Elevator Emergency Stop Gravity Jump Prevention
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Solution Overview
Problem
In elevator systems, emergency stops can result in 'gravity jumps' due to the delay in brake engagement, leading to uncomfortable rides, potential overshooting of floors, and increased risk of brake and drive device failures, as the drive force is removed before sufficient braking force is applied.
Innovation Solution
Implementing a method where the drive device continues to operate for a predetermined period after triggering the brake device during an emergency stop, allowing the brake to generate substantial force before the drive device is stopped, thereby mitigating gravity jumps and reducing the likelihood of excessive brake wear or failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the power supply to the drive system is interrupted immediately upon emergency stop detection, then the drive force is removed quickly, but the brake device cannot produce braking force instantly due to brake-drop delay, resulting in gravity jump and uncomfortable ride
Solution Approach 1:
The brake device is activated in advance before the drive force is completely removed. The control method maintains drive force during the brake-drop delay period, so when the brakes engage, the drive force is already present to counteract gravity and prevent the gravity jump, ensuring ride comfort.
Solution Approach 2:
The system prepares compensatory drive force in advance to counteract the expected gravity jump. By maintaining drive force output during the brake activation period, the system cushions the gravitational effect that would otherwise occur when brakes engage without sufficient force.
2Loss of time
If the drive force is removed before sufficient braking force is applied, then the emergency stop response is quick, but the car may accelerate briefly (gravity jump) causing overshooting of floor stopping position
Solution Approach 1:
The brake device is activated in advance while maintaining drive force, preparing the braking system before the drive force is removed. This ensures that when the drive force is finally cut, the brakes are already engaged and can immediately counteract gravity, preventing position overshoot.
Solution Approach 2:
The drive force continues to be applied during the brake activation period, maintaining continuous useful action to counteract gravity. This continuity prevents the interruption that would cause gravity jump and subsequent position inaccuracy.
3Speed
If the brake device is activated immediately upon emergency stop, then braking force is applied as quickly as possible, but excessive brake wear or failure may occur due to aggressive and prolonged braking
Solution Approach 1:
The brake device is activated in advance while drive force is maintained, allowing the braking system to engage gradually rather than abruptly. This preliminary activation reduces shock loads and thermal stress on brake components, improving reliability.
Solution Approach 2:
The control method changes the parameter of drive force output, maintaining it during brake activation rather than removing it immediately. This parameter change allows smoother brake engagement and reduces the aggressiveness of braking, decreasing wear and failure risk.
Data Source
Figure 1
Figure 2~3
AI summary
A method of controlling an elevator car (22), the method comprising: driving the elevator car (22) with a drive system (30) including a drive device (32) and a brake device (36); detecting an emergency stop condition; triggering the brake device (36) in response to detecting an emergency stop condition; determining a delay to be applied between triggering the brake device (36) and stopping the drive device (32); and waiting for a time period corresponding to the delay before stopping the drive device (32).