Automated Warehouse Vehicle Watchdog Loop for Safe Operator Access
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Solution Overview
Problem
Automated warehouses with shuttle and satellite systems face challenges in ensuring human safety during operator intervention due to incomplete wireless communication coverage, leading to potential vehicle operation risks when operators attempt to enter the area, as current safety-certified transmission systems are costly and technically limiting.
Innovation Solution
Implementing a safety-certified watchdog timer system on each vehicle with safety modules and a non-certified communication protocol for communication between the shuttle and satellite, ensuring de-energization through a closed signal loop and safety contactors, even in the absence of safe communication, by using a watchdog timer to detect communication interruptions and automatically de-energize vehicles if communication fails.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If safety-certified wireless transmission systems are implemented to ensure human safety during operator intervention, then the safety level is improved, but the system complexity and cost increase significantly due to requiring extensive access points and customized planning
Solution Approach 1:
The patent introduces a wireless repeater system that relays communication signals between the access point and vehicles. The repeater acts as an intermediary device that extends wireless coverage without requiring a complete reconfiguration of the safety-certified network infrastructure. This allows safety-certified communication to reach vehicles in areas where direct access point coverage is insufficient, thereby improving safety level while avoiding the complexity of installing numerous access points throughout the warehouse.
2Reliability
If safety-certified wireless transmission systems are implemented to guarantee signal coverage at all points in the warehouse, then the safety level is improved, but the cost increases due to requiring a very large number of antennas and access points
Solution Approach 1:
The patent divides the wireless communication function into separate components: access points for centralized control and wireless repeaters for distributed signal extension. Instead of deploying many access points throughout the warehouse, the system uses a few access points combined with repeaters mounted on vehicles to segment the coverage function. This reduces the total number of safety-certified devices required while maintaining comprehensive signal coverage for safety monitoring.
Solution Approach 2:
The wireless repeater system enables vehicles to serve themselves in extending communication coverage. Each vehicle equipped with a repeater automatically provides wireless signal extension in its operational area, eliminating the need for the system administrator to manually install and configure numerous access points throughout the warehouse. This self-service approach reduces both the quantity of devices needed and the complexity of system deployment.
3Productivity
If the shuttle and satellite move away from each other to perform simultaneous operations, then the productivity is improved, but the communication reliability deteriorates due to distance limitations of current wireless systems
Solution Approach 1:
The patent extends the wireless communication dimension by deploying repeaters in three-dimensional space throughout the warehouse, including on vehicles themselves. This spatial distribution of repeaters creates multiple communication pathways and extends the effective range of wireless communication beyond what fixed access points alone could achieve. Vehicles can maintain communication reliability even when separated by large distances because signals can relay through multiple repeaters positioned at different locations and heights.
Data Source
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AI summary
An automated warehouse comprises a main path (10) and secondary paths (11) with storage stations (12), a main vehicle (20) with electric traction, movable along the main path and one or more auxiliary vehicles (30) with electric traction powered by a battery, movable along secondary paths. An access point (40) is installed in a fixed position in the warehouse. On each vehicle (20, 30) a wireless device (21, 31) to receive and send wireless signals and a respective control unit (22, 32) with associated safety modules including a respective safety-certified watchdog timer (23, 33) and a counter are installed. The wireless devices send check signals containing the value of the counter of the respective vehicle to the access point (40) at predetermined intervals; the access point (40) sends signals in response to the received check signals to the wireless devices. Each time a response signal is received from a wireless device (21, 31), the respective counter is incremented and the associated watchdog timer starts to measure the time from when the value of the respective counter in the vehicle differs from the value of the counter received via the verification signal. Each control unit de-energizes the relative vehicle when it detects, via the watchdog timer, that a time longer than a predetermined time has elapsed.