Motor Control Device for Multi-Axis Machine Tool Safety
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Solution Overview
Problem
In machine tools with multiple axes, there is a delay in detecting abnormal loads due to coupling mechanisms, leading to inaccurate safety operations and potential tool or workpiece damage, as well as machine tool failures.
Innovation Solution
A motor control device with independent motor control units, abnormality detection units, and safety operation control units that communicate directly to swiftly initiate a safety operation when an abnormality is detected, using direct drive or linear motors to reduce detection time and improve accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a load monitoring unit is provided for the motor to detect abnormal loads, then the safety operation can be initiated based on detection results, but there is a time lag between abnormal load occurrence and detection due to coupling mechanisms
Solution Approach 1:
The patent introduces an abnormality detection unit as an intermediary device that directly monitors the axis for abnormalities and transmits detection signals to the safety operation control unit. This intermediary bypasses the delayed motor-based load monitoring, enabling direct and immediate detection of axis abnormalities without the time lag introduced by coupling mechanisms between the motor and axis.
2Ease of operation
If coupling mechanisms such as ball screws or decelerators are used between the motor and axis, then the motor can drive the axis, but forces such as friction from the coupling mechanism affect the accuracy of load monitoring
Solution Approach 1:
The patent extracts the abnormality detection function from the motor-based load monitoring system and places it directly on the axis through a separate abnormality detection unit. This extraction eliminates the interference of coupling mechanism forces (such as friction) from the detection process, as the abnormality detection unit directly monitors the axis without being affected by forces introduced by coupling mechanisms between the motor and axis.
3Reliability
If the safety operation is initiated with delay after abnormal load occurrence, then the system can respond to detected abnormalities, but the tool may not move away from the workpiece in time causing damage
Solution Approach 1:
The patent implements preliminary action by having the abnormality detection unit continuously monitor the axis for abnormalities and immediately transmit detection signals to the safety operation control unit upon detecting an abnormality. This preliminary detection and immediate signal transmission enables the safety operation to be initiated without delay, allowing the tool to move away from the workpiece in time and prevent damage.
Data Source
AI summary
A motor control device for a machine tool having a plurality of axes includes a plurality of motor control units that control motors; an abnormality detection unit provided for at least one of the motor control units and configured to output an abnormality detection signal upon detecting an abnormality with respect to the axis driven by the motor controlled by the motor control unit provided with the abnormality detection unit; a safety operation control unit provided for a motor control unit that is not the motor control unit provided with the abnormality detection unit, the safety operation control unit configured to control the motor upon receiving the abnormality detection signal in such a way that the tool comes out of contact with the workpiece; and a communication unit that transmits the abnormality detection signal outputted by the abnormality detection unit to the safety operation control unit.