Control method and control device for electric vehicle

Patent metadata

Field	Value
Publication number	US-10972020-B2
Application number	US-201716618002-A
Country	US
Kind code	B2
Filing date	Jun 1, 2017
Priority date	Jun 1, 2017
Publication date	Apr 6, 2021
Grant date	Apr 6, 2021

Abstract

The control method for an electric vehicle sets a motor torque command value based on vehicle information and controls torque of a first motor connected to a first drive wheel which is one of a front drive wheel and a rear drive wheel. The control method for an electric vehicle calculates a first torque command value by a feedforward computation based on the motor torque command value, detects a rotation angular velocity of the first motor, and estimates a rotation angular velocity of the first motor based on the first torque command value by using a vehicle model Gp(s) that simulates a transfer characteristic from a torque input to the first drive wheel to a rotation angular velocity of the first motor.

First claim

The invention claimed is:

1. A control method for an electric vehicle, the control method configured to set a motor torque command value based on vehicle information and to control torque of a first motor connected to a first drive wheel, the first drive wheel being one of a front drive wheel and a rear drive wheel, the control method comprising:
calculating a first torque command value by a feedforward computation based on the motor torque command value;
detecting a rotation angular velocity of the first motor;
estimating a rotation angular velocity of the first motor based on the first torque command value by using a vehicle model Gp(s) that simulates a transfer characteristic from a torque input to the first drive wheel to a rotation angular velocity of the first motor;
calculating a second torque command value from a deviation between a detected value and an estimated value of the rotation angular velocity of the first motor by using a filter H(s)/Gp(s) composed of an inverse characteristic of the vehicle model Gp(s) and a band-pass filter H(s) with a center frequency close to a torsional vibration frequency of the vehicle;
controlling the torque of the first motor according to a first final torque command value obtained by adding the first torque command value and the second torque command value together; and
correcting, when a braking/driving torque for a second drive wheel being the drive wheel other than the first drive wheel is input, the estimated value of the rotation angular velocity of the first motor based on the braking/driving torque.

2. The control method for an electric vehicle according to claim 1 , wherein:
when the braking/driving torque for the second drive wheel being the drive wheel other than the first drive wheel is input, a motor rotation angular velocity correction amount is calculated by using a transfer function of the rotation angular velocity of the first motor for the second drive wheel, the transfer function modeled in advance and using the braking/driving torque as an input; and
the estimated value of the rotation angular velocity of the first motor is corrected based on the motor rotation angular velocity correction amount.

3. The control method for an electric vehicle according to claim 1 ,
wherein, when the electric vehicle includes a second motor as a power source for the second drive wheel, the vehicle model Gp(s) is a 4WD vehicle model that simulates a transfer characteristic from torque inputs to the first drive wheel and the second drive wheel to motor rotation angular velocities of the first motor and the second motor, and
wherein the control method further comprises:
calculating a third torque command value by a feedforward computation based on the motor torque command value;
detecting a rotation angular velocity of the second motor;
calculating a fourth torque command value from a deviation between a detected value and an estimated value of the rotation angular velocity of the second motor by using a filter H(s)/Gpr(s) composed of an inverse characteristic of a vehicle model Gpr(s) that simulates a transfer characteristic from a torque input to the second drive wheel to a motor rotation angular velocity of the second motor, and a band-pass filter H(s) with a center frequency close to a torsional vibration frequency of the vehicle;
controlling torque of the second motor according to a second final torque command value obtained by adding the third torque command value and the fourth torque command value together; and
calculating a rotation angular velocity estimated value of the first motor and a rotation angular velocity estimated value of the second motor by using the first torque command value and the third torque command value as inputs and using the 4WD vehicle model, and correcting the rotation angular velocity estimated value of the first motor based on the third torque command value.

4. The control method for an electric vehicle according to claim 1 ,
wherein, when the electric vehicle includes a second motor as a power source for the second drive wheel, the vehicle model Gp(s) is a 4WD vehicle model that simulates a transfer characteristic from torque inputs to the first drive wheel and the second drive wheel to motor rotation angular velocities of the first motor and the second motor,
wherein the control method further comprises:
calculating a third torque command value by a feedforward computation based on the motor torque command value;
detecting a rotation angular velocity of the second motor;
calculating a fourth torque command value from a deviation between a detected value and an estimated value of the rotation angular velocity of the second motor; and
controlling torque of the second motor according to a second final torque command value obtained by adding the third torque command value and the fourth torque command value together, and

wherein the feedforward computation comprises:
dividing the motor torque command value into a first target torque command value for the first drive wheel and a second target torque command value for the second drive wheel;
calculating a rotation angular velocity estimated value of the first motor, a rotation angular velocity estimated value of the second motor, a drive shaft torsional angular velocity estimated value of the first drive wheel, and a drive shaft torsional angular velocity estimated value of the second drive wheel by using the first target torque command value and the second target torque command value as inputs and using the 4WD vehicle model, and correcting the rotation angular velocity estimated value of the first motor based on the second target torque command value;
calculating the first torque command value by subtracting from the first target torque command value a value obtained by multiplying the drive shaft torsional angular velocity estimated value of the first drive wheel by a predetermined gain; and
calculating the third torque command value by subtracting from the second target torque command value a value obtained by multiplying the drive shaft torsional angular velocity estimated value of the second drive wheel by a predetermined gain.

5. The control method for an electric vehicle according to claim 3 ,
wherein, when a drive shaft torsional vibration frequency of the first drive wheel and a drive shaft torsional vibration frequency of the second drive wheel differ from each other, a model response used in the feedforward computation that calculates the first torque command value and a model response used in the feedforward computation that calculates the third torque command value are matched to each other.

6. The control method for an electric vehicle according to claim 5 , wherein:
when the drive shaft torsional vibration frequency of the second drive wheel is smaller than the drive shaft torsional vibration frequency of the first drive wheel, the model response used in the feedforward computation that calculates the first torque command value is matched to the model response used in the feedforward computation that calculates the third torque command value; and
when the drive shaft torsional vibration frequency of the first drive wheel is smaller than the drive shaft torsional vibration frequency of the second drive wheel, the model response used in the feedforward computation that calculates the third torque command value is matched to the model response used in the feedforward computation that calculates the first torque command value.

7. The control method for an electric vehicle according to claim 5 , further comprising:
calculating the first torque command value by the feedforward computation using a filter having a transfer characteristic that damps the drive shaft torsional vibration frequency of the first drive w

Assignees

• Nissan Motor

Inventors

• Sawada Akira
• Itou Ken
• Fujiwara Kengo

Classifications

• Y02T10/72

  Electric energy management in electromobility · CPC title

• Y02T10/64

  Electric machine technologies in electromobility · CPC title

• B60L15/20 Primary

  for control of the vehicle or its driving motor to achieve a desired performance, e.g. speed, torque, programmed variation of speed · CPC title

• H02P21/18

  Estimation of position or speed · CPC title

• H02P5/46

  for speed regulation of two or more dynamo-electric motors in relation to one another · CPC title