JP7596773B2 - Electric vehicle control method and control device - Google Patents

Description

The present invention relates to a control method and control device for an electric vehicle.

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 the 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 motor output torque, thereby correcting the torque command value so that vehicle body vibrations are suppressed.

JP 2013-240258 A

However, in the above control device, a filtering process is performed on the motor output torque to reduce the gain in a specified frequency range. This results in a torque response in which the driving force command value differs from the driving force command value from the upper controller, and the desired acceleration cannot be obtained. As such, there are cases in which the desired acceleration cannot be obtained while suppressing vehicle body vibration.

The present invention aims to provide a method for controlling an electric vehicle that can suppress vehicle body vibration and obtain the desired acceleration.

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 control 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; an actual pitch angle calculation step of calculating an actual pitch angle based on the front wheel drive force command value and the rear wheel drive force command value using an actual pitch angle model; a norm pitch angle calculation step of calculating a norm pitch angle based on the front wheel drive force command value and the rear wheel drive force command value using a norm pitch angle model; a front/rear drive force transfer amount calculation step of calculating a front/rear drive force transfer amount based on a difference between the actual pitch angle and the norm pitch angle so that the actual pitch angle coincides with the norm pitch angle; and an actual drive command value calculation step of calculating a front wheel actual drive force command value and a rear wheel actual drive force command value to be input to the first motor and the second motor, respectively, by correcting the front wheel drive force command value and the rear wheel drive force command value based on the front/rear drive force transfer amount.

According to one aspect of the present invention, a method for controlling an electric vehicle is provided that can suppress vehicle body vibration and obtain a desired acceleration.

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

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

[Overall configuration]
1 is a diagram showing the overall configuration of an electric vehicle (hereinafter, simply referred to as a "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.

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.

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 response to the switching operation of the front inverter 20. The front wheels 14 rotate in response to the output drive torque from the front reduction gear 30.

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 response to the switching operation of the rear inverter 22. The rear wheels 16 rotate in response to the output drive torque from the rear reduction gear 32 controlled by the motor controller 5.

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

The motor controller 5 controls the front motor 10 and the rear motor 12. Digital signals indicating vehicle conditions such as vehicle speed V, accelerator opening θ, front rotor phase αf of the front motor 10, 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 to the motor controller 5. The front rotor phase αf as an electrical angle is detected by the front rotation sensor 11, and the rear rotor phase αr is detected by the rear rotation sensor 13.

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 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].

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

The motor controller 5 generates PWM signals for controlling the front motor 10 and the rear motor 12 based on the above input signals. The motor controller 5 also generates drive signals for the front inverter 20 and the rear inverter 22 based on these PWM signals.

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

The currents ifu, ifv, ifw of the front motor 10 are acquired by the front current sensor 26, and the currents iru, irv, irw of the rear motor 12 are acquired by the rear current sensor 28. Since the sum of the current values of these three phases is 0, for example, the current ifw may be obtained from the values of the currents ifu and ifv.

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 this 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).

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

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

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 the accelerator opening θ and vehicle speed V in the accelerator opening-driving force table shown in FIG. 3. As shown in FIG. 3, the relationship between the motor rotation speed and the motor torque is determined according to the accelerator opening θ. That is, FIG. 3 shows a basic driving force command value determined to realize the driving force required for the vehicle.

Then, the front/rear driving force distribution ratio Kf of the target driving force command value F* from a higher-level controller (not shown) is set between 0 and 1 by the front/rear driving force distributor 401 shown in FIG. 4. The 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. The 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).

In step S203, the motor controller 5 executes pitch angle vibration suppression processing. In particular, in this pitch angle vibration suppression processing, the motor controller 5 inputs the front wheel driving force command value Ff* and the rear wheel driving force command value Fr* to calculate the front wheel actual driving force command value Fλf* and the rear wheel actual driving force command value Fλr*. Details of the pitch angle vibration suppression processing will be described later.

In step S204, the motor controller 5 executes the torsional vibration suppression process. The motor controller 5 inputs the first front and rear motor torque command values Tmf1*, Tmr1*, which are 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 the command values Tmf2*, Tmr2* after the torsional vibration suppression process, which are the front and rear torque command values. The command values Tmf2*, Tmr2* after the torsional vibration suppression process suppress driving force transmission system vibrations such as the torsional vibration 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 for vehicles without a drive shaft or when the torsional vibration is suppressed mechanically.

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

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 the 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 the 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 the 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.

In this way, the motor controller 5 uses the PWM signals calculated by the processing of 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 the desired torques specified by their respective torque command values.

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

First, an example of the equation of motion for a vehicle 1 having drive motors on both the front and rear wheels is described. Based on this equation of motion, the transfer characteristics 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 are calculated. If the sprung mass of the vehicle body is assumed to be a rigid body, as shown in Figure 5, the driving force reaction force, inertia force, and vertical forces due to the instantaneous rotation angles θf,r that represent the operating state of the suspension act on the sprung mass of the vehicle body during acceleration and deceleration.

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

Using the above variables, the pitching moment Mλ is expressed as the following formula (1). Note that the instantaneous rotation angles θf,r are fixed values, as changes during the stroke are minimal.

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

By performing a Laplace transform on the above equation (2), we obtain the transfer function equation (4).

In this way, the transfer characteristics 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 are expressed as a second-order system response as shown in the above equation (4).

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 front/rear driving force transfer amount Fd*. 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. That is, when the driving force (torque) is transferred from the rear wheels 16 to the front wheels 14, the front/rear 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 front/rear driving force transfer amount Fd* is a negative value. Therefore, in this embodiment, the dynamic characteristics of the pitch angle λ are derived to be 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, based on the prerequisites and the derived pitch angle model, the actual pitch angle response when the longitudinal driving force transfer amount Fd* is applied is expressed as in the following equation (5).

The standard 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 vehicle body vibration is reduced to the lowest.

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

Transforming equation (7) gives equation (8).

As shown in equation (8), the control for suppressing pitch angle vibration can be expressed by an inverse model of the pitch angle based on the difference between the actual pitch angle response (actual pitch angle response) Gpλ(s) and the reference response Grλ(s) and the forward/rearward driving force movement amount Fd.

[Functional 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.

The reference pitch angle model calculation unit 901 shown in FIG. 7 receives the front wheel driving force command value Ff* and the rear wheel driving force command value Fr* as input, performs filtering using the reference pitch angle model Grλ(s) of the above formula (6), and calculates the reference pitch angle response. Note that although the reference pitch angle λ* in this example was calculated using formula (6), any reference pitch angle response using a rate of change limiter or the like may be used.

The actual pitch angle model calculation unit 902 shown in FIG. 8 receives the front wheel driving force command value Ff* and the rear wheel driving force command value Fr* as input, 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^ was 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 also be used.

The longitudinal driving force transfer amount calculation unit 903 shown in FIG. 9 receives the difference between the reference pitch angle λ and the actual pitch angle λ^ as input, and performs filtering processing using an inverse model of the pitch angle from the longitudinal driving force transfer amount Fd* derived from the above equation (4). This calculates the longitudinal driving force transfer amount Fd* such that the actual pitch angle response matches the reference pitch angle response.

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

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 of 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 of the rear wheels 16, a situation may arise in which a positive driving force is applied to the front wheels 14 (powered driving) while a negative driving force is applied to the rear wheels 16 (regenerative driving). If such a situation occurs, it is considered that the vehicle 1 may sway back or the load on the vehicle 1 may increase, making it impossible to achieve 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 of the rear wheels 16.

Specifically, the driving force transfer amount limiter 904 calculates the smaller of the rear wheel driving force command value Fr* and the front-rear driving force transfer amount Fd* (positive value) in the previous stage. In the next stage, the larger of this value and the sign-inverted value (negative value) of the front wheel driving force command value Ff* is calculated 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 front-rear 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 front-rear driving force transfer amount Fd*.

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 front-rear driving force movement amount Fd* is limited to an amount of movement equal to or less than the driving force of the front wheels 14.

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 (powered driving) has been described. However, a configuration may be adopted in which the limited driving force transfer amount Fdl* is calculated so 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 driving).

Returning to FIG. 6, the front and rear wheel phase adjustment unit 905 receives the value (limited front wheel driving force command value Ff*) obtained by adding the limited driving force movement amount Fdl* to the front wheel driving force command value Ff*, and the value (limited rear wheel driving force command value Fr*) obtained by subtracting the limited driving force movement amount Fdl* from the 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 due to the electrical configuration. Specifically, the front and rear wheel phase adjustment unit 905 applies a filter consisting of the transfer characteristic Gr from the front motor torque command value to the front motor rotation speed including vibration control and the 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*, and calculates the front wheel actual driving force command value Fλf*. Note that the rear wheel actual driving force command value Fλr* is output as it is after the above-mentioned limit.

[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.

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

In this embodiment, the pitch angle is controlled by the difference between the front and rear driving forces to suppress a decrease in the total driving force. Therefore, compared to the comparative example, it is possible to reduce pitch angle overshoot while achieving 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 swaying due to pitch during acceleration while achieving the acceleration intended by the driver.

The effects of this embodiment are explained below.

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 the front wheels 14 and a rear motor (second motor) 12 for driving the rear wheels 16, and includes a command value calculation step for 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 step for 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 method includes an actual pitch angle response calculation step, a front-rear driving force movement amount calculation step for calculating a front-rear driving force movement amount Fd, which is determined as the driving force to be moved between the front wheels 14 and the rear wheels 16 based on the actual pitch angle response so as to obtain a driving force distribution ratio Kf that reduces the degree of vibration, and an actual driving force calculation step for 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.

According to this embodiment, the total driving force of the vehicle 1 is distributed between the front wheels 14 and the rear wheels 16 in such a way that vibrations are reduced. Therefore, the vibrations of the vehicle 1, particularly those in the pitch direction, are suppressed while maintaining the desired vehicle output without reducing the total driving force.

The control method for an electric vehicle according to this embodiment further includes a standard pitch angle calculation step for calculating a standard 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 standard pitch angle response with the actual pitch angle response.

According to this embodiment, the longitudinal driving force transfer amount Fd* is determined based on a comparison with a standard pitch angle response that reduces vibration, which has been determined in advance through experiments, etc. Therefore, it is possible to determine the longitudinal driving force transfer amount Fd that more accurately reduces the vibration of the vehicle 1.

In addition, in the longitudinal driving force calculation step, the control method for an electric vehicle of this embodiment calculates the difference between the reference pitch angle response and the actual pitch angle response, and calculates the longitudinal driving force transfer amount Fd* 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*.

According to this embodiment, the difference between the standard pitch angle response and the actual pitch angle response that reduces vibrations determined in advance through experiments, etc., is calculated 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 the longitudinal driving force transfer amount Fd* that can evaluate the vibrations of the vehicle 1 with higher accuracy and then appropriately remove them can be obtained. As a result, the vibrations of the vehicle 1 can be reduced more accurately while keeping the total driving force constant.

In addition, in the control method for an electric vehicle of this embodiment, in the standard pitch angle calculation step, the standard pitch angle response is determined so as to be the same as the actual pitch angle response in a steady state.

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 fluctuations in pitch motion (pitch angle) are small enough to be practically negligible, the standard pitch angle response is designed to match the actual pitch angle response. As a result, in the steady state, the front-rear driving force movement amount Fd* based on the difference between the standard pitch angle response and the actual pitch angle response is calculated to be "0", and the basic distribution ratio Kf before correction is maintained. In other words, in a scene where it is considered that practically no vehicle body vibration occurs, the basic distribution ratio Kf that is originally required can be maintained without practically executing the pitch angle vibration suppression process.

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

As a result, since the instantaneous rotation angles θf and 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 and 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 and 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 and θr derived by experiments, etc., it is possible to calculate a highly accurate standard pitch angle λ that takes into account the actual behavior of the vehicle 1.

In addition, in the actual driving force calculation step, the control method for an electric vehicle of this embodiment matches the sign of the longitudinal driving force transfer amount Fd* with the sign of the driving force transferred from the rear wheels 16 to the front wheels 14, and calculates the front wheel actual driving force command value Fλf* as the front wheel driving force command value Ff* plus the longitudinal driving force transfer amount Fd*. In addition, the rear wheel actual driving force command value Fλr* is calculated as the rear wheel driving force command value Fr* minus the longitudinal driving force transfer amount Fd*.

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 is 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*, i.e., that can suppress vehicle body vibration while driving the vehicle 1 at a desired acceleration.

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 the 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 the same.

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 that cause the sign to be reversed.

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 the front and rear wheels.

For example, the phase difference between the front and rear wheels as a dynamic characteristic of the front and rear wheels can be suppressed, so that a state in which the driving force is reliably constant can be maintained. Specifically, in a vehicle 1 equipped with multiple drive motors, if the dynamic characteristics and phases up to 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 desired actual driving force 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.

The control method of this embodiment also includes a torsional vibration suppression control step for suppressing vibration in the driving force transmission system of the vehicle 1.

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 in the vehicle 1, torsional vibrations can also be appropriately suppressed.

Although the embodiments of the present invention have been described above, the above embodiments merely show some of the application examples of the present invention, and are not intended to limit the technical scope of the present invention to the specific configurations of the above embodiments.

For example, in this embodiment, the case of powered driving has been described, but in the same way, during regenerative driving, the pitch angle can be controlled based on the difference between the front and rear braking/driving forces to prevent a decrease in the total braking/driving force, thereby suppressing the feeling of backswing during deceleration while achieving the deceleration intended by the driver.

1 Vehicle 10 Front motor 12 Rear motor Fd* Front-rear driving force movement amount

Claims (8)

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. A method for controlling 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. A method for controlling an electric vehicle according to claim 1 or 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. 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. 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. 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. 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. 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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