Elevator Load Detection Using Cable Stretch for Dispatch Control
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Solution Overview
Problem
Elevator systems face challenges in accurately determining car loads without costly and maintenance-intensive hoistway-mounted sensors, which can malfunction during emergencies, affecting dispatch efficiency and passenger wait times.
Innovation Solution
A system that uses position devices outside the elevator cars to measure load based on cable stretch, combined with dispatch controllers to optimize elevator operations based on real-time load data, eliminating the need for hoistway-mounted sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If hoistway-mounted load-weighing devices are used to determine elevator car load, then load measurement accuracy is improved, but device cost and maintenance complexity increase
Solution Approach 1:
The patent introduces cable stretch as an intermediary physical quantity to indirectly measure elevator car load. Instead of directly weighing the car, the system measures the stretch of the cable supporting the car, which correlates with load changes. This intermediary measurement approach eliminates the need for complex hoistway-mounted load cells while maintaining measurement capability.
Solution Approach 2:
The patent replaces the mechanical load-weighing device system with an optical measurement system. Instead of using mechanical load cells in the hoistway, the system uses optical sensors to measure cable stretch, substituting a simpler optical/mechanical hybrid system for the complex mechanical weighing system, thereby reducing cost and maintenance requirements.
2Measurement precision
If hoistway-mounted load-weighing devices are installed, then occupancy weight can be determined, but reliability decreases during emergency situations
Solution Approach 1:
The patent uses cable stretch as an intermediary measurement that remains reliable during emergencies. The cable stretch measurement is taken from the hoistway side where the cable is stationary and supported by the building structure, rather than from within the elevator car where sensors could fail during power outages or emergency conditions. This intermediary approach maintains reliability while preserving measurement capability.
3Ease of operation
If traditional load-weighing devices are used, then dispatch control is possible, but productivity decreases due to longer wait times
Solution Approach 1:
The patent implements preliminary action by continuously monitoring cable stretch to determine occupancy weight before the elevator car arrives at the dispatch point. This allows the dispatch controller to have advance knowledge of the car's load status and make informed dispatch decisions proactively, rather than reacting after the car arrives, thereby improving traffic flow and reducing wait times.
Solution Approach 2:
The patent establishes a feedback loop where cable stretch measurements continuously inform the dispatch controller about elevator car occupancy status. This real-time feedback enables dynamic dispatch adjustments, allowing the system to optimize elevator routing and timing based on actual load conditions, thereby improving productivity and reducing passenger wait times.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enhances elevator traffic flow by accurately dispatching cars based on occupancy weight, reducing wait times and improving system reliability without the limitations of traditional load-weighing devices.
Implementation Method 1
uses position devices outside the elevator cars to measure load based on cable stretch
Data Source
AI summary
A method for dispatching an elevator car that includes determining the elevator car is located at a first location of a plurality of locations, and a predefined positional count corresponds to each of the plurality of locations. The method includes determining a positional count of the elevator car at the first location, and determining a load of the elevator car at the first location based on a difference between the positional count and the predefined positional count corresponding to the first location. The method includes controlling an operation of the elevator car based on the load of the elevator car at the first location.