Multi-Motor U-Axis Position Control With Abnormality Detection
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Solution Overview
Problem
Conventional U-axis mechanisms in industrial machines fail to establish effective full-closed control and abnormality detection when using multiple motors, due to tangled cables and handling issues with scale detectors during axis rotation.
Innovation Solution
A motor control device that includes first and second position acquiring units, a position calculation unit, and an abnormality detection unit, which acquires and calculates positional changes from multiple motors and a separate scale detector to detect abnormalities in the U-axis mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a scale is provided to a machine end for full-closed control, then position detection capability is improved, but the cable of the scale becomes tangled and difficult to handle due to rotation of the axis
Solution Approach 1:
The patent replaces the mechanical scale with a non-contact laser interferometer for position detection. The laser interferometer measures the position of the U-axis by detecting the interference pattern of laser beams, eliminating the need for physical cables that become tangled during rotation. This substitution of mechanical measurement with optical measurement resolves the cable handling issue while maintaining high position detection precision.
2Measurement precision
If full-closed control is implemented by providing position detectors to multiple motors, then control precision is improved, but the system complexity increases and abnormality detection capability deteriorates
Solution Approach 1:
The patent extracts the position detection function from the motor-mounted detectors and implements it separately using a laser interferometer that measures the actual position of the U-axis. This separation allows the control system to use simplified open-loop control while maintaining high precision through the independent measurement system, thereby reducing overall system complexity while preserving control precision.
Solution Approach 2:
The patent implements a feedback mechanism where the laser interferometer continuously monitors the actual position of the U-axis and provides correction signals to the control system. This feedback loop enables the system to compensate for positioning errors without requiring complex multi-motor coordination, thus maintaining control precision while simplifying the control architecture.
3Measurement precision
If multiple position detectors are used for full-closed control, then position accuracy is improved, but abnormality detection capability deteriorates due to lack of reference comparison
Solution Approach 1:
The patent introduces an intermediary reference system - the laser interferometer - that provides an independent, highly accurate measurement of the U-axis position. This reference measurement serves as a mediator between the motor control system and the actual position, enabling both high position accuracy and reliable abnormality detection through comparison with the reference values. The interferometer acts as a trusted third-party verifier of system performance.
Data Source
AI summary
Provided is a technique capable of detecting an abnormality of an industrial machine when performing full-closed control on one axis by a plurality of motors in the industrial machine. This motor control device comprises: a first position acquiring unit for acquiring the position change of each motor on the basis of each of the detection signals of a plurality of first position detectors with which the plurality of motors are respectively provided; a second position acquiring unit for acquiring the position change of the one axis on the basis of the detection signal of a second position detector for directly detecting the position change of the one axis; a position calculation unit for calculating a position change of the one axis on the basis of the position change of each motor acquired by the first position acquiring unit; and an abnormality detection unit for detecting an abnormality of the industrial machine on the basis of the position change of the one axis calculated by the position calculation unit and the position change of the one axis acquired by the second position acquiring unit.