Elevator Safety Controller Delayed Brake Activation
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Solution Overview
Problem
Conventional elevator systems face the risk of entrapment of passengers or maintenance personnel when the elevator car is stopped between floors due to a fault, as the immediate activation of the brake can prevent occupants from safely exiting.
Innovation Solution
The elevator system incorporates a safety controller that assesses the condition of the elevator system based on signals from safety devices. If a fault is detected that is not safety-critical, the elevator car is allowed to move for a predetermined time or distance to the nearest landing, enabling occupants to exit before the brake is activated.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the brake is activated immediately upon fault detection, then the safety of the elevator system is improved, but the risk of entrapment of occupants increases
Solution Approach 1:
The system changes the parameter of brake activation timing from immediate to delayed based on the type of fault detected. For non-safety-critical faults, the brake is activated after a predetermined time or distance has elapsed, allowing the elevator car to move to the nearest landing first. This parameter change resolves the contradiction by providing occupants with time to exit while still ensuring safety through eventual brake activation.
Solution Approach 2:
The system dynamically adjusts the brake activation strategy based on the fault condition. Instead of a static immediate activation, the system implements dynamic control that distinguishes between safety-critical and non-safety-critical faults, applying different response times accordingly. This dynamic approach allows the system to optimize both safety and occupant egress opportunities.
2Reliability
If the elevator car is stopped immediately upon fault detection, then the safety response time is improved, but the ability of occupants to exit the elevator car deteriorates
Solution Approach 1:
The system performs preliminary action by allowing the elevator car to move to the nearest landing before activating the brake for non-safety-critical faults. This preliminary movement enables occupants to exit the car at the landing, improving ease of operation while maintaining safety through subsequent brake activation after the predetermined time or distance.
3Object-affected harmful factors
If the brake is activated after a predetermined time or distance, then the entrapment risk is reduced, but the safety protection against critical faults deteriorates
Solution Approach 1:
The system applies local quality by differentiating between types of faults and applying different brake activation strategies accordingly. For non-safety-critical faults, delayed activation allows occupant egress, while for safety-critical faults, immediate activation ensures protection. This localized differentiation of response strategies resolves the contradiction by tailoring the safety response to the specific fault condition.
Data Source
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AI summary
An elevator system (100) comprises an elevator car (101), an elevator controller (117), and a safety controller (121), connected to a plurality of safety devices (126a, 126b, 127, 129, 131, 138a, 138b, 140, 141) arranged to monitor the elevator system. The safety controller is configured to receive a signal in response to a change of state of any of the safety devices, and to determine a condition of the elevator system in response to the change of state of one or more of the safety devices. If the safety controller renders a determination that the elevator system is in a first condition, the safety controller causes an elevator brake to be deployed, preventing movement of the elevator car. If the safety controller renders a determination that the elevator system is in a second condition, the safety controller allows movement of the elevator car for a predetermined duration or until the elevator car has travelled a predetermined distance.