Emergency Stop Circuit Failure Detection in Robot Systems
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Solution Overview
Problem
Existing emergency-stop devices in robot systems and machine tools lack reliable detection of failure in emergency-stop signal circuits, particularly in controllers requiring long continuous operation, leading to a risk of successive failures going undetected before they are detected.
Innovation Solution
The emergency-stop device includes a processor that monitors the open/closed states of emergency-stop signal circuits and issues shut-off commands to switches in the power supply line, allowing for periodic checking of the circuits without stopping the servomotor, using switching means to bring the input circuits into an off-state for inspection, ensuring continuous operation and immediate detection of failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dualized emergency stop circuit is used with separate emergency stop circuits for two CPU's, then reliability of emergency stop function is improved, but failure detection capability deteriorates when emergency stop signal is rarely supplied
Solution Approach 1:
The invention applies preliminary action by introducing a test signal transmission function that proactively checks the emergency stop signal circuits during normal operation. The CPU transmits test signals through the emergency stop input circuits to verify their functionality, rather than waiting for actual emergency stop events. This allows failure detection even when emergency stop signals are rarely supplied, resolving the contradiction between maintaining reliability and enabling failure detection.
2Difficulty of detecting and measuring
If controller is stopped to check input circuits, then failure detection is achieved, but working efficiency deteriorates
Solution Approach 1:
The invention implements continuity of useful action by enabling failure detection during normal controller operation. The test signal transmission and reception mechanism operates continuously or periodically without requiring controller shutdown, allowing both productive operation and failure detection to occur simultaneously. This eliminates the need to stop the controller for checking input circuits, maintaining working efficiency while achieving failure detection.
Data Source
AI summary
An emergency-stop device provided in a robot system, a machine tool or the like, arranged to promptly detect failure of a circuit through which an emergency stop signal is supplied to an CPU, without stopping the robot system, the machine tool or the like, to improve reliability. When at least one of emergency stop switches is opened, a CPU #1 or #2 issues an emergency stop command through one of input circuits, so that a switch SW10 or SW20 is opened by an output circuit #1 or #2 to emergency-stop the system. Switching means #1, #2 are opened separately, at appropriate intervals, and change of output of each photo coupler is recognized. In this manner, it is checked that open/closed-state outputs related to contacts C11 and C21/C12 and C22, each connected to one of the input circuits, indicate an open state. If regarding any of the contacts, change of output of the corresponding photo coupler is not recognized, the system is stopped and an action such as causing a buzzer and displaying of an alarm is taken.