# US 8,541,972 B2 · Method for suppressing speed ripple by using torque compensator based on activation function

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- Number: US 8,541,972 B2
- Document ID: US8541972B2
- Status: Granted
- Kind: B2
- Application number: 13/315,245
- Filed: 2011-12-08
- Published: 2013-05-09
- Granted: 2013-09-24
- Earliest claimed: 2011-11-04
- Assignees: Kyungsung University Industry Cooperation Foundation
- Applicants: Dong Hee Lee; Jin Woo Ahn
- Inventors: Dong Hee Lee; Jin Woo Ahn
- Web page: https://patentgrep.com/patent/US8541972B2

## CPC

- H02P 21/05: specially adapted for damping motor oscillations, e.g. for reducing hunting
- H02P 21/18: Estimation of position or speed
- H02P 21/20: Estimation of torque
- H02P: CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS

## Abstract

Disclosed is a method for suppressing a speed ripple occurring during an operation of an AC motor by using a torque compensator based on an activation function. The method includes the steps of calculating a speed error ωerr based on a reference speed ωref and an actual speed ωact; calculating a controller output Trm by using the speed error ωerr as an input of a PI control and an operation of a compensated torque Tcom; and determining a torque variation based on the controller output Trm and a reference torque Tref and operating the torque variation in relation to an anti-windup gain Ka to use torque variation as an input of an integral (I) control. The method suppresses the speed ripple by compensating for the torque ripple through a controller which calculates the compensated torque by taking the signs of the speed error and the differential speed error into consideration.

## Claims

### Claim 1

A method for suppressing a speed ripple occurring during an operation of an AC motor by using a torque compensator based on an activation function, the method comprising:
(a) calculating a speed error ωerr based on a reference speed ωref and an actual speed ωact;
(b) calculating a controller output Trm by using the speed error ωerr as an input of a PI control and an operation of a compensated torque Tcom; and
(c) determining a torque variation based on the controller output Trm and a reference torque Tref and operating the torque variation in relation to an anti-windup gain Ka to use the torque variation as an input of an integral (I) control,
wherein in step (b), an output of the compensated torque Tcom is determined based on
f
⁡
(
ω
err
·
ⅆ
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err
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=
0
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(
when
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err
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<
0
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⁢
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and
⁢
f
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=
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>
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.

### Claim 2 (depends on 1)

The method of claim 1, wherein, in step (b), the compensated torque Tcom is determined based on
Tcom=f(χ)·Kc·ωerr, in which Kc is a compensator gain.

### Claim 3 (depends on 1)

The method of claim 1, wherein, in step (c), an output of the compensated torque is determined based on a sign of the speed error and a sign of a differential speed error.