Elevator Landing Door Monitoring to Avoid Unnecessary Emergency Stops
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Solution Overview
Problem
Elevator safety systems face issues with unnecessary emergency stops due to worn or malfunctioning landing door opening mechanisms, which can incorrectly detect open doors during elevator motion, leading to inappropriate brake activation.
Innovation Solution
An elevator safety system with sensors to monitor the position, speed, and direction of the elevator car, along with the location of open landing doors, determines whether to send an emergency stop signal based on the car's proximity, speed, and direction relative to the open door, preventing unnecessary stops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the elevator safety system implements an emergency stop whenever a landing door is detected open during car motion, then passenger safety is improved, but unnecessary emergency stops occur due to worn or malfunctioning door mechanisms
Solution Approach 1:
The safety system dynamically adjusts the emergency stop decision based on real-time evaluation of multiple parameters including car speed, direction of travel, distance to the open door, and door opening speed. This dynamic assessment allows the system to distinguish between genuine safety threats and false alarms from worn mechanisms, optimizing both safety and operational efficiency.
Solution Approach 2:
The system changes the decision parameters from a simple binary trigger to a multi-parameter evaluation including car speed thresholds, direction vectors, distance measurements, and door opening velocity. By monitoring these parameter changes over time, the system can differentiate between intentional door openings and mechanical failures.
2Measurement precision
If the landing door opening mechanism is monitored with simple sensors, then false alarms from worn mechanisms are detected, but the system cannot distinguish between intentional door opening and mechanical malfunction
Solution Approach 1:
The monitoring system serves multiple functions: it detects door position, measures door opening speed, determines car position and speed, calculates distance to the door, and evaluates the overall safety situation. This multi-functional approach consolidates several monitoring tasks into a single integrated system, reducing overall complexity while improving detection precision.
Solution Approach 2:
The controller acts as an intermediary that receives data from multiple sensors (door position sensor, car position sensor, speed sensor) and processes this information to generate the emergency stop decision. This intermediary processing layer integrates information from various sources and applies the evaluation criteria, simplifying the overall system architecture.
3Reliability
If the elevator car stops immediately when a landing door opens, then safety is maximized, but the system cannot account for the car's speed and distance to the door
Solution Approach 1:
The system performs preliminary evaluation of the situation before triggering an emergency stop. It assesses the car's speed, direction, and distance to the open door in advance, and only initiates an emergency stop when the evaluation confirms a genuine safety threat. This preliminary assessment prevents premature stops and reduces unnecessary loss of time.
Solution Approach 2:
The system applies preliminary anti-action by preventing the emergency stop from occurring when the evaluation shows no genuine safety threat. By anticipating false alarm scenarios through speed and distance analysis, the system counteracts the tendency to stop unnecessarily, thereby reducing time loss while maintaining safety.
Data Source
AI summary
An safety system (40) including: a plurality of landing door sensors (26), each landing door sensor (26) being configured to provide a warning signal (52) when a respective landing door (22) is open; at least one position sensor (14) configured to determine a current position (54) of an elevator car (10) moving within a hoistway (2); an elevator brake (7) configured to halt the motion of the elevator car (10); and a controller (8) configured to send an emergency stop signal (58) to the elevator brake (7). The controller (8) is configured to determine whether to send the emergency stop signal (58) based on: a direction of travel of the elevator car (10) with respect to the open landing door (22); a current speed of the elevator car (10); and a distance (D) between the open landing door (22) and the current position of the elevator car (10).