Motor Current Control with Delay Feedback for Back-EMF Disturbance

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Solution Overview

Problem

Feedforward-type back electromotive voltage compensation lacks robustness against disturbance factors such as variation in motor characteristics due to individual differences and changes caused by temperature or aging.

Innovation Solution

A motor control device with a current command value calculation unit, current value detection unit, current control unit, and voltage disturbance control unit, which includes a delay element and driving circuit to enhance robustness against disturbances.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If feedforward-type back electromotive voltage compensation is used, then the control response is improved, but the robustness against disturbance factors deteriorates

Engineering Contradiction:

Improvecontrol response speedVSAvoidrobustness against disturbance factors

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The patent introduces a feedback mechanism by detecting the actual current flowing through the motor and comparing it with the current command value. The current control unit uses this feedback to generate a voltage command that compensates for deviations, thereby improving robustness against disturbance factors while maintaining control response speed.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent introduces a current control unit as an intermediary between the current command value calculation unit and the driving circuit. This intermediary unit processes the current deviation and generates appropriate voltage commands, enabling better handling of disturbance factors without sacrificing control responsiveness.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Device complexity

If feedforward-type back electromotive voltage compensation is used, then the control simplicity is maintained, but the adaptability to motor characteristic variations deteriorates

Engineering Contradiction:

Improvecontrol structure simplicityVSAvoidadaptability to motor characteristic variations

Core Design Contradiction:

Device complexityVSAdaptability or versatility

Solution Approach 1:

The feedback mechanism allows the system to automatically adapt to motor characteristic variations by continuously monitoring current deviations and adjusting voltage commands accordingly, without requiring complex adaptive algorithms or multiple sensors.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The current control unit performs self-adjustment by using the detected current deviation to generate appropriate voltage commands, enabling the system to adapt to motor characteristic variations autonomously without external intervention or complex control logic.

Inventive Principle:

Principle #25Self-service

Data Source

PatentUS12454308B2Motor control device, electric actuator product, and electric power steering device

Publication Date: 2025.10.28 NSK LTD

AI summary

A motor control device including: a current command value calculation unit configured to calculate a current command value for driving a motor; a current value detection unit configured to detect current flowing through the motor; a current control unit configured to output a first voltage command value according to deviation between a current detected value, the current detected value being a detected value of current detected by the current value detection unit, and the current command value; a voltage disturbance control unit configured to calculate a second voltage command value by adding output from a delay element to the first voltage command value and also input the second voltage command value to the delay element; and a driving circuit configured to drive the motor, based on the second voltage command value.