Elevator Overspeed Detection Using Zone-Based References
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Solution Overview
Problem
Elevator safety systems fail to reliably detect overspeed conditions, especially after a power outage, due to drifting car position detection, leading to erroneous overspeed disregard levels and potential failure in detecting actual overspeed.
Innovation Solution
An elevator safety apparatus that includes a zone detecting system and a processor using stepped and continuous overspeed references, allowing for accurate overspeed detection by comparing car speed with zone-specific reference levels and continuous references, respectively, even when the exact car position is unknown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If continuous car position detection is used to determine overspeed, then real-time monitoring is improved, but position drift occurs during power outages leading to erroneous overspeed detection
Solution Approach 1:
The hoistway is divided into multiple zones with discrete zone reference levels. Instead of relying solely on continuous position detection, the system segments the detection into zone-based discrete levels. When the car is stopped in a zone, the stepped overspeed reference for that zone is used, eliminating the need for precise continuous position measurement and preventing drift-related errors.
Solution Approach 2:
The system switches between two different overspeed reference parameters based on car state: stepped overspeed reference (zone-based discrete levels) when the car is stopped, and continuous overspeed reference (smooth curve) when the car is moving. This parameter change adapts the detection method to the operational state, preventing erroneous detection during power outages while maintaining smooth operation during movement.
2Measurement precision
If absolute car position detection is used to correct drift, then position accuracy is improved, but detection cannot occur until power is restored after outage
Solution Approach 1:
Zone reference levels are predetermined and stored in the system before power outages occur. When the car is stopped in a zone, the system immediately uses the pre-stored stepped overspeed reference for that zone without needing to detect or calculate absolute position first. This preliminary preparation eliminates the time delay that would otherwise occur while waiting for power restoration and absolute position detection.
3Reliability
If stepped overspeed reference is used when car is stopped, then overspeed detection reliability is improved, but system complexity increases with zone management
Solution Approach 1:
The zone detecting apparatus serves multiple functions: it identifies which zone the car is in, determines the appropriate stepped overspeed reference level, and provides this information to the processor for reliable overspeed detection. By making the zone detection system multi-functional, the patent avoids adding separate complexity for zone management while achieving improved reliability.
Data Source
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AI summary
A zone detecting apparatus detects a zone in which a car is present among a plurality of zones that are contiguous in a direction of movement of the car, and also detects presence or absence of passage of the car through a switchover position that is positioned at a boundary between each of the zones. A movement detecting device generates a signal that corresponds to movement of the car. A processor finds a speed of the car based on information from the movement detecting device, and finds a position of the car after the car has passed through the switchover position. A stepped overspeed reference that includes zone reference levels that are determined individually for each of the zones, and a continuous overspeed reference that is constituted by values that are greater than or equal to those of the stepped overspeed reference in each of the zones are set in the processor. The processor identifies the zone in which the car is present as a stopping zone when the car is stopped, and determines presence or absence of an overspeed in the speed of the car by comparing the stepped overspeed reference and the speed of the car when the car is inside the stopping zone, and determines presence or absence of an overspeed by comparing the continuous overspeed reference and the speed of the car when the car is outside the stopping zone.