Detection of offset errors in phase current measurement for motor control system

Patent metadata

Field	Value
Publication number	US-9966890-B2
Application number	US-201615379990-A
Country	US
Kind code	B2
Filing date	Dec 15, 2016
Priority date	Feb 16, 2016
Publication date	May 8, 2018
Grant date	May 8, 2018

Abstract

A system for detecting offset error in a power steering system is provided. The system includes a programmable high pass filter module configured to filter a final voltage command and generate a filtered final voltage command. The filtered final voltage command includes the sinusoidal component, a gain and phase compensation module configured to perform a gain compensation and a phase compensation on the filtered final voltage command to generate a compensated final voltage command. An error detection module is configured to determine an offset of the compensated final voltage command in a stator reference frame.

First claim

What is claimed is:

1. A system for detecting current measurement offset error in a motor control system comprising:
a control module that generates a final voltage command for a motor in response to an operator command;
a transformation module that converts the final voltage command from a synchronous reference frame into a stator reference frame, the transformation module transforms the final voltage command using an inverse park transform to transform the final voltage command to the stator reference frame;
a programmable low pass filter module that filters the transformed final voltage command and generate a filtered final voltage command that includes a constant component corresponding to the current measurement offset error; and
an error detection module that determines the current measurement offset error based on the filtered final voltage command in the stator reference frame, the final voltage command causes the motor to generate a corresponding amount of torque.

2. The system of claim 1 , the programmable low pass filter module including a transfer function based on a synchronous motor frequency and a calibratable constant.

3. The system of claim 1 , wherein the transformation module transforms a sinusoidal component corresponding to the current measurement offset error in the final voltage command into the constant component.

4. The system of claim 1 , wherein the programmable low pass filter module uses a first order filtering that utilizes a transfer function of

L
⁡

(
s
)

=

k
⁢

ω
~

e

s
+

k
⁢

ω
~

e

,

where k is a constant value and ω e is a synchronous frequency of a motor associated with the motor control.

5. The system of claim 1 , wherein the low pass filter module performs the low pass filtering in a discrete domain.

6. The system of claim 5 , wherein the discrete domain used is according to:

s
=

2

T
s

⁢

1
-

z

-
1

1
+

z

-
1

,

where T s is a sampling time.

7. The system of claim 1 , the current measurement offset error is further determined based on the final voltage command in a rotor reference frame.

8. A method for detecting current measurement offset error in a motor control system comprising:
receiving an input command to generate a torque using a motor controlled by the motor control system;
determining a voltage difference of a reference voltage command and a final voltage command in a rotor reference frame, the voltage difference includes a constant component and a sinusoidal component;
transforming the voltage difference from a rotor reference frame to a transformed voltage difference in a stator reference frame using an inverse park transform;
filtering the transformed voltage difference to generate a filtered voltage difference that includes the constant component; and
determining a current measurement offset error based on the filtered voltage difference in the stator reference frame, the final voltage command causing the motor to generate the torque.

9. The method of claim 8 , wherein the filtering is based on a transfer function that is based on a synchronous motor frequency of a motor of the motor control and a calibratable constant.

10. The method of claim 8 , wherein the transformation of the voltage difference from the rotor reference frame to the stator reference frame transforms the sinusoidal component corresponding to the current measurement offset error in the final voltage command into a constant component in the transformed voltage difference.

11. The method of claim 8 , wherein the filtering includes first order low pass filtering using a transfer function of:

L
⁡

(
s
)

=

k
⁢

ω
~

e

s
+

k
⁢

ω
~

e

,

where k is a constant value and ω e is a synchronous frequency of a motor of the motor control.

12. The method of claim 8 , wherein the filtering is low pass filtering performed in a discrete domain.

13. The method of claim 8 , wherein the transformed voltage offset is based on the difference of a feedforward voltage command and the final voltage command in a rotor reference frame, and the current measurement offset is determined at least in part on the transformed voltage offset.

14. The method of claim 13 , wherein an error flag signal is generated based on a magnitude of the current measurement offset error.

15. A system for detecting current measurement offset error in a motor control system comprising:
a voltage difference calculation module that determines a voltage difference of a reference voltage command and a final voltage command in a rotor reference frame, the voltage difference includes a first constant component and a first sinusoidal component, the final voltage command generated in response to an input command for generating torque using a motor controlled by the motor

Assignees

• Steering Solutions Ip Holding

Inventors

• Pramod Prerit
• Ballal Siddharth
• Kleinau Julie A

Classifications

• H02P27/08

  with pulse width modulation · CPC title

• H02P6/28

  Arrangements for controlling current (H02P6/10 takes precedence) · CPC title

• H02P6/10

  Arrangements for controlling torque ripple, e.g. providing reduced torque ripple · CPC title

• H02P21/22 Primary

  Current control, e.g. using a current control loop · CPC title

• G01R31/34

  Testing dynamo-electric machines · CPC title