Motor Controller Safety Stop Logic for Mismatched Dual Commands
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Solution Overview
Problem
In industrial machine systems using multiple-axis motors, the burden of monitoring safety systems increases, and the failure rate due to wiring issues rises, making it challenging to construct a reliable safety system.
Innovation Solution
A controller is designed with a command monitoring unit that checks if safety commands from external devices match, and if they don't within an allowable time, it generates a safe stop command to halt the motor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If safety signals are duplicated and monitored externally, then safety reliability is improved, but monitoring burden and wiring failure rate increase
Solution Approach 1:
The patent combines the safety signal monitoring function with the motor controller by integrating a monitoring unit that receives multiple safety signals directly from external devices. This merging eliminates the need for separate external monitoring systems, reducing overall system complexity while maintaining safety reliability through internal command comparison and mismatch detection.
2Difficulty of detecting and measuring
If command monitoring is implemented, then safety detection capability is improved, but system complexity increases
Solution Approach 1:
The motor controller is designed with multi-functionality, serving both as the primary control device and as a safety monitoring system. The monitoring unit within the controller compares multiple safety commands internally, enabling safety detection without requiring separate dedicated monitoring hardware, thus improving safety detection capability while minimizing system complexity.
Data Source
AI summary
A controller 1 is provided with: a motor controller (10, 11, etc.) that supplies a drive current to a motor 3, which is a power source of a processing device so as to place the motor 3 in a normal operating state, and, in response to multiplexed commands (S1, S2) that are sent from outside and relate to a safety function operation of the processing device, controls the drive current so as to place the motor 3 and the processing device in a safety stop state; and a command monitoring unit 16 that monitors whether or not the commands (High/Low of S1, S2) match each other. If a period during which the commands do not match exceeds an allowable value, the command monitoring unit 16 generates a safety stop signal Sd (High) for safely stopping the motor 3, and continuously sends the safety stop signal Sd (High) to the motor controller. This configuration makes it possible to facilitate construction of a safety system that uses the controller.