Motor Controller Abnormality Detection for Power Transmission Units
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Solution Overview
Problem
Existing methods for detecting abnormalities in power transmission units between motors and main shafts in machine tools face challenges in accurately detecting issues across the entire range of rotation speeds, with delays occurring at high speeds due to filter application and at low speeds due to infrequent one-rotation signal detection.
Innovation Solution
A motor controller that includes units for acquiring motor and main shaft rotation angles, calculating rotation speeds, and determining abnormalities based on change in motor rotation angle and speed differences, with temporary determination units that apply filters to remove noise and detect abnormalities when deviations exceed prescribed ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a filter is applied to the speed difference between motor and main shaft rotation speeds to eliminate momentary slip influence, then measurement precision is improved, but detection delay increases due to the filter's time constant particularly at high speeds
Solution Approach 1:
The patent divides the abnormality detection process into two independent determination methods: (1) comparing motor and main shaft rotation speeds with filter application for precision, and (2) calculating change amount of motor rotation angle between one-rotation signals for rapid response. This segmentation allows each method to optimize for its strength while compensating for the other's weaknesses.
Solution Approach 2:
The patent merges two different determination methods into a unified abnormality detection system. The first determination unit handles speed comparison with filtering for accurate detection, while the second determination unit handles rotation angle change calculation for rapid detection. By combining these methods, the system achieves both measurement precision and rapid response across all rotation speeds.
2Device complexity
If abnormality detection is performed only when one-rotation signal is detected, then device complexity is reduced, but detection delay occurs at low speeds due to infrequent signal detection
Solution Approach 1:
The patent ensures continuous abnormality detection by implementing two determination units that operate continuously rather than intermittently. The first determination unit continuously monitors speed difference, and the second continuously calculates rotation angle changes, ensuring that useful detection action continues without interruption regardless of one-rotation signal frequency.
Solution Approach 2:
The patent makes the detection system dynamic by adapting the determination method to operating conditions. At high speeds, the system effectively uses the first determination unit with filtering for precision. At low speeds, the system transitions to using the second determination unit based on rotation angle changes, which provides rapid response without requiring frequent one-rotation signals.
Data Source
AI summary
A motor controller includes: a motor rotation angle acquisition unit acquiring the rotation angle of the motor; a main shaft rotation angle acquisition unit acquiring the rotation angle of the main shaft; a one-rotation signal acquisition unit acquiring a one-rotation signal output every time the main shaft rotates once; a motor rotation speed calculation unit calculating the rotation speed of the motor from the rotation angle of the motor; a main shaft speed calculation unit calculating the rotation speed of the main shaft from the rotation angle of the main shaft; and an abnormality determination unit in which, when a change amount of the rotation angle of the motor or when the difference between the rotation speed of the motor and the rotation speed of the main shaft deviates from a second range, it is determined that an abnormality has occurred in the power transmission unit.