Control Method for Electric Vehicle and Control Device for Electric Vehicle

Abstract

A control method for an electric vehicle, the electric vehicle using one or more electric motors as a driving source for traveling, wherein the control method includes: a motor torque command value calculation step of calculating a motor torque command value; an angular velocity detection step of detecting an angular velocity related to the rotational speed of a drive shaft that transmits the driving force of the motor to drive wheels; a disturbance torque estimation step of estimating a disturbance torque acting on the motor based on the motor torque command value and the angular velocity; a limit torque setting step of setting a limit torque corresponding to the disturbance torque so that the slip ratio of the drive wheels does not exceed a first specified value; and a motor torque limit step of limiting the motor torque command value using the limit torque.

Description

Technical Field

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

[0002] JP2018-058584A of Japan discloses the following structure: In an electric vehicle having an electric motor as a driving source for traveling, the output torque of the electric motor is limited according to the friction coefficient of the traveling road to prevent slippage of the driving wheels.

[0003] However, since the friction coefficient varies greatly depending on the road surface condition of the traveling road, it is difficult to calculate the correct friction coefficient, and thus it is difficult to achieve appropriate slip control. Summary of the Invention

[0004] Therefore, an object of the present invention is to provide a control method for an electric vehicle and a control device for an electric vehicle that can achieve appropriate slip control without calculating the friction coefficient of the traveling road.

[0005] According to one aspect of the present invention, there is provided a control method for an electric vehicle having one or more electric motors as driving sources for traveling. The control method includes: a motor torque command value calculation step of calculating a motor torque command value; an angular velocity detection step of detecting an angular velocity related to the rotational speed of a drive shaft that transmits the driving force of the electric motor to the driving wheels; a disturbance torque estimation step of estimating a disturbance torque acting on the electric motor based on the motor torque command value and the angular velocity; a limit torque setting step of setting a limit torque corresponding to the disturbance torque so that the slip ratio of the driving wheels does not exceed a first specified value; and a motor torque limitation step of limiting the motor torque command value using the limit torque. Brief Description of the Drawings

[0006] Figure 1 is a block diagram showing the basic structure of an electric vehicle control system for explaining the control method of the electric vehicle according to the present embodiment.

[0007] Figure 2 is a flowchart showing the main processing of the drive control of the electric vehicle.

[0008] Figure 3 is a diagram showing an example of an accelerator opening - torque table.

[0009] Figure 4 is a diagram for explaining the front - rear distribution process of the driving force.

[0010] Figure 5 is a diagram showing the mechanical system model of an electric vehicle equipped with an electric vehicle control system.

[0011] Figure 6 is a block diagram showing the disturbance torque estimation process.

[0012] Figure 7 It is a block diagram illustrating the front interference torque estimation process.

[0013] Figure 8 It is a block diagram illustrating the rear interference torque estimation process.

[0014] Figure 9 It is a block diagram illustrating the torque limit process.

[0015] Figure 10 It is a block diagram illustrating the front switching determination process.

[0016] Figure 11 It is a block diagram illustrating the front limit torque setting process.

[0017] Figure 12 It is a block diagram illustrating the rear limit torque setting process.

[0018] Figure 13 It is a map showing the set accelerator opening addition torque.

[0019] Figure 14 It is a map showing the set front motor speed addition torque.

[0020] Figure 15 It is a map showing the set rear motor speed addition torque.

[0021] Figure 16 It is a timing chart of the case where, in the drive control of an electric vehicle with the control method of this embodiment, the accelerator is gently depressed to start the vehicle from a stopped state.

[0022] Figure 17 It is a timing chart of the case where, in the drive control of an electric vehicle with the control method of this embodiment, the accelerator is quickly depressed to start the vehicle from a stopped state.

[0023] Figure 18 It is a timing chart of the case where, in the drive control of an electric vehicle with the control method of this embodiment, the electric vehicle enters a region with different driving resistances during driving.

[0024] Figure 19 It is a diagram illustrating the structure of the electric vehicle control system of the first modification example.

[0025] Figure 20 It is a diagram illustrating the structure of the electric vehicle control system of the second modification example.

[0026] Figure 21 It is a diagram illustrating the structure of the electric vehicle control system of the third modification example.

[0027] Figure 22 This is a diagram showing the structure of an electric vehicle control system according to a fourth modified example. Detailed implementation

[0028] Hereinafter, embodiments of the present invention will be described.

[0029] Figure 1 This is a block diagram showing the main structure of an electric vehicle system 100 that applies the control method (control device) of the electric vehicle according to this embodiment.

[0030] In addition, the electric vehicle in this embodiment refers to an automobile that has a drive motor 4 (electric motor) as a drive source of the vehicle and can travel by the driving force of the drive motor 4, including an electric vehicle and a hybrid vehicle. In particular, the electric vehicle system 100 according to this embodiment applicable to an electric vehicle has two drive motors 4 (front drive motor 4f and rear drive motor 4r). Hereinafter, the structure of the electric vehicle system 100 will be described in more detail.

[0031] As Figure 1 shown, the electric vehicle system 100 includes a front drive system fds, a rear drive system rds, a storage battery 1, and a motor controller 2.

[0032] In the front drive system fds, various sensors and actuators for controlling the front drive motor 4f that drives the front drive wheels 9f (left front drive wheel 9fL, right front drive wheel 9fR) are provided.

[0033] On the other hand, in the rear drive system rds, various sensors and actuators for controlling the rear drive motor 4r that drives the rear drive wheels 9r (left rear drive wheel 9rL, right rear drive wheel 9rR) are provided.

[0034] Moreover, the front drive system fds and the rear drive system rds are each independently controlled by the motor controller 2.

[0035] The storage battery 1 functions as a power source for supplying (discharging) drive power to the drive motors 4 (front drive motor 4f, rear drive motor 4r) respectively. On the other hand, it is connected to the inverters 3 (front inverter 3f, rear inverter 3r) so that it can be charged by receiving the supply of regenerative power from the drive motors 4 (front drive motor 4f, rear drive motor 4r) respectively.

[0036] The motor controller 2 is a computer composed of a central processing unit (CPU), a read-only memory (ROM), a random access memory (RAM), and an input / output interface (I / O interface), for example. The motor controller 2 constitutes the control device of the electric vehicle of the present invention and is a constituent element for executing the control method of the electric vehicle of the present invention.

[0037] Signals of various vehicle variables representing the vehicle state, such as the accelerator opening APO, vehicle speed V, vehicle longitudinal acceleration detected by the longitudinal acceleration sensor, rotor phase α of the drive motor 4 (front rotor phase α f , rear rotor phase α r ), and current Im of the drive motor 4 (front motor current Imf, rear motor current Imr), are input to the motor controller 2 (motor torque command value calculation unit (performing the motor torque command value calculation process)), disturbance torque setting unit (performing the disturbance torque setting process), limit torque setting unit (performing the limit torque setting process), and motor torque limiting unit (performing the motor torque limiting process) as digital signals. In addition, a signal from a mode switch (on, off) is input to the motor controller 2, and this mode switch determines whether to perform the torque limiting process described later based on the driver's operation.

[0038] The motor controller 2 generates a PWM signal for controlling each drive motor 4 based on the input signals. In addition, drive signals for each inverter 3 are generated according to the generated PWM signals.

[0039] Each inverter 3 is provided with 2 switching elements (such as power semiconductor elements such as IGBT or MOS-FET) corresponding thereto. In particular, each inverter 3 converts or inverse-converts the DC current supplied from the storage battery 1 into an AC current by turning on / off the switching elements according to an instruction from the motor controller 2, and adjusts the current supplied to each drive motor 4 to a desired value.

[0040] Each drive motor 4 is configured as a three-phase AC motor. Each drive motor 4 (front drive motor 4f, rear drive motor 4r) generates a driving force using the AC current supplied from the corresponding inverter 3 (front inverter 3f, rear inverter 3r), and transmits this driving force to each drive wheel 9 (front drive wheel 9f, rear drive wheel 9r) via the corresponding speed reducers 5 (front speed reducer 5f, rear speed reducer 5r) and drive shafts 8 (front drive shaft 8f, rear drive shaft 8r).

[0041] In addition, when the drive motor 4 is rotated by the drive wheels 9 during vehicle travel, the kinetic energy of the vehicle is recovered as electric energy by generating regenerative electric power. In this case, the inverter 3 converts the alternating current (regenerative electric power) generated during regenerative operation into direct current and supplies it to the storage battery 1.

[0042] Rotation sensors 6 (front rotation sensor 6f, rear rotation sensor 6r), which serve as the angular velocity detection unit (performing the angular velocity detection process), respectively detect the rotor phases α (front rotor phase α f , rear rotor phase α r ) of the drive motor 4 and output them to the motor controller 2. In addition, the rotation sensor 6 is constituted by, for example, a resolver or an encoder.

[0043] Current sensors 7 (front current sensor 7f, rear current sensor 7r) respectively detect the three-phase alternating currents (iu, iv, iw) flowing through each drive motor 4. In addition, since the sum of the three-phase alternating currents (iu, iv, iw) is 0, it is also possible to detect the currents of any two phases by the current sensor 7 and calculate the current of the remaining one phase through calculation. In particular, the current sensor 7 detects the three-phase alternating current (iu f , iv f , iw f ) flowing through the front drive motor 4f and the three-phase alternating current (iu r , iv r , iw r ) flowing through the rear drive motor 4r. Although not shown in the figure, the front and rear acceleration sensors detect, for example, the acceleration (component of the gravitational acceleration) in a specified direction (a direction perpendicular to the chassis of the electric vehicle).

[0044] Figure 2 is a flowchart for explaining the basic processing in the control device of the electric vehicle performed by the motor controller 2 of the present embodiment. In addition, the motor controller 2 is programmed to execute the processing of steps S201 to S206 shown in Figure 2 at every prescribed operation cycle.

[0045] In step S201, the motor controller 2 performs an input process of obtaining various parameters for executing the processing after step S202 according to the following processes 1 to 3.

[0046] 1. Detection values of each sensor

[0047] The motor controller 2 obtains the accelerator opening APO (%), rotor phase α [rad], three-phase alternating current (iu, iv, iw) [A] flowing through the drive motor 4, and the DC voltage value Vdc [V] of the storage battery 1 from the above-mentioned accelerator opening sensor and each sensor not shown. In addition, the motor controller 2 obtains a mode switch signal (ON, OFF).

[0048] 2. Previous value of the motor torque command value T m

[0049] The motor controller 2 obtains the motor torque command value T described later stored in the internal memory m (front motor torque command value T mf , rear motor torque command value T mr ).

[0050] 3. Control parameters obtained through calculation

[0051] Based on the respective parameters obtained according to the above "1.", the motor controller 2 calculates the motor electrical angular velocity ω e [rad / s], motor speed ω m [rad / s], motor speed N m [rpm], and wheel speed ω w [km / h].

[0052] (i) Motor electrical angular velocity ω e

[0053] The motor controller 2 performs time differentiation on the rotor phase α (front rotor phase α f and rear rotor phase α r ) to obtain the respective motor electrical angular velocities ω e (front motor electrical angular velocity ω ef , rear motor electrical angular velocity ω er ).

[0054] (ii) Motor speed ω m

[0055] The motor controller 2 divides the motor electrical angular velocity ω e by the number of pole pairs of the drive motor 4 to calculate the motor speed ω as the mechanical angular velocity of the drive motor 4 m (front motor speed ω mf , rear motor speed ω mr ). In addition, the relationship between the motor speed ω m and the speed of the drive shaft 8 as the drive shaft is appropriately determined according to the transmission ratio of the speed reducer 5. That is, the motor speed ω m ​is a speed parameter related to the rotational speed of the drive shaft 8.

[0056] (iii) Motor rotational speed N m

[0057] The motor controller 2 calculates the motor rotational speed N by multiplying the motor rotational speed ω m by the unit conversion coefficient (60 / 2π). m (Front motor rotational speed N mf , rear motor rotational speed N mr ).

[0058] (iv) Wheel speed ω w

[0059] First, the motor controller 2 multiplies the front motor rotational speed ω mf by the dynamic radius R of the tire, and calculates the left front drive wheel speed ω wfL and the right front drive wheel speed ω wfR based on the value obtained by this multiplication operation and the transmission ratio of the front reduction gear 5f. In addition, the motor controller 2 multiplies the rear motor rotational speed ω mr by the dynamic radius R of the tire, and calculates the left rear drive wheel speed ω wrL and the right rear drive wheel speed ω wrR based on the value obtained by this multiplication operation and the transmission ratio of the final gear of the rear reduction gear 5r. Then, in the present embodiment, the unit conversion coefficient (3600 / 1000) is applied to each wheel speed ω w thus obtained, and the unit of the wheel speed ω w is changed from "m / s" to "km / h".

[0060] The vehicle speed is obtained from sensors such as GPS, or for example, among the above rotational speeds (ω mf , ω mr ), the lower rotational speed is selected during acceleration, the higher rotational speed is selected during deceleration, and either one can be selected when traveling at a substantially constant speed, and the wheel speed is calculated as described above. Furthermore, regarding the vehicle speed, a vehicle speed estimated value using front and rear acceleration sensors or the like such as JP2002 - 127881A can also be used.

[0061] Next, in step S202, the motor controller 2 calculates the basic target torque required by the driver based on the vehicle information.

[0062] Specifically, first, the motor controller 2 refers to the accelerator opening - torque table and calculates the first torque target value T based on the accelerator opening APO obtained in step S201 and the front motor rotational speed ω mf (it can also be the rear motor rotational speed ω mr ).m1 .

[0063] In Figure 3 it shows an example of the accelerator opening - torque table referred to by the motor controller 2 of this embodiment.

[0064] Next, based on this first torque target value T m1 , according to the pre - determined front - rear motor torque distribution, the motor controller 2 calculates the front target torque command value T mf1 and the rear target torque command value T mr1 .

[0065] Figure 4 is a diagram for explaining the front - rear distribution process of the driving force and is a block diagram for explaining the calculation of the front target torque command value T mf1 and the rear target torque command value T mr1 .

[0066] As shown in the figure, the motor controller 2 multiplies the first torque target value T m1 by the front - rear driving force distribution gain Kf (0 ≤ Kf ≤ 1) and 1 - Kf respectively, so as to obtain the front target torque command value T mf1 and the rear target torque command value T mr1 .

[0067] In step S203, the motor controller 2 performs disturbance torque estimation processing. Specifically, the motor controller 2 inputs the front motor speed ω mf and the rear motor speed ω mr obtained in step S201, the front motor torque command value T mf (last value) and the rear motor torque command value T mr (last value) calculated in the previous cycle's step S204 (described later), and performs the disturbance torque estimation processing shown in Figure 6 to estimate the front disturbance torque estimated value T df and the rear disturbance torque estimated value T dr . In addition, in the disturbance torque estimation processing, in addition to the front motor speed ω mf and the rear motor speed ω mr , the rotational speeds related to the drive shaft such as the rotational speeds of the front drive wheel 9f and the rear drive wheel 9r can also be applied. The details of the disturbance torque estimation processing will be described later.

[0068] In step S204, the motor controller 2 performs torque limit processing. Specifically, as shown in Figure 9 - 12, the motor controller 2 uses the front limit torque T calculated based on the front disturbance torque estimated value T df ​rf Limit the front motor torque command value T mf Similarly, the rear disturbance torque estimated value T dr Calculated rear limit torque T rr To limit the rear motor torque command value T mr The details of the torque limit process will be described later.

[0069] In step S205, the motor controller 2 executes a current command value calculation process. Specifically, the motor controller 2 calculates the current command value based on the front motor torque command value T calculated in step S204. mf , rear motor torque command value T mr 、Front motor speedω mf 、Rear motor speedω mr , and the DC voltage value V obtained in step S201 dc , and refer to the predetermined table to calculate the dq axis current target value (i d *、i q *). In particular, the motor controller 2 calculates the dq axis current target value (i d *、i q *) of the front dq axis current target value (i df *、i qf *), and the dq axis current target value (i d *、i q *) of the rear dq axis current target value (i dr *、i qr *).

[0070] In step S206, the motor controller 2 performs current control calculation processing. Specifically, the motor controller 2 first calculates the dq axis current value (i d 、i q Then, the motor controller 2 controls the dq axis current value (i d 、i q ) and the dq axis current target value (i d *、i q *) deviation, calculate the dq axis voltage command value (v d 、v q In particular, the motor controller 2 calculates the dq axis voltage command value (v d 、v q ) of the front dq axis voltage command value (vdf , v qf ), and the dq-axis voltage command values (v d , v q ) set for the rear drive motor 4r, that is, the rear dq-axis voltage command values (v dr , v qr ).

[0071] Furthermore, the motor controller 2 calculates the three-phase AC voltage command values (vu, vv, vw) based on the dq-axis voltage command values (v d , v q ) and the rotor phase α. In particular, the motor controller 2 calculates the front three-phase AC voltage command values (vu f , vv f , vw f ) set for the front drive motor 4f as the three-phase AC voltage command values (vu, vv, vw), and the rear three-phase AC voltage command values (vu f , vv f , vw f ) set for the rear drive motor 4r as the three-phase AC voltage command values (vu, vv, vw).

[0072] Then, the motor controller 2 obtains the PWM signals (tu, tv, tw) (%) based on the calculated three-phase AC voltage command values (vu, vv, vw) and the DC voltage value Vdc. By turning on and off the switching elements of the inverter 3 according to the thus obtained PWM signals (tu, tv, tw), it is possible to drive the drive motor 4 (front drive motor 4f, rear drive motor 4r) with the desired torque indicated by the motor torque command value T m (front motor torque command value T mf , rear motor torque command value T mr ).

[0073] (Model of the driving force transmission system of the electric vehicle and its transmission characteristics)

[0074] Next, before explaining the disturbance torque estimation process (S601, S602) of the above step S203, the model of the driving force transmission system of the electric vehicle as its premise and each transmission characteristic based on this model will be explained in detail.

[0075] 1. Transfer characteristic G mf from the front motor torque command value T mf to the front motor speed ω pff (s)

[0076] First, in the electric vehicle system 100, for the transfer from the front motor torque command value T mfTo the rotational speed ω of the front motor mf The transfer characteristic G pff (s) will be described. This transfer characteristic G pff (s) is used as a vehicle model that models (simulates) the vehicle's driving force transmission system in the interference torque estimation process described later. First, refer to Figure 5 To describe the equation of motion from the front motor torque command value T mf To the rotational speed ω of the front motor mf .

[0077] Figure 5 Is a diagram that models the driving force transmission system of the vehicle (hereinafter also referred to as a 4WD vehicle) of the electric vehicle system 100. Figure 5 The parameters in are as follows. In addition, the auxiliary notation f represents the front and r represents the rear.

[0078] J mf 、J mr : Motor inertia

[0079] J wf 、J wr : Driving wheel inertia (per axle)

[0080] K df 、K dr : Torsional stiffness of the drive system

[0081] K tf 、K tr : Coefficient related to the friction between the tire and the road surface

[0082] N f 、N r : Total transmission ratio

[0083] r f 、r r : Tire load radius

[0084] ω mf 、ω mr : Motor rotational speed

[0085] ω^ mf 、ω^ mr : Estimated value of motor rotational speed

[0086] θ mf 、θ mr : Motor angle

[0087] ω wf 、ω wr : Driving wheel angular velocity

[0088] θ wf 、θ wr: Driving wheel angle

[0089] T mf , T mr : Motor torque

[0090] T df , T dr : Drive shaft torque

[0091] F f , F r : Driving force (two-axis quantity)

[0092] θ df , θ dr : Drive shaft torsional angle

[0093] V: Vehicle speed

[0094] M: Vehicle body weight

[0095] According to Figure 5 , the equations of motion of a 4WD vehicle are represented by the following equations (1) to (11).

[0096] [Equation 1]

[0097]

[0098] [Equation 2]

[0099]

[0100] [Equation 3]

[0101]

[0102] [Equation 4]

[0103]

[0104] [Equation 5]

[0105]

[0106] [Equation 6]

[0107] T df = K df ·θ df …(6)

[0108] [Equation 7]

[0109] T dr = K dr ·θ dr …(7)

[0110] [Equation 8]

[0111] Ff = K tf ·(r f ω mf - V)…(8)

[0112] [Equation 9]

[0113] F r = K tr ·(r r ω mr - V)…(9)

[0114] [Equation 10]

[0115] θ df = θ mf / N f - θwf…(10)

[0116] [Equation 11]

[0117] θ dr = θ mr / N r - θ wr

[0118] From the front motor torque command value T mf to the front motor speed ω mf The transfer characteristic becomes the following Equation (12) after performing Laplace transform on the above Equations (1) to (11).

[0119] [Equation 12]

[0120] ω mf = G pff (s)·T mf

[0121]

[0122] Among them, each parameter in Equation (12) is represented by the following Equations (13) to (17).

[0123] [Equation 13]

[0124] b6 = χ 21 δ 21 …(13)

[0125] b5 = χ 11 δ 11 + χ 21 δ 22 + χ 22 δ 21

[0126] b4 = χ 11 δ 12 + χ 21δ 23 -χ 22 δ 22 +χ 23 δ 21

[0127] b3 = χ 11 δ 13 +χ 12 δ 11 +χ 22 δ 23 +χ 23 δ 22 +χ 24 δ 21

[0128] b2 = χ 12 δ 13 +χ 12 δ 12 +χ 23 δ 23 +χ 24 δ 22

[0129] b1 = χ 12 δ 12 +χ 24 δ 23

[0130] b0 = χ 12 δ 14

[0131] [Equation 14]

[0132] a6 = χ 21 δ 41 …(14)

[0133] a5 = χ 11 δ 31 +χ 22 δ 41 +χ 21 δ 44

[0134] a4 = χ 11 δ 32 +χ 23 δ 41 +χ 22 δ 42 +χ 21 δ 43

[0135] a3 = χ 12 δ 31 +χ 11 δ 33 +χ 24 δ 41 +χ23 d 42 +x 22 d 43 +x 21 d 44

[0136] a2=x 12 d 32 +x 11 d 34 +x 24 d 42 +x 23 d 43 +x 22 d 44

[0137] a1=x 12 d 33 +x 24 d 43 +x 23 d 44

[0138] a0=x 12 d 34 +x 24 d 44

[0139] [formula 15]

[0140] x 11 =2J wr K tr 2 r r N r 2 J mr …(15)

[0141] x 12 =(2J wr +N r 2 J mr )K dr r r K tr 2

[0142] x 21 =2J wr K tr r r N r 2 J mr

[0143] x 22 =K tr 2 r r3 N r 2 J mr

[0144] χ 23 (2J wr +N r 2 J mr )K dr K tr r r

[0145] χ 24 =K dr K tr 2 r r 3

[0146] [Equation 16]

[0147] δ 1I =2J wf M…(16)

[0148] δ 12 =2J wf K tf +K tf r f 2 M

[0149] δ 13 =K df M

[0150] δ 14 =K df K tf

[0151] δ 21 =2J<79]] wf

[0152] δ 22 =K tf r f 2

[0153] δ 23 =K df

[0154] [Equation 17]

[0155] δ 31 =N f 2 2J mf J wf M…(17)

[0156] δ 32= N f 2 2J wf K tf J mf + N f 2 r f 2 MK tf J mf

[0157] δ 33 = N f 2 J mf K df M

[0158] δ 34 = 2J wf K df K tf + N f 2 J mf K df K tf + r f 2 MK df K tf

[0159] δ 41 = N f 2 2J mf J wf

[0160] δ 42 = N f 2 r f 2 K tf J mf

[0161] δ 43 = 2J wf K df + N f 2 J mf K df

[0162] δ 44 = r f 2 K df K tf

[0163] To investigate the poles and zeros of the transfer function shown in Equation (12), factor Equation (12) with respect to s, and it becomes the following Equation (18).

[0164] [Equation 18]

[0165]

[0166] Among them, in the formula, "M pff ", "α", "α'", "β", "β'", "ζ pr ", "ζ pr '", "ω pr ", "ω pr '", "ζ zr ", "ζ pf ", "ω zf " and "ω pf " are constants independent of s.

[0167] Here, "α" and "α'", "β" and "β'", "ζ pr " and "ζ pr '", and "ω pr " and "ω pr '" in Equation (18) take values that are very close to each other. Therefore, by approximating α≒α', β≒β', ζ pr ≒ζ pr ', ω pr ≒ω pr ', a part of the zero point (the s value at which the numerator becomes 0) and a part of the pole point (the s value at which the denominator becomes 0) are approximately the same. Under this approximation, pole-zero cancellation (pole-zero cancellation) is performed to cancel the zero point term of the numerator and the pole point term of the denominator in Equation (18). Thus, the transfer characteristic G pff (s) shown in the following Equation (19) can be formed.

[0168] [Equation 19]

[0169]

[0170] Among them, "M pff '" in Equation (19) is a constant obtained by appropriately correcting "M pff " while considering the offset of the assumed zero point and pole point during pole-zero cancellation based on the above constants.

[0171] As a result, if the transfer characteristic from the front motor torque command value T mf to the front motor speed ω mf is investigated based on the motion equation of a 4WD vehicle, G pff (s) can be approximated as a quadratic / cubic expression.

[0172] Here, the standard response for suppressing the torsional vibration caused by the front drive shaft 8f is set as follows in Equation (20).

[0173] [Equation 20]

[0174]

[0175] In this case, the feedforward compensator that suppresses the torsional vibration of the front drive system fds can be expressed by the following equation (21).

[0176] [Equation 21]

[0177]

[0178] 2. From the rear motor torque command value T mr to the rear motor speed ω mr of the transfer characteristic G prr (s)

[0179] Next, by the same method as the above method for obtaining the transfer characteristic G mf from the front motor torque command value T mf to the front motor speed ω pff (s), obtain the transfer characteristic G mr from the rear motor torque command value T mr to the rear motor speed ω prr (s). This transfer characteristic G prr (s) is expressed by the following equation (22).

[0180] [Equation 22][[ID=4३]]

[0181] ω mr = G prr (s)·T mr

[0182]

[0183] Here, set the standard response that suppresses the torsional vibration caused by the rear drive shaft 8r as follows in equation (23).

[0184] [Equation 23]

[0185]

[0186] In this case, the feedforward compensator that suppresses the torsional vibration of the rear drive system rds can be expressed by the following equation (24).

[0187] [Equation 24]

[0188]

[0189] 3. From the rear motor torque command value T mr to the front motor speed ω mfTransfer characteristic G prf (s)

[0190] From the rear motor torque command value T mr To the front motor speed ω mf Transfer characteristic G prf (s) becomes the following equation (25) after performing Laplace transform on the above equations (1) to (11).

[0191] [Equation 25]

[0192] ω mf =C prf (s)·T mr …(25)

[0193]

[0194] If the poles of the transfer function shown in Equation (25) are investigated, it becomes the following equation (26).

[0195] [Equation 26]

[0196]

[0197] However, the poles of Equation (26) ("s = -α" and "s = -β") are located far from the origin and the dominant poles, so the influence on the transfer characteristic represented by G prf (s) is small. Therefore, Equation (26) can be approximated by the transfer function represented by the following equation (27).

[0198] [Equation 27]

[0199]

[0200] Furthermore, if the rear damping control algorithm (ζ prf ≒1) is considered in the vehicle model (transfer characteristic G pr ), it becomes the transfer function shown in the following equation (28).

[0201] [Equation 28]

[0202]

[0203] In addition, according to the standard response of the estimated value ω^ mf of the front motor speed in the front drive system fds, the transfer function for suppressing torsional vibration of the front drive system fds is the following equation (29).

[0204] [Equation 29]

[0205]

[0206] (Disturbance torque estimation process)

[0207] Hereinafter, a detailed description will be given of the disturbance torque estimation process shown in step 203 of Figure 2 . Figure 6 is a block diagram illustrating the disturbance torque estimation process. Figure 7 is a block diagram illustrating the front disturbance torque estimation process. Figure 8 is a block diagram illustrating the rear disturbance torque estimation process.

[0208] As Figure 6 shown, in step S601, the motor controller 2 estimates the front disturbance torque estimated value T mf based on the front motor speed ω mf (previous value), the front motor torque command value T mr (previous value), and the rear motor torque command value T df .

[0209] Specifically, as Figure 7 shown, in step S701A, the motor controller 2 adds the front motor torque command value T mf (previous value) and the rear motor torque command value T mr (previous value) to calculate the total torque command value of the entire electric vehicle.

[0210] In addition, when there are differences between the front and rear side parameters to such an extent that they affect the calculation of appropriate disturbance torque estimated values (front disturbance torque estimated value T df , rear disturbance torque estimated value T dr ), for example, due to differences in the gear ratios of the front and rear reducers 5f and 5r, or differences in the dynamic tire radii of the front and rear drive wheels 9f and 9r, appropriately, a gain considering these differences can also be set. For example, the total torque command value can also be obtained by multiplying the rear motor torque command value T mr (previous value) by a gain converted to the front motor torque conversion value.

[0211] Next, in step S702A, the motor controller 2 performs a filtering process on the front motor speed ω mf based on the transfer functions (H1(s) and G r (s)) to calculate the first motor torque estimated value.

[0212] Here, the vehicle response G r (s) that forms the numerator of the above transfer function is a function set as G rrf (s) in Equation (21), and is calculated using the vehicle body mass M and the front motor inertia J mf, the inertia J of the rear motor mr , the inertia J of the front drive wheel wf and the inertia J of the rear drive wheel wr The equivalent mass M obtained V is set according to the following formula (30).

[0213] [Formula 30]

[0214]

[0215] On the other hand, the low-pass filter H1(s) that constitutes the denominator of the above transfer function is a low-pass filter having a transfer characteristic such that the difference between the denominator order and the numerator order is greater than or equal to the difference between the denominator order and the numerator order of the vehicle response G r (s). More specifically, the low-pass filter H1(s) is represented by the following formula (31).

[0216] [Formula 31]

[0217]

[0218] Next, in step S703A, the motor controller 2 uses the low-pass filter H1(s) of formula (31) to filter the total torque command value calculated in the above step S701, and calculates the second motor torque estimated value.

[0219] Then, in step S704A, the motor controller 2 calculates the deviation between the first motor torque estimated value obtained in step S702A and the second motor torque estimated value obtained in step S703A, and obtains the front interference torque estimated value T df .

[0220] Here, as the interference acting on the electric vehicle, the driving resistance on sandy ground, air resistance, modeling errors caused by changes in vehicle mass (number of passengers, load), rolling resistance of tires, inclination resistance, etc. can be considered. The interference factors vary depending on the driving conditions, but in the interference torque estimation process (step S601, step S602), based on the front motor torque command value T mf (previous value), the rear motor torque command value T mr (previous value), the front motor speed ω mf , the equivalent mass MV, and the vehicle model (H1(s), G r (s)), the front interference torque estimated value T df (and the rear interference torque estimated value T described later dr ) is calculated, so that the interference factors can be uniformly estimated. As a result, the driving resistance on sandy ground and the like can be accurately estimated.

[0221] In addition, as Figure 6 shown, in step S602, the motor controller 2 estimates the rear disturbance torque estimation value T mr based on the rear motor speed ω mf (previous value), the front motor torque command value T mr (previous value), and the rear motor torque command value T dr .

[0222] As Figure 7 shown, the motor controller 2 estimates the rear disturbance torque estimation value T dr by performing the processes of step S701B, step S702B, step S703B, and step S704B.

[0223] Here, step S701B is the same as step S701A of Figure 7 . Step S702B is the same as step S702A of Figure 7 , but the object of filtering is the rear motor speed ω mr , and G r (s) is a function set as G rrr (s) in Equation (24). In Equation (30), K M = N r 2 / r r 2 . Step S703B is the same as step S703A of Figure 7 . Step S704B is the same as step S704A, but the first torque motor value is the value obtained by filtering the rear motor speed ω mr .

[0224] As described above, by using the front motor speed ω mf , the rear motor speed ω mr , the front motor torque command value T mf (previous value), and the rear motor torque command value T mr (previous value), it is possible to independently estimate the disturbance torque received from the road surface in the front drive motor 4f( Figure 1 ) and the rear drive motor 4r( Figure 1 ).

[0225] (Torque Limiting Process)

[0226] Hereinafter, the torque limiting process shown in step S204( Figure 2 ) will be described in detail. Figure 9 is a block diagram illustrating the torque limiting process.

[0227] As Figure 9As shown, in the torque limit process, based on the vehicle front and rear acceleration sensor values, vehicle speed V, estimated value of the front interference torque T df , estimated value of the rear interference torque T dr , front target torque command value T mf1 , rear target torque command value T mr1 , front motor speed ω mf , rear motor speed ω mr , and accelerator opening APO, the motor controller 2 performs the processing from step S801 to step S809 to calculate the front motor torque command value T mf and the rear motor torque command value T mr .

[0228] In the road surface gradient calculation process of step S801, the motor controller 2 calculates the road surface gradient θ based on the vehicle front and rear acceleration sensor values and vehicle speed V and outputs it. The road surface gradient θ is calculated by the difference between the acceleration obtained by differentiating the vehicle speed V and the vehicle front and rear acceleration sensor values.

[0229] In the front switching determination process of step S802, the motor controller 2 outputs a switching signal based on the estimated value of the front interference torque T df , the gradient θ calculated in step S801, etc. In addition, the details of the front switching determination process of step S802 will be described later (refer to Figure 10 ).

[0230] In the rear switching determination process of step S803, the motor controller 2 sets a switching flag based on the estimated value of the rear interference torque T dr , the gradient θ calculated in step S801, etc. In addition, the switching determination processes of steps S202 and S203 are executed in such a way that they are the same judgment.

[0231] In the front limit torque setting process of step S804, the motor controller 2 calculates the front limit torque T df based on the estimated value of the front interference torque T, the front motor speed ω mf , and the accelerator opening APO. The details of the front limit torque setting process of step S804 will be described later (refer to rf Figure 11 ).

[0232] In the rear limit torque setting process of step S805, the motor controller 2 calculates the rear limit torque T dr based on the estimated value of the rear interference torque T, the rear motor speed ω mr , and the accelerator opening APO. rr ​The details of the rear limit torque setting process of step S805 will be described later (see Figure 12 ).

[0233] In the front torque limiting process of step S806, the motor controller 2 sets the front target torque command value T mf1 and the front limit torque T calculated in step S804 rf Compare and select the smaller value to output.

[0234] In the rear torque limiting process of step S807, the motor controller 2 sets the rear target torque instruction value T mr1 and the rear limit torque T calculated in step S805 rr Compare and select the smaller value to output.

[0235] In the front torque switching process of step S808, when the switching flag outputted in step S802 is OFF (0), the motor controller 2 selects the front target torque command value T mf1 , and use it as the front motor torque command value T mf In addition, when the switching flag output in step S802 is on (1), the motor controller 2 selects the output of the front torque limiting process in step S806 and uses it as the front motor torque command value T mf That is, when the switching signal is an on signal, the output of the front torque limit process, that is, the front target torque command value T mf1 and front limiting torque T rf The smaller value is the front motor torque command value T mf Output.

[0236] In the rear torque switching process of step S809, when the switching flag outputted in step S803 is OFF (0), the motor controller 2 selects the rear target torque command value T mr1 , and use it as the rear motor torque command value T mr In addition, when the switching flag output in step S803 is on (1), the motor controller 2 selects the output of the rear torque limiting process in step S807 and uses it as the rear motor torque command value T mr That is, when the switching flag is on (1), the output of the rear torque limit process, that is, the rear target torque command value T mr1 And rear limit torque T rr The smaller value is taken as the rear motor torque command value T mr Output.

[0237] By performing the above torque limit processing, in a 4WD vehicle, as described later, it is possible to perform torque control that suppresses excessive rotation such as getting stuck (being trapped) in sandy areas and poor acceleration.

[0238] (Front switching determination process)

[0239] Hereinafter, the front switching determination process in step S802 ( Figure 9 ) will be described in detail. Figure 10 It is a block diagram illustrating the front switching determination process.

[0240] In the front switching determination process, based on the front interference torque estimated value T df , slope θ, and mode switch, the switching flag is set by performing the processes of steps S901 to S903.

[0241] In step S901, the motor controller 2 calculates the slope interference torque (Mgsinθ) balanced by the road surface slope based on the slope θ and the vehicle body mass M.

[0242] In step S902, the motor controller 2 subtracts the slope interference torque calculated in step S901 from the front interference torque estimated value T df to remove the slope interference torque included in the front interference torque estimated value T df and calculates the driving resistance Δd of sand or the like.

[0243] In step S903, when the driving resistance Δd is greater than a second specified value (which can be set arbitrarily), the motor controller 2 determines that the sand resistance or the like is greater than the normal road surface resistance and sets the switching flag to ON (1). In addition, when the driving resistance Δd is equal to or less than the second specified value, the motor controller 2 sets the switching flag to OFF (0). In addition, the motor controller 2 may set the switching flag to ON (1) when the mode switch is turned on by the driver's switch operation regardless of the driving resistance Δd, and set the switching flag to OFF (0) when the mode switch is turned off.

[0244] In addition, although not shown in the figure, in the rear switching determination process of step S803, based on the rear interference torque estimated value T dr , slope θ, and mode switch, the switching flag is set by performing the same processes as steps S901 to S903.

[0245] (Front limit torque setting process)

[0246] Hereinafter, the front limit torque setting process in step S804 ( Figure 9 ) will be described in detail. Figure 11 It is a block diagram illustrating the front limit torque setting process. Figure 13It is a map showing the set accelerator opening addition torque. Figure 15 It is a map showing the set rear motor speed addition torque.

[0247] As Figure 11 shown, in the front limit torque setting process, based on the front disturbance torque estimated value T df , the front motor speed ω mf , and the accelerator opening APO, by performing the processes of step S1001, step S1002A, and step S1003A, the front limit torque T rf is calculated.

[0248] In step S1001, the motor controller 2 uses the map shown in Figure 13 to set the APO addition torque corresponding to the accelerator opening APO. Figure 13 The map shown is such that as the accelerator opening APO increases, the APO addition torque increases linearly, but it can also be a curve where the APO addition torque increases monotonically as the accelerator opening APO increases. Additionally, the APO addition torque can be set to a constant value regardless of the size of the accelerator opening APO.

[0249] In step S1002A, the motor controller 2 uses the map shown in Figure 14 to set the front motor speed addition torque corresponding to the front motor speed ω mf . Similarly to the above, Figure 14 the map shown becomes such that as the front motor speed ω mf increases, the front motor speed addition torque increases linearly, but it can also be a monotonically increasing curve as described above, and can also be set to a constant value.

[0250] In step S1003A, the motor controller 2 adds the addition torque (APO addition torque and front motor speed addition torque) to the front disturbance torque estimated value T df to calculate and output the front limit torque T rf . Here, the front limit torque T rf becomes a value that is only higher than the front disturbance torque estimated value T df by the amount of the addition torque, but can be set such that the slip ratio of the front drive wheel 9f is, for example, in the range of 10% to 20%, and can be set to not exceed a first specified value (for example, 20%) (in the characteristic curve showing the relationship between the slip ratio of the drive wheel 9 and the longitudinal friction force, the slip ratio does not exceed the slip ratio near the peak of the longitudinal friction force). Thus, as long as the front motor torque command value T mf is set to the front limit torque T rf, the front drive wheels 9f can then apply longitudinal acceleration to the electric vehicle regardless of the road surface conditions.

[0251] (Rear Limiting Torque Setting Process)

[0252] Hereinafter, the rear limiting torque setting process in step S805 ( Figure 9 ) will be described in detail. Figure 12 is a block diagram illustrating the rear limiting torque setting process. Figure 15 is a map showing the addition torque of the rear motor speed setting.

[0253] As Figure 12 shown, in the rear limiting torque setting process, based on the rear disturbance torque estimated value T dr , the rear motor speed ω mr , and the accelerator opening APO, in addition to the above step S1001, the processes of step S1002B and step S1003B are also performed, thereby calculating the rear limiting torque T rr . Here, step S1002B is the same as step S1002A in Figure 11 , but uses the rear motor speed ω mr as the input value. Similar to the setting of the addition torque of the front motor speed above, based on the map shown in Figure 15 (preferably the same as the map shown in Figure 14 ), the addition torque of the rear motor speed is set. Step S1003B is the same as step S1003A in Figure 11 , but adds the addition torque (APO addition torque and addition torque of the rear motor speed) to the rear disturbance torque estimated value T dr to calculate the rear limiting torque T rr and output it. Similar to the above, as long as the rear motor torque command value T mr is set to the rear limiting torque T rr , the rear drive wheels 9r can then apply longitudinal acceleration to the electric vehicle regardless of the road surface conditions.

[0254] (Timing Chart of the Present Embodiment)

[0255] The operation when driving the electric vehicle by the control method (control device) of the present embodiment will be described.

[0256] [Case of Slowly Depressing the Accelerator]

[0257] Figure 16 is the drive control of the electric vehicle based on the control method of the present embodiment, and is a timing chart of the case where the electric vehicle starts by slowly depressing the accelerator from a stopped state. In Figure 16In FIG. 4 , it is assumed that the accelerator is depressed from time t1 and is depressed to a desired depression amount during the period from time t1 to time t4 .

[0258] exist Figure 16 (described later Figure 17 、 Figure 18 Similarly), (A) is a timing chart when the conventional technology is applied, (B) is a timing chart when the added torque is fixed to the first predetermined value in the present embodiment, and (C) is a timing chart when the added torque is correlated with the accelerator opening APO and the front motor speed ω in the present embodiment. mf Although the timing chart for the rear motor side is omitted, its operation is the same as that for the front motor side.

[0259] At time t1, the driver steps on the accelerator and the front motor torque command value T mf (Torque driving the front drive wheels 9f) increases, but as a result, the front disturbance torque estimated value T df (The torque for braking the front drive wheel 9f) also increases, and T is satisfied until time t2. mf =T df Therefore, T mf -T df Maintained roughly at zero, vehicle speed and front motor speed ω mf , the front and rear acceleration of the vehicle also remains at zero, and the electric vehicle remains in a stopped state.

[0260] At time t2 to t3, the front motor torque command value T mf becomes the front disturbance torque estimated value T df Therefore, T mf -T df Start to rise, vehicle speed, front motor speed ω mf , the vehicle's front and rear acceleration also begins to increase, and the electric vehicle starts to move.

[0261] In the case of (A), at time t3 to t4, the front motor torque command value T mf As the accelerator opening APO continues to rise, the front motor torque command value T mf and the front disturbance torque estimated value T df The difference between the two becomes larger, and the slip ratio of the drive wheel 9 increases. When the slip ratio exceeds a first predetermined value (e.g., 20%), the friction force in the vehicle front-rear direction with respect to the drive wheel 9 decreases, so the front disturbance torque estimated value T df Therefore, since the slip ratio increases sharply, the front motor speed ω mfSharp rise (over-rotation state). On the other hand, the vehicle longitudinal acceleration decreases sharply, resulting in poor acceleration and the vehicle speed not rising.

[0262] Here, in (A), when the driving road surface has a significantly low driving resistance, such as an icy road surface, if the vehicle longitudinal angular velocity becomes zero, the front drive wheel 9f continues to rotate and the vehicle longitudinal acceleration is approximately zero, and the vehicle speed is also approximately constant. In addition, when the driving road surface is sandy, if the vehicle longitudinal acceleration becomes zero, the vehicle speed rapidly decelerates to zero, the vehicle longitudinal acceleration also temporarily becomes negative and then converges to zero, and the front drive wheel 9f gets stuck in the sand while rotating, and the electric vehicle becomes unable to move forward (a state where only sand is dug out backward).

[0263] In the case of (B), at time t3 - t4, the front motor torque command value T mf is limited to T mf -T df not exceeding the added torque. At this time, since the slip ratio is maintained not to exceed the first specified value (e.g., 20%), the estimated value of the front disturbance torque T df hardly decreases, and the front motor torque command value T mf maintains the specified value. Therefore, the front motor speed ω mf continues to rise, but the vehicle longitudinal acceleration maintains an approximately constant value, and the vehicle speed also continues to rise. Based on the above, in the case of (B), the front drive wheel 9f does not get stuck, and the vehicle speed can rise with a specified acceleration.

[0264] Similarly, in the case of (C), at time t3 - t4, the front motor torque command value T mf is limited to make T mf -T df not exceed the added torque. Here, the added torque is set to increase as the accelerator opening APO and / or the front motor speed ω mf increases. Therefore, for example, as the front motor speed ω mf rises, T mf -T df gradually rises, and accordingly, the front motor torque command value T mf also gradually rises. Therefore, the rising speed of the front motor speed ω mf is higher than that in the case of (B).

[0265] On the other hand, since the slip ratio is maintained not to exceed the first specified value (e.g., 20%), it is possible to keep the estimated value of the front disturbance torque T df hardly decreasing, and make the front motor torque command value T mfGradually increase. Therefore, it is possible to control in such a way that the longitudinal acceleration of the vehicle gradually increases, and the vehicle speed can also increase faster than in the case of (B).

[0266] According to the above, in the case of (C), the front drive wheel 9f does not get stuck, and the vehicle speed can increase with the desired acceleration based on the accelerator opening APO and / or the front motor speed ω mf and can increase the vehicle speed faster than in the case of (B).

[0267] In any of the cases of (B) and (C), by adding an addition torque to the disturbance torque estimated values (front disturbance torque estimated value T df , rear disturbance torque estimated value T dr ), the torque command values (front target torque command value T mf1 , rear target torque command value T mr1 ) generated by the driver's acceleration operation are restricted, whereby the motor torque command values (front motor torque command value T mf , rear motor torque command value T mr ) corresponding to the road surface disturbance can be restricted to obtain a desired acceleration that does not cause the front drive wheel 9f and the rear drive wheel 9r ( Figure 1 ) to sink into sand or the like.

[0268] [Case of quickly stepping on the accelerator]

[0269] Figure 17 is the drive control of an electric vehicle based on the control method of the present embodiment, and is a timing chart of the case where the electric vehicle starts by quickly stepping on the accelerator from a stopped state. In Figure 17 , it is assumed that the accelerator is stepped on starting from time t1 and is stepped on to the desired stepping amount during the period from time t1 to time t2. In addition, the description of the case of (C) above is omitted here.

[0270] In the case of (A), if the accelerator is stepped on sharply at t1, the front motor torque command value T mf rises sharply, but the front disturbance torque estimated value T df cannot follow this situation, and T mf −T df rises sharply at the initial stage. After that, even if the front disturbance torque estimated value T df rises, T mf −T df continues to rise although the rising rate decreases. Therefore, in the latter half of t1 to t2, the longitudinal acceleration of the vehicle rises sharply, and the vehicle speed and the front motor speed ω mf also rise. However, when T mf −T dfWhen it exceeds the specified value, the slip ratio rises sharply, and thus the longitudinal accelerations of the vehicle decrease sharply and become zero at time t2.

[0271] At this time, the vehicle speed remains constant at a low speed. Similarly to the above, when the road surface is sandy, the vehicle speed immediately becomes zero and the front drive wheel 9f gets stuck. Therefore, in Figure 17 Although the illustration is omitted, after time t2, the longitudinal accelerations of the vehicle become negative temporarily and then converge to zero, and the vehicle speed is maintained at zero.

[0272] At time t2, the front motor torque command value T mf converges to a specified value based on the depression amount of the accelerator and maintains this value even after t2. On the other hand, the front motor speed ω mf continues to rise even after t2, and the estimated value of the front disturbance torque T df decreases. Therefore, T mf −T df rises as the estimated value of the front disturbance torque T df decreases.

[0273] In the case of (B), it is the same as the case of (A). If the accelerator is depressed sharply at t1, then T mf −T df rises sharply. However, in (B), the front motor torque command value T mf is limited so that T mf −T df does not exceed the added torque and remains at a constant value after a moment slightly past time t1 as shown in Figure 17 . Therefore, the rising speed of the front motor speed ω mf is lower than that in (A), and the front motor torque command value T mf also rises more slowly than in the case of (A) as the estimated value of the front disturbance torque T df rises.

[0274] In addition, the added torque is set so that the slip ratio does not exceed a first specified value (for example, 20%). Therefore, it is possible to suppress the decrease of the estimated value of the front disturbance torque T df , and the longitudinal accelerations of the vehicle can also be maintained at a constant value. Therefore, the vehicle speed can also rise corresponding to the longitudinal accelerations of the vehicle.

[0275] In this way, even during a quick depression operation of the driver's accelerator, it is possible to limit the motor torque command values corresponding to road surface disturbances (the front motor torque command value T mf , the rear motor torque command value T mr ), and it is possible to obtain a desired acceleration that does not cause the front drive wheel 9f and the rear drive wheel 9r ( Figure 1 ) to get stuck.

[0276] [When entering a road surface with different driving resistances during driving]

[0277] Figure 18 This is the drive control of an electric vehicle based on the control method of this embodiment, and it is a timing chart of the situation where the electric vehicle enters a region with different driving resistances during driving. Here, the situation where the electric vehicle enters a region with a small driving resistance (e.g., a paved road) from a region with a large driving resistance (e.g., sandy ground) during driving will be described. In addition, the descriptions of the above cases (A) and (C) are omitted, and the description is made on the premise of case (B).

[0278] At time t1, by the driver stepping on the accelerator, the front motor torque command value T mf rises. However, as described above, the front motor torque command value T mf is limited so that T mf −T df does not exceed the added torque. Therefore, from time t1 to time t2, the front motor speed ω mf rises while maintaining a specified vehicle longitudinal acceleration, and the vehicle speed also increases corresponding to this longitudinal acceleration.

[0279] At time t2, the electric vehicle enters a region with a small driving resistance (e.g., a paved road) from a region with a large driving resistance (e.g., sandy ground), and at this time, the vehicle longitudinal acceleration increases stepwise. However, after time t2, due to the reduction of the driving resistance, the estimated value of the front disturbance torque T df decreases and converges to a specified value. In addition, as described above, since the front motor torque command value T mf is limited so that T mf −T df does not exceed the added torque, the front motor torque command value T mf also decreases and converges to a specified value after time t2. Therefore, the front motor speed ω mf continues to rise. On the other hand, the vehicle longitudinal acceleration decreases and converges to a specified value, and the sharp rise in the vehicle speed is also suppressed. As described above, by controlling the front motor torque command value T mf , even when entering a region with different driving resistances, smooth driving with less impact can be achieved.

[0280] In this way, even in a situation where the driving resistance decreases, the motor torque command value corresponding to the road surface disturbance (the front motor torque command value T mf , the rear motor torque command value T mr ) can be limited, the excessive rotation of the front drive wheels 9f and rear drive wheels 9r ( Figure 1 ) can be suppressed, and the desired acceleration can be obtained.

[0281] As described above, by applying the control method (control device) of the present invention to an electric vehicle, in an electric vehicle having a drive motor 4, the estimated value of disturbance torque that can be calculated in the electric vehicle is used as the estimated value of driving resistance, and the motor torque is limited by using this estimated value of driving resistance. Thus, acceleration control of a 4WD vehicle can be achieved without using the vehicle body speed.

[0282] (First Modification Example)

[0283] Figure 19 FIG. is a diagram showing the configuration of an electric vehicle control system 200 according to the first modification example. In the following description, the same reference numerals are given to the same components as those in the above-described embodiment, and the description thereof is omitted except as necessary.

[0284] As Figure 19 shown, in the electric vehicle control system 200 of the first modification example, different from the above-described embodiment, there is one drive motor 4, and the front wheels or the rear wheels are drive wheels 9. The electric vehicle control system 200 of the first modification example is mounted on a 2WD vehicle equipped with two drive motors 4. The control method (control device) of the electric vehicle of the present invention can also be applied to the electric vehicle control system 200 of the first modification example.

[0285] That is, when the drive wheel 9 is only the front drive wheel 9f ( Figure 1 ), in the disturbance torque estimation process, step S602 ( Figure 6 ), step S701A ( Figure 7 ), and steps S701B - S704B (<( Figure 8 ) can be omitted. In addition, in step S703A, the object of filtering is not the front motor torque command value T mf (previous value), but Figure 4 the first torque target value T m1 (previous value) before the driving force distribution shown.

[0286] In the torque limit process, step S803, step S805, step S807, step S809 ( Figure 9 ) and Figure 12 steps S1001, S1002B, and S1003B ( Figure 12 ) can be omitted. In addition, regarding the process of step S801 ( Figure 9 ), the vehicle speed can be calculated based on the rotational speed of the follower wheels on the rear side.

[0287] On the other hand, when the drive wheel 9 is only the rear drive wheel 9r ( Figure 1 ), in the disturbance torque estimation process, step S601 (<( Figure 6) Steps S701A - S704A( Figure 7 ) Step S701B( Figure 8 ) That's all. Additionally, in Step S703B, the object of filtering is not the front motor torque command value T mf (last value), but Figure 4 the first torque target value T m1 (last value) before drive force distribution as shown

[0288] In the torque limit process, Steps S802, S804, S806, and S808( Figure 9 ) and Figure 11 Steps S1001, S1002A, and S1003A( Figure 11 ) can be omitted. Additionally, regarding the process of Step S801( Figure 9 ), the vehicle speed can be calculated based on the rotational speed of the driven wheel on the front side.

[0289] (Second Variation Example)

[0290] Figure 20 is a diagram showing the structure of the electric vehicle control system 300 of the second variation example. As Figure 20 shown, in the electric vehicle control system 300 of the second variation example, two drive motors 4 are configured, but there is no front drive system fds. Instead, there is a right rear drive system rdsR for driving the right rear drive wheel 9rR and a left rear drive system rdsL for driving the left rear drive wheel 9rL.

[0291] The right rear drive system rdsR has a structure where the right rear drive motor 4rR can drive the right rear drive wheel 9rR via the right rear reducer 5rR, and also has a right rear rotation sensor 6rR. The left rear drive system rdsL has a structure where the left rear drive motor 4rL can drive the left rear drive wheel 9rL via the left rear reducer 5rL, and also has a left rear rotation sensor 6rL.

[0292] In the electric vehicle control system 300 of the second variation example, for example, in the above - mentioned embodiment, the respective parameters of the front drive system fds and the rear drive system rds are replaced with the parameters related to the right rear drive system rdsR and the left rear drive system rdsL, and appropriate corrections such as setting a proper vehicle model are applied. Thus, the control method (control device) of the electric vehicle of the present invention can be realized.

[0293] For example, by appropriately performing the replacement of the front motor rotational speed ω mf and the rear motor rotational speed ω mr in the above - mentioned embodiment with the right rear motor rotational speed ω mrRand the rotational speed ω of the left-rear motor mrL and replace the estimated value T of the front interference torque df and the estimated value T of the rear interference torque dr with the estimated value T of the right-rear interference torque drR and the estimated value T of the left-rear interference torque drL and replace the front motor torque command value T mf and the rear motor torque command value T mr with the right-rear motor torque command value T mrR and the left-rear motor torque command value T mrL By changing parameters such as the above, the control method (control device) of the electric vehicle of the present invention can be executed.

[0294] (Third Modification Example)

[0295] Figure 21 FIG. is a diagram showing the structure of the electric vehicle control system 400 of the third modification example. As Figure 21 shown, the electric vehicle control system 400 of the third modification example includes a front drive system fds, a right-rear drive system rdsR, and a left-rear drive motor 4rL. That is, the third modification example includes a total of three drive motors 4, namely, a front drive motor 4f that drives the front drive shaft 8f, a right-rear drive motor 4rR that drives the right-rear drive wheel 9rR, and a left-rear drive motor 4rL that drives the left-rear drive wheel 9rL. In particular, the electric vehicle control system 400 of the third modification example is mounted on a 4WD vehicle having a total of three drive motors 4.

[0296] In the electric vehicle control system 400 of the third modification example, for example, by executing the same control method as the above-described embodiment and setting an appropriate gain for distributing the parameters set in the rear drive system rds to the right-rear drive system rdsR and the left-rear drive system rdsL (see Figure 4 ), the control method (control device) of the electric vehicle of the present invention can be realized.

[0297] (Fourth Modification Example)

[0298] Figure 22 FIG. is a diagram showing the structure of the electric vehicle control system 500 of the fourth modification example. As Figure 22 shown, the electric vehicle control system 500 of the fourth modification example includes a right-front drive system fdsR, a left-front drive system fdsL, a right-rear drive system rdsR, and a left-rear drive system rdsL, and is mounted on a 4WD vehicle having four drive motors 4.

[0299] The right front drive system fdsR includes a right front drive motor 4fR capable of driving a right front drive wheel 9fR via a right front speed reducer 5fR, and further includes a right front rotation sensor 6fR. The left front drive system fdsL includes a left front drive motor 4fL capable of driving a left front drive wheel 9fL via a left front speed reducer 5fL, and further includes a left front rotation sensor 6fL.

[0300] In the electric vehicle control system 500 of the fourth modification, for example, the same control method as in the above-described embodiment is executed, and the parameters of the front drive system fds are distributed to the right front drive system fdsR and the left front drive system fdsL by appropriate distribution gains (see Figure 4 ), on the other hand, the parameters of the rear drive system rds are distributed to the right rear drive system rdsR and the left rear drive system rdsL by appropriate distribution gain (refer to Figure 4 ), which can realize the control method (control device) of the electric vehicle of the present invention.

[0301] (Effects of this embodiment)

[0302] The control method of the electric vehicle according to the present embodiment is a control method of the electric vehicle using one or more electric motors (drive motors 4) as driving sources for driving, comprising: a motor torque command value calculation step (executed by the motor controller 2), calculating the motor torque command value (front motor torque command value T mf , rear motor torque command value T mr ); angular velocity detection process (executed by the rotation sensor 6), detecting the angular velocity (front motor speed ω) related to the rotation speed of the drive shaft that transmits the driving force of the motor (drive motor 4) to the drive wheel 9 mf 、Rear motor speedω mr ); Interference torque estimation process (executed by the motor controller 2), based on the motor torque command value and angular velocity estimation acting on the motor (drive motor 4) interference torque (front interference torque estimated value T df , rear disturbance torque estimated value T dr ); limit torque setting process (executed by the motor controller 2), corresponding to the disturbance torque (front disturbance torque estimated value T df , rear disturbance torque estimated value T dr ) Set the limit torque (front limit torque T rf , rear limit torque T rr ) so that the slip ratio of the driving wheel 9 does not exceed the first specified value; the motor torque limiting process (motor controller 2), using the limiting torque (front limiting torque T rf , rear limit torque T rr) to limit the motor torque command value (front motor torque command value T mf , rear motor torque command value T mr ).

[0303] In the above method, the first specified value is set, for example, to a slip ratio between 10% and 20%. In addition, the first specified value uses, as an upper limit, a value of the slip ratio in the characteristic curve showing the relationship between the slip ratio of the drive wheel 9 and the frictional force in the front-rear direction that does not exceed the slip ratio (e.g., 20%) near the peak value of the frictional force in the front-rear direction.

[0304] By the above method, based on the estimated disturbance torque value corresponding to the driving resistance of the road surface, the motor torque command value determined by the driver's accelerator operation is limited so that the slip ratio of the drive wheel 9 does not exceed the first specified value. Thus, even in the case of variations in mass balance deviation, tire ground load, change in the friction coefficient μ of the road surface, gradient resistance, and other driving resistance variations such as in sandy areas, the limit torque can be appropriately set, and the slip of the drive wheel 9 can be appropriately controlled. Therefore, over-rotation of the drive wheel 9 or acceleration failure such as getting stuck in sandy areas can be suppressed.

[0305] In the present embodiment, in the limit torque setting process (performed by the motor controller 2), an addition torque (accelerator opening addition torque, front (rear) motor speed addition torque) is added to the disturbance torque (front disturbance torque estimated value T df , rear disturbance torque estimated value T dr ) so that the slip ratio of the drive wheel 9 does not exceed the first specified value. Thereby, over-rotation of the drive wheel 9 can be suppressed, getting stuck in sandy areas and the like can be prevented, and a desired acceleration can be obtained.

[0306] In the present embodiment, the larger the accelerator opening APO (the amount of depression of the accelerator), the higher the addition torque is set. Thus, by setting the addition torque larger corresponding to the accelerator operation, acceleration failure of the drive wheel 9 getting stuck can be prevented, and the acceleration of the electric vehicle and the slip state of the drive wheel 9 can be increased corresponding to the intention. In addition, since a large acceleration is obtained in proportion to the amount of depression of the accelerator, discomfort during acceleration when the driver operates the accelerator can be reduced.

[0307] In the present embodiment, the higher the vehicle speed, the higher the addition torque is set. In sandy areas or deep snow, when the electric vehicle starts from a stopped state, if the initial driving force is large, the drive wheel 9 has a tendency to get stuck in the sand or snow. Therefore, in the low-speed region, by setting the addition torque smaller to make it start slowly, getting stuck of the drive wheel 9 during starting can be prevented.

[0308] In the present embodiment, in the case where a plurality of electric motors (front drive motor 4f, rear drive motor 4r) are arranged, disturbance torques (front restraint torque T rf , rear restraint torque T rr ) are respectively estimated for the electric motors (front drive motor 4f, rear drive motor 4r), and based on the disturbance torques (front restraint torque T rf , rear restraint torque T rr ), restraint torques (front restraint torque T rf , rear restraint torque T rr ) are respectively set for the electric motors (front drive motor 4f, rear drive motor 4r). In an electric vehicle having two or more independent electric motors, the disturbance torque can be estimated independently using the respective motor speeds. Therefore, the motor torque command values of two or more electric motors can be appropriately controlled independently.

[0309] In the present embodiment, the motor torque restriction process (performed by the motor controller 2) is turned on / off controlled by the driver's switch operation. By performing the determination of making the restraint torque effective through the switch operation, the driver's intention can be reflected in the control.

[0310] In the present embodiment, in the motor torque restriction process (performed by the motor controller 2), a gradient torque caused by the gradient of the road surface is estimated. When the difference (Δd) between the disturbance torque (front disturbance torque estimated value T df , rear disturbance torque estimated value T dr ) and the gradient torque is equal to or greater than a second specified value, the restraint torque (front restraint torque T rf , rear restraint torque T rr ) is used to restrict the motor torque command values (front motor torque command value T mf , rear motor torque command value T mr ). Thereby, it is possible to distinguish the gradient disturbance (gradient component in the disturbance torque) caused by the inclination of the road surface from the running resistance disturbance such as sandy ground (running resistance component in the disturbance torque) in the disturbance torque. When the running resistance disturbance is relatively large compared to the gradient disturbance, the restraint torque can be used to restrict the motor torque command value.

[0311] In addition, the control device for an electric vehicle according to the present embodiment is a control device for an electric vehicle having one or more electric motors (drive motor 4) as a running drive source, and includes: a motor torque command value calculation unit (motor controller 2) that calculates motor torque command values (front motor torque command value T mf , rear motor torque command value T mr); an angular velocity detection unit (rotation sensor 6) that detects an angular velocity (front motor rotational speed ω mf , rear motor rotational speed ω mr ) related to the rotational speed of the drive shaft that transmits the driving force of the motor (drive motor 4) to the drive wheels 9; a disturbance torque estimation unit (motor controller 2) that estimates, based on the motor torque command values (front motor torque command value T mf , rear motor torque command value T mr ), the disturbance torque acting on the motor (drive motor 4) (front disturbance torque estimated value T df , rear disturbance torque estimated value T dr ); a limit torque setting unit (motor controller 2) that sets limit torques (front limit torque T df , rear limit torque T dr ) corresponding to the disturbance torques (front disturbance torque estimated value T rf , rear disturbance torque estimated value T rr ) so that the slip ratio of the drive wheels 9 does not exceed a first specified value; a motor torque limiting unit (motor controller 2) that uses the limit torques (front limit torque T rf , rear limit torque T rr ) to limit the motor torque command values (front motor torque command value T mf , rear motor torque command value T mr ).

[0312] In the above structure, the first specified value is set, for example, such that the slip ratio is between 10% and 20%. Further, the first specified value has, as an upper limit, a value that does not exceed the slip ratio near the peak value of the longitudinal friction force (e.g., 20%) in the characteristic curve showing the relationship between the slip ratio of the drive wheels 9 and the longitudinal friction force.

[0313] According to the above structure, by using the disturbance torque estimated value corresponding to the driving resistance on the road surface to limit the motor torque command value determined by the accelerator operation of the driver, even in the case of variations in mass balance deviation, tire ground load, variation in the friction coefficient μ of the road surface, gradient resistance, and other driving resistance variations such as on sandy ground, the limit torque can be appropriately set and the slip of the drive wheels 9 can be appropriately controlled. Therefore, excessive rotation of the drive wheels 9 or acceleration failure such as getting stuck in sandy ground (being stuck) can be suppressed.

[0314] As described above, the embodiments of the present invention have been described, but the structures described in the above embodiments and each modification merely represent a part of the application examples of the present invention and are not intended to limit the technical scope of the present invention.

[0315] For example, within the scope of being able to implement the technical idea of the present invention, particularly the idea of calculating the estimated value of the interference torque and limiting the torque, various vehicle models envisioned in the above-described embodiments and various parameters determined thereby can be arbitrarily changed.

[0316] In addition, in the above-described embodiments and various modified examples, "right" and "left" are merely determinations of directions used for convenience of explanation, and do not assume strict consistency with the left and right directions relative to the front of the vehicle body.

Claims

1. A control method for an electric vehicle that uses one or more electric motors as a driving source for traveling, wherein, The control method includes: a motor torque command value calculation step of calculating a motor torque command value; an angular velocity detection step of detecting an angular velocity related to the rotational speed of a drive shaft that transmits the driving force of the motor to a drive wheel; a disturbance torque estimation step of estimating a disturbance torque acting on the motor based on the motor torque command value and the angular velocity; a limit torque setting step of setting a limit torque corresponding to the disturbance torque so that the slip ratio of the drive wheel does not exceed a first specified value; a motor torque limitation step of limiting the motor torque command value using the limit torque.

2. The control method of an electric vehicle according to claim 1, wherein in the limit torque setting step, an addition torque is added to the disturbance torque so that the slip ratio of the drive wheel does not exceed the first specified value.

3. The control method of an electric vehicle according to claim 2, wherein the greater the accelerator opening degree, the higher the addition torque is set.

4. The control method of an electric vehicle according to claim 2, wherein the higher the vehicle speed, the higher the addition torque is set.

5. The control method of an electric vehicle according to any one of claims 1 to 4, wherein in the case where a plurality of the motors are provided, the disturbance torque is estimated for each of the motors, and the limit torque is set for each of the motors based on the disturbance torque.

6. The control method of an electric vehicle according to any one of claims 1 to 4, wherein on / off control is performed on the motor torque limitation step by a switch operation of a driver.

7. The control method of an electric vehicle according to any one of claims 1 to 4, wherein in the motor torque limitation step, a gradient torque caused by the gradient of a road surface is estimated, and when the difference between the disturbance torque and the gradient torque becomes equal to or greater than a second specified value, the motor torque command value is limited using the limit torque.

8. A control device for an electric vehicle, the electric vehicle having one or more electric motors as a driving source for traveling, wherein, The control device includes: a motor torque command value calculation unit that calculates a motor torque command value; an angular velocity detection unit that detects an angular velocity related to the rotational speed of a drive shaft that transmits the driving force of the motor to a drive wheel; a disturbance torque estimation unit that estimates a disturbance torque acting on the motor based on the motor torque command value and the angular velocity; a limit torque setting unit that sets a limit torque corresponding to the disturbance torque so that the slip ratio of the drive wheel does not exceed a first specified value; a motor torque limitation unit that limits the motor torque command value using the limit torque.

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