Motor Control Device Offset Correction via Q-Axis Amplitude
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Solution Overview
Problem
Conventional motor control devices face challenges in accurately determining the offset value due to noise from surrounding electrical equipment and temperature variations, leading to motor noise and vibration.
Innovation Solution
A motor control device that includes multi-phase coils, current sensors, and a controller which adjusts the origin learning value based on the amplitude of the q-axis current, using a fast Fourier transform to correct the offset value when the amplitude switches from a decreasing to an increasing tendency, thereby reducing motor noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the offset value is determined by storing the current sensor signal when the current is 0 A, then the offset correction is simplified, but the measurement precision deteriorates due to noise from surrounding electrical equipment and temperature variations
Solution Approach 1:
The patent applies feedback by detecting the q-axis current amplitude and using it to iteratively adjust the origin learning value. The controller continuously monitors the amplitude and refines the offset correction until the amplitude reaches a minimum, ensuring high precision offset value determination despite noise and temperature variations.
Solution Approach 2:
The patent performs preliminary action by conducting offset correction during periods when the motor is not operating or under controlled conditions. The controller detects the q-axis current amplitude and adjusts the origin learning value before normal operation begins, eliminating the need for complex real-time corrections during motor operation.
2Measurement precision
If the origin learning value is changed by a predetermined value to correct the offset, then the measurement precision improves, but the loss of time increases due to iterative amplitude detection
Solution Approach 1:
The patent applies partial action by making incremental adjustments to the origin learning value rather than attempting to determine the complete correction amount in a single step. The controller adjusts the origin learning value by a predetermined amount, detects the amplitude, and repeats the process only until the amplitude reaches its minimum, avoiding excessive iterations and reducing time loss.
3Ease of operation
If the current sensor detects the current value when the switch element is stopped, then the offset value can be obtained, but the reliability deteriorates because the detected value includes noise from surrounding electrical equipment
Solution Approach 1:
The patent replaces direct current magnitude measurement with q-axis current amplitude detection. Instead of relying on the absolute current value from the sensor (which includes noise), the system transforms the signal and measures the amplitude of the q-axis current, which is more resistant to noise and temperature variations, thereby improving reliability.
Solution Approach 2:
The patent changes the parameter being measured from the raw current value to the q-axis current amplitude. By transforming the detection parameter and using amplitude rather than absolute value, the system becomes less sensitive to noise and temperature effects, improving the reliability of offset value determination.
Data Source
AI summary
A motor control device includes a motor that generates torque corresponding to a current for energizing multi-phase coils, a current sensor that detects a current value of the current for energizing the multi-phase coils, and a controller that obtains a current value of a current flowing through a predetermined coil by adding an origin learning value to a signal input from the current sensor and that controls a current for energizing the predetermined coil based on the current value. The motor control device obtains, each time the origin learning value is changed by a predetermined value, an amplitude of a predetermined order in a q-axis current of the motor based on the changed origin learning value and the signal input from the current sensor, and performs correction based on the origin learning value at the time when the amplitude switches from a decreasing tendency to an increasing tendency.