Elevator Rope Stalling Detection via Pulley Rotation Correlation
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Solution Overview
Problem
Current elevator systems face challenges in reliably detecting stalling situations, as existing methods rely on indirect parameters like motor current or torque, which can also occur during normal operation, leading to potential safety risks due to delayed detection of abnormal rope slackening.
Innovation Solution
A direct monitoring system that senses the rotation of pulleys at the elevator car and counterweight, using sensors to compare the rotation data of these pulleys and the traction sheave, allowing for independent detection of stalling conditions by evaluating the movement of both the car and counterweight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If indirect parameters like motor current or torque are monitored to detect stalling, then the detection system is simpler to implement, but the detection reliability is reduced because these parameters can also occur during normal operation
Solution Approach 1:
The patent replaces indirect electrical parameter monitoring (current, torque) with direct mechanical motion monitoring using encoders on the traction sheave and car. This substitution of measurement methodology eliminates the ambiguity of electrical parameters that can vary during normal operation, thereby improving detection reliability while maintaining reasonable system complexity through the use of standard encoder technology.
Solution Approach 2:
The patent introduces an intermediary measurement approach by using encoder pulses as a mediator between the mechanical motion and the detection system. Instead of directly measuring electrical parameters or mechanical stress, the system measures the intermediary quantity of rotational position and uses this to infer stalling conditions, improving reliability without excessive complexity.
2Ease of operation
If threshold values are used to characterize abnormal situations, then the detection system is easier to operate, but the measurement precision is reduced because threshold values cannot distinguish between normal and abnormal conditions accurately
Solution Approach 1:
The patent transitions from static threshold-based detection to dynamic relationship-based detection. Instead of comparing a single parameter against a fixed threshold, the system continuously monitors the dynamic relationship between traction sheave rotation and car motion. This dynamic approach allows the system to adapt to varying operating conditions while maintaining precise abnormal condition detection through the evaluation of motion consistency.
3Reliability
If the friction between suspension ropes and traction sheave is high to prevent free fall, then safety is improved, but the risk of rope slackening and subsequent free fall increases during stalling situations
Solution Approach 1:
The patent applies preliminary action by detecting stalling conditions before they progress to dangerous rope slackening and free fall. By continuously monitoring the relationship between traction sheave rotation and car motion, the system identifies stalling early and can trigger protective measures, preventing the accumulation of slack rope that would otherwise lead to sudden free fall and extraordinary loads on the suspension ropes.
Data Source
Figure 1
AI summary
The invention concerns a method, system and computer program for monitoring the run of a roping interconnecting a car and a counterweight of an elevator and for detecting an abnormal operation condition during the drive of a traction sheave intending therewith the car and the counterweight to be moved via said roping. Said roping is running on its way from the car to the traction sheave via at least one pulley and on its way from the counterweight to the traction sheave via at least one pulley, wherein the rotation of said at least two pulleys is monitored by sensing their rotation. These rotation data are then analysed in view of a mutual correlation indicating therewith a synchronized run of the roping on either side of the traction sheave, and detecting therewith an abnormal situation when detecting an absence of such correlation.