Motor Control Device with Variable Gain and Frequency Adaptation
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Solution Overview
Problem
Conventional motor control devices face challenges in stabilizing and optimizing rotation speed control across a wide range due to varying response characteristics of DC motors, particularly brushless motors, as the proportional gain and integral corner frequency are fixed, leading to instability when the motor operates at speeds different from the target speed.
Innovation Solution
A motor control device with a target speed generation unit, speed detection unit, error amplification unit, and gain/corner frequency control unit that adjusts the proportional gain and integral corner frequency based on the current speed, amplifying speed errors with a variable gain and shifting the integral corner frequency to a lower frequency as the speed increases, ensuring stable and optimal rotation control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If fixed feedback gain is used for rotation speed control, then the control system is simple, but it is difficult to stably control rotation speed in a wide range due to significant changes in response characteristics depending on rotation speed
Solution Approach 1:
The feedback gain is made dynamic by making it variable according to the rotation speed. The gain switching unit switches between multiple feedback gains (first feedback gain for low speed, second feedback gain for high speed) based on the detected rotation speed, allowing the control system to adapt to changing response characteristics while maintaining stability across a wide speed range.
2Speed
If proportional gain is variable in accordance with target rotation speed, then response characteristics are optimized for target speed, but rotation becomes instable when motor is not rotated at speed around target rotation speed
Solution Approach 1:
The feedback gain is dynamically adjusted based on the detected rotation speed rather than target speed. The gain switching unit continuously monitors the actual rotation speed and switches between feedback gains accordingly, ensuring stability is maintained regardless of whether the motor is operating near the target speed or not.
Solution Approach 2:
The system uses feedback from the rotation speed detection unit to determine which feedback gain to apply. The detected rotation speed is fed back to the gain switching unit, which selects the appropriate feedback gain based on the actual operating conditions, creating a closed-loop control that maintains stability.
3Stability of the object's composition
If gain is determined considering only rotation fluctuation, then rotation stability is improved, but it is difficult to optimize response characteristics and stability simultaneously
Solution Approach 1:
The feedback gain is made dynamic and variable according to the rotation speed regime. By switching between different feedback gains based on the detected speed, the system simultaneously optimizes both response characteristics (through appropriate gain selection for different speed ranges) and stability (through continuous adaptation to actual operating conditions).
Data Source
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AI summary
A motor control device (1) controls a speed of a motor (3). The motor control device (1) includes: a target speed generating unit (11) that generates a target speed (TgtSp); a speed detecting unit (14) that detects a current speed of the motor (3); a speed comparing unit (12) that compares the target speed (TgtSp) with the current speed to calculate a speed error; an error amplifying unit (13) that amplifies the speed error and outputs a control value; and a motor driving unit that drives the motor (3) in accordance with the control value. The error amplifying unit (13) has proportional integral characteristics by which the speed error is amplified with a proportional gain and integration is performed in a lower frequency range than an integral corner frequency, increases the proportional gain as the current speed is higher, and shifts the integral corner frequency to a lower frequency as the current speed is higher.