Electric vehicle control method and electric vehicle control system

Abstract

The present invention provides a control method for an electric vehicle and a control system for the electric vehicle. The control method for the electric vehicle comprises the following steps: using a first motor (4r) and a second motor (4f) as driving sources, driving and controlling the first motor by sending a first torque command value (Tmr) to a first inverter (3r), and driving and controlling the second motor by sending a second torque command value (Tmf) to a second inverter (3f), and switching control of the second inverter between an on state for driving the second motor and an off state for stopping the driving control based on a required driving force. The control method for the electric vehicle aims to calculate a torque variation (ΔT) generated in the second motor during the switching control based on the number of revolutions of the second motor, and to correct the first torque command value based on the torque variation, thereby reducing a torque step when switching the driving state.

Description

Technical Field

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

[0002] (Japan) JP6485202B has disclosed a technology that, in an electric vehicle having a front-wheel drive motor and a rear-wheel drive motor, stops either the front-wheel drive motor or the rear-wheel drive motor according to the required driving force, and drives the vehicle with the other motor. Summary of the Invention

[0003] However, in JP6485202B, a clutch is provided between the motor and the drive wheels, and switching control is performed so that the clutch on the drive-stopping side is not connected. Therefore, a torque step occurs when switching between connection and release of the clutch.

[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 reduce a torque step when switching driving states.

[0005] According to one embodiment of the present invention, a control method for an electric vehicle comprises: using a first motor and a second motor as driving sources for travel, driving and controlling the first motor by sending a first torque command value to a first inverter, and driving and controlling the second motor by sending a second torque command value to a second inverter; and switching control of the second inverter between an on state, in which drive control of the second motor is performed, and an off state, in which drive control of the second motor is stopped, based on a required driving force. This control method calculates a torque change in the second motor during switching control based on the rotational speed of the second motor, and corrects the first torque command value based on the torque change. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 This is a block diagram illustrating a basic configuration of an electric vehicle system to which the electric vehicle control method according to the present embodiment is applied.

[0007] Figure 2 This is a flowchart illustrating the main processing of driving control of an electric vehicle.

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

[0009] Figure 4 This is a flowchart illustrating the torque correction process of an electric vehicle.

[0010] Figure 5 This is a graph showing the relationship between the motor rotation speed and the torque change.

[0011] Figure 6 This is a timing diagram of the rear motor torque, front motor torque, and total torque when the front inverter switching control is switched from the off state to the on state and torque control is performed without considering the generation of a torque step.

[0012] Figure 7 This is a timing chart of the rear motor torque, front motor torque, and total torque when the front inverter switching control is switched from the off state to the on state and torque control (part 1) is performed taking into account the generation of a torque step.

[0013] Figure 8 This is a timing diagram of the rear motor torque, front motor torque, and total torque when torque control (part 2) is performed taking into account the torque step generated when the front inverter switching control switches from the off state to the on state.

[0014] Figure 9 This is a time chart of the rear motor torque, front motor torque, and total torque when torque control is performed without considering the torque step generated when the front inverter switching control switches from the on state to the off state.

[0015] Figure 10 This is a time chart of the rear motor torque, front motor torque, and total torque when torque control is performed taking into account the torque step generated when the front inverter switching control switches from the on state to the off state. DETAILED DESCRIPTION

[0016] Next, embodiments of the present invention will be described.

[0017] <Electric Vehicle System Structure>

[0018] Figure 1 This is a block diagram illustrating a main configuration of an electric vehicle system 100 to which the electric vehicle control method (control system) according to the present embodiment is applied.

[0019] It should be noted that the electric vehicle of this embodiment is a motor vehicle that includes a drive motor 4 (electric motor) as a vehicle drive source and is driven by the driving force of this drive motor 4, including electric vehicles and hybrid vehicles. In particular, the electric vehicle system 100 of this embodiment, which is used in electric vehicles, has two drive motors 4 (a front drive motor 4f and a rear drive motor 4r). The structure of the electric vehicle system 100 will be described in more detail below.

[0020] like Figure 1 As shown, the electric vehicle system 100 includes a front drive system fds, a rear drive system rds, a battery 1, and a motor controller 2 (control unit).

[0021] The front drive system fds is provided with various sensors and actuators for controlling the front drive motor 4f that drives the front drive wheels 9f (the left front drive wheel 9fL and the right front drive wheel 9fR).

[0022] On the other hand, the rear drive system rds is provided with various sensors and actuators for controlling the rear drive motor 4r that drives the rear drive wheels 9r (the left rear drive wheel 9rL and the right rear drive wheel 9rR).

[0023] Furthermore, the front drive system fds and the rear drive system rds are each independently controlled by the motor controller 2 .

[0024] The battery 1 is used as a power source for supplying (discharging) driving power to the drive motors 4 (front drive motor 4f, rear drive motor 4r), and on the other hand, is connected to the inverter 3 (front inverter 3f, rear inverter 3r) so as to be charged by receiving regenerative power from the drive motors 4 (front drive motor 4f, rear drive motor 4r).

[0025] Motor controller 2 is, for example, a computer composed of a central processing unit (CPU), read-only memory (ROM), random access memory (RAM), and input / output interfaces (I / O interfaces). Motor controller 2 constitutes the control device of the electric vehicle of the present invention and is a key component having a program for executing the electric vehicle control method of the present invention.

[0026] Signals representing various vehicle variables indicating the vehicle state, such as the accelerator opening APO, vehicle speed V, the rotor phase α of the drive motor 4 (front rotor phase αf, rear rotor phase αr), and the current Im of the drive motor 4 (front motor current Imf, rear motor current Imr), are input as digital signals to the motor controller 2. Furthermore, a signal from a mode switch that determines the vehicle's driving mode is input to the motor controller 2 based on the driver's operation. Examples of driving modes include a 2WD mode in which only the rear drive motor 4r (or the front drive motor 4f) is driven; a 4WD mode in which both the front drive motor 4f and the rear drive motor 4r are driven full-time; and a switching mode in which switching between the 2WD mode and the 4WD mode is controlled based on the vehicle's state.

[0027] The motor controller 2 generates a PWM signal for controlling each drive motor 4 based on the input signal. In addition, the motor controller 2 generates a drive signal for each inverter 3 based on each generated PWM signal.

[0028] Each inverter 3 has two corresponding switching elements (e.g., power semiconductor elements such as IGBTs and MOS-FETs). Specifically, each inverter 3 switches the switching elements on and off based on commands from the motor controller 2, thereby converting the DC current supplied from the battery 1 into AC current or vice versa, and regulating the current supplied to each drive motor 4 to a desired value.

[0029] 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 driving force using AC current supplied from the corresponding inverter 3 (front inverter 3f, rear inverter 3r). The driving force is then transmitted to the drive wheels 9 (front drive wheels 9f, rear drive wheels 9r) via the corresponding speed reducers 5 (front speed reducer 5f, rear speed reducer 5r) and the propeller shafts 8 (front propeller shaft 8f, rear propeller shaft 8r).

[0030] Furthermore, when the drive motor 4 is rotated by the drive wheels 9 during vehicle travel, it generates regenerative power, thereby recovering the vehicle's kinetic energy as electrical energy. In this case, the inverter 3 converts the AC current (regenerative power) generated during regenerative operation into DC current, which is then supplied to the battery 1.

[0031] Here, a winding-excited motor is preferably used as the drive motor 4. Furthermore, the inverter 3 is preferably configured to switch the current flowing through the excitation winding of the rotor of the drive motor 4. For example, if the switching of the current flowing through the stator winding is stopped while current is flowing through the excitation winding of the rotor of the drive motor 4, negative torque is generated due to the magnetic flux generated by the excitation winding. However, the above-described configuration can avoid the generation of negative torque due to magnetic flux.

[0032] The angular velocity detection unit (performs the angular velocity detection process), namely the rotation sensor 6 (the front rotation sensor 6f and the rear rotation sensor 6r), respectively detects the rotor phase α (the front rotor phase α f 、Rear rotor phase α r ) is detected and output to the motor controller 2. It should be noted that the rotation sensor 6 is composed of, for example, a resolver, an encoder, etc.

[0033] The current sensor 7 (the front current sensor 7f and the rear current sensor 7r) detects the three-phase AC current (iu, iv, iw) flowing through each drive motor 4. It should be noted that since the sum of the three-phase AC current (iu, iv, iw) is 0, the current sensor 7 can also detect the current of any two phases, and the current of the remaining phase can be calculated. In particular, the current sensor 7 detects the current flowing through the front drive motor 4f, that is, the three-phase AC current (iuf ,iv f , iw f ), and the current flowing in the rear drive motor 4r, namely the three-phase AC current (iu r ,iv r , iw r ) for testing.

[0034] Figure 2 This is a flowchart illustrating the basic processing of the electric vehicle control device of the motor controller 2 of this embodiment. It should be noted that the motor controller 2 is programmed to execute the operation in each predetermined operation cycle. Figure 2 The processing of steps S201 to S205 is shown.

[0035] In step S201 , the motor controller 2 acquires various parameters used for executing the processes in step S202 and subsequent steps according to the following processes 1 to 3 and performs input processing.

[0036] 1. Detection values ​​of each sensor

[0037] The motor controller 2 obtains the accelerator opening APO (%), rotor phase α (rad), three-phase AC current (iu, iv, iw) (A) flowing through the drive motor 4, and the DC voltage value Vdc (V) of the battery 1 from the accelerator opening sensor (not shown) and other sensors. The motor controller 2 also obtains a mode switching signal.

[0038] 2. Previous value of the motor torque command value

[0039] The motor controller 2 acquires previous values ​​of motor torque command values ​​(front motor torque command value Tmf, rear motor torque command value Tmr) described later, which are stored in an internal memory.

[0040] 3. Control parameters obtained through calculation

[0041] The motor controller 2 calculates the motor electrical angular velocity ω based on the parameters obtained according to the above "1." e [rad / s], motor rotation speed ω m [rad / s], motor speed N m [rpm], and wheel speed ω w [km / h].

[0042] (i) Motor electrical angular velocity ω e

[0043] Motor controller 2 for rotor phase α (front rotor phase α f , and the rear rotor phase α r) to perform time differentiation and calculate the electrical angular velocity ω of each motor e (Front motor electrical angular velocity ω ef 、Rear motor electrical angular velocity ω er ).

[0044] (ii) Motor rotation speed ω m

[0045] Motor controller 2 converts the motor electrical angular velocity ω e Divide by the number of pole pairs of the drive motor 4 to calculate the mechanical angular velocity of the drive motor 4, that is, the motor rotation speed ω m (Front motor rotation speed ω mf , rear motor rotation speed ω mr ). It should be noted that the motor rotation speed ω m The relationship between the rotation speed of the drive shaft, ie, the transmission shaft 8, can be appropriately determined according to the gear ratio of the speed reducer 5. That is, the motor rotation speed ω m It is a speed parameter related to the rotation speed of the transmission shaft 8.

[0046] (iii) Motor speed N m

[0047] Motor controller 2 sets the motor rotation speed ω m Multiply by the unit conversion coefficient (60 / 2π) to calculate the motor speed N m (Front motor speed N mf , Rear motor speed N mr ).

[0048] (iv) Wheel speed ω w

[0049] First, the motor controller 2 sets the front motor rotation speed ω mf Multiplying by the tire movement radius R, and based on the value obtained by the multiplication and the gear ratio of the front speed reducer 5f, the left front drive wheel speed ω is calculated. wfL and right front drive wheel speed ω wfR In addition, the motor controller 2 sets the rear motor rotation speed ω mr The left rear drive wheel speed ω is calculated based on the value obtained by multiplication and the gear ratio of the final gear of the rear speed reducer 5r. wrL and right rear drive wheel speed ω wrR In this embodiment, the wheel speed ω obtained in this way is w Use the unit conversion factor (3600 / 1000) to convert the wheel speed ω w Convert the unit [m / s] to [km / h].

[0050] The vehicle speed is obtained from a sensor such as GPS, or for example, from the rotation speed (ω mf 、ω mr ), a speed with a lower rotational speed is selected during acceleration, and a speed with a higher rotational speed is selected during deceleration. When traveling at a roughly constant speed, either speed is selected and the wheel speed is calculated as described above.

[0051] Next, in step S202 , the motor controller 2 calculates the basic target torque requested by the driver based on the vehicle information.

[0052] Specifically, first, the motor controller 2 refers to the accelerator opening-torque table and calculates the accelerator opening APO and the rear motor rotation speed ω obtained in step S201. mr (It can also be the front motor rotation speed ω mf ), calculate the first torque target value Tm1.

[0053] exist Figure 3 , an example of an accelerator opening-torque table referred to by the motor controller 2 of the present embodiment is shown.

[0054] Next, the motor controller 2 calculates the front motor torque command value Tmf and the rear motor torque command value Tmr based on the first torque target value Tm1 , for example, according to a predetermined front and rear motor torque ratio.

[0055] The motor controller 2 obtains the front motor torque command value Tmf and the rear motor torque command value Tmr by, for example, multiplying the first torque target value Tm1 by the front and rear drive force distribution gain Kf (0≦Kf≦1) and 1−Kf, respectively.

[0056] In step S203, the motor controller 2 executes a torque correction process. The details of the torque correction process will be described later.

[0057] In step S204, the motor controller 2 performs a current command value calculation process. Specifically, the motor controller 2 calculates the current command value based on the front motor torque command value Tmf, the rear motor torque command value Tmr, and the front motor rotation speed ω calculated in step S202 (S203). mf , rear motor rotation speed ω mr , and the DC voltage value V obtained in step S201 dc , refer to the pre-determined table and 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 *) is the target value of the front dq axis current (idf *,i qf *), and the dq axis current target value (i d *,i q *) is the target value of the post-dq axis current (i dr *,i qr *).

[0058] In step S205, 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 calculates 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 ) is the leading dq axis voltage command value (v df , v qf ), and the dq axis voltage command value (v d , v q ) is the post-dq axis voltage command value (v dr , v qr ).

[0059] In addition, the motor controller 2 is based on the dq axis voltage command value (v d , v q ) and rotor phase α, calculate the three-phase AC voltage command value (vu, vv, vw). In particular, the motor controller 2 calculates the three-phase AC voltage command value (vu, vv, vw) set in the front drive motor 4f, that is, the front three-phase AC voltage command value (vu f , vv f , vw f ), and the three-phase AC voltage command value (vu, vv, vw) set in the rear drive motor 4r, namely the rear three-phase AC voltage command value (vu f , vv f , vw f ).

[0060] The motor controller 2 then calculates the PWM signals (tu, tv, tw) [%] based on the calculated three-phase AC voltage command values ​​(vu, vv, vw) and DC voltage value Vdc. The thus calculated PWM signals (tu, tv, tw) are used to open and close the switching elements of the inverter 3, thereby driving the drive motors 4 (front drive motor 4f and rear drive motor 4r) at the desired torque indicated by the total torque command value (front motor torque command value Tmf and rear motor torque command value Tmr).

[0061] Torque Correction Processing

[0062] Next, for Figure 2 The torque correction processing shown in step S203 is described in detail. As described above, the electric vehicle system 100 of the present embodiment has a switching mode for performing switching control between the 2WD mode and the 4WD mode based on the vehicle state. As a scenario for performing switching control, for example, there is a scenario in which the 2WD mode is switched to the 4WD mode when the total torque T exceeds a prescribed value, and the 4WD mode is switched to the 2WD mode when the total torque T is below the prescribed value. In addition, there is also a scenario in which the difference between the vehicle speed estimated by the rear drive motor 4r (front drive motor 4f) and the vehicle speed V exceeds a prescribed value, or when the rear motor rotation speed ω mr When the rotation speed difference of the rear drive motor 4r from the previous value corresponding to the rear motor torque command value Tmr exceeds a predetermined value, the 2WD mode is switched to the 4WD mode to avoid slip. When it is below the predetermined value, the 4WD mode is switched to the 2WD mode.

[0063] On the other hand, the front inverter 3f of this embodiment performs switching control on the current flowing through the excitation winding provided on the rotor of the front drive motor 4f. When the front drive motor 4f is not driven, the front inverter 3f switches the switching control to the off state. In this way, the rotor of the front drive motor 4f switches from a self-driven state to a state in which it rotates following the drive of the rear drive motor 4r. In addition, when the front drive motor 4f is driven, the front inverter 3f switches the switching control to the on state. In this way, the rotor of the front drive motor 4f switches from a driven state in which it rotates following the drive of the rear drive motor 4r to a driven state in which it is self-driven.

[0064] The above-mentioned switching of the front drive motor 4f between driving and driven by the switching control of the front inverter 3f generates a torque step in the front drive motor 4f, which may cause an uncomfortable torque shock to the driver. Here, the torque step is not related to the magnitude of the front motor torque command value Tmf and the front motor torque Tf, but is caused by the current responsiveness and mechanical inertia (mechanical responsiveness) of the front drive motor 4f and the rear drive motor 4r, which is equivalent to the torque step described later. Figure 4 ΔT shown.

[0065] Therefore, in the torque correction process of this embodiment, the torque change amount corresponding to the torque step is calculated and reflected in the rear motor torque command value Tmr of the rear drive motor 4r, thereby performing control to reduce or eliminate the torque step.

[0066] <Torque correction process flow>

[0067] Figure 4 This is a flowchart illustrating the torque correction process of an electric vehicle. Figure 5 Graph showing the relationship between the motor rotation speed and the torque variation. In this embodiment, the steps S301 to S309 shown below are executed in a predetermined cycle.

[0068] In step S301, motor controller 2 determines whether front motor torque command value Tmf is greater than a first threshold value Tth1. If the determination is YES, the process determines that the switching control of front inverter 3f is in the ON state, and the process proceeds to step S307. If the determination is NO, the process proceeds to step S302. First threshold value Tth1 is an indicator used to determine whether the switching control of front inverter 3f has transitioned from the OFF state to the ON state, and can be set to, for example, 0 [Nm] or any value greater than 0 [Nm].

[0069] In step S302, motor controller 2 determines whether front motor torque command value Tmf is greater than a second threshold value. If the answer is YES, the process proceeds to step S307. If the answer is NO, the process determines that the switching control of front inverter 3f is in the OFF state, and the process proceeds to step S303. Here, second threshold value Tth2 is an indicator used to determine whether the switching control of front inverter 3f has transitioned from the ON state to the OFF state. For example, it can be set to 0 [Nm] or any value greater than 0 [Nm].

[0070] In step S303, after step S302, the motor controller 2 determines whether the front motor torque command value Tmf is greater than the first threshold value Tth1. When it is YES, it determines that the switch control of the front inverter 3f is in the on state and moves to step S304. When it is NO, it maintains step S303.

[0071] In step S304 , the motor controller 2 calculates a torque variation ΔT for canceling a torque step generated in a short period from when the front motor torque command value Tmf exceeds the first threshold to when the front motor torque Tf of the front drive motor 4 f becomes zero.

[0072] Torque change ΔT is used Figure 5 The graph shown uses the rotational speed of the front drive motor 4f as an input value and calculates the difference between characteristic lines Tf1 and Tf2. Characteristic line Tf1 represents the front motor torque Tf when the front drive motor 4f switches from a driven state to a driven state, that is, when the front motor torque command value Tmf exceeds a first threshold value Tth1 (e.g., 0). Characteristic line Tf2 represents the front motor torque Tf at the end of the torque step (e.g., Tf = 0).

[0073] It should be noted that the torque variation is set to offset torque steps by taking into account the current responsiveness and mechanical inertia (mechanical responsiveness) of the front drive motor 4f and the rear drive motor 4r. For example, if the front drive motor 4f and the rear drive motor 4r have the same current responsiveness and mechanical inertia (mechanical responsiveness), the torque variation can be set to the same magnitude as the torque step, thereby offsetting the torque step.

[0074] In step S305 , the motor controller 2 corrects the rear motor torque command value Tmr from [Tmr] to [Tmr−ΔT]. As a result, the rear motor torque command value Tmr changes instantaneously from [Tmr] to [Tmr−ΔT].

[0075] In step S306 , the motor controller 2 monotonically increases the rear motor torque command value Tmr from [Tmr−ΔT] to [Tmr] (value before correction) at a speed that the rear motor torque Tr of the rear drive motor 4 r can follow.

[0076] In step S307, the motor controller 2 determines whether the front motor torque command value Tmf is below the second threshold value after step S301 or step S302. When it is YES, it determines that the switch control of the front inverter 3f is in the disconnected state and moves to step S308. When it is NO, it maintains step S307.

[0077] In step S308, the motor controller 2 calculates the torque change ΔT, which is used to offset the torque step generated in a short period of time when the front drive motor 4f moves from the driving state to the driven state, that is, when the front motor torque command value Tmf is the second threshold value Tth2 (for example, 0) to the torque value when the front motor torque Tf of the front drive motor 4f is in the driven state.

[0078] The torque variation ΔT is the same as above, using Figure 5 The graph shown uses the rotational speed of the front drive motor 4f as an input value and calculates the difference between characteristic curves Tf1 and Tf2. Characteristic curve Tf1 represents the front motor torque Tf when the torque step is complete and the front drive motor 4f is fully driven. Characteristic curve Tf2 represents the front motor torque Tf of the front drive motor 4f when the front motor torque command value Tmf is at a second threshold value Tth2 (e.g., 0) (e.g., Tf = 0).

[0079] In step S309 , the motor controller 2 corrects the rear motor torque command value Tmr from [Tmr] to [Tmr+ΔT]. As a result, the rear motor torque command value Tmr changes instantaneously from [Tmr] to [Tmr+ΔT].

[0080] <Timing diagram for changing switch control from OFF to ON>

[0081] Figure 6 This is a timing chart of the rear motor torque Tr, the front motor torque Tf, and the total torque T when the switching control of the front inverter 3f is switched from the off state to the on state and torque control is performed without considering the occurrence of a torque step.

[0082] Figure 7 This is a timing chart of the rear motor torque Tr, the front motor torque Tf, and the total torque T when the switching control of the front inverter 3f is switched from the off state to the on state and torque control (part 1) is performed in consideration of the generation of a torque step.

[0083] Figure 8 This is a timing chart of the rear motor torque Tr, the front motor torque Tf, and the total torque T when torque control (part 2) is performed taking into account a torque step generated when the switching control of the front inverter 3f is switched from the off state to the on state.

[0084] exist Figure 6 - Figure 8 , there is shown a timing chart when the front drive motor 4f is switched from the driven state to the driving state while the rear drive motor 4r is maintained in the driving state.

[0085] The front motor torque Tf varies in accordance with the front motor torque command value Tmf, and the rear motor torque Tr varies in accordance with the rear motor torque command value Tmr. The total torque T is the sum of the front motor torque Tf and the rear motor torque Tr.

[0086] exist Figure 6 In the process, the rear motor torque command value Tmr is maintained at a constant value, and thus the rear motor torque Tr is also maintained at a constant value.

[0087] The front motor torque command value Tmf remains at 0 until time t1. As a result, the switching control of the front inverter 3f is turned off (PWM OFF), the front drive motor 4f is in a driven state, and a negative torque lower than 0 by ΔT is applied to the drive system.

[0088] When the front motor torque command value Tmf exceeds a first threshold value Tth1 (e.g., 0) at time t1, reaching [Tmf(t1)], the front inverter 3f is switched to the on state (PWM ON). This switches the front drive motor 4f from a driven state to a driven state. However, a torque step occurs between time t1 and time t2 before the front motor torque Tf reaches 0.

[0089] After time t2, the front motor torque Tf increases with a predetermined gradient based on the value of the front motor torque command value Tmf [Tmf(t1)]. At time t3, the front motor torque Tf converges to the value indicated by the front motor torque command value Tmf [Tmf(t1)].

[0090] Meanwhile, total torque T increases from time t2 to t3 as front motor torque Tf increases. However, from time t1 to t2, rear motor torque command value Tmr remains constant, and thus rear motor torque Tr also remains constant. Therefore, the torque step generated by front drive motor 4f from time t1 to t2 is directly reflected in total torque T, causing an uncomfortable torque shock for the driver.

[0091] On the other hand, Figure 7 As shown, in this embodiment, before time t1, the motor controller 2 executes Figure 4 Then, when the front motor torque command value Tmf is greater than the first threshold value Tth1 (for example, 0) at time t1 and is [Tmf(t1)] ( Figure 4 , step S303), the motor controller 2 calculates the torque variation (ΔT) ( Figure 4 , step S304), the rear motor torque command value Tmr is corrected from the value before time t1 [Tmr(<t1)] to the value at time t1 [Tmr(t1)=Tmr(<t1)-ΔT] (step S305).

[0092] As a result, the rear motor torque Tr changes from [Tr(t1)] to [Tr(t2)=Tr(t1)-ΔT] with a predetermined gradient between time t1 and time t2, and converges to the value [Tmr(t1)] of the corrected rear motor torque command value Tmr.

[0093] Therefore, from time t1 to time t2, the torque step generated by the front drive motor 4f is offset by the torque change caused by the corrected rear motor torque command value Tmr ([Tmr(t1)]) input to the rear inverter 3r, eliminating the torque step generated by the total torque T and maintaining a roughly constant value.

[0094] After time t2, the motor controller 2 gradually increases the rear motor torque command value Tmr from [Tmr(t1)] to [Tmr(t1)+ΔT] ( Figure 4 , step S306), causing the rear motor torque Tr to increase smoothly.

[0095] As a result, the total torque T also rises gently and converges to the total value of [Tmr(t1)+ΔT] and [Tmf(t1)] around time t3.

[0096] Figure 8 The timing diagram and Figure 7 The timing diagram is the same as that of Figure 4 According to the situation of step S306. Figure 7 、 Figure 8 It can be seen that in this embodiment, by executing at least step S303 , step S304 , and step S305 , the torque step generated when the front drive motor 4 f switches from the driven state to the driving state can be eliminated.

[0097] <Timing diagram when switching the switch from the on state to the off state>

[0098] Figure 9 This is a time chart of the rear motor torque Tr, the front motor torque Tf, and the total torque T when torque control is performed without considering a torque step generated when the switching control of the front inverter 3f is switched from the on state to the off state.

[0099] Figure 10 This is a time chart of the rear motor torque Tr, the front motor torque Tf, and the total torque T when torque control is performed taking into account a torque step generated when the switching control of the front inverter 3f is switched from the on state to the off state.

[0100] exist Figure 9 、 Figure 10 , there is shown a timing chart when the driving state of the front drive motor 4f is switched to the driven state while the driving state of the rear drive motor 4r is maintained.

[0101] exist Figure 9 In the process, the rear motor torque command value Tmr is maintained at a constant value, and thus the rear motor torque Tr is also maintained at a constant value.

[0102] Before time t1, the front motor torque command value Tmf and the front motor torque Tf decrease monotonically but maintain values ​​greater than 0. Consequently, the front inverter 3f maintains an on-state (PWM ON) switching control until before time t1, driving the front drive motor 4f and applying positive torque to the drive system.

[0103] Furthermore, the total torque T is affected by the front motor torque Tf and decreases monotonically until time t1.

[0104] At time t1, when the front motor torque command value Tmf and the front motor torque Tf are zero, the switching control of the front inverter 3f is in the off state (PWM OFF), the front drive motor 4f stops driving and enters the driven state, and begins to apply negative torque to the drive system. After time t2, the front motor torque Tf applies a negative torque that is ΔT lower than zero to the drive system. Therefore, between time t1 and time t2, the front drive motor 4f generates a torque step (ΔT).

[0105] Meanwhile, rear motor torque command value Tmr remains constant between time t1 and time t2. Consequently, total torque T decreases dramatically between time t1 and time t2 due to a torque step, causing an uncomfortable torque shock for the driver. Furthermore, after time t2, it remains at a value only ΔT lower than the value at time t1.

[0106] like Figure 10 As shown, in this embodiment, before time t1, the motor controller 2 executes step S301 (YES). Then, when the front motor torque command value Tmf is a value [Tmf(t1)] less than the second threshold value Tth2 (for example, 0) at time t1 ( Figure 4 , step S307), the motor controller 2 calculates the torque variation (ΔT) ( Figure 4 , step S308), the rear motor torque command value Tmr is corrected from the value before time t1 (Tmr(<t1)) to the value at time t1 [Tmr(t1)=Tmr(<t1)+ΔT) (step S309).

[0107] As a result, the rear motor torque Tr changes from [Tr(t1)] to [Tr(t2)=Tr(t1)+ΔT] with a predetermined gradient between time t1 and time t2, and converges to the value [Tmr(t1)] of the corrected rear motor torque command value Tmr.

[0108] Therefore, from time t1 to time t2, the torque step generated by the front drive motor 4f is offset by the torque change caused by the corrected rear motor torque command value Tmr ([Tmr(t1)]) input to the rear inverter 3r, and the torque step generated by the total torque T is eliminated, so that a roughly constant value can be maintained.

[0109] Therefore, according to Figure 10 It can be seen that in this embodiment, by executing at least step S307 , step S308 , and step S309 , the torque step generated when the front drive motor 4 f switches from the driving state to the driven state can be eliminated.

[0110] <Effects of this embodiment>

[0111] According to the control method of the electric vehicle of the present embodiment, the control method of the electric vehicle is as follows: using the first motor (rear drive motor 4r) and the second motor (front drive motor 4f) as driving sources, the first motor (rear drive motor 4r) is driven and controlled (switched) by sending a first torque command value (rear motor torque command value Tmr) to the first inverter (rear inverter 3r), and the second motor (front drive motor 4f) is driven and controlled (switched) by sending a second torque command value (front motor torque command value Tmf) to the second inverter (front inverter 3f), and based on the required driving force, the second inverter (front inverter 3f) switches between an on state in which the drive control (switched) of the second motor (front drive motor 4f) is performed and an off state in which the drive control (switched) is stopped. The control method of this electric vehicle is to calculate the torque change (to offset the torque step) generated by the second motor (front drive motor 4f) during switching control based on the number of revolutions of the second motor (front drive motor 4f), and based on the torque change, correct the first torque command value (rear motor torque command value Tmr).

[0112] The above method uses the first torque command value (rear motor torque command value Tmr) corrected by the torque variation (torque step) to offset the torque step in the overall drivetrain response (total torque T) during switching control of the second inverter (front inverter 3f). This allows control to be executed and stopped for driving the second motor (front drive motor 4f) without causing the driver to experience the uncomfortable torque shock associated with the torque step.

[0113] In this embodiment, the second motor (front drive motor 4f) is a winding-excited motor, and the second inverter (front inverter 3f) switches the drive control (switch control) to the on state when the second torque command value (front motor torque command value Tmf) is greater than the first threshold value (Tth1), and switches the drive control (switch control) to the off state when the second torque command value (front motor torque command value Tmf) is less than the second threshold value (Tth2). When the second torque command value (front motor torque command value Tmf) is greater than the first threshold value (Tth1) or the second torque command value (front motor torque command value Tmf) is less than the second threshold value (Tth2), the torque change (torque step) is calculated.

[0114] Therefore, the motor controller 2 does not need to confirm the switching of the second inverter (front inverter 3f) to the on state or the off state, and can calculate the torque change (torque step) at the moment when the second inverter (rear inverter 3r) performs switching control, and can reduce the error in the torque change caused by the offset at the above moment.

[0115] In this embodiment, when the second torque command value (front motor torque command value Tmf) is greater than the first threshold value (Tth1) or when the second torque command value (front motor torque command value Tmf) is less than the second threshold value (Tth2), the first torque command value (rear motor torque command value Tmr) is corrected based on the torque change.

[0116] Thus, the torque step can be reliably offset by the corrected first torque command value (rear motor torque command value Tmr) without changing the timing.

[0117] Furthermore, according to the control system of the electric vehicle of the present embodiment, a control method for the electric vehicle includes: a first motor (rear drive motor 4r) and a second motor (front drive motor 4f) serving as driving sources for the vehicle; a first inverter (rear inverter 3r) for driving and controlling (switching control) the first motor (rear drive motor 4r); a second inverter (front inverter 3f) for driving and controlling the second motor (front drive motor 4f); and a control unit (motor controller 2) for transmitting a first torque command value (rear motor torque command value Tmr) to the first inverter (rear inverter 3r) and a second torque command value (front motor torque command value Tmf) to the second inverter (front inverter 3f); and switching control for switching the second inverter (rear inverter 3r) between an on state in which drive control (switching control) of the second motor (rear drive motor 4r) is performed and an off state in which the drive control (switching control) is stopped, based on a required driving force. The control method of this electric vehicle is as follows: the control unit (motor controller 2) calculates the torque change (to offset the torque step) generated by the second motor (front drive motor 4f) during switching control based on the number of revolutions of the second motor (front drive motor 4f), and based on the torque change, corrects the first torque command value (rear motor torque command value Tmr).

[0118] With this configuration, the first torque command value (rear motor torque command value Tmr), corrected by the torque variation (torque step), can be used to offset the torque step that occurs in the overall drivetrain response (total torque T) during switching control of the second inverter (front inverter 3f). Consequently, control of driving the second motor (front drive motor 4f) and stopping this drive control can be executed without causing the driver the uncomfortable torque shock associated with the torque step.

[0119] While the embodiments of the present invention have been described above, the configurations described in the embodiments and modifications are merely examples of applications of the present invention and are not intended to limit the technical scope of the present invention.

[0120] For example, in this embodiment, the second inverter (front inverter 3f) that drives and controls the second motor (front drive motor 4f) is switched between an on state in which the drive control (switch control) is performed and an off state in which the drive control (switch control) is stopped. However, a structure in which the first inverter (rear inverter 3r) that drives and controls the first motor (rear drive motor 4r) is switched may also be employed.

[0121] In this case, during driving, the drive control (switch control) of the second inverter (front inverter 3f) is always in the on state, the torque change (torque step) generated in the first motor (rear drive motor 4r) due to the switching control is calculated, and the second torque command value (front motor torque command value Tmf) is corrected based on the torque change.

[0122] In addition, in each of the above-mentioned embodiments and modifications, "left" and "right" are used merely to designate directions for convenience of explanation and should not be considered to completely coincide with the left and right directions relative to the front of the vehicle body.

Claims

1. A control method for an electric vehicle, comprising: a first motor for driving a first drive wheel and a second motor for driving a second drive wheel different from the first drive wheel as driving sources for travel; performing mode switching control based on a driver's operation; the mode switching control switching between a first mode in which only the first motor is driven and a second mode in which both the first motor and the second motor are driven; driving and controlling the first motor by sending a first torque command value to a first inverter and driving and controlling the second motor by sending a second torque command value to a second inverter; and switching control of the second inverter between an on state in which drive control of the second motor is performed and an off state in which the drive control is stopped based on the mode switching control; the control method for an electric vehicle is characterized in that: A torque variation amount generated in the second motor during the switching control is calculated based on the number of revolutions of the second motor, and the first torque command value is corrected based on the torque variation amount.

2. The control method of the electric vehicle according to claim 1, wherein: The second motor is a winding excitation motor, The second inverter switches the drive control to the on state when the second torque command value is larger than the first threshold value, and switches the drive control to the off state when the second torque command value is smaller than the second threshold value. The torque variation is calculated when the second torque command value is larger than the first threshold value or when the second torque command value is smaller than the second threshold value.

3. The control method of the electric vehicle according to claim 2, wherein: When the second torque command value is larger than the first threshold value, or when the second torque command value is smaller than the second threshold value, the first torque command value is corrected based on the torque change amount.

4. A control system for an electric vehicle, comprising: a first motor for driving a first drive wheel and a second motor for driving a second drive wheel different from the first drive wheel, which serve as driving sources for travel; a first inverter, which drives and controls the first motor; a second inverter, which drives and controls the second motor; a motor controller that sends a first torque command value to the first inverter and sends a second torque command value to the second inverter; Based on the mode switching control, the second inverter switches between an on state for performing drive control of the second motor and an off state for stopping the drive control. The control system of the electric vehicle is characterized in that: The motor controller calculates a torque variation amount generated in the second motor during the switching control based on the number of revolutions of the second motor, and corrects the first torque command value based on the torque variation amount.

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