JP2017085681A - Control method for electric vehicle, and control apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for suppressing a vehicle from swinging longitudinally even a slip occurs between a drive wheel and the road surface during stop control.SOLUTION: A control method, for use in an electric vehicle having a motor to generate drive torque or regenerative torque in accordance with an accelerator operation of a driver, includes: detecting a rotation speed of the motor to estimate disturbance torque forced to the motor; executing, as the vehicle nears a vehicular stop, stop-time torque control for controlling motor torque so as to converge to an estimation value of the disturbance torque as rotation speeds of the motor decrease, on the basis of a vehicular model produced by modelling transmission characteristics from a torque target value for the motor to the rotation speed of the motor; determining whether the vehicular model is established correspondingly to the actual vehicular response; and cancelling the stop-time torque control, in the case of the vehicular model not being established after the vehicle has neared the vehicular stop, and executing torque control on the basis of a drive force characteristics calculated in accordance with an accelerator opening degree and the rotation speed of the motor.SELECTED DRAWING: Figure 11

Description

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

  2. Description of the Related Art Conventionally, a regenerative brake control device for an electric vehicle that includes a setting unit that can arbitrarily set a regenerative braking force of an electric motor and performs regeneration of the electric motor with a regenerative braking force set by the setting unit is known (see Patent Document 1). ).

JP-A-8-79907

  However, in the technique disclosed in Patent Document 1, when the regenerative braking force set by the setting unit is large, when the electric vehicle decelerates with the set regenerative braking force and the speed becomes zero, the vehicle body There is a problem that vibration (acceleration vibration) occurs in the front-rear direction.

  In response to this problem, the inventors of the present invention use a vehicle model configured on the basis of the transfer characteristic from the motor torque to the motor rotation speed, and adjust the motor torque as the motor rotation speed decreases, resulting in a generally gradient resistance. By executing stop control that converges to the estimated disturbance torque, smooth deceleration without acceleration vibration can be achieved just before stopping, regardless of flat roads, uphill roads, and downhill roads, and the stopped state can be maintained. Are considering.

  However, when estimating the disturbance torque using the above vehicle model, it is assumed that the characteristics of the drive wheels and the road surface are those on a high μ road that shows a general friction coefficient. When the driving wheel and the road surface slip on the μ road, the behavior of the vehicle model and the actual vehicle deviate, and the disturbance torque cannot be estimated normally. Therefore, when the above-described stop control is executed in the slip state, there is a problem that the vehicle swings back and forth until the estimated disturbance torque value converges to a true value.

  An object of the present invention is to provide a technique for preventing a vehicle from swinging back and forth even when a drive wheel and a road surface slip during stop control.

  A method for controlling an electric vehicle according to the present invention is a method for controlling an electric vehicle including a motor that generates a drive torque or a regenerative torque in accordance with an accelerator operation of the driver, and detects the rotational speed of the motor and acts on the motor. The disturbance torque to be estimated is estimated. Then, when the electric vehicle is about to stop, based on the vehicle model that models the transfer characteristics from the torque target value for the motor to the motor rotation speed, the motor torque decreases with the estimated value of the disturbance torque as the motor rotation speed decreases. Torque control at the time of stop is executed to control so as to converge. It is determined whether or not the vehicle model is established with respect to the actual vehicle response. If the vehicle model is not established immediately after stopping, the torque control at the time of stopping is stopped, and the accelerator opening and the motor are Torque control based on the driving force characteristic calculated according to the rotational speed is executed.

  According to the present invention, it is determined whether or not a vehicle model is established. If the vehicle model is not established, torque control at the time of stop based on the vehicle model is stopped, and the accelerator opening and the rotation speed of the motor are stopped. Torque control based on the driving force characteristics corresponding to the driver's intention calculated according to the above is executed. Thereby, even if the drive wheel and the road surface slip during the stop control, it is possible to prevent the vehicle from swinging back and forth due to the stop control being executed in a state where the vehicle model is not established.

FIG. 1 is a block diagram illustrating a main configuration of an electric vehicle including an electric vehicle control device according to an embodiment. FIG. 2 is a flowchart showing a flow of processing of motor current control performed by the motor controller. FIG. 3 is a diagram illustrating an example of a first accelerator opening-torque table. FIG. 4 is a diagram illustrating an example of a second accelerator opening-torque table. FIG. 5 is a diagram illustrating an example of a third accelerator opening-torque table. FIG. 6 is a diagram for explaining torque switching executed based on the slip determination result in the slip determination process. FIG. 7 is a flowchart showing the flow of the slip determination process. FIG. 8 is a diagram modeling a vehicle driving force transmission system. FIG. 9 is a block diagram for explaining the vibration suppression control process. FIG. 10 is a block diagram for realizing the vibration suppression control process. FIG. 11 is a block diagram for realizing the stop control process. FIG. 12 is a diagram for explaining a method of calculating the motor rotation speed F / B torque based on the motor rotation speed. FIG. 13 is a block diagram for realizing calculation of the disturbance torque estimated value by the disturbance torque estimator. FIG. 14 is a diagram for explaining a control result by the control device for an electric vehicle in one embodiment. FIG. 15 is a diagram for explaining a control result by the control device for the electric vehicle according to the embodiment.

  Below, the example which applied the control apparatus of the electric vehicle by this invention to the electric vehicle which is equipped with braking devices, such as a friction brake, and uses an electric motor (motor) as a drive source is demonstrated.

  FIG. 1 is a block diagram illustrating a main configuration of an electric vehicle including an electric vehicle control device according to an embodiment. In particular, the vehicle control device in the present embodiment can be applied to a vehicle that can control acceleration / deceleration and stop of the vehicle only by operating an accelerator pedal. In this vehicle, the driver depresses the accelerator pedal at the time of acceleration and reduces the amount of depression of the accelerator pedal at the time of deceleration or stop, or sets the depression amount of the accelerator pedal to zero. On an uphill road, the vehicle may approach a stop state while depressing the accelerator pedal to prevent the vehicle from moving backward.

  The motor controller 2 receives signals indicating the vehicle state such as the vehicle speed V, the accelerator opening AP, the rotor phase α of the motor (three-phase AC motor) 4, and the currents iu, iv, iw of the motor 4 as digital signals. The The motor controller 2 generates a PWM signal for controlling the motor 4 based on the input signal. The motor controller 2 generates a drive signal for the inverter 3 in accordance with the generated PWM signal. The motor controller 2 further generates a friction braking amount command value by a method described later.

  The inverter 3 converts the direct current supplied from the battery 1 into alternating current by turning on / off two switching elements (for example, power semiconductor elements such as IGBT and MOS-FET) provided for each phase. Then, a desired current is passed through the motor 4.

  The motor 4 generates a driving force by the alternating current supplied from the inverter 3, and transmits the driving force to the left and right driving wheels 9 a and 9 b via the speed reducer 5 and the drive shaft 8. Further, the motor 4 collects the kinetic energy of the vehicle as electric energy by generating a regenerative driving force when the motor 4 is rotated by the drive wheels 9a and 9b during rotation of the vehicle and rotates. In this case, the inverter 3 converts an alternating current generated during the regenerative operation of the motor 4 into a direct current and supplies the direct current to the battery 1.

  The current sensor 7 detects three-phase alternating currents iu, iv, iw flowing through the motor 4. However, since the sum of the three-phase alternating currents iu, iv, and iw is 0, any two-phase current may be detected, and the remaining one-phase current may be obtained by calculation.

  The rotation sensor 6 is, for example, a resolver or an encoder, and detects the rotor phase α of the motor 4.

  The hydraulic pressure sensor 10 detects the brake hydraulic pressure of the friction brake 12.

  The brake controller 11 generates a brake fluid pressure corresponding to the friction braking amount command value generated by the motor controller 2. The brake controller 11 also performs feedback control so that the brake fluid pressure detected by the fluid pressure sensor 10 follows a value determined according to the friction braking amount command value.

  The friction brake 12 functions as a friction braking unit. Specifically, the friction brake 12 is provided on the left and right drive wheels 9a, 9b, and presses the brake pad against the brake rotor according to the brake fluid pressure to generate a braking force on the vehicle.

  In addition, although not shown, the electric vehicle to which the control device of the present embodiment is applied includes vehicle body speed acquisition means for detecting or estimating vehicle body speed Vc (hereinafter referred to as vehicle body speed Vc).

  FIG. 2 is a flowchart showing a flow of processing of motor current control performed by the motor controller 2.

In step S <b> 201, a signal indicating the vehicle state is input to the motor controller 2. Here, the vehicle speed V (m / s), the accelerator opening θ (%), the rotor phase α (rad) of the motor 4, the rotational speed Nm (rpm) of the motor 4, the three-phase alternating current iu flowing through the motor 4, iv, iw, a DC voltage value V _dc (V) between the battery 1 and the inverter 3, a vehicle body speed Vc [m / s], and a brake braking amount B are input.

  The vehicle speed V (m / s) is a wheel speed of a wheel (braking wheel) that transmits a braking force or a wheel (driving wheels 9a and 9b) that transmits a driving force when the vehicle is driven. The vehicle speed V is acquired by communication from a vehicle speed sensor (not shown) or another controller. Alternatively, the vehicle speed V (km / h) is obtained by multiplying the rotor mechanical angular velocity ωm by the tire moving radius r and dividing by the gear ratio of the final gear.

  The accelerator opening degree θ (%) is acquired from an accelerator opening sensor (not shown), or is acquired by communication from another controller such as a vehicle controller (not shown).

  The rotor phase α (rad) of the motor 4 is acquired from the rotation sensor 6. The rotational speed Nm (rpm) of the motor 4 is obtained by dividing the rotor angular speed ω (electrical angle) by the pole pair number p of the motor 4 to obtain the motor rotational speed ωm (rad / s) that is the mechanical angular speed of the motor 4. It is obtained by multiplying the obtained motor rotation speed ωm by 60 / (2π). The rotor angular velocity ω is obtained by differentiating the rotor phase α.

  Currents iu, iv, iw (A) flowing through the motor 4 are acquired from the current sensor 7.

The DC voltage value V _dc (V) is obtained from a power supply voltage value transmitted from a voltage sensor (not shown) provided in a DC power supply line between the battery 1 and the inverter 3 or a battery controller (not shown).

  The vehicle body speed Vc [m / s] is obtained directly from a driven wheel speed sensor value as vehicle body speed acquisition means for detecting the wheel speed of the driven wheel, or a vehicle body speed estimated value estimated by another controller (not shown). Acquired by communication.

  The brake braking amount B is acquired from the brake hydraulic pressure sensor value detected by the hydraulic pressure sensor 10. Alternatively, the friction braking amount command value generated by the motor controller 2 is set as the brake braking amount B.

In the torque target value calculation process in step S202, the motor controller 2 sets the first torque target value Tm1 ^* . Specifically, refer to the first accelerator opening-torque table shown in FIG. 3 showing one aspect of the driving force characteristics calculated according to the accelerator opening θ and the motor rotational speed ωm input in step S201. Thus, the first torque target value Tm1 ^* is set.

However, when it is determined in the slip determination process in step S203 described later that the vehicle is in the slip state, the motor controller 2 refers to the second accelerator opening-torque table shown in FIG. A fourth torque target value Tm4 ^* is set as the torque target value. Note that the third accelerator opening-torque shown in FIG. 5 outputs a so-called creep torque in which the torque target value [Nm] at the accelerator opening 0 [%] and the motor rotation speed 0 [rpm] is a positive torque. The fourth torque target value Tm4 ^* may be set by referring to the table.

  In the slip determination process in step S203, the tire slip state (slip amount, slip rate) is estimated based on the vehicle speed V corresponding to the wheel speed detected in step S201 and the vehicle body speed Vc, and the slip amount or slip rate is predetermined. If it is equal to or greater than the value, it is determined that the vehicle is in the slip state, and the slip state determination flag flg_slip is set to 1.

  The determination of whether or not the vehicle is in a slip state is a slip state if a differential process is performed on the motor rotational speed and the vehicle speed V [m / s] and the value obtained by the differential process is equal to or greater than a predetermined value. You may judge. Further, the rate of change of the disturbance torque estimated value may be calculated based on the past value of the disturbance torque estimated value, and if the calculated value is equal to or greater than a predetermined value, it may be determined that the vehicle is in the slip state.

  Then, after the slip state determination flag flg_slip returns from 1 (slip state) to 0 (grip state), until the predetermined time elapses, various control parameters in the stop control process in step S204 are normally used in the grip state. The control parameter is set to the control parameter at the start of stop control with higher speed response than the control parameter (control parameter at normal time). Details of the slip control process will be described later.

In step S204, the controller 2 performs a stop control process. Specifically, the controller 2 determines whether or not the vehicle is about to stop ^. If the vehicle is not about to stop, the controller sets the first target torque value Tm1 ^* calculated in step S202 to the third motor torque command value Tm3 ^*. When the vehicle is about to stop, the second torque target value Tm2 ^* is set to the third motor torque command value Tm3 ^* . The second torque target value Tm2 ^* converges to the disturbance torque command value Td as the motor rotational speed decreases, and is positive torque on an uphill road, negative torque on a downhill road, and almost zero on a flat road. Thereby, a stop state can be maintained regardless of the gradient of the road surface.

Further, the third motor torque command value Tm3 ^* is switched as shown in FIG. 6 according to the slip state determination flag flg_slip determined in the above-described step 203, and the fifth motor torque command value Tm3 ^* is set as the final torque target value. The torque target value Tm5 ^* is set.

FIG. 6 is a diagram for explaining torque switching executed based on the slip determination result in the slip determination process. As shown in FIG., The third torque target value Tm3 ^*, when flg_slip = 0 in (gripping state), is set to the fifth torque target value Tm5 ^*. When flg_slip = 1 (slip state), the second or third accelerator opening-torque table expressing one aspect of the driving force characteristic calculated according to the accelerator opening and the rotation speed of the motor 4 fourth torque target value Tm4 ^* references to be calculated is set to the fifth torque target value Tm5 ^*. Details of the stop control process will be described later.

In step S205, the motor controller 2 performs a vibration suppression control process. Specifically, the motor controller 2 performs vibration suppression control processing on the motor torque command value Tm3 ^* calculated in step S204 and the motor rotation speed ωm. Thus, the calculated motor torque command value Tm ^* suppresses torque transmission system vibration (such as torsional vibration of the drive shaft) without sacrificing the response of the drive shaft torque. Details of the vibration suppression control process will be described later.

In subsequent step S206, the controller 2 performs a current command value calculation process. Specifically, in addition to the motor torque target value Tm ^* calculated in step S205, the d-axis current target value id ^* and the q-axis current target value iq ^* are obtained based on the motor rotation speed ωm and the DC voltage value Vdc. For example, by preparing in advance a table that defines the relationship between the torque command value, the motor rotation speed, the DC voltage value, the d-axis current target value, and the q-axis current target value, and referring to this table, The d-axis current target value id ^* and the q-axis current target value iq ^* are obtained.

In step S207, current control is performed to match the d-axis current id and the q-axis current iq with the d-axis current target value id ^* and the q-axis current target value iq ^* obtained in step S206, respectively. For this reason, first, the d-axis current id and the q-axis current iq are obtained based on the three-phase AC current values iu, iv, iw input in step S201 and the rotor phase α of the electric motor 4. Subsequently, d-axis and q-axis voltage command values vd and vq are calculated from a deviation between the d-axis and q-axis current command values id ^* and iq ^* and the d-axis and q-axis current id and iq.

Then, three-phase AC voltage command values vu, vv, vw are obtained from the d-axis and q-axis voltage command values vd, vq and the rotor phase α of the electric motor 4. The PWM signals tu (%), tv (%), and tw (%) are obtained from the obtained three-phase AC voltage command values vu, vv, and vw and the current voltage value Vdc. The electric motor 4 can be driven with a desired torque indicated by the torque command value Tm ^* by opening and closing the switching element of the inverter 3 by the PWM signals tu, tv, and tw thus obtained.

<Slip judgment processing>
Here, the details of the slip determination process executed in the above-described step S203, which is characteristic of the present invention, will be described with reference to the flowchart shown in FIG.

FIG. 7 is a flowchart showing the slip determination process. The slip determination process is always executed in a constant cycle in the motor controller 2 to determine whether or not the drive wheels 9a and 9b of the vehicle and the road surface are in a slip state. If it is determined that the slip state, in the stop control process, as described above with reference to FIG. 6, the fourth torque target value Tm4 ^* is set to the fifth torque target value Tm5 ^*. Then, in comparison with the previous process, if the vehicle state is determined to have returned from the slipping state to the gripping state, the third torque target value Tm3 ^* is set to the fifth torque target value Tm5 ^*.

In the slip determination process described below, various control parameters used in the stop control process related to the calculation of the third torque target value Tm3 ^* executed in step S204 of FIG. The control parameter at the time of starting the stop control, which has higher speed response than (normal control parameter), is set for a predetermined time T1. Hereinafter, the flow of the process for continuing the control parameter at the start of the stop control, which is set immediately after returning from the slip state to the grip state, for a predetermined time T1, which is executed in step S203. Explain to the original.

  In step S701, the motor controller 2 determines the absolute value of the value obtained by differentiating the motor rotational speed ωm, that is, the motor rotational acceleration represented by the absolute value of the difference between the previous value ωm_z of the motor rotational speed and the current value ωm of the motor rotational speed. | Dω / dt | is calculated. Then, the motor rotational acceleration | dω / dt | is compared with the motor rotational acceleration slip1 [rad / s ^ 2] that can be determined that the driving wheel of the vehicle is in the slip state, and | dω / dt | <slip1 is established. If so, it is determined that the vehicle is not in the slip state, and the subsequent process of step S702 is executed. When | dω / dt | ≧ slip1 is satisfied, it is determined that the vehicle is in the slip state, and the process of step S706 is executed. It should be noted that the motor rotational acceleration that can be determined that the vehicle drive wheels are in the slip state is a value that is equal to or greater than the amount of change based on the normal vehicle deceleration and road surface gradient change.

  In step S702, the motor controller 2 calculates the slip amount Vslip [m / s] of the drive wheels 9a and 9b based on the deviation between the vehicle speed Vc [m / s] and the vehicle speed V [m / s]. Then, the slip amount Vslip [m / s] of the drive wheels 9a and 9b is compared with the slip amount slip2 [m / s] that can be determined that the drive wheel of the vehicle is in the slip state. When Vslip <slip2 is satisfied, it is determined that the vehicle is not in a slip state, and the subsequent process of step S703 is executed. When Vslip ≧ slip2 is established, it is determined that the vehicle is in a slip state, and the process of step S706 is executed.

  In step S703, the motor controller 2 calculates the slip ratio slip of the drive wheels 9a and 9b based on the vehicle speed Vc [m / s] and the vehicle speed V [m / s]. The slip ratio slip at the time of braking is calculated by dividing the vehicle body speed Vc by a value obtained by subtracting the vehicle speed V from the vehicle body speed Vc. That is, the slip ratio slip is calculated by slip = (Vc−V) / Vc. Then, the slip amount slip [−] of the drive wheels 9a and 9b is compared with the slip ratio slip3 [−] that can be determined that the drive wheel of the vehicle is in a slip state. If slip <slip3 is satisfied, the vehicle Is determined not to be in a slip state, and the subsequent processing of step S704 is executed. If slip ≧ slip3 is satisfied, it is determined that the vehicle is in a slip state, and the process of step S706 is executed.

  In step S704, the motor controller 2 calculates a rate of change | d (dist) / dt | [Nm / s] of the estimated disturbance torque value based on the past value of the estimated disturbance torque value [Nm]. Then, the change rate | d (dist) / dt | of the disturbance torque estimated value is compared with the change rate slip4 [Nm / s] of the disturbance torque estimated value at which it can be determined that the driving wheel of the vehicle is in the slip state. If | d (dist) / dt | <slip4 is satisfied, it is determined that the vehicle is not in a slip state, and the subsequent process of step S705 is executed. When | d (dist) / dt | ≧ slip4 is satisfied, it is determined that the vehicle is in the slip state, and the process of step S706 is executed. Since the disturbance torque estimated value is calculated in consideration of the braking force by the brake braking amount B and the regenerative torque, the rate of change of the disturbance torque estimated value at which it can be determined that the driving wheel of the vehicle is in a slip state is It can be set considering only the change in the road surface gradient.

  In step S705, the motor controller 2 determines that the drive wheels 9a and 9b of the vehicle are in the grip state by the processing in steps S701 to S704, and therefore sets the slip state determination flag flg_slip to 0. After setting flg_slip = 0 (grip state), the process of the subsequent step S707 is executed.

  On the other hand, in step S706, the motor controller 2 sets the slip state determination flag flg_slip to 1 because it is determined that the vehicle is in the slip state in the process related to at least one of steps S701 to S704. After setting flg_slip = 1 (slip state), the process of the subsequent step S707 is executed.

  In step S707, the motor controller 2 determines whether or not the slip state determination flag flg_slip has shifted from 1 (slip state) to 0 (grip state). If it is determined that the slip state determination flag flg_slip has shifted from 1 to 0, the process of the subsequent step S708 is executed. When it is not determined that the slip state determination flag flg_slip has shifted from 1 to 0, that is, when the drive wheels 9a and 9b of the vehicle continue to be in the slip state or the grip state from the previous processing, or the drive wheels of the vehicle In the case where 9a and 9b have shifted to the slip state from the grip state, the process of step S709 is executed.

  In step S708, the motor controller 2 sets a predetermined timer time T1 in the timer 1. The timer 1 is a timer for measuring the timing for returning to the control parameter at the normal time from the control parameter at the start of the stop control set in the process of step S712 described later. After the timer time T1 is set in the timer 1, the process of step S711 for performing the timer 1 countdown process is executed.

  In step S709, the motor controller 2 determines whether the count value of the timer 1 is zero. When the timer 1 is 0, it is the timing to return the control parameter of the stop control process from the control parameter at the start of the stop control to the control parameter at the normal time, so the process of the subsequent step S710 is executed. If the timer 1 is not 0, the process of step S711 for performing the count-down process of the timer 1 is executed.

  In step S710, the motor controller 2 sets a normal control parameter as a control parameter used for the stop control process, and ends this process.

  In step S711, the motor controller 2 performs a process of counting down the timer 1 every calculation cycle by subtracting 1 from the count value of the timer 1 and storing it again in the timer 1. After the timer 1 is counted down, the subsequent process of step S712 is executed.

  In step S712, the motor controller 2 sets a parameter at the start of stop control as a control parameter used for the stop control process, and ends this process. The parameter at the time of starting the stop control is a control parameter that is faster than the normal control parameter as described above, and is set by performing the following three processes on the normal control parameter.

  That is, (i) In the multiplier 601 of FIG. 12, the gain Kvref multiplied by the motor rotation speed ωm when the motor rotation speed feedback torque Tω is calculated is set to a value larger than normal. (Ii) In a filter composed of a quadratic numerator of Hz (s) and a denominator of the quadratic expression shown in the control block 805 of FIG. Is set to a value smaller than the normal value. (Iii) The time constant of the low-pass filter H (s) indicated by the control block 802 in FIG. 13 is set to a value smaller than the normal time. Thereby, the parameter at the time of the start of stop control with increased responsiveness is set.

<Vehicle model>
Here, the transmission characteristic G _p (s) from the motor torque Tm to the motor rotational speed ωm of the control device for the electric vehicle in the present embodiment will be described. This transfer characteristic Gp (s) is a vehicle model used in stop control processing including estimation of disturbance torque.

FIG. 8 is a diagram in which a driving force transmission system of a vehicle is modeled, and each parameter in the figure is as shown below.
J _m : Inertia of electric motor J _w : Inertia of drive wheel M: Vehicle weight K _d : Torsional rigidity of drive system K _t : Coefficient related to friction between tire and road surface N: Overall gear ratio r: Tire load radius ω _m : motor speed T _m: torque target value Tm ^*
T _d : Driving wheel torque F: Force applied to the vehicle V: Vehicle speed ω _w : Driving wheel angular velocity T _b : Friction braking amount (motor shaft equivalent torque) (≧ 0)
From FIG. 8, the following equation of motion can be derived.

However, the asterisk ( ^* ) attached to the upper right of the code | symbol in Formula (1)-(3) represents the time differentiation. For convenience, ± in equation (2) is + for uphill roads and flat roads, and-for downhill roads.

  When the transfer characteristic Gp (s) from the torque target value Tm of the motor 4 to the motor rotation speed ωm is obtained based on the equation of motion represented by the expressions (1) to (5), it is expressed by the following expression (6).

  However, each parameter in Formula (6) is represented by following Formula (7).

  When the poles and zeros of the transfer function shown in equation (6) are examined, it can be approximated to the transfer function of the following equation (8), and one pole and one zero show extremely close values. This corresponds to that α and β in the following formula (8) show extremely close values.

Therefore, by performing pole-zero cancellation (approximate α = β) in equation (8), G _p (s) is expressed as (second order) / (third order) as shown in the following equation (9). Configure transfer characteristics.

  When the vibration suppression control (feedforward compensator) in step S205 is used in combination, the vehicle model Gp (s) is controlled by Gp (s) and the vibration suppression control algorithm as shown by the following equation (10). It can be regarded as the vehicle response Gr (s) when vibration control is applied.

<Vibration control processing>
Here, the vibration suppression control process executed in step S205 will be described before the description of the stop control process according to step S204 in FIG. In this step, the motor torque command value Tm ^* is obtained by performing the vibration suppression control process on the fifth torque target value Tm5 ^* as the final torque target value. Hereinafter, a specific description will be given with reference to FIGS. 9 and 10.

FIG. 9 is a block diagram of the vibration suppression control process used in the present embodiment. Here, the fifth torque target value Tm5 ^* calculated in step S204 and the motor rotation speed ωm are input to the vibration suppression control block 901, and the torque transmission system vibration (drive) without sacrificing the response of the drive shaft torque. A motor torque command value Tm ^* that suppresses torsional vibration of the shaft is calculated. Hereinafter, an example of the vibration suppression control process performed in the vibration suppression control block 901 will be described with reference to FIG.

FIG. 10 is a block diagram illustrating details of the vibration suppression control process used in the present embodiment. A feedforward compensator 908 (hereinafter referred to as an F / F compensator) is a model Gp () of the vehicle response Gr (s) expressed by the above equation (10), the torque input to the vehicle, and the transfer characteristic of the motor rotational speed. s), which functions as a filter having a transfer characteristic of Gr (s) / Gp (s) composed of an inverse system of s), and by performing a filtering process on the fifth torque target value Tm5 ^* , Performs vibration suppression control processing by feedforward compensation.

  Note that the damping control F / F compensation performed by the F / F compensator 908 may be damping control described in Japanese Patent Laid-Open No. 2001-45613, or described in Japanese Patent Laid-Open No. 2002-152916. Damping control may be used.

  Control blocks 903 and 904 are filters used in feedback control (hereinafter, feedback is referred to as F / B). The control block 903 is a filter having the above-mentioned transfer characteristic Gp (s), and is obtained by adding the output of the F / F compensator 908 and the output of the control block 904 described later, which are output from the adder 905. Filter the value. Then, the motor rotation speed ωm is subtracted from the value output from the control block 903 in the subtractor 906. The subtracted value is input to the control block 904. The control block 904 is composed of a low-pass filter H (s) and H (s) / Gp (s) composed of a reverse system of the model Gp (s) of the torque input to the vehicle and the transfer characteristic of the rotational speed of the motor. It is a filter having a transfer characteristic, and performs a filtering process on the output from the subtractor 906. The filtering process is performed, and the value calculated as the F / B compensation torque is output to the gain compensator 907.

Gain compensator 907 is a filter having a gain K _FB, by adjusting the value of the gain K _FB, it is possible to adjust the stability of the F / B compensator used in damping control processing. The F / B compensation torque T _{F / B} whose gain has been adjusted by the gain compensator 907 is output to the adder 905.

Then, the adder 905 adds the third torque target value Tm3 ^* subjected to the vibration damping control process by the F / F compensator 908 and the value T _{F / B} calculated as the F / B compensation torque described above. Thus, a motor torque command value Tm ^* that suppresses vibration of the torque transmission system of the vehicle is calculated.

  Note that the vibration suppression control performed in the vibration suppression control block 901 may be vibration suppression control described in Japanese Patent Application Laid-Open No. 2010-288332.

<Stop control process>
Next, details of the stop control process performed in step S204 of the flowchart of FIG. 2 will be described.

  FIG. 11 is a block diagram for realizing the stop control process. The stop control process is performed using a motor rotation speed F / B torque setter 501, a disturbance torque estimator 502, an adder 503, and a torque comparator 504. Details of each configuration will be described below.

  The motor rotation speed F / B torque setter 501 calculates a motor rotation speed feedback torque (hereinafter referred to as “motor rotation speed F / B torque”) Tω based on the detected motor rotation speed ωm. Details will be described with reference to FIG.

  FIG. 12 is a diagram for explaining a method of calculating the motor rotation speed F / B torque Tω based on the motor rotation speed ωm. The motor rotation speed F / B torque setter 501 includes a multiplier 601 and calculates a motor rotation speed F / B torque Tω by multiplying the motor rotation speed ωm by a gain Kvref. However, Kvref is a negative (minus) value required to stop the electric vehicle just before the electric vehicle stops, and is appropriately set based on, for example, experimental data. The motor rotation speed F / B torque Tω is set as a torque that provides a greater braking force as the motor rotation speed ωm increases.

  The motor rotation speed F / B torque setter 501 has been described as calculating the motor rotation speed F / B torque Tω by multiplying the motor rotation speed ωm by the gain Kvref. The motor rotation speed F / B torque Tω may be calculated using a regenerative torque table that defines torque, an attenuation rate table that stores in advance the attenuation rate of the motor rotation speed ωm, or the like.

The disturbance torque estimator 502 in FIG. 11 calculates a disturbance torque estimated value _Td based on the detected motor rotation speed ωm and the third torque target value Tm3 ^* . Details will be described with reference to FIG.

FIG. 13 shows the disturbance torque estimated value _Td based on the motor rotational speed ωm, the third torque target value Tm3 ^*, and the brake torque estimated value calculated based on the friction brake braking amount B and the vehicle speed V. It is a block diagram for demonstrating the method to calculate. The disturbance torque estimator 502 includes a control block 801, a control block 802, a brake torque estimator 803, a subtractor 804, and a control block 805.

The control block 801 functions as a filter having a transfer characteristic of H (s) / Gr (s), and performs a filtering process on the motor rotation speed ωm, thereby obtaining the first motor torque estimated value. calculate. H (s) is the difference between the denominator order and the numerator order, the denominator of the transfer characteristic G _r (s) (see equation (10)) between the motor torque Tm and the motor rotational speed ωm when the damping control is applied. It is a low-pass filter having a transfer characteristic that is equal to or greater than the difference between the order and the numerator order.

The control block 802 functions as a low-pass filter having a transfer characteristic of H (s), and performs the filtering process on the third torque target value Tm3 ^* to obtain the second motor torque estimated value. calculate.

  The brake torque estimator 803 calculates a brake torque estimated value based on the friction brake braking amount B and the vehicle speed V. The brake torque estimator 803 estimates the brake torque based on the friction brake braking amount B and performs a multiplication process for converting the torque of the motor shaft, or the actual braking force based on the hydraulic pressure sensor value detected by the hydraulic pressure sensor 10. A brake torque estimated value is calculated in consideration of responsiveness and the like.

The subtractor 804 calculates a disturbance torque estimated value _Td by subtracting the first motor torque estimated value and the brake torque estimated value from the second motor torque estimated value.

  The control block 805 is a filter having a transfer characteristic of Hz (s), and calculates a disturbance torque estimated value Td by performing a filtering process on the output of the subtractor 804.

  Here, the transfer characteristic Hz (s) will be described. When the above equation (10) is rewritten, the following equation (11) is obtained. However, ζz, ωz, and ωp in equation (11) are each expressed by equation (12).

  As described above, Hz (s) can be expressed by the following equation (13).

  The estimated disturbance torque value Td calculated as described above is estimated by a disturbance observer as shown in FIG. 13 and is a parameter representing a disturbance acting on the vehicle.

Here, disturbances acting on the vehicle may include air resistance, modeling error due to changes in vehicle mass due to the number of passengers and loading capacity, tire rolling resistance, road surface slope resistance, etc. The disturbance factor that becomes dominant at the start is gradient resistance. Although the disturbance factor varies depending on the driving conditions, the disturbance torque estimator 502 determines the disturbance based on the motor torque command value Tm ^* , the motor rotation speed ωm, and the vehicle model Gr (s) when vibration suppression control is applied. Since the estimated torque value Td is calculated, the disturbance factors described above can be estimated collectively. This makes it possible to realize a smooth stop from deceleration under any driving condition.

Returning to FIG. 11, the description will be continued. The adder 503 adds the motor rotation speed F / B torque Tω calculated by the motor rotation speed F / B torque setting unit 501 and the disturbance torque estimation value T _d calculated by the disturbance torque estimator 502. Then, a second torque target value Tm2 ^* is calculated. When the motor rotation speed ωm decreases and approaches 0, the motor rotation speed F / B torque Tω also approaches 0. Therefore, the second torque target value Tm2 ^* is estimated as disturbance torque according to the decrease in the motor rotation speed ωm. It converges to the value _Td .

The torque comparator 504 compares the magnitudes of the first torque target value Tm1 ^* and the second torque target value Tm2 ^* , and sets the larger torque target value as the third torque target value Tm3 ^* . . While the vehicle is running, the second torque target value Tm2 ^* is smaller than the first torque target value Tm1 ^* , and when the vehicle decelerates and comes to a stop (the vehicle speed is equal to or less than a predetermined vehicle speed), the first torque target value Tm1 ^* Be bigger than. Therefore, if the first torque target value Tm1 ^* is larger than the second torque target value Tm2 ^* , the torque comparator 504 determines that the vehicle is just before stopping and determines the first torque target value Tm1 ^* as the third torque. Set as target value Tm3 ^* . In addition, when the second torque target value Tm2 ^* becomes larger than the first torque target value Tm1 ^* , the torque comparator 504 determines that the vehicle is about to stop and sets the third torque target value Tm3 ^* to the first torque target value Tm3 ^* . It switched from the torque target value Tm1 ^* of the second torque target value Tm2 ^*. In order to maintain the stop state, the second torque target value Tm2 ^* converges to a positive torque on an uphill road, a negative torque on a downhill road, and approximately zero on a flat road.

As described above with reference to FIG. 6, in the slip determination process, when the slip state determination flag flg_slip is set to 0 (grip state), the third torque target value Tm3 ^* is the final torque target value. As a fifth torque target value Tm5 ^* .

  The above is the details of the stop control process. By performing such processing, the vehicle can be stopped smoothly only with the motor torque and the stopped state can be maintained regardless of the gradient of the road surface on which the vehicle is traveling.

  Hereinafter, in the scene where the vehicle is braking on the regenerative torque command of the motor 4 while traveling on a flat road, the control result when the control device for the electric vehicle in this embodiment is applied to the electric vehicle will be described as the conventional example. This will be described based on the comparison.

  FIG. 14A shows a time chart of the control result according to the conventional example, and FIG. 14B shows a time chart of the control result according to the present embodiment. FIG. 14 shows the torque command value, the vehicle speed, the slip ratio, the longitudinal acceleration, and the disturbance torque estimated value in order from the top. A dotted line in the figure representing the torque command value indicates a slip state determination flag flg_slip (0: grip state, 1: slip state). A dotted line in the drawing showing the vehicle speed V indicates the vehicle speed Vc.

  On the time axis shown on the horizontal axis, the road surface condition changes as follows. That is, time t0 to t1 is a high μ road such as a normal asphalt road surface, time t1 to t3 is a low μ road such as an icing road surface, and time t3 to t6 is a high μ road.

  First, the control result according to the conventional example will be described with reference to FIG.

  At time t0, braking is being performed with a regenerative torque command, and the estimated disturbance torque value is estimated to be a value equivalent to a flat road.

  From time t1 to t3, the traveling road surface of the vehicle becomes a low μ road, and the vehicle is in a slipping state, so the vehicle speed tends to be steeply approaching zero. Therefore, it is erroneously estimated that the traveling road surface of the vehicle tends to climb up, and the disturbance torque estimated value increases. Thereafter, when the vehicle returns to the grip state from the slip state and the vehicle speed increases steeply, it is erroneously estimated that the traveling road surface of the vehicle has a downward slope tendency, and the disturbance torque estimated value decreases. As described above, the estimated disturbance torque value is estimated in a state where the vehicle model and the actual vehicle behavior are deviated, and thus the estimated disturbance torque value is increased and decreased. Thereby, the torque command value (motor torque) calculated based on the estimated disturbance torque value also vibrates. As a result, the longitudinal acceleration is shaken back and forth, which gives an unpleasant vibration to the driver.

  Next, a control result according to the present embodiment will be described with reference to FIG.

  At time t0, braking is being performed with a regenerative torque command, and the estimated disturbance torque value is estimated to be a value equivalent to a flat road.

From time t1 to t3, the road surface of the vehicle becomes a low μ road, and the vehicle speed tends to be locked toward zero. Therefore, it is determined that the vehicle is in the slip state, the slip state determination flag flg_slip is set to 1, and the third torque target value Tm3 ^* calculated in the stop control process is shown in FIG. 4 and FIG. Switching to the fourth torque target value Tm4 ^* calculated with reference to the second or third accelerator opening-torque table. As a result, the stop control is stopped, and the control is switched to a control that does not converge the motor torque to the estimated disturbance torque immediately before the stop, so that the vehicle is based on the fourth torque target value Tm4 ^* calculated according to the driver's accelerator operation. Since the slip tends to converge, the vibration of the estimated disturbance torque generated in the conventional example can be suppressed, so that the vibration of the longitudinal acceleration can be eliminated.

  At times t3 to t5, the road surface state returns from the low μ road to the high μ road, and the slip state determination flag flg_slip is set to 0. Thereafter, the motor torque is converged to the estimated disturbance torque by the stop control based on the speed parameter at the start of the stop control that has increased the speed response set in step S711 in FIG. Decelerate.

  Then, at t5 to t6 after the lapse of T1, the vehicle is stopped by the stop control in which the normal control parameters are set.

  Next, when the vehicle is traveling on a flat road, in addition to the regenerative torque command of the motor 4, in addition to the friction brake braking by the driver, the control device for the electric vehicle according to the present embodiment is applied to the electric vehicle. The control result when applied will be described based on a comparison with a conventional example.

  FIG. 15A shows a time chart of the control result according to the conventional example, and FIG. 15B shows a time chart of the control result according to the present embodiment. FIG. 15 shows the torque command value, the vehicle speed V, the slip rate, the longitudinal acceleration, the estimated disturbance torque value, and the friction brake braking amount B in order from the top. A dotted line in the figure representing the torque command value indicates a slip state determination flag flg_slip (0: grip state, 1: slip state). A dotted line in the drawing showing the vehicle speed V indicates the vehicle speed Vc.

  On the time axis shown on the horizontal axis, the road surface condition changes as follows. That is, time t0 to t2 is a high μ road such as a normal asphalt road surface, time t2 to t4 is a low μ road such as an icing road surface, and time t4 to t6 is a high μ road.

  First, the control result according to the conventional example will be described with reference to FIG.

  At time t0, braking is being performed with a regenerative torque command, and the estimated disturbance torque value is estimated to be a value equivalent to a flat road.

  At time t1, the longitudinal acceleration is further increased to the negative side, that is, the braking side by adding the friction brake braking amount B to the regenerative braking and braking. The estimated disturbance torque value is equivalent to a flat road in accordance with the actual road surface condition by correcting the estimated brake torque value.

  From time t2 to t4, the road surface of the vehicle becomes a low μ road, and the vehicle slips and the vehicle speed steeply approaches zero. After that, the vehicle returns to the grip state from the slip state, and the vehicle speed increases sharply. As a result, the estimated disturbance torque value rises and falls and becomes oscillating. Therefore, the torque command value (motor torque) calculated based on the estimated disturbance torque is also oscillating. As a result, the longitudinal acceleration is shaken back and forth, which gives an unpleasant vibration to the driver.

  Next, a control result according to the present embodiment will be described with reference to FIG.

  At time t0, braking is being performed with a regenerative torque command, and the estimated disturbance torque value is estimated to be a value equivalent to a flat road.

  At time t1, in addition to regenerative braking, the longitudinal acceleration increases to the braking side due to the rise of the friction brake braking amount B. However, by correcting the brake torque estimated value based on the friction brake braking amount B, the disturbance torque estimated value Is equivalent to a flat road.

From time t2 to t4, the traveling road surface of the vehicle becomes a low μ road, and the vehicle speed tends to lock toward zero. Therefore, it is determined that the vehicle is in the slip state, the slip state determination flag flg_slip is set to 1, and the second or third accelerator opening is determined from the third torque target value Tm3 ^* calculated in the stop control process. Switching to the fourth torque target value Tm4 ^* calculated with reference to the degree-torque table. As a result, the vehicle is operated based on the accelerator operation of the driver, and the slip tends to converge. Therefore, the motor torque, the motor rotation speed, the vehicle speed V, the estimated disturbance torque, and the longitudinal acceleration of the conventional example Vibration can be suppressed.

  From time t4 to t5, the road surface state returns from the low μ road to the high μ road, and the slip state determination flag flg_slip is set to 0. Thereafter, the motor torque is converged to the estimated disturbance torque by the stop control based on the speed parameter at the start of the stop control that has increased the speed response set in step S711 in FIG. Decelerate.

  Then, at time t6 after the lapse of T1, the vehicle is stopped by stop control in which the normal control parameters are set.

  As described above, the control apparatus for an electric vehicle according to an embodiment is a method for controlling an electric vehicle including a motor that generates a drive torque or a regenerative torque in accordance with the driver's accelerator operation, and detects the rotational speed of the motor 4. The disturbance torque acting on the motor 4 is estimated. When the electric vehicle is about to stop, the motor torque is estimated as disturbance torque as the motor rotational speed decreases based on a vehicle model that models the transmission characteristics from the torque target value to the motor 4 to the motor rotational speed. Torque control at the time of stop is executed to control to converge to the value. Then, it is determined whether or not the vehicle model is established with respect to the actual vehicle response. If the vehicle model is not established immediately after stopping, the torque control at the time of stop is stopped, and the accelerator opening Torque control based on the driving force characteristic calculated according to the rotational speed of the motor is executed.

  As a result, when the vehicle model used in the stop control process is not established, the stop control is stopped and the control is switched to a control that does not converge the motor torque to the estimated disturbance torque immediately before the stop. Can be prevented from shaking. In other words, when the vehicle model is not established, the control based on the driving force characteristic calculated from the accelerator opening and the motor rotation speed makes it possible to control the braking force according to the driver's intention. Vibration of the motor rotation speed and disturbance torque estimated value is suppressed, and unpleasant vibration felt by the driver can be suppressed.

  Moreover, according to the control apparatus for an electric vehicle according to an embodiment, when it is estimated that the vehicle is slipping, it is determined that the vehicle model is not established. When the vehicle is in a slip state, the vehicle can be prevented from shaking back and forth due to the influence of stop control.

  In addition, the control device for an electric vehicle according to an embodiment estimates that the vehicle is in a slip state when the slip rate or the slip amount estimated based on the vehicle body speed and the drive wheel speed is equal to or greater than a predetermined value. . Thereby, the slip state between the drive wheels 9a and 9b and the road surface can be determined based on the vehicle speed Vc and the vehicle speed Vc.

  In addition, the control device for an electric vehicle according to an embodiment estimates that the vehicle is in a slip state when the rate of change in the rotation speed of the motor is equal to or greater than a predetermined value. Thus, the slip state can be determined based on the motor rotation speed without adding a new sensor.

  Further, the control device for an electric vehicle according to an embodiment estimates that the vehicle is in a slip state when the rate of change in the estimated value of the disturbance torque is equal to or greater than a predetermined value. As a result, the slip state can be determined from the rate of change of the estimated disturbance torque value without adding a new sensor.

  The electric vehicle control device according to the embodiment determines that the vehicle model is established when it is determined that the vehicle model is established after it is determined that the vehicle model is not established. Until a predetermined time elapses, the control parameter for the torque control at the time of stopping is increased, and the torque control based on the driving force characteristics is stopped to execute the torque control at the time of stopping. As a result, when the vehicle returns to the grip state, the estimated disturbance torque can be quickly matched with the gradient disturbance. Moreover, even if the road surface condition when the vehicle returns to the grip state and the stop control is resumed is an uphill road, the backward movement of the vehicle is suppressed and the vehicle can stop immediately.

  The present invention is not limited to the embodiment described above. For example, in the flow relating to the slip determination process described with reference to FIG. 7, all the processes in steps S701 to S704 are sequentially executed. However, it is not always necessary to execute all the processes, and any one process is performed. It may be determined whether or not the vehicle is in a slip state by executing.

2 ... Motor controller (disturbance torque estimation unit, determination unit)
4 ... motor 6 ... rotation sensor (motor rotation speed detector)
9a, 9b ... Drive wheels

Claims (7)

In a control method of an electric vehicle including a motor that generates a driving torque or a regenerative torque in accordance with an accelerator operation of a driver,
Detecting the rotational speed of the motor,
Estimating the disturbance torque acting on the motor,
When the electric vehicle is about to stop, based on a vehicle model that models a transmission characteristic from a torque target value to the motor to the rotational speed of the motor, the motor torque decreases with the disturbance torque as the rotational speed of the motor decreases. Execute torque control at stop to control to converge to the estimated value of
Determine whether the vehicle model is established for the actual vehicle response,
If the vehicle model is not established immediately after the stop, the torque control at the time of the stop is stopped, and torque control based on the driving force characteristic calculated according to the accelerator opening and the rotation speed of the motor is performed. Run,
An electric vehicle control method characterized by the above. A slip estimation unit that estimates whether or not the drive wheels of the electric vehicle are slipping,
When it is estimated that the slip estimation unit is slipping, it is determined that the vehicle model is not established,
The method for controlling an electric vehicle according to claim 1. Detecting the vehicle body speed of the electric vehicle,
Detecting the driving wheel speed of the electric vehicle;
The case where the slip estimation unit estimates that the vehicle is slipping is a case where the slip rate estimated based on the vehicle body speed and the driving wheel speed, or the slip amount is a predetermined value or more.
The method for controlling an electric vehicle according to claim 2. The case where the slip estimation unit estimates that the slip is occurring is a case where the rate of change of the rotation speed of the motor is a predetermined value or more.
The method for controlling an electric vehicle according to claim 2. The case where the slip estimation unit estimates that the slip is occurring is a case where the rate of change of the estimated value of the disturbance torque is a predetermined value or more.
The method for controlling an electric vehicle according to claim 2. After it is determined that the vehicle model is not established, if it is determined that the vehicle model is established,
From the time when it is determined that the vehicle model is established until the predetermined time elapses, the control parameter for the torque control at the time of stopping is increased, and the torque control based on the driving force characteristics is stopped. Execute torque control at the time of the stop,
The method for controlling an electric vehicle according to any one of claims 2 to 5, wherein: In a control device for an electric vehicle provided with a motor that generates a driving torque or a regenerative torque in accordance with the driver's accelerator operation,
A motor rotation speed detector for detecting the rotation speed of the motor;
A disturbance torque estimating unit for estimating a disturbance torque acting on the motor;
A determination unit that determines whether or not the vehicle model is established with respect to an actual vehicle response,
When the electric vehicle is about to stop, based on a vehicle model that models a transmission characteristic from a torque target value to the motor to the rotational speed of the motor, the motor torque decreases with the disturbance torque as the rotational speed of the motor decreases. Execute torque control at stop to control to converge to the estimated value of
If it is determined that the vehicle model is not established immediately after the stop, the torque control at the time of the stop is stopped, and the driving force characteristic calculated according to the accelerator opening and the rotation speed of the motor is used. Based on torque control,
A control apparatus for an electric vehicle.

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