Control device of electric vehicle

Abstract

To provide a control device of an electric vehicle in which a target rotation number of a motor responds to accelerator operation to control torque of the motor to restrict difference of slip velocity of each wheel.SOLUTION: A control device of an electric vehicle comprises: a motor which is arranged in a drive wheel of a vehicle; a rotation number detection part which detects rotation number of the motor; and a controller which controls torque of the motor. The controller controls torque of the motor through feed back control based on difference between the rotation number of the motor and target rotation number of the motor in which acceleration correction value relative to torque correction quantity that is difference between torque command value of the motor determined by accelerator operation and the torque of the motor are, when the target rotation number of the motor is calculated, added thereto.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present disclosure relates to a control device for an electric vehicle.

Background Art

[0002] Patent Document 1 discloses a technique in which an MG-ECU controls motor torque (MG torque) by feedback control according to the difference between the rotational speed of a motor (MG speed) and the target rotational speed of a drive wheel.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] For example, when restricting the MG torque so that the MG speed does not exceed the target MG speed, even if the torque command of the EV-ECU reflecting the accelerator operation changes in a region larger than the MG torque command, the MG speed and the MG torque do not change. Therefore, it is impossible to realize a function of changing the slip amount by the driver's accelerator operation and controlling the vehicle attitude. In order to change the MG speed and the MG torque, it is necessary to change the target MG speed, and thus there is room for improvement in the technique disclosed in Patent Document 1.

[0005] The present disclosure has been made in view of the above, and an object thereof is to provide a control device for an electric vehicle capable of controlling the torque of a motor so that the target rotational speed of the motor responds to an accelerator operation and restricts the difference in slip speed between each wheel.

Means for Solving the Problems

[0006] The control device for an electric vehicle according to the present disclosure includes a motor provided on a drive wheel of the vehicle, a rotation speed detection unit that detects the rotation speed of the motor, and a control unit that controls the torque of the motor. The control unit controls the torque of the motor by feedback control according to the difference between the rotation speed of the motor and the target rotation speed of the motor, and when calculating the target rotation speed of the motor, an acceleration correction value proportional to a torque correction amount, which is the difference between the torque command value of the motor determined by an accelerator operation and the torque of the motor, is added.

Advantages of the Invention

[0007] In the present disclosure, when calculating the target rotation speed of the motor, by taking into account the acceleration correction value, the target rotation speed of the motor responds to the accelerator operation, and the torque of the motor can be controlled so as to limit the difference in slip speed between each wheel.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0009] A control device for an electric vehicle according to an embodiment of the present disclosure will be described with reference to the drawings. Note that the components in the following embodiments include those that can be replaced and are easy for those skilled in the art, or those that are substantially the same.

[0010] (Control Device for Electric Vehicle) The configuration of the control device for an electric vehicle according to the embodiment will be described with reference to FIG. 1. The control device for an electric vehicle according to the embodiment is applied to an electric vehicle without a mechanical differential, in which each wheel can be independently driven. Examples of such electric vehicles include hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), fuel cell electric vehicles (FCEVs), battery electric vehicles (BEVs), and the like.

[0011] As shown in FIG. 1, for example, an electric vehicle to which the control device for an electric vehicle according to the embodiment is applied includes a motor (MG: Motor Generator) 11, a rotation speed detection unit 12, and a control unit 13. In the same figure, only the configurations necessary to implement the control device for an electric vehicle according to the embodiment are extracted and illustrated among the configurations of the electric vehicle 1, and other configurations are omitted from the illustration.

[0012] The motor 11 independently drives each wheel of the electric vehicle 1 based on the control of the control unit 13. This motor 11 is provided, for example, on each wheel of the electric vehicle 1.

[0013] The rotation speed detection unit 12 detects the rotation speed of the motor 11. This rotation speed detection unit 12 is provided, for example, on each motor 11. Further, the rotation speed detection unit 12 is composed of, for example, a phase sensor such as a resolver, a rotation speed sensor, and the like. Also, the rotation speed detection unit 12 outputs the detected rotation speed of the motor 11 to the control unit 13.

[0014] The control unit 13 controls the torque of the motor 11. This control unit 13 is an electronic control unit (ECU) mainly composed of a microcomputer including, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), etc. Specifically, the control unit 13 is composed of an EV-ECU and an MG-ECU.

[0015] The control unit 13 controls the torque of the motor 11 (hereinafter referred to as "MG torque") by feedback control according to the difference between the rotational speed of the motor 11 (hereinafter referred to as "MG speed") and the target rotational speed of the motor 11 (hereinafter referred to as "target MG speed"). This feedback control is also referred to as "speed FB control" in this embodiment.

[0016] Also, when calculating the target MG speed, the control unit 13 adds an acceleration correction value proportional to the torque correction amount, which is the difference between the torque command value of the motor 11 (hereinafter referred to as "MG torque command") determined by the accelerator operation and the MG torque. Hereinafter, the details of the processes executed by the EV-ECU and the MG-ECU constituting the control unit 13 will be described.

[0017] FIG. 2 shows the flow when the EV-ECU calculates the target MG speed for each wheel. First, the EV-ECU converts the MG speed of each wheel (FR, FL, RR, RL) detected by the rotational speed detection unit 12 into the MG speed at the center of gravity position (hereinafter referred to as "center of gravity speed"). Subsequently, the EV-ECU selects the minimum value among the center of gravity speeds of each wheel, and converts the selected minimum value of the center of gravity speed into the MG speed at each wheel position. This MG speed is defined as the "reference MG speed" in this embodiment.

[0018] Further, the EV-ECU calculates the acceleration correction value (slip acceleration) of each wheel by dividing the MG torque correction amount of each wheel (FR, FL, RR, RL) by the inertia of each wheel. That is, "acceleration correction value = MG torque correction amount / inertia". Subsequently, the EV-ECU selects the minimum value among the calculated acceleration correction values of each wheel. Then, the EV-ECU calculates the target MG speed of each wheel by adding the target slip speed difference and the minimum value of the acceleration correction value of each wheel to the reference MG speed of each wheel (see parts A and B of FIG. 2).

[0019] FIG. 3 shows the flow when the MG-ECU performs speed FB control. The MG-ECU acquires the MG speed of each wheel from the rotation speed detection unit 12 and controls the MG torque. Also, as shown in the figure, the MG-ECU controls the MG torque so that the MG speed of each wheel does not exceed the target MG speed. Further, the MG-ECU determines the start and end of the speed FB control.

[0020] The MG-ECU can arbitrarily control the slip speed difference (= target MG speed - MG speed) of each wheel by setting the target MG speed of each wheel. Note that the upper limit (upper limit torque) of the MG torque is the torque command of the EV-ECU. Also, the target MG speed of each wheel does not need to be changed at a high frequency.

[0021] Here, (a) of FIG. 4 shows the transition of the MG torque and MG speed during the conventional speed FB control. In the conventional speed FB control, even if the EV-ECU torque command reflecting the accelerator operation changes in a region where it is larger than the MG torque command, the MG speed and MG torque do not change. Therefore, in the conventional speed FB control, the MG speed cannot be controlled by the accelerator operation.

[0022] On the other hand, (b) of FIG. 4 shows the transition of the MG torque and MG speed during the speed FB control by the control device of the electric vehicle according to the embodiment. In the speed FB control according to the embodiment, the slip speed difference is controlled with high responsiveness by adding the acceleration correction value proportional to the MG torque correction amount to the target MG speed.

[0023] That is, in the speed FB control according to the embodiment, when the speed FB control is inoperative, as shown in FIG. 2, the torque correction amount generates an acceleration correction value (slip acceleration). Also, the torque correction amount changes according to the torque command of the EV-ECU that reflects the accelerator operation. Therefore, as shown in the figure, by converting the torque correction amount into an acceleration correction value and adding it to the target MG speed (see part B of the figure), it becomes possible to control the slip acceleration and the MG speed by the accelerator operation.

[0024] Also, in the speed FB control according to the embodiment, the target MG speed corresponding to the acceleration correction value according to the torque correction amount is added. Also, in the speed FB control according to the embodiment, the target MG speed increases while being integrated by the amount by which the MG speed rises following the addition of the target MG speed.

[0025] Note that in the speed FB control according to the embodiment, as shown in FIG. 2, the target MG speed is based on the minimum value of each wheel, and the above torque correction amount selects the minimum value of each wheel, making it possible for the MG speed of each wheel to follow the target MG speed. As a result, it is possible to achieve both the function of making the MG speed of each wheel follow the target MG speed and the function of limiting the slip speed difference between each wheel. Also, since the motor 11 without a torque correction amount is at the upper limit torque, even if the target MG speed is increased, the MG speed cannot follow.

[0026] (Control Method of Electric Vehicle) The flow of the control method of the electric vehicle executed by the control device of the electric vehicle according to the embodiment will be described with reference to FIG. 5. In the figure, the arrows between the steps indicate the input / output of the values calculated (or detected) in each step.

[0027] First, the control unit 13 detects the accelerator opening (step S1). Subsequently, the control unit 13 calculates the total driving force required value (step S2). Subsequently, the control unit 13 performs the driving force distribution for each wheel (step S3). Subsequently, the control unit 13 calculates the torque correction amount for each wheel (step S4).

[0028] Subsequently, the control unit 13 calculates the acceleration correction value (step S5). In step S5, the control unit 13 divides the MG torque correction amount for each wheel by the inertia of each wheel to calculate the acceleration correction value (slip acceleration) for each wheel, and selects the minimum value among them to calculate the acceleration correction value.

[0029] Subsequently, the control unit 13 calculates the reference MG speed of the center of gravity position (step S6). In step S5, the control unit 13 converts the MG speed of each wheel to the MG speed of the center of gravity position, and selects the minimum value among them to calculate the reference MG speed of the center of gravity position.

[0030] Subsequently, the control unit 13 calculates the reference MG speed for each wheel (step S7). In step S7, the control unit 13 calculates the reference MG speed for each wheel by converting the reference MG speed of the center of gravity position to the MG speed of each wheel position.

[0031] Subsequently, the control unit 13 calculates the target MG speed for each wheel (step S8). In step S8, the control unit 13 calculates the target MG speed for each wheel by adding the target slip speed difference and the acceleration correction value to the reference MG speed for each wheel.

[0032] Subsequently, the control unit 13 determines whether to start / end the speed FB control (step S9). In step S9, if it is determined that the speed FB control has ended, the control unit 13 drives the motor 11 of each wheel based on the EV-ECU torque command calculated in step S3. On the other hand, in step S9, if it is determined that the speed FB control is to start, the control unit 13 drives the motor 11 of each wheel based on the torque command resulting from the speed FB control (step S10). Subsequently, the control unit 13 detects the MG speed of each wheel through the rotation speed detection unit 12 (step S11), and returns to the process of step S2.

[0033] In the control device for an electric vehicle according to the embodiment described above, when calculating the target rotation speed of the motor 11, by taking into account the acceleration correction value, the target rotation speed of the motor 11 responds to the accelerator operation, and the torque of the motor 11 can be controlled so as to limit the difference in slip speed between each wheel.

[0034] Also, the speed FB control executed by the control device for an electric vehicle according to the embodiment can increase the FB gain and achieve higher responsiveness compared to the conventional speed FB control because it has a FB control loop with less wasted time.

[0035] Also, for example, when the slip ratios of the wheels of an electric vehicle are uneven, the change in yaw moment is large, and it is difficult to estimate the total change for the four wheels. On the other hand, in the control device for an electric vehicle according to the embodiment, by suppressing the difference in slip ratio (slip speed difference) between each wheel while responding to the accelerator operation, the change in slip ratio and the change in yaw moment can be stabilized, so the change in vehicle attitude can be estimated.

[0036] Further effects and modification examples can be easily derived by those skilled in the art. Therefore, the broader aspects of the present invention are not limited to the specific details and representative embodiments presented and described as above. Accordingly, various changes can be made without departing from the spirit or scope of the general inventive concept defined by the appended claims and their equivalents.

Explanation of Reference Numerals

[0037] 1 Electric vehicle 11 Motor 12 Rotation speed detection unit 13 Control unit

Claims

[Claim 1] A motor provided on a drive wheel of the vehicle; A rotation speed detection unit that detects the rotation speed of the motor; A control unit for controlling the torque of the motor; Equipped with The control unit: controlling a torque of the motor by feedback control in accordance with a difference between a rotation speed of the motor and a target rotation speed of the motor; When calculating the target rotation speed of the motor, an acceleration correction value proportional to a torque correction amount which is a difference between a torque command value of the motor determined by an accelerator operation and the torque of the motor is added. A control device for an electric vehicle.

Images