Elevator Brake Cycling for Sag Reduction
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Solution Overview
Problem
Conventional elevator systems face challenges in optimizing re-leveling and brake control operations, particularly in high-rise buildings, due to the need for precise timing of brake cycling and power cycling, which can lead to excessive movement or delay, affecting safety and user experience.
Innovation Solution
A control system that determines the optimal time for brake cycling and power cycling operations based on parameters such as motor torque, load weighing, and car acceleration, using a controller to initiate these operations when the elevator car arrives within a threshold distance of a landing, thereby minimizing re-leveling delays and elevator car sag.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If brake cycling is performed shortly after arrival at destination landing, then re-leveling operation can be initiated early, but fast load transfer causes excessive movement representing safety risk
Solution Approach 1:
The system performs preliminary actions by pre-torquing the motor and positioning the brake for imminent engagement before the actual re-leveling operation begins. The controller anticipates the need for re-leveling based on predicted load transfer patterns and prepares the mechanical system in advance, allowing the brake to engage precisely when needed without causing excessive movement during load transfer.
Solution Approach 2:
The system continuously monitors actual car position, load transfer rates, and brake engagement status, using this feedback to dynamically adjust the re-leveling operation. The controller compares real-time position data against threshold values and modifies brake engagement timing and duration based on observed load transfer characteristics, preventing excessive movement while maintaining efficient re-leveling.
2Reliability
If brake cycling is delayed until just before elevator car is ready to depart, then excessive movement is avoided, but start delay increases representing user nuisance
Solution Approach 1:
The system initiates the re-leveling sequence in advance based on predicted departure timing and load transfer patterns. The controller calculates the optimal brake engagement moment by considering the elevator car's remaining travel distance to the departure point and the expected load transfer duration, allowing the brake to be engaged before the car is fully ready to depart, thus reducing start delay while maintaining control precision.
Solution Approach 2:
The system dynamically adjusts the brake engagement timing based on real-time conditions including load transfer rate, car position, and predicted departure time. The controller continuously optimizes the re-leveling operation parameters, extending or shortening the brake engagement duration as needed to balance control precision with minimizing start delay, adapting to varying operational conditions rather than using fixed timing.
3Reliability
If re-leveling operation is performed frequently in high-rise systems, then load transfer stability is maintained, but operational complexity and delay increase
Solution Approach 1:
The system changes critical parameters including brake engagement threshold values, motor torque levels, and re-leveling operation duration based on the specific conditions of high-rise operations. The controller adjusts these parameters dynamically to match the increased elasticity and longer cable lengths characteristic of high-rise systems, allowing stable load transfer management without proportionally increasing operational complexity.
Solution Approach 2:
The system uses enhanced feedback mechanisms that continuously monitor car position, load transfer rates, and cable tension characteristics specific to high-rise operations. This feedback allows the controller to detect and respond to subtle position variations caused by cable elasticity and long drop distances, maintaining load transfer stability through adaptive control rather than frequent manual intervention or complex multi-step procedures.
Data Source
AI summary
A method includes determining that an elevator car is arriving at a landing at which re-leveling is anticipated; upon the elevator car arriving at the landing at which re-leveling is anticipated, initiating the at least one of a brake cycling operation and a power cycling operation to reduce elevator car sag at the landing; monitoring transfer of weight to or from the elevator car at the landing over a period of time; terminating the at least one of the brake cycling operation and the power cycling operation upon at least one of (i) the transfer of weight to or from the elevator car at the landing over the period of time being less than a threshold and (ii) the elevator car sag at the landing meeting a sag threshold.