Machine Control System Disconnecting Path for Press Safety
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Solution Overview
Problem
Existing machine control systems face challenges in ensuring rapid and safe responses to operator safety, particularly in press brake controls where quick shutdowns are critical to prevent injuries, due to limitations in cycle time and safety distance constraints.
Innovation Solution
The machine control system directly maps control commands onto a printed circuit board as logic, enabling fast signal transmission without cycle time, and incorporates a dual-channel switch-off path with test circuits and filter circuits to ensure safety and tolerance against interference, allowing for testing during safe machine actions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If control commands are processed through microprocessors with cycle time, then the control system can perform complex safety evaluations, but the response time increases and safety distance must be increased
Solution Approach 1:
The control system is segmented into two distinct paths: a fast switch-off path for immediate safety responses and a slower control path for normal operation and complex evaluations. This segmentation allows critical safety functions to bypass microprocessor cycle times while other functions use full processing capability.
Solution Approach 2:
A test circuit acts as an intermediary between the safety input and the switch-off path, enabling the fast response mechanism to be activated and tested independently without interfering with normal microprocessor-controlled operations.
2Reliability
If the switch-off path is always active for safety, then rapid shutdown is ensured, but testing of the control system becomes difficult without risking safety
Solution Approach 1:
The switch-off path's activation state is made dynamic through the test circuit, which can selectively enable or disable the path based on operational mode. During normal operation, the path is active for safety; during testing, it can be controlled to allow system verification.
Solution Approach 2:
The testing function is extracted from the normal operational path by introducing a separate test circuit that can independently control the switch-off path's activation, allowing safety systems to be tested without compromising operational safety requirements.
3Productivity
If the machine operates at high speed for productivity, then production efficiency increases, but the safety distance required to protect operators increases
Solution Approach 1:
The mechanical safety distance requirement is substituted by an electrical/fast response system that can detect and respond to hazardous conditions within milliseconds, replacing the need for physical distance buffers with electronic safety mechanisms.
4Loss of time
If discrete electronic components are used for fast response, then cycle time is eliminated, but the system becomes more susceptible to interference and requires filtering
Solution Approach 1:
Filter circuits are introduced as intermediary elements between the discrete electronic components and the external environment, allowing the fast response path to benefit from component speed while the filters attenuate electromagnetic interference and signal noise.
Data Source
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AI summary
The controller has a disconnecting path (ABSCH) for disconnecting an output of the controller based on the change in a state at the inputs. The disconnecting path comprises of logic circuits (LSA, LSB) for the time-critical control commands independent of the cyclic time of the controller. The disconnecting path has a test circuit with which the inputs of the path are definitely controlled in an "open" period.