Electric vehicle control method and control device

Abstract

To provide a control method of an electric vehicle which can suppress vehicle body vibration and obtain a desired acceleration.SOLUTION: The control method of an electric vehicle is given in which: a front wheel drive force command value of a first motor 10 and a rear wheel drive force command value of a second motor 12 are calculated based on a target drive force; an actual pitch angle response representing a degree of vibration occurred in a vehicle body is estimated based on the front wheel drive force command value and the rear wheel drive force command value; a front and rear drive force movement amount Fd which is defined as drive force to be transferred between a front wheel 14 and a rear wheel 16 is calculated to be a distribution ratio of drive force to decrease the degree of vibration based on the actual pitch angle response; and the front wheel drive force command value and the rear wheel drive force command value are corrected based on the front and rear drive force movement amount to calculate a front wheel actual drive force command value Fλf* and a rear wheel actual drive force command value Fλr* which are respectively inputted into the first motor 10 and the second motor 12.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a control method and a control device for an electric vehicle. [Background technology]

[0002] Conventionally, a vehicle control device that suppresses vehicle body vibrations caused by pitching motion in an electric vehicle is known (see Patent Document 1). This control device estimates dynamic fluctuations at a position a predetermined distance away from the center of the pitching motion. Then, in accordance with the estimated fluctuations, a filtering process is performed on the output torque of the motor, thereby correcting the torque command value so as to suppress the vehicle body vibrations. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-240258 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the above-mentioned control device, a filtering process is performed on the output torque of the motor to reduce the gain in a predetermined frequency range. As a result, the torque response differs from the driving force command value from the upper controller, and the desired acceleration cannot be obtained. In this way, there are cases where the desired acceleration cannot be obtained while suppressing the vehicle body vibration.

[0005] An object of the present invention is to provide a method for controlling an electric vehicle that can suppress vehicle body vibration and obtain a desired acceleration. [Means for solving the problem]

[0006] According to this aspect, there is provided a vehicle drive control method for controlling drive of an electric vehicle having a first motor for driving front wheels and a second motor for driving rear wheels, the method including: a command value calculation step of calculating a front wheel drive force command value for the first motor and a rear wheel drive force command value for the second motor based on a target drive force for the electric vehicle; Using the real pitch angle model, Based on the front wheel driving force command value and the rear wheel driving force command value, Actual pitch angle calculation step and, a reference pitch angle calculation step of calculating a reference pitch angle based on a front wheel driving force command value and a rear wheel driving force command value using a reference pitch angle model; and a reference pitch angle calculation step of calculating a reference pitch angle based on a difference between the actual pitch angle and the reference pitch angle so that the actual pitch angle coincides with the reference pitch angle. There is provided a control method for an electric vehicle, the control method including: a front-rear driving force movement amount calculation step of calculating a front-rear driving force movement amount; and an actual driving command value calculation step of calculating a front wheel actual driving force command value and a rear wheel actual driving force command value to be input to a first motor and a second motor, respectively, by correcting a front wheel driving force command value and a rear wheel driving force command value based on the front-rear driving force movement amount. Effect of the Invention

[0007] According to one aspect of the present invention, there is provided a method for controlling an electric vehicle that is capable of suppressing vehicle body vibration and obtaining a desired acceleration. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram illustrating an example of the overall functional configuration of a control device according to the first embodiment. [Diagram 2] FIG. 2 is a flowchart showing an example of a control method according to this embodiment. [Diagram 3] FIG. 3 is a diagram showing an example of the relationship between the accelerator opening and the output torque in this embodiment. [Figure 4] FIG. 4 is a diagram showing an example of the driving force distribution process of this embodiment. [Diagram 5] FIG. 5 is a diagram showing an example of modeling of the vehicle motion in this embodiment. [Figure 6] FIG. 6 is a diagram showing an example of a pitch control calculation for a vehicle according to this embodiment. [Figure 7] FIG. 7 is a diagram showing a reference pitch angle model of this embodiment. [Figure 8]FIG. 8 is a diagram showing an actual pitch angle model of this embodiment. [Figure 9] FIG. 9 is a diagram showing an example of an inverse model calculation of the driving force transfer amount in this embodiment. [Figure 10] FIG. 10 is a diagram showing an example of a driving force movement amount limiter of the present embodiment. [Figure 11] FIG. 11 is a diagram showing an example of each output value of the electric vehicle of this embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Each embodiment will be described below with reference to the drawings.

[0010] [Overall configuration] FIG 1 is a diagram showing the overall configuration of an electric vehicle (hereinafter simply referred to as "vehicle") equipped with a control device for an electric vehicle according to a first embodiment. The vehicle 1 of this embodiment is a vehicle that uses the power of an electric motor as part of its driving force, such as an electric vehicle, a hybrid vehicle, or a fuel cell vehicle. The vehicle 1 of this embodiment is a so-called 4WD vehicle 1.

[0011] The vehicle 1 includes a front drive system 2, a rear drive system 3, a battery 4, and a motor controller 5. In the vehicle 1, the front drive system 2 and the rear drive system 3 are configured to be electrically and mechanically symmetrical with respect to the motor controller 5.

[0012] The front drive system 2 includes a front motor 10, a front inverter 20, a front reduction gear 30, and front wheels 14. The front drive system 2 is controlled by a motor controller 5. The front motor 10 generates a drive torque (including regenerative torque) to the front reduction gear 30 in accordance with a switching operation in the front inverter 20. The front wheels 14 rotate in accordance with the output drive torque from the front reduction gear 30.

[0013] The rear drive system 3 includes a rear motor 12, a rear inverter 22, a rear reduction gear 32, and rear wheels 16. The rear drive system 3 is controlled by a motor controller 5. The rear motor 12 generates drive torque (including regenerative torque) to the rear reduction gear 32 in accordance with the switching operation of the rear inverter 22. The rear wheels 16 rotate in accordance with the output drive torque from the rear reduction gear 32 controlled by the motor controller 5.

[0014] The battery 4 supplies power to the front inverter 20 and the rear inverter 22. Although not shown, the DC voltage Vdc [V] from the battery 4 is determined by a voltage sensor provided on the DC power supply line or a power supply voltage value transmitted from a battery controller.

[0015] The motor controller 5 controls the front motor 10 and the rear motor 12. Signals indicating vehicle states such as the vehicle speed V, accelerator opening θ, a front rotor phase αf of the front motor 10, a rear rotor phase αr of the rear motor 12, currents ifu, ifv, ifw of the front motor 10, and currents iru, irv, irw of the rear motor 12 are input as digital signals to the motor controller 5. The front rotor phase αf as an electrical angle is detected by a front rotation sensor 11, and the rear rotor phase αr is detected by a rear rotation sensor 13.

[0016] The vehicle speed V [km / h] is obtained by communication from another controller such as a meter or brake controller, or by multiplying the motor rotational angular velocity ωm by the tire dynamic radius R and dividing it by the gear ratio of the final gear to obtain the vehicle speed v [m / s], and then applying a unit conversion coefficient (3600 / 1000) from [m / s] to [km / h].

[0017] The accelerator opening degree θ [%] may be obtained by an accelerator opening degree sensor, or may be obtained by a vehicle controller or another controller through communication. The accelerator opening degree θ will be described later.

[0018] Based on the above input signals, the motor controller 5 generates PWM signals for controlling the front motor 10 and the rear motor 12. In addition, the motor controller 5 generates drive signals for the front inverter 20 and the rear inverter 22 based on these PWM signals.

[0019] The front inverter 20 and the rear inverter 22 receive a drive signal from the motor controller 5, convert the DC current supplied from the battery 4 into AC current, and output the current to each of the front motor 10 and the rear motor 12. A current value if from the front inverter 20 is detected by a front current sensor 26, and a current value ir from the rear inverter 22 is detected by a rear current sensor 28.

[0020] The currents ifu, ifv, ifw of the front motor 10 are obtained by a front current sensor 26, and the currents iru, irv, irw of the rear motor 12 are obtained by a rear current sensor 28. Since the sum of the three-phase current values ​​is zero, for example, the current ifw may be determined from the values ​​of the currents ifu, ifv.

[0021] The motor rotational angular speed Nm [rpm] is calculated by dividing the rotor angular speed ω (electrical angle) by the number of pole pairs of the electric motor to obtain the motor rotational angular speed ωm [rad / s], which is the mechanical angular speed of the electric motor, and then multiplying it by the unit conversion coefficient (60 / 2π) from [rad / s] to [rpm]. The rotor angular speed ω (electrical angle) [rad / s] is calculated as the differential value of the rotor phase α (electrical angle).

[0022] [Overall control] Next, a method of controlling the entire vehicle 1 by the motor controller 5 will be described with reference to FIG.

[0023] In step S201, the motor controller 5 acquires signals necessary for the calculation of various processes described below through sensor input or communication from another controller.

[0024] In step S202, the motor controller 5 executes a basic target driving force calculation process. The motor controller 5 sets a target driving force command value F* by referring to an accelerator opening degree-driving force table shown in Fig. 3 based on the accelerator opening degree θ and the vehicle speed V. As shown in Fig. 3, the relationship between the motor rotation speed and the motor torque is determined according to the accelerator opening degree θ. That is, Fig. 3 shows a basic driving force command value determined to realize a driving force required for the vehicle.

[0025] 4 sets a front / rear driving force distribution ratio Kf of the target driving force command value F* from a higher-level controller (not shown) between 0 and 1. A front wheel driving force command value Ff* for the driving force of the front wheels 14 is set by multiplying the target driving force command value F* by Kf. A rear wheel driving force command value Fr* for the rear wheels 16 is set by multiplying the target driving force command value F* by (1-Kf).

[0026] In step S203, the motor controller 5 executes a pitch angle vibration suppression process. In particular, in this pitch angle vibration suppression process, the motor controller 5 receives the front wheel driving force command value Ff* and the rear wheel driving force command value Fr* as inputs and calculates a front wheel actual driving force command value Fλf* and a rear wheel actual driving force command value Fλr*. The pitch angle vibration suppression process will be described in detail later.

[0027] In step S204, the motor controller 5 executes a torsional vibration suppression process. The motor controller 5 inputs the first front and rear motor torque command values ​​Tmf1*, Tmr1* obtained by converting the front wheel actual driving force command value Fλf* and the rear wheel actual driving force command value Fλr* into motor torque equivalents based on the gear ratio and tire radius, and the front and rear motor rotational angular velocities ωmf, ωmr, and calculates command values ​​after torsional vibration suppression process Tmf2*, Tmr2*, which are front and rear torque command values. The command values ​​after torsional vibration suppression process Tmf2*, Tmr2* suppress vibrations in the driving force transmission system, such as torsional vibrations of the drive shaft, without sacrificing the response of the drive shaft torque. Note that the torsional vibration suppression process in step S204 may be omitted in a vehicle without a drive shaft or when torsional vibrations are suppressed mechanically.

[0028] In step S205, the motor controller 5 executes a process of calculating the front and rear current command values. The motor controller 5 refers to a table to determine the front and rear dq-axis current target values ​​id*, iq* from the post-torsional vibration suppression process command values ​​Tmf2*, Tmr2*, the motor rotational angular velocities ωmf, ωmr, and the DC voltage Vdc calculated in step S204.

[0029] In step S206, the motor controller 5 executes a current control calculation process. In each of the front and rear current controls, the motor controller 5 first calculates dq-axis currents id and iq from the three-phase current values ​​iu, iv, and iw and the rotor phase α of the electric motor. Next, the motor controller 5 calculates dq-axis voltage command values ​​vd and vq from the deviation between the dq-axis current target values ​​id* and iq* calculated in step S205 and the dq-axis currents id and iq. Note that non-interference control may be added to the calculation of the dq-axis voltage command values ​​vd and vq. Then, the motor controller 5 calculates three-phase voltage command values ​​vu, vv, and vw from the dq-axis voltage command values ​​vd and vq and the rotor phase α of the electric motor. The motor controller 5 calculates the duty ratios tu[%], tv[%], and tw[%] of the PWM signal from the three-phase voltage command values ​​vu, vv, and vw and the DC voltage Vdc.

[0030] In this way, the motor controller 5 uses the PWM signals calculated by the processes in steps S201 to S206 to control the opening and closing of the switching elements of the front inverter 20 and the rear inverter 22. As a result, the front motor 10 and the rear motor 12 are driven at desired torques instructed by their respective torque command values.

[0031] [Pitch angle vibration suppression processing] Next, the pitch angle vibration suppression process executed in step S203 will be described.

[0032] First, an example of the equation of motion for a vehicle 1 having a drive motor for each of the front and rear wheels will be described. Based on this equation of motion, the transfer characteristic from the input of the front wheel drive force command value Ff* and the rear wheel drive force command value Fr* to the output of the pitch angle λ is obtained. If the sprung mass of the vehicle body is assumed to be a rigid body, as shown in Fig. 5, the driving force reaction force, the inertial force, and the vertical force due to the instantaneous rotation angle θf,r that represents the operating state of the suspension act on the sprung mass of the vehicle body during acceleration and deceleration.

[0033] The parameters used in the equation of motion described below are as follows: Center of gravity height [m] Tire rolling radius [m] Distance from center of front wheel to center of gravity [m] Distance from rear wheel center to center of gravity [m] Front and rear spring rates [N / m] Front and rear damping coefficients [N / (m / s)] Pitch moment of inertia around the center of gravity [kg / m2] Pitch angle [rad] Front and rear instantaneous rotation angles [rad]

[0034] Using the above variables, the pitching moment Mλ is expressed as the following equation (1): Note that the instantaneous rotation angle θf,r is a fixed value, since its change during the stroke is minimal.

[0035]

number

[0036] Therefore, the equations of motion around the center of pitch rotation are expressed as equations (2) and (3).

[0037]

number

[0038]

number

[0039] By performing a Laplace transform on the above equation (2), the equation (4) as a transfer function is obtained.

[0040]

number

[0041] In this way, the transfer characteristic from the input of the front wheel driving force command value Ff* and the rear wheel driving force command value Fr* to the output of the pitch angle λ is expressed by a second-order system response as shown in the above equation (4).

[0042] Next, the pitch angle vibration suppression process will be described. In this embodiment, the total driving force command value (the sum of the front wheel driving force command value Ff* and the rear wheel driving force command value Fr*) is kept constant, while the front wheel driving force command value Ff* and the rear wheel driving force command value Fr* are added or subtracted by the longitudinal driving force transfer amount Fd*. The sign of the longitudinal driving force transfer amount Fd* is made to match the sign of the driving force transferred from the rear wheels 16 to the front wheels 14. That is, when the driving force (torque) is transferred from the rear wheels 16 to the front wheels 14, the longitudinal driving force transfer amount Fd* is a positive value. On the other hand, when the driving force is transferred from the front wheels 14 to the rear wheels 16, the longitudinal driving force transfer amount Fd* is a negative value. Therefore, in this embodiment, the dynamic characteristic of the pitch angle λ is derived so as to become an arbitrary standard response, on the premise that the longitudinal driving force transfer amount Fd* is added to the front wheel driving force command value Ff* and the longitudinal driving force transfer amount Fd* is subtracted from the rear wheel driving force command value Fr*. First, from the preconditions and the derived pitch angle model, the actual pitch angle response when the longitudinal driving force transfer amount Fd* is applied is expressed as the following equation (5).

[0043]

number

[0044] The reference pitch angle response is set as shown in the following equation (6) so that the steady-state characteristics are equal to the actual pitch angle response and the dynamic characteristics are free of overshoot. The following equation (6) is a transfer function that indicates the state in which the damping coefficient ζ in the above equation (4) is 1, i.e., the state in which the vehicle body vibration is reduced to the lowest.

[0045]

number

[0046] Then, by simultaneously setting up the above equations (5) and (6) and solving the longitudinal driving force movement amount Fd so that λ=λ*, the following equation (7) is obtained.

[0047]

number

[0048] By transforming equation (7), we obtain equation (8).

[0049]

number

[0050] In this way, as shown in equation (8), the control for suppressing the pitch angle vibration can be expressed by an inverse model of the pitch angle from the difference between the actual pitch angle response (actual pitch angle response) Gpλ(s) and the reference response Grλ(s) and the longitudinal driving force transfer amount Fd.

[0051] [Function configuration] Next, a functional configuration of the pitch angle vibration suppression process for the front wheel drive force command value Ff* and the rear wheel drive force command value Fr* will be described using the transfer characteristics derived as described above.

[0052] 7 receives the front wheel driving force command value Ff* and the rear wheel driving force command value Fr*, and performs filtering using the reference pitch angle model Grλ(s) of the above equation (6) to calculate the reference pitch angle response. Note that although the reference pitch angle λ* is calculated using equation (6) in this example, any reference pitch angle response using a rate of change limiter or the like may be used.

[0053] 8 receives the front wheel driving force command value Ff* and the rear wheel driving force command value Fr*, performs filtering using the pitch angle actual model (actual pitch angle response) Gpλ(s) of the above equation (4), and calculates the actual pitch angle λ^ as an estimated value of the pitch angle actual response. Note that although the actual pitch angle λ^ is estimated using the above equation (4), a measured value of the pitch rate actual response measured by a pitch rate sensor or the like may be used.

[0054] 9 receives the difference between the reference pitch angle λ and the actual pitch angle λ^ and performs filtering processing using an inverse model of the pitch angle from the reference pitch angle Fd* derived from the above equation (4). This calculates the reference pitch angle response Fd* that matches the reference pitch angle response.

[0055] The driving force transfer amount limiter 904 shown in Figure 10 receives as input the front wheel driving force command value Ff*, the rear wheel driving force command value Fr*, and the front / rear driving force transfer amount Fd* calculated by the front / rear driving force transfer amount calculation unit 903, and calculates a limited driving force transfer amount Fdl*, which is a limit value for the transfer amount (change amount) of the driving force of the rear wheels 16 based on the front / rear driving force transfer amount Fd*.

[0056] For example, when the longitudinal driving force transfer amount Fd* is a positive value, that is, when the driving force is transferred from the rear wheels 16 to the front wheels 14, it is desirable to make the longitudinal driving force transfer amount Fd* smaller than the driving force possessed by the rear wheels 16. This is because, if the longitudinal driving force transfer amount Fd* is set to be equal to or greater than the driving force possessed by the rear wheels 16, a situation may arise in which a positive driving force is applied to the front wheels 14 (powered), while a negative driving force is applied to the rear wheels 16 (regeneratively driven). If such a situation arises, it is considered that the vehicle 1 may sway back or the load on the vehicle 1 may increase, making it impossible to realize the desired driving. Therefore, the driving force transfer amount limiter 904 performs a calculation to limit the longitudinal driving force transfer amount Fd* to the limit that can be transferred from the rear wheels 16 to the front wheels 14 within the range of the driving force possessed by the rear wheels 16.

[0057] Specifically, the driving force transfer amount limiter 904 calculates the smaller of the rear wheel driving force command value Fr* and the longitudinal driving force transfer amount Fd* (positive value) in the previous stage. The larger of this value and the sign-inverted value (negative value) of the front wheel driving force command value Ff* is obtained in the next stage as the limited driving force transfer amount Fdl*, but since it is compared with a negative value, the output value of the previous stage is always selected. As a result, the longitudinal driving force transfer amount Fd* is limited to a value smaller than the front wheel driving force command value Ff*, and the driving force transfer amount limiter 904 outputs the limited driving force transfer amount Fdl* as a command value corresponding to the limited longitudinal driving force transfer amount Fd*.

[0058] On the other hand, when the longitudinal driving force transfer amount Fd* is a negative value, that is, when the driving force is transferred from the front wheels 14 to the rear wheels 16, it is desirable that the absolute value of the longitudinal driving force transfer amount Fd* (negative value) is smaller than the absolute value of the driving force (negative value) possessed by the front wheels 14. Specifically, the driving force transfer amount limiter 904 selects and outputs the smaller value of the longitudinal driving force transfer amount Fd* (negative value) and the rear wheel driving force command value Fr* (positive value) in the front stage. Note that the longitudinal driving force transfer amount Fd*, which is a negative value, is always selected in the front stage. Then, the driving force transfer amount limiter 904 selects the larger value of the longitudinal driving force transfer amount Fd* (negative value) and the sign-inverted value (negative value) of the front wheel driving force command value Ff* in the rear stage. In other words, in the rear stage, the driving force possessed by the front wheels 14 and the absolute value of the longitudinal driving force transfer amount Fd* are compared, and the smaller absolute value is output. In other words, the longitudinal driving force movement amount Fd* is limited to an amount of movement equal to or less than the driving force possessed by the front wheels 14 .

[0059] As a result, the driving force transfer amount limiter 904 outputs the limited driving force transfer amount Fdl* such that the signs of the front wheel driving force command value Ff* and the rear wheel driving force command value Fr* are kept the same. Note that the case where the signs of the front wheel driving force command value Ff* and the rear wheel driving force command value Fr* are mutually positive (powering drive) has been described. However, a configuration may be adopted in which the limited driving force transfer amount Fdl* is calculated such that the signs of the front wheel driving force command value Ff* and the rear wheel driving force command value Fr* are mutually negative (regenerative drive).

[0060] Returning to FIG. 6, the front and rear wheel phase adjustment unit 905 receives as inputs a value obtained by adding the limited driving force movement amount Fdl* to the front wheel driving force command value Ff* (limited front wheel driving force command value Ff*) and a value obtained by subtracting the limited driving force movement amount Fdl* from the rear wheel driving force command value Fr* (limited rear wheel driving force command value Fr*), and adjusts the phase difference of the transmission of the driving force between the front wheels 14 and the rear wheels 16, which is caused by the electrical configuration. Specifically, the front and rear wheel phase adjustment unit 905 applies a filter formed by a transfer characteristic Gr from the front motor torque command value to the front motor rotation speed including vibration damping control and a transfer characteristic Grr from the rear motor torque command value to the rear motor rotation speed to the limited front wheel driving force command value Ff* and the rear wheel driving force command value Fr*, thereby calculating a front wheel actual driving force command value Fλf*. Note that the rear wheel actual driving force command value Fλr* is output as it is as the limited rear wheel driving force command value Fr*.

[0061] [Vehicle operation] The operation of the vehicle 1 to which the control method of this embodiment is applied will be described below. Fig. 11 shows waveforms of the driving torque command value of the front motor 10, the driving torque command value of the rear motor 12, the pitch angle, the pitch rate, and the longitudinal acceleration in a scene in which the vehicle accelerates when the driver suddenly depresses the accelerator from a stopped state and increases the target torque command value in steps in an electric 4WD vehicle having independent motors for the front and rear drive wheels.

[0062] In the comparative example, the overshoot of the pitch angle is suppressed from time t1 to t2, but it can be seen that the torque command value of the front motor 10 and the torque command value of the rear motor 12 cannot realize the longitudinal acceleration intended by the driver. This is because the torque command value is limited by a filter that takes into account the characteristics of the pitch angle.

[0063] In this embodiment, the pitch angle is controlled by the difference between the front and rear driving forces so as to suppress the reduction in the total driving force. Therefore, compared to the comparative example, it is possible to reduce the overshoot of the pitch angle while realizing the front and rear acceleration intended by the driver from time t1 to t2. In this way, it is possible to suppress the feeling of rocking caused by the pitch during acceleration while realizing the acceleration intended by the driver.

[0064] The effects of this embodiment will be described.

[0065] The control method for an electric vehicle of this embodiment is a vehicle drive control method for controlling the drive of an electric vehicle having a front motor (first motor) 10 for driving front wheels 14 and a rear motor (second motor) 12 for driving rear wheels 16, and includes a command value calculation step of calculating a front wheel drive force command value Ff* for the first motor and a rear wheel drive force command value Fr* for the second motor based on a target drive force for the electric vehicle, and a command value calculation step of estimating an actual pitch angle response indicating the degree of vibration generated in the vehicle body based on the calculated front wheel drive force command value Ff* and rear wheel drive force command value Fr*. the actual pitch angle response calculation step of calculating a front-rear driving force movement amount Fd based on the actual pitch angle response, the front-rear driving force movement amount Fd being determined as the driving force to be moved between the front wheels 14 and the rear wheels 16 so as to achieve a driving force distribution ratio Kf that reduces the degree of vibration; and an actual driving force calculation step of calculating a front wheel actual driving force command value Fλf* and a rear wheel actual driving force command value Fλr* to be input to the first motor and the second motor, respectively, by correcting the front wheel driving force command value Ff* and the rear wheel driving force command value Fr* based on the front-rear driving force movement amount Fd.

[0066] According to this embodiment, the total driving force of the vehicle 1 is distributed between the front wheels 14 and the rear wheels 16 so as to reduce vibrations. Therefore, the vibrations of the vehicle 1, particularly those in the pitch direction, are suppressed while maintaining a desired vehicle output without reducing the total driving force.

[0067] In addition, the control method for an electric vehicle of this embodiment further includes a normative pitch angle calculation step of calculating a normative pitch angle response having a lower degree of vibration than the actual pitch angle response, based on the front wheel driving force command value Ff* and the rear wheel driving force command value Fr*, and in the front / rear driving force calculation step, the front / rear driving force movement amount Fd* is calculated by comparing the normative pitch angle response with the actual pitch angle response.

[0068] According to this embodiment, the longitudinal driving force transfer amount Fd* is determined based on a comparison with a reference pitch angle response that reduces vibration and that is determined in advance by experiments, etc. Therefore, the longitudinal driving force transfer amount Fd that reduces the vibration of the vehicle 1 more accurately can be determined.

[0069] In addition, in the control method for an electric vehicle of this embodiment, in the longitudinal driving force calculation step, the difference between the reference pitch angle response and the actual pitch angle response is calculated, and the longitudinal driving force transfer amount Fd* is calculated so as to cancel out the difference using the transfer characteristic from the actual pitch angle response to the longitudinal driving force transfer amount Fd*.

[0070] According to this embodiment, a difference between the standard pitch angle response and the actual pitch angle response that reduces vibration determined in advance by experiments or the like is obtained as an index of the appropriate degree of vibration of the vehicle 1. Then, the longitudinal driving force transfer amount Fd is calculated so as to make the difference "0" using the above-mentioned transfer characteristic, so that a longitudinal driving force transfer amount Fd* that can evaluate the vibration of the vehicle 1 with higher accuracy and then remove it appropriately is obtained. Therefore, the vibration of the vehicle 1 can be reduced more accurately while keeping the total driving force constant.

[0071] Moreover, in the control method for an electric vehicle of this embodiment, in the reference pitch angle calculation step, the reference pitch angle response is determined so as to be the same as the actual pitch angle response in a steady state.

[0072] According to this embodiment, the vehicle 1 is maintained in a constant acceleration state (total driving force does not change) and in a steady state where the fluctuation of the pitch movement (pitch angle) is small enough to be substantially negligible, the standard pitch angle response is designed to match the actual pitch angle response. As a result, in the steady state, the longitudinal driving force movement amount Fd* based on the difference between the standard pitch angle response and the actual pitch angle response is calculated as "0" and the basic distribution ratio Kf before correction is maintained. In other words, in a scene where it is considered that substantially no vehicle body vibration occurs, the pitch angle vibration suppression process is not substantially executed and the basic distribution ratio Kf that is originally required can be maintained.

[0073] In the control method for an electric vehicle of this embodiment, in the reference pitch angle calculation step and / or the actual pitch angle response calculation step, a vertical force (pitching moment Mλ) that causes pitch vibration acting on the vehicle is calculated based on instantaneous rotation angles θf, θr that are determined in advance in consideration of a driving force reaction force, an inertial force, and an operating state of a suspension that are generated in the vehicle. Then, based on the vertical force, a reference pitch angle response (reference pitch angle λ) and / or an actual pitch angle response (actual pitch angle λ^) are determined (reference pitch angle model calculation unit 901 and / or actual pitch angle model calculation unit 902).

[0074] As a result, since the instantaneous rotation angles θf, θr determined in advance are used, the standard pitch angle response and / or the actual pitch angle response can be obtained without delay, compared to the case where vibration is obtained from a vibration detection sensor attached to the suspension. In particular, the instantaneous rotation angles θf, θr in this embodiment are fixed values, as an example, assuming that changes during stroke are minute. Therefore, it is possible to omit the calculation of the instantaneous rotation angles θf, θr according to the operating state of the vehicle, and it is possible to more easily obtain the standard pitch angle response and / or the actual pitch angle response. In addition, since the standard pitch angle response is determined based on the instantaneous rotation angles θf, θr derived by experiments or the like, it is possible to calculate a highly accurate standard pitch angle λ taking into account the actual behavior of the vehicle 1.

[0075] In the control method for an electric vehicle of this embodiment, in the actual driving force calculation step, the sign of the front-rear driving force transfer amount Fd* is made to match the sign of the driving force transferred from the rear wheels 16 to the front wheels 14, and the front wheel actual driving force command value Fλf* is calculated as a value obtained by adding the front-rear driving force transfer amount Fd* to the front wheel driving force command value Ff*. In addition, the rear wheel actual driving force command value Fλr* is calculated as a value obtained by subtracting the front-rear driving force transfer amount Fd* from the rear wheel driving force command value Fr*.

[0076] This realizes a more specific control logic that can adjust the distribution ratio Kf of the driving forces of the front wheels 14 and the rear wheels 16 so that the total amount of driving force due to the front wheel driving force command value Ff* and the rear wheel driving force command value Fr* from the motor controller 5 becomes equal to the total amount of the front wheel actual driving force command value Fλf* and the rear wheel actual driving force command value Fλr*, in other words, that can suppress body vibration while driving the vehicle 1 at a desired acceleration.

[0077] In the front / rear driving force transfer amount calculation step (driving force transfer amount limiter 904), the front / rear driving force transfer amount Fd* is limited to a limited driving force transfer amount Fdl*, which is a value that can be taken within the range in which the signs of the front wheel actual driving force command value Fλf* and the rear wheel actual driving force command value Fλr* are mutually identical.

[0078] According to this embodiment, even if the driving force is transferred between the front wheels 14 and the rear wheels 16, the signs of the front wheel driving force command value Ff* and the rear wheel driving force command value Fr* can be maintained. This makes it possible to suppress vibrations caused by unintentional reversal of the sign of the front wheel driving force command value Ff* or the rear wheel driving force command value Fr*. Furthermore, it is also possible to suppress electrical and mechanical loads on the vehicle 1 and deterioration of fuel efficiency caused by excessive fluctuations in the command values ​​such as reversal of the sign.

[0079] The actual driving force command value calculation step includes a phase adjustment filter process (front / rear wheel phase adjustment unit 905) that adjusts the phase difference from the front wheel driving force command value Ff* and the rear wheel driving force command value Fr* to the front wheel actual driving force command value Fλf* and the rear wheel actual driving force command value Fλr* in accordance with the dynamic characteristics of each of the front and rear wheels.

[0080] For example, the phase difference between the front and rear wheels as the dynamic characteristics of the front and rear wheels can be suppressed, so that the driving force can be reliably maintained at a constant state. Specifically, in a vehicle 1 equipped with multiple drive motors, if the dynamic characteristics and phases of the actual driving torque of the front and rear wheels are different, it is not possible to realize an actual pitch angle response that matches the standard response. Even if the responses from the front wheels 14 and the rear wheels 16 to the actual driving force are different, by applying a phase adjustment filter, it is possible to achieve the actual driving force as desired and to realize an actual pitch angle response that matches the standard pitch angle response. This makes it possible to more accurately reduce the vibration of the vehicle 1.

[0081] Moreover, the control method of this embodiment further includes a torsional vibration suppression control step for suppressing vibration in the driving force transmission system of the vehicle 1.

[0082] According to this embodiment, it is possible to suppress vibrations in the driving force transmission system, such as torsional vibrations of the drive shaft, without sacrificing the response of the drive shaft torque. In addition to vibrations in the pitch direction of the vehicle 1, torsional vibrations can also be appropriately suppressed.

[0083] Although the embodiments of the present invention have been described above, the above-mentioned embodiments merely show some of the application examples of the present invention, and it is not intended that the technical scope of the present invention be limited to the specific configurations of the above-mentioned embodiments.

[0084] For example, although the present embodiment has been described with reference to powered driving, the same is true for regenerative driving; by controlling the pitch angle based on the difference between the front and rear braking / driving forces so as to prevent a decrease in the total braking / driving force, it is possible to achieve the deceleration intended by the driver while suppressing the feeling of backswing during deceleration. [Explanation of symbols]

[0085] 1 vehicle 10 Front motor 12 Rear motor Fd* Front and rear drive force movement

Claims

1. A vehicle drive control method for controlling drive of an electric vehicle having a first motor for driving front wheels and a second motor for driving rear wheels, comprising: a command value calculation step of calculating a front wheel driving force command value for the first motor and a rear wheel driving force command value for the second motor based on a target driving force for the electric vehicle; an actual pitch angle calculation step of calculating an actual pitch angle based on the front wheel driving force command value and the rear wheel driving force command value by using an actual pitch angle model; a reference pitch angle calculation step of calculating a reference pitch angle based on the front wheel driving force command value and the rear wheel driving force command value by using a reference pitch angle model; a longitudinal driving force movement amount calculation step of calculating a longitudinal driving force movement amount based on a difference between the actual pitch angle and the standard pitch angle so that the actual pitch angle coincides with the standard pitch angle; and an actual driving force command value calculation step of calculating a front wheel actual driving force command value and a rear wheel actual driving force command value to be input to the first motor and the second motor, respectively, by correcting the front wheel driving force command value and the rear wheel driving force command value based on the front / rear driving force movement amount. A method for controlling an electric vehicle.

2. A control method for an electric vehicle according to claim 1, comprising: In the standard pitch angle calculation step, the standard pitch angle is determined so as to be equal to the actual pitch angle in a steady state. A method for controlling an electric vehicle.

3. A control method for an electric vehicle according to claim 1 or claim 2, comprising: In the reference pitch angle calculation step and / or the actual pitch angle calculation step, A vertical force acting on the electric vehicle and causing a pitch vibration is calculated based on an instantaneous rotation angle determined in advance in consideration of a driving force reaction force, an inertial force, and an operating state of a suspension generated in the electric vehicle; The reference pitch angle and / or the actual pitch angle is determined based on the vertical force. A method for controlling an electric vehicle.

4. A method for controlling an electric vehicle according to any one of claims 1 to 3, comprising: In the actual drive command value calculation step, the sign of the front-rear drive force transfer amount is made to coincide with the sign of the drive force transferred from the rear wheels to the front wheels; calculating the front wheel actual driving force command value as a value obtained by adding the front-rear driving force movement amount to the front wheel driving force command value; the rear wheel actual driving force command value is calculated as a value obtained by subtracting the front-rear driving force movement amount from the rear wheel driving force command value; A method for controlling an electric vehicle.

5. A method for controlling an electric vehicle according to any one of claims 1 to 4, comprising: In the longitudinal driving force transfer amount calculation step, the longitudinal driving force transfer amount is limited to a value that can be taken within a range in which the signs of the front wheel actual driving force command value and the rear wheel actual driving force command value are the same. A method for controlling an electric vehicle.

6. A method for controlling an electric vehicle according to any one of claims 1 to 5, comprising: the actual driving force command value calculation step includes a phase adjustment filter process for adjusting a phase difference from the front wheel driving force command value and the rear wheel driving force command value to the front wheel actual driving force command value and the rear wheel actual driving force command value in accordance with dynamic characteristics of the front and rear wheels, A method for controlling an electric vehicle.

7. A method for controlling an electric vehicle according to any one of claims 1 to 6, comprising: The torsional vibration suppression control step further includes suppressing vibration of a driving force transmission system of the electric vehicle. A method for controlling an electric vehicle.

8. A control device for an electric vehicle that controls driving of an electric vehicle having a first motor for driving front wheels and a second motor for driving rear wheels, calculating a front wheel driving force command value for the first motor and a rear wheel driving force command value for the second motor based on a target driving force for the electric vehicle; Calculating an actual pitch angle based on the front wheel driving force command value and the rear wheel driving force command value using an actual pitch angle model; calculating a reference pitch angle based on the front wheel driving force command value and the rear wheel driving force command value using a reference pitch angle model; calculating a longitudinal driving force movement amount based on a difference between the actual pitch angle and the standard pitch angle so that the actual pitch angle coincides with the standard pitch angle; calculating a front wheel actual driving force command value and a rear wheel actual driving force command value to be input to the first motor and the second motor, respectively, by correcting the front wheel driving force command value and the rear wheel driving force command value based on the front / rear driving force movement amount; A control device for an electric vehicle.

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