Motor Control Torque Ripple Compensation via Advance Angle

Solution Overview

Problem

Conventional motor control systems face challenges in effectively compensating for torque ripple, especially in high-frequency ranges, due to insufficient responsivity of current controllers, which also increases sensitivity to sensor noise.

Innovation Solution

A motor control system that includes a torque ripple compensation calculation unit, which calculates a compensation value based on actual angular velocity and target current command values, and applies this compensation to the current command value to address response delays and improve responsivity, thereby reducing torque ripple and operating noise.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the responsivity of the current controller is increased to cover high frequency range for torque ripple compensation, then torque ripple compensation is improved, but sensitivity to sensor noise increases causing degradation of operating noise

Engineering Contradiction:

Improvetorque ripple compensationVSAvoidoperating noise

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The control system is segmented into two independent parts: a basic current controller for fundamental wave control and a torque ripple compensator for high-frequency torque ripple compensation. This segmentation allows each part to operate optimally without the other suffering from their respective drawbacks.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A torque ripple compensator is introduced as an intermediary component between the basic current controller and the inverter. This compensator generates compensation current values that are superimposed on the basic current command values, enabling torque ripple compensation without requiring the basic current controller to operate at high frequencies where noise sensitivity becomes problematic.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Speed

If the responsivity of the current controller is designed for practical fundamental wave frequency band, then the current controller responds adequately to fundamental wave, but torque ripple compensation is insufficient in high frequency range

Engineering Contradiction:

Improvecurrent controller responsivityVSAvoidtorque ripple compensation

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The control system is segmented into two independent parts: a basic current controller for fundamental wave control and a torque ripple compensator for high-frequency torque ripple compensation. This segmentation allows each part to operate optimally without the other suffering from their respective drawbacks.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The torque ripple compensator performs preliminary calculation of compensation current values based on predicted rotor position and stored torque ripple characteristics. This preliminary action allows the compensation to be applied in advance, ensuring effective torque ripple compensation without requiring the basic current controller to respond at high frequencies.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If feedback control is used to compensate torque ripple by adding current command value with opposite phase, then torque ripple compensation works in frequency range where current controller responds sufficiently, but compensation fails in high frequency range where current controller response is delayed

Engineering Contradiction:

Improvetorque ripple compensationVSAvoidresponse delay

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The torque ripple compensator performs preliminary calculation of compensation current values based on predicted rotor position and stored torque ripple characteristics. This preliminary action allows the compensation to be applied in advance, ensuring effective torque ripple compensation without requiring the basic current controller to respond at high frequencies.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

A torque ripple compensator is introduced as an intermediary component between the basic current controller and the inverter. This compensator generates compensation current values that are superimposed on the basic current command values, enabling torque ripple compensation without requiring the basic current controller to operate at high frequencies where noise sensitivity becomes problematic.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS11251731B2Motor control system and power steering system

Publication Date: 2022.02.15 NIDEC CORP(JP)

AI summary

A motor control system includes an inverter, and a control unit that feedback-controls the inverter. The control unit includes a voltage control unit that calculates a voltage command value indicating a voltage to be applied to the motor from the inverter based on a current deviation between a current command value and an actual current detection value, and a torque ripple compensation unit that adds a compensation value for compensating a torque ripple in the motor to a signal value on at least one of an upstream side and a downstream side in a signal flow passing through the voltage control unit. The torque ripple compensation unit calculates the compensation value based on an actual angular velocity at which the motor rotates and the target current command value, and based on advance angle control for compensating a response delay of the motor control system with respect to the compensation value.