that the rotation speed NRL of the left rear wheel motor approaches the target rotation speed tNRL of the left rear wheel motor. For example, proportional control is performed as in the following equation to calculate a torque command value tTRL for the left rear wheel motor. Kp1 is a proportional gain.
tTRL = Kp1 * (tNRL-NRL)

In step S805, feedback control is performed so that the rotational speed NRR of the right rear wheel motor approaches the target rotational speed tNRR of the right rear wheel motor. For example, proportional control is performed as in the following equation to calculate the torque command value tTRR for the right rear wheel motor. Kp1 is the same proportional gain as in step S804.
tTRR = Kp1 * (tNRR + NRR)

  In step S806, a rear wheel steering command value tδr is calculated. For example, tδr = 0. In addition, a table associated in accordance with the steering wheel rotation angle δ may be provided in the ROM, and a calculation may be performed with reference to the table. After the calculation in step S806, this routine ends.

  By performing the above calculation, as shown in FIG. 16 (a), it becomes possible to perform an operation of turning the vehicle in a small turn around the vicinity of the rear wheel of the turning inner wheel (excluding the tire width) as the turning center.

[Calculation routine in mode B]
In the calculation routine in mode B of step S412 in FIG. 3, the flowchart of FIG. 10 is executed.

  In step S1101, it is determined whether or not a turning operation is performed. When the accelerator calculation APS is 0, it is determined that f_MB = 0 and the turning operation is not performed, and otherwise f_MB = 1 is set and the turning operation is performed.

  In step S1102, the target rotational speed tNRL of the left rear wheel motor and the target rotational speed tNRR of the right rear wheel motor are calculated according to the steering wheel rotational angle δ. At this time, tNRL and tNRR are set so that the signs are reversed (the left and right wheels rotate in reverse), especially when the absolute value of the steering wheel rotation angle δ is maximum, the absolute value of tNRL and the absolute value of tNRR It is recommended that the values match. Thus, when the absolute value of the steering wheel rotation angle δ is maximum, the turning center of the vehicle can be realized in the vicinity of the center position of the rear wheel shaft. When the steering wheel rotation angle δ is between 0 and the maximum value, if the tNRL / tNRR value is set to change monotonously, the turning center of the vehicle increases as the steering wheel rotation angle δ increases. A continuous movement approaching the vicinity of the position can be realized.

In step S1104, the torque command value tTRL for the left rear wheel is calculated as follows. Kp2 is a proportional gain.
tTRL = Kp2 * (RAT * tNRL-NRL)
Here, the initial value of RAT is set to 0, and is increased so as to match 1 at a predetermined speed when f_MB = 1 (for example, it approaches 0.001 in 5 ms at 5 ms), and at a predetermined speed when f_MB = 0. It is a variable that has been manipulated to be reduced to 0 (for example, 0.005 in steps of 5 ms). By doing so, the vehicle behavior is continuously changed at the time of switching between f_MB = 0 and f_MB = 1.

In step S1105, the torque command value tTRR for the right rear wheel is calculated as follows. Kp2 is the same proportional gain as in step S1104.
tTRR = Kp2 * (RAT * tNRR-NRR)
Here, RAT uses the same value as in step S1104.

  In step S1106, a rear wheel steering command value tδr is calculated. For example, tδr = 0. In addition, a table associated in accordance with the steering wheel rotation angle δ may be provided in the ROM, and a calculation may be performed with reference to the table. After the calculation in step S1106, this routine ends.

  By performing the above calculation, as shown in FIG. 16 (b), it is possible to perform a small turn where the vehicle is rotated with the point between the left and right rear wheels as the turning center, and the vehicle is further turned from mode A. To be able to.

[Calculation routine in mode R]
In the calculation routine in the mode R of step S422 in FIG. 3, the flowchart of FIG. 12 is executed.

  In step S1301, a target driving force tTD for the vehicle is calculated. The calculation is performed by referring to the map MAP_tTDR (V, APS) stored in advance in the ROM. The map MAP_tTDR (V, APS) is characteristic data with the vehicle speed V and the accelerator opening APS as axes, and is set as shown in FIG. 13, for example.

In step S1302, a target left / right driving force difference tU is calculated. The target left / right driving force difference tU is calculated by the following equation so as to be proportional to the steering wheel rotation angle δ.
tU ＝ KK * δ
When the steering wheel is turned to the left, KK is set to a negative value so that the vehicle rotates clockwise as viewed from above the vehicle.

In step S1303, torque command values tTRL and tTRR for the rear wheels are calculated from the target driving force tTD and the target left / right driving force difference tU by the following equations.
tTRL = tTD * Rr / GG / 2−tU * Rr / GG
tTRR ＝ tTD * Rr / GG / 2 ＋ tU * Rr / GG

In step S1304, a rear wheel steering command value tδr is calculated. For example, tδr = 0. In addition, a table associated in accordance with the steering wheel rotation angle δ may be provided in the ROM, and a calculation may be performed with reference to the table. After the calculation in step S1304, this routine ends.
By performing the above calculation, the vehicle can be moved backward.

[Calculation routine in mode AR]
In the calculation routine in the mode AR of step S421 in FIG. 3, the flowchart of FIG. 14 is executed.

  In step S1501, a target speed tV at the center position of the rear wheel shaft is calculated. For example, when the accelerator calculation APS is 0, tV = 0, and when the APS is 100%, tV = −3 [m / s] is assigned proportionally.

In step S1502, a target value tρ that is an inverse value of the turning radius of the center position of the rear wheel shaft is calculated. The target value tρ is a positive value when turning left, that is, when the vehicle's turning center is on the left, and negative when turning right, that is, when the vehicle's turning center is on the right. According to δ, for example, the characteristics as shown in FIG. 9 are set. Here, when the length of half of the tire width is Wt and the length of half of the tread base distance of the rear wheel is Lt, the target value tρ is -1 / (Lt + Wt) and 1 / (Lt + Set to be in the range between (Wt) .

In step S1503, the target rotational speeds tNRL and tNRR of the left rear wheel motor and the right rear wheel motor are calculated from the target speed tV at the center position of the rear wheel shaft and the target value tρ of the reciprocal value of the turning radius at the center position of the rear wheel shaft by the following equations: Calculate with.
tNRL = tV * (1-Lt * tρ) / Rr * GG
tNRR ＝ tV * (1 + Lt * tρ) / Rr * GG… (D1)

In step S1504, feedback control is performed so that the rotation speed NRL of the left rear wheel motor approaches the target rotation speed tNRL of the left rear wheel motor. For example, proportional control is performed as in the following equation to calculate a torque command value tTRL for the left rear wheel motor. Kp3 is a proportional gain.
tTRL = Kp3 * (tNRL-NRL)

In step S1505, feedback control is performed so that the rotational speed NRR of the right rear wheel motor approaches the target rotational speed tNRR of the right rear wheel motor. For example, proportional control is performed as in the following equation to calculate the torque command value tTRR for the right rear wheel motor. Kp3 is the same proportional gain as in step S1504.
tTRR = Kp3 * (tNRR-NRR)

In step S1506, a rear wheel steering command value tδr is calculated. For example, tδr = 0. In addition, a table associated in accordance with the steering wheel rotation angle δ may be provided in the ROM, and a calculation may be performed with reference to the table. After the calculation in step S1506, this routine ends.
By performing the above calculation, the vehicle can be rotated slightly while moving backward.

[Running effect on electric vehicle]
The conventional electric vehicle described in Japanese Patent Laid-Open No. 48-44914 is configured to turn with a difference in the left and right driving force applied to the front wheels, and therefore the behavior when the vehicle turns is shown in FIG. As shown in FIG. 4, the rear end of the vehicle turns around. On the other hand, the vehicle behavior of a normal front-wheel steering automobile is a behavior in which the front end of the vehicle turns largely as shown in FIG. Therefore, when a driver accustomed to a normal front-wheel-steered vehicle operates an electric vehicle described in Japanese Patent Laid-Open No. 48-44914, there is a great sense of discomfort.

On the other hand, in the first embodiment, the rear wheels 2RL and 2RR that generate a braking / driving force and a braking / driving force difference between the left and right wheels by the electric motors 3RL and 3RR, and the center of gravity of the vehicle body are located closer to the rear wheels, and the rear wheels Compared with 2RL and 2RR, only a small force is generated in the lateral direction of the vehicle body, and the front wheels 42FL and 42FR that steer following the direction of the vehicle body, the turning command value, the acceleration / deceleration command value, and the vehicle speed, The electric vehicle is configured to include an integrated controller 30 that calculates the outputs of the electric motors 3RL and 3RR. With this configuration, the following actions can be achieved simultaneously.
1) When turning, it is possible to turn in a vehicle posture in which the front end of the vehicle turns as shown in FIG. 15 (b), and even a driver who is accustomed to a normal front-wheel-steering vehicle can operate the vehicle with less discomfort.
2) Similar to the electric vehicle disclosed in Japanese Patent Laid-Open No. 48-44914, the vehicle can make a smaller turn than an ordinary vehicle (the operations shown in FIGS. 16A and 16B).
3) Since the rear wheel left / right driving force difference is adjusted according to not only the turn command value but also the vehicle speed, even if the vehicle speed changes greatly and the turning characteristics of the vehicle change accordingly, the change In addition, it is possible to realize a turning behavior that keeps the behavior of the vehicle stable.
4) Brake performance as an automobile can be achieved by adding a brake mechanism to each wheel.
5) Since the front wheel turning angle adjustment mechanism is not required, the vehicle can be lightened. Further, the passenger compartment space can be expanded by setting a passenger seat at the front of the vehicle. Furthermore, the degree of freedom in designing the front part of the vehicle is also increased.

Further, a link 51 and a steering motor 52 for steering the rear wheels 2RL and 2RR according to the turning command value are provided. As a result, the following actions, which are more preferable as the turning motion performance of the automobile, can be achieved at the same time.
1) The moving speed of the vehicle in the lateral direction can be improved, and the responsiveness when the vehicle moves laterally can be increased. In the case of the first embodiment, if a left / right driving force difference is generated when a turn command is generated, a yaw moment is generated in the vehicle, a slip angle is given to the rear wheel accordingly, and a lateral force is generated accordingly. Therefore, there is a delay from the generation of the turn command to the generation of force in the lateral direction of the vehicle. On the other hand, since it is now possible to generate force in the lateral direction of the vehicle by steering the rear wheel at the same time as the turn command is generated, more agile motion in the lateral direction of the vehicle such as quick lane change operation is possible. It became.
2) The turning motion (turning radius and yaw rate) and turning posture of the vehicle can be adjusted independently. By having two operation inputs that can adjust the vehicle behavior, the difference between the left and right driving force of the rear wheel and the turning angle of the rear wheel, the vehicle's turning motion (turning radius and yaw rate) and turning posture are made transient. In addition, it is possible to independently adjust the desired characteristics.

  Furthermore, the vehicle has a driving mode A in which the vehicle is turned with the vicinity of the rear wheel of the turning inner wheel as the turning center. As a result, the turning operation with a small turning radius, that is, the vehicle operation shown in FIG. 16 (a) is possible, and the handling of the vehicle at low speed is facilitated.

  In addition, in the driving mode A, when the turning center of the vehicle is in the ground contact surface of the inner ring of the rear wheel, the tire surface of the inner wheel of the rear wheel is twisted about the turning center (the front wheel when the normal wheel is worn out) As the tire wears, the tire surface and the road surface are deviated from each other (hereinafter referred to as a “set-off sound”). Therefore, in the first embodiment, in the operation mode A, the inside width of the rear wheel of the turning inner wheel is excluded as the turning center. As a result, it is possible to suppress the wear of the rear inner ring and to suppress the tired sound of the tire.

  When the vehicle speed V is equal to or higher than the first set threshold value Va, the shift to the operation mode A is prohibited. As a result, vehicle behavior instability due to abrupt transition to driving mode A while the vehicle is traveling can be suppressed.

  In addition, the vehicle has an operation mode B in which the vehicle is rotated with the point between the left and right rear wheels as a turning center. As a result, the turning operation can be performed with a turning radius smaller than that of the operation mode A (FIG. 16B). Therefore, handling of the vehicle at low speed is further facilitated.

  When the vehicle speed V is equal to or higher than the second set threshold value Vb, the transition to the operation mode B is prohibited. As a result, vehicle behavior instability due to abrupt transition to driving mode B while the vehicle is traveling can be suppressed.

Next, the effect will be described.
In the electric vehicle according to the first embodiment, the effects listed below can be obtained.

  (1) The rear wheels 2RL and 2RR, which generate a braking / driving force difference between the left and right wheels by the electric motors 3RL and 3RR, and the center of gravity of the vehicle body are closer to the rear wheels, compared with the rear wheels 2RL and 2RR. The output of the electric motors 3RL and 3RR is generated in accordance with the front wheels 42FL and 42FR which generate only a small force in the lateral direction of the vehicle body and rotate following the direction of the vehicle body, and the turn command value, the acceleration / deceleration command value and the vehicle speed. Since the electric vehicle is configured with the integrated controller 30 that calculates, the driver who is used to a normal car can turn with a sense of incongruity while having a simple configuration that does not have a tire turning mechanism on the front wheels 42FL and 42FR. High-speed driving as an automobile and turning operation at the vehicle speed can be performed.

  (2) Since there is a link 51 and a steering motor 52 that steer the rear wheels 2RL and 2RR according to the turn command value, the rear wheel 2RL and 2RR are steered at the same time as the turn command is generated. As a control input that can adjust the vehicle behavior as well as a more agile movement in the lateral direction of the vehicle, such as a quick lane change operation, the left and right driving force difference between the rear wheels 2RL and 2RR and the rear wheel 2RL can be generated. The two turning angles of 2RR can be adjusted so that the two characteristics of the turning operation and the turning posture of the vehicle have independent desired characteristics even transiently.

  (3) Since the integrated controller 30 has the operation mode A in which the vehicle is turned with the vicinity of the rear wheel of the turning inner wheel as the turning center, the turning operation can be performed with a reduced turning radius, and the vehicle can be handled at a low speed. Can be easily.

  (4) When the operation mode A is selected, the integrated controller 30 excludes the inside of the tire width of the turning inner wheel as the turning center, so that it is possible to suppress the wear of the inner wheel of the rear wheel and also suppress the tired sound of the tire. can do.

  (5) Since the integrated controller 30 prohibits the transition to the operation mode A when the vehicle speed V is equal to or higher than the first vehicle speed threshold value Va, the behavior of the vehicle due to abrupt transition to the operation mode A while the vehicle is traveling is suppressed. Stabilization can be suppressed.

  (6) Since the integrated controller 30 has an operation mode B in which the vehicle is rotated with the point between the left and right rear wheels as a turning center, the turning operation can be performed with a turning radius smaller than that of the operation mode A, and the vehicle speed can be reduced. It is possible to further facilitate the handling of the vehicle.

  (7) The integrated controller 30 prohibits the transition to the operation mode B when the vehicle speed V is equal to or higher than the second vehicle speed threshold value Vb. Stabilization can be suppressed.

  As mentioned above, although the electric vehicle of this invention has been described based on Example 1, it is not restricted to this Example 1 about a concrete structure, The summary of the invention which concerns on each claim of a claim Unless it deviates, design changes and additions are allowed.

  The drive system is not limited to the form shown in FIG. 1. For example, the drive form of the rear wheels may be as shown in FIG. FIG. 17 shows that the rear wheel is a clutch motor 60 (both the inner and outer motors are rotationally supported, and reverse torque is applied to the left and right wheels via the speed reducers 63R and 63L by generating torque in the motor. This is a motor that can be used, and is disclosed in Japanese Patent Application Laid-Open No. 4-332927.) A driving force difference is applied to the left and right rear wheels, and the vehicle is controlled by a driving motor 61 via a differential gear 62. It is a form that generates force. As long as the left and right wheel torques of the rear wheels can be adjusted independently as described above, it is only necessary.

  Further, the form of the front wheel may be any as long as it does not easily generate a lateral force of the vehicle body, and is not necessarily a caster type. For example, the front wheels are not steered at all, and a large number of cylindrical rubber rotating bodies having a rotation axis (axis Z) in the rolling surface direction are arranged at the ground contact portion on the road surface as shown in FIG. It is good to have done.

The configuration without the rear wheel steering means in FIG. 1 can be similarly realized. That is, it can be realized by changing the above-described first embodiment as follows.
1) The step of calculating the rear wheel steering command value is deleted in all modes P, D, A, B, R, and AR.
2) For mode D, in Example 1, the yaw rate response to the steering wheel rotation angle δ matches the reference model response, and the response of the vehicle slip angle to the steering wheel rotation angle δ also matches the reference model response. I was trying to do it. However, in the form without the rear wheel steering means, the operation input is reduced by 1, so this cannot be realized. Therefore, the driving force difference command value tU for the left and right wheels is calculated so that only the response of the yaw rate with respect to the steering wheel rotation angle δ matches the reference model response. That is, instead of the second formula of formula (A7), using _{Q 23 (s) / Qden (} s) * P1 (s) = G γδ, derives P1 (s), it similarly based The driving force difference command value tU for the left and right wheels may be calculated.

  In the first embodiment, the electric vehicle including the drive system for driving the left and right rear wheels with independent electric motors and the rear wheel steering means is shown. However, as described above, the left and right wheel torques of the rear wheels are independently adjusted. The present invention can also be applied to an electric vehicle equipped with a drive system capable of being applied, and can also be applied to an electric vehicle without rear wheel steering means as described above.

1 is an overall system diagram illustrating an electric vehicle according to a first embodiment. It is the side view and top view which show the front wheel applied to the electric vehicle of Example 1. FIG. 6 is a flowchart illustrating a flow of mode selection control processing executed by the integrated controller of the first embodiment. It is a figure explaining the calculation method at the time of mode D in the integrated controller of Example 1. FIG. 6 is a flowchart illustrating a calculation routine in mode D according to the first embodiment. 6 is a ROM data characteristic diagram of a target driving force tTD used in a calculation routine in mode D in Embodiment 1. FIG. It is a figure which shows the example of a turning behavior simulation at the time of the mode D in Example 1. FIG. 6 is a flowchart illustrating a calculation routine in mode A according to the first embodiment. It is a ROM data characteristic view of the reciprocal value target value tρ of the turning radius used in the calculation routine in mode A and mode AR in the first embodiment. 3 is a flowchart illustrating a calculation routine in mode B according to the first embodiment. FIG. 6 is a ROM data characteristic diagram of motor target rotational speeds tNRL and tNRR used in a calculation routine in mode B in the first embodiment. 6 is a flowchart illustrating a calculation routine in mode R according to the first embodiment. FIG. 6 is a ROM data characteristic diagram of a target driving force tTD used in a calculation routine at the time of mode R in the first embodiment. 7 is a flowchart illustrating a calculation routine in a mode AR in the first embodiment. It is a figure which shows the turning behavior in the boarding of the turning behavior of a prior art example, and normal front-wheel steering. It is a figure which shows the turning behavior example in Example 1. FIG. It is a figure which shows the other Example of a drive system. It is a figure which shows the other Example of a front wheel.

Explanation of symbols

2RL, 2RR Rear wheel 3RL, 3RR Electric motor 8 Yaw rate sensor 11 Steering wheel 21 Steering angle sensor (turning command value detecting means)
22 Brake pedal sensor 23 Accelerator pedal sensor 24 Acceleration sensor 25 Shift lever 30 Integrated controller (motor output calculation means)
42FL, 42FR Front wheels 49, 50 Front wheel rotation sensor 51 Link (rear wheel steering means)
52 Steering motor (rear wheel steering means)

Claims (8)

A rear wheel that generates a braking / driving force difference between the left and right wheels by an electric motor;
The front center wheel is positioned near the rear wheel, generates less force in the lateral direction of the vehicle compared to the rear wheel, and rotates following the direction of the vehicle,
Motor output calculating means for calculating the output of the electric motor in accordance with a turning command value, an acceleration / deceleration command value and a vehicle speed detection value;
Equipped with a,
The motor output calculating means adjusts outputs of the electric motors of the left and right wheels according to the turning command value and the detected vehicle speed so that the turning characteristic of the vehicle becomes a desired turning characteristic. . In the electric vehicle according to claim 1,
An electric vehicle comprising rear wheel turning means for turning a rear wheel in accordance with a turn command value. In the electric vehicle according to claim 1 or 2,
The electric vehicle characterized in that the motor output calculation means adjusts a braking / driving force difference between the electric motors of the left and right wheels in accordance with a detected vehicle speed at a turn command. In the electric vehicle according to any one of claims 1 to 3,
The electric vehicle characterized in that the motor output calculation means has an operation mode A in which the vehicle is turned with the vicinity of the rear wheel of the turning inner wheel as the turning center. In the electric vehicle according to claim 4,
The motor output calculating means, when the driving mode A is selected, excludes within the tire width of the turning inner wheel as a turning center. In the electric vehicle according to claim 4 or 5,
The motor output calculating means prohibits the transition to the operation mode A when the vehicle speed detection value is equal to or greater than a first vehicle speed threshold value. In the electric vehicle according to any one of claims 1 to 6,
The motor output calculating means has an operation mode B in which the vehicle is rotated with a point between the left and right rear wheels as a turning center. In the electric vehicle according to claim 7,
The motor output calculating means prohibits the transition to the operation mode B when the vehicle speed detection value is equal to or greater than a second vehicle speed threshold value.

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