# US 8,786,244 B2 · System and method for current estimation for operation of electric motors

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- Number: US 8,786,244 B2
- Document ID: US8786244B2
- Status: Granted
- Kind: B2
- Application number: 13/241,103
- Filed: 2011-09-22
- Published: 2013-03-28
- Granted: 2014-07-22
- Earliest claimed: 2011-09-22
- Assignees: GM Global Technology Operations LLC
- Applicants: Jihoon Jang
- Inventors: Jihoon Jang
- Web page: https://patentgrep.com/patent/US8786244B2

## CPC

- H02P 23/14: Estimation or adaptation of motor parameters, e.g. rotor time constant, flux, speed, current or voltage
- H02P 21/22: Current control, e.g. using a current control loop
- Y02T 10/72: Electric energy management in electromobility
- H02P: CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION

## Abstract

Methodologies and systems are provided for current estimation in electric motor. The system comprises an electric motor having sensors for sensing at least motor current, motor temperature and motor speed. A vehicle controller is coupled to the sensors and includes a closed-loop current control system for the electric motor having a current compensation circuit for providing a current compensation signal that is used to adjust a current command for the electric motor. The current compensation circuit includes a short-circuit current calculator for providing a short-circuit current value based upon the motor temperature and the motor speed, a compensation gain calculator for providing a gain compensation value based upon the motor speed, and circuitry for combining the motor current, the short-circuit current value and the gain compensation value to provide the current compensation signal. Methods for current estimation in electric motor are also provided.

## Claims

### Claim 1

A method, comprising:
providing a current compensation signal for a closed loop current control system for a motor of a vehicle based upon measured currents in the motor and a short-circuit current value from a two dimensional lookup table using a motor speed and a motor temperature; and
adjusting a current command signal using the current compensation signal to control current provided to the motor of the vehicle.

### Claim 2 (depends on 1)

The method of claim 1, determining a short-circuit current value further comprises providing a short-circuit id value from a second two dimensional lookup table.

### Claim 3 (depends on 1)

The method of claim 1, wherein providing the current compensation signal further comprises determining a compensation gain value using the motor temperature.

### Claim 4 (depends on 2)

The method of claim 2, wherein providing the current compensation signal further comprises determining the current compensation signal from the short-circuit current value and the compensation gain value.

### Claim 5 (depends on 3)

The method of claim 3, wherein the compensation gain value is based upon the number of magnet pole pairs of the motor.

### Claim 6

A method, comprising:
sensing an electric motor during operation to provide measured motor current, motor temperature and motor speed;
providing a current compensation signal based upon the measured motor current and a short-circuit current value from a two dimensional lookup table using a motor temperature and a motor speed;
adjusting a current command signal to provide an adjusted current command signal;
processing the adjusted current command signal in a closed-loop current control system to control the operation of the electric motor.

### Claim 7 (depends on 6)

The method of claim 6, wherein determining a short-circuit current value further comprises providing a short-circuit id value from a second two dimensional lookup table.

### Claim 8 (depends on 6)

The method of claim 6, determining a short-circuit current value further comprises computing a short-circuit id value from the equation:
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### Claim 9 (depends on 6)

The method of claim 6, wherein determining a short-circuit current value further comprises computing a short-circuit iq value from the equation:
I
q
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=
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### Claim 10 (depends on 6)

The method of claim 6, wherein providing the current compensation signal further comprises determining a compensation gain value using the motor temperature.

### Claim 11 (depends on 10)

The method of claim 10, wherein providing the current compensation signal further comprises determining the current compensation signal from the short-circuit current value and the compensation gain value.

### Claim 12 (depends on 10)

The method of claim 10, wherein the compensation gain value is based upon the number of magnet pole pairs of the motor.

### Claim 13

A vehicle, comprising:
an electric motor;
sensors coupled to the electric motor for sensing at least motor current, motor temperature and motor speed;
a vehicle controller coupled to the sensors and including a closed-loop current control system for the electric motor;
a current compensation circuit within the closed-loop current control system for providing a current compensation signal to adjust a current command for the electric motor, the current compensation circuit comprising:
a short-circuit current calculator for providing a short-circuit current value based upon the motor temperature and the motor speed;
a compensation gain calculator for providing a gain compensation value based upon the motor speed; and
circuitry for combining the motor current, the short-circuit current value and the gain compensation value to provide the current compensation signal.

### Claim 14 (depends on 13)

The vehicle of claim 13, wherein the short-circuit current calculator includes a two-dimensional lookup table to provide an iq component of the short-circuit current value.

### Claim 15 (depends on 14)

The vehicle of claim 14, wherein the two-dimensional lookup table to provide an iq component of the short-circuit current value includes iq values computed by the equation:
I
q
,
SC
=
-
ω
r
⁢
R
s
⁢
λ
PM
R
s
2
+
ω
r
2
⁢
L
d
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L
q
.

### Claim 16 (depends on 13)

The vehicle of claim 13, wherein the short-circuit current calculator includes a two-dimensional lookup table to provide an id component of the short-circuit current value.

### Claim 17 (depends on 16)

The vehicle of claim 16, wherein the two-dimensional lookup table to provide an id component of the short-circuit current value includes id values computed by the equation:
I
d
,
SC
=
-
ω
r
2
⁢
L
q
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λ
PM
R
s
2
+
ω
r
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L
q
.

### Claim 18 (depends on 13)

The vehicle of claim 13, wherein the closed-loop current control system controls an inverter coupled to a battery and the electric motor.

### Claim 19 (depends on 13)

The vehicle of claim 13, wherein the compensation gain value is based upon the number of magnet pole pairs of the motor.