Elevator Control System for Friction Slip Detection
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Solution Overview
Problem
Elevator systems with polymer-coated tension members face challenges in maintaining sufficient frictional engagement over extended periods, leading to potential movement of the elevator car, which can create safety hazards when stopped at landings for extended times, especially with counterweights.
Innovation Solution
An elevator control system that includes a car holding position monitoring unit to detect movement of the elevator car during holding periods by comparing initial and final positions using trigger signals from car position reference systems, ensuring the frictional engagement between the traction sheave and tension member is sufficient to prevent unwanted movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If polymer-coated tension members are used in traction drive elevators, then the frictional engagement between the traction sheave and tension member may be insufficient during extended holding periods, but using traditional steel wire ropes ensures sufficient frictional engagement
Solution Approach 1:
The control system continuously monitors the position of the elevator car during holding periods and compares it with the initial position. When position deviation exceeds a threshold, the system automatically activates the holding brake to correct the position, creating a closed-loop feedback control that maintains reliability with polymer-coated tension members
Solution Approach 2:
The control system is configured to detect position deviations and activate the holding brake before the position deviation becomes significant, preventing safety hazards from occurring in the first place by taking preliminary corrective action
2Duration of action of stationary object
If the elevator car is stopped at a landing for an extended period of time, then the frictional engagement between the tension member and traction sheave must be sufficiently large to balance the weight, but extended holding periods increase the risk of frictional engagement loss
Solution Approach 1:
The monitoring unit continuously checks the car position during the entire holding period and compares it with the initial position. If any deviation occurs, the system immediately activates the holding brake to restore the correct position, enabling safe extended holding periods
Solution Approach 2:
The system automatically detects and corrects position deviations without human intervention by comparing positions and activating the holding brake when needed, making the system self-monitoring and self-correcting during extended holding periods
3Reliability
If a holding brake is used to secure the rotational position of the traction sheave, then the car remains in position due to frictional engagement, but the frictional engagement may still be insufficient for extended periods
Solution Approach 1:
The control system uses position monitoring and comparison to detect deviations and activate the holding brake, creating an automated feedback loop that enhances position holding reliability without requiring complex manual intervention systems
Solution Approach 2:
The system replaces reliance on purely mechanical frictional engagement with an automated control system that uses position detection, comparison, and electronic control of the holding brake to maintain position, substituting mechanical passivity with active control
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
The system effectively detects and prevents upward or downward movement of the elevator car, ensuring safety by engaging the holding brake and correcting any slip phenomena, thereby maintaining the car's position at desired landings even during extended holding periods.
Implementation Method 1
The traction sheave is frictionally engaged by the tension member such that rotation of the traction sheave is transferred into linear movement of the tension member around the traction sheave
Implementation Method 2
the rotational position of the traction sheave is secured by way of a holding brake engaging the traction sheave or the drive train between the motor and the traction sheave
Data Source
AI summary
Disclosed is an elevator control system configured to control movement of an elevator car (12) along an elevator hoistway (26) between a starting position and a destination position (L2), the control system comprising a car holding position monitoring unit configured to monitor whether the elevator car (12) has moved upwards or downwards in the hoistway (26) during a holding period (68) where the car (12) was intended to remain stationary at the destination position (L2). The car holding position monitoring unit is configured to: Receive a first trigger signal (62) from a first car position reference system (40); upon receipt of the first trigger signal, receive signals from a further car position reference system to detect a first indicator (66) indicative of a travel distance (X2) between the position of the elevator car (12) in the hoistway (26) when receiving the first trigger signal (62) and the position of the elevator car (12) in the hoistway (26) when stopping at the destination position (L2); upon receipt of a further service call for the elevator car (12), receive further signals from the further car position reference system and receive a second trigger signal (70A) from the first car position reference system (40) to detect a second indicator (74A) indicative of a travel distance between the position of the elevator car (12) in the hoistway (26) at the end of the holding period (68) and the position of the elevator car (12) in the hoistway (26) when the elevator car (12) receives the second trigger signal (72A) from the first car position reference system (40); and detect whether the elevator car (12) has moved during the holding period (68) based on a comparison of the first indicator (66) and the second indicator (74A).