Storage-Retrieval Unit Voltage Cutoff for Risk-State Motion Prevention
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Solution Overview
Problem
Automated rack storage systems face challenges in safely preventing the movement of storage and retrieval units during risk situations due to uncertainties in production tolerances, design variations, and voltage fluctuations, which can lead to unintended movement and risk to operators.
Innovation Solution
A method where the voltage applied to the rail line is measured, and the current path between the rail line and the drive motor is disconnected when the voltage falls below a threshold value associated with a risk situation, ensuring the storage and retrieval unit is supplied with minimal energy to prevent movement while maintaining safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the rail line is set to normal-operation voltage during risk situations, then the storage and retrieval unit can move freely for operational purposes, but operator safety is compromised due to potential unintended movement
Solution Approach 1:
The system changes the voltage parameter from normal-operation voltage to risk-operation voltage when a risk situation is detected. This parameter change ensures that the storage and retrieval unit cannot be actuated during risk situations, preventing unintended movement while maintaining operator safety. The voltage level is specifically adjusted to a range that eliminates actuation risk but preserves essential functions.
Solution Approach 2:
The system dynamically adjusts the voltage supplied to the storage and retrieval unit based on the operational context. During normal operation, full voltage is supplied for complete mobility. During risk situations, the voltage is automatically reduced to risk-operation voltage, creating a dynamic safety mechanism that adapts to changing operational conditions without requiring manual intervention.
2Reliability
If the rail line voltage is reduced to risk-operation voltage during risk situations, then operator safety is improved by preventing unit movement, but the storage and retrieval unit cannot perform essential operations or fault analysis
Solution Approach 1:
The system applies different voltage levels to different functional requirements. The risk-operation voltage is specifically designed to supply sufficient power for essential functions including fault analysis, diagnostics, and control systems, while simultaneously being too low to actuate the drive motors. This local quality approach ensures that safety-critical functions receive adequate power while movement functions are restricted.
Solution Approach 2:
The system provides partial power supply during risk situations by maintaining risk-operation voltage that is sufficient for essential operations and diagnostics but insufficient for movement. This partial action allows the storage and retrieval unit to perform fault analysis and maintain basic functionality without the excessive power needed for actuation, enabling operators to diagnose and resolve issues safely.
3Device complexity
If production tolerances and design variations are not accounted for, then the system design is simplified, but voltage fluctuations can cause unintended movement during risk situations
Solution Approach 1:
The system incorporates beforehand cushioning by designing the risk-operation voltage to account for potential voltage fluctuations, production tolerances, and design variations. The voltage is set with a safety margin that prevents actuation even under adverse conditions such as maximum tolerance deviations or transient voltage spikes. This prior cushioning ensures reliable movement prevention without requiring complex real-time compensation mechanisms.
Data Source
AI summary
A method for operating a storage and retrieval unit (3) is specified, in which a rail line (1)/power-supply rail (6) is set to a risk-operation voltage when a risk posed by the storage and retrieval unit (3) is detected. In the storage and retrieval unit (3) the level of the voltage applied to the rail line (1)/power-supply rail (6) is measured and a current path between the rail line (1)/power-supply rail (6) and a drive motor (5, 5a . . . 5c) of the storage and retrieval unit (3) disconnected when the voltage measured is below a threshold value associated with a risk situation. Furthermore, a storage and retrieval unit (3) as well as an automated rack storage system for performing the proposed method is specified.