Spindle Abnormality Detection Using Multi-Speed Motor Feedback
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Solution Overview
Problem
Existing methods struggle to accurately detect tiny foreign matters caught in machine tool spindles or drive units without increasing facility costs or computational complexity, and fail to distinguish between tool eccentricity and other abnormalities like tool wear or workpiece unevenness.
Innovation Solution
An abnormality detection device monitors spindle response at various rotational speeds, analyzing feedback signals to detect eccentricity and foreign matter presence using a control unit, drive unit information acquisition, and state determination without additional sensors, employing frequency and statistical analyses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a high-precision sensor is used to detect tiny foreign matters, then detection precision is improved, but facility costs increase and computational cost increases
Solution Approach 1:
The system uses the machine tool's own motor as both the drive source and the detection sensor. By monitoring the motor's current consumption and vibration during operation, the system performs self-diagnosis to detect foreign matter without requiring external high-precision sensors, thereby reducing facility costs while maintaining detection precision
Solution Approach 2:
The patent replaces physical high-precision sensors with electrical and vibrational measurements. By analyzing current consumption patterns and vibration characteristics from the motor itself, the system achieves foreign matter detection without mechanical contact sensors, reducing both facility and computational costs
2Device complexity
If a simple abnormality detection function is used, then device complexity is reduced, but detection accuracy for tiny foreign matters deteriorates
Solution Approach 1:
The system performs periodic detection operations at multiple rotational speeds (e.g., 100 rpm, 200 rpm, 300 rpm) to capture varying vibration and current patterns. This periodic multi-speed measurement approach enables detection of tiny foreign matters that would be imperceptible at single speeds, improving accuracy without complex device architecture
Solution Approach 2:
The detection system dynamically adjusts measurement parameters based on operational conditions. By varying rotational speeds during detection and analyzing changes in current consumption and vibration patterns across different speeds, the system achieves high detection accuracy using simple monitoring equipment
3Reliability
If vibration waveform analysis is performed at all times, then detection capability is improved, but computational cost increases
Solution Approach 1:
The system pre-stores threshold values for current consumption and vibration levels that indicate foreign matter presence. During operation, it performs simple threshold comparisons rather than continuous complex waveform analysis, enabling reliable detection while minimizing computational cost and energy consumption
Solution Approach 2:
The system changes detection parameters (rotational speed, measurement duration) based on operational context. By performing measurements at specific speeds and comparing against pre-established thresholds rather than continuously analyzing all vibration waveforms, the system maintains high detection capability while reducing computational burden
Data Source
AI summary
This abnormality detection device: causes a motor that drives a drive unit at a plurality of rotational speeds to perform a detection operation based on a command for diagnosing the state of the drive unit, acquires, as information indicating the operating state of the drive unit, a control command for the motor driving the drive unit or a feedback signal from the motor driving the drive unit, during the detection operation; analyzes the control instruction for the motor driving the drive unit or the feedback signal from the motor; determines the state of the drive unit based on the result of the analysis, and notifies, based on the determination result, that the state of the drive unit is different from that in normal time.