Elevator Ride Control Instability Prevention
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Solution Overview
Problem
Active ride control systems in elevator installations can become unstable due to high feedback gain, leading to passenger discomfort and loss of confidence, as the acceleration controller is prone to instability and can produce large resonance forces.
Innovation Solution
A system with position and acceleration sensors that temporarily deactivates the controller if a selected component of the acceleration controller's output exceeds a predetermined value, using a comparator to monitor the root mean square (RMS) value of the acceleration signal and comparing it to a temperature-dependent maximum value to prevent instability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high feedback gain is used in the acceleration controller to improve vibration damping performance, then ride quality is improved, but system stability deteriorates
Solution Approach 1:
The system performs preliminary detection of instability conditions by monitoring the RMS value of acceleration controller output before actual instability occurs. When the monitored value approaches critical thresholds, the system preemptively reduces feedback gain or deactivates the acceleration controller, preventing instability from developing while maintaining optimal performance during normal operation.
Solution Approach 2:
The system implements a monitoring feedback mechanism that continuously measures the RMS value of the acceleration controller output and compares it against predetermined thresholds. This feedback loop enables real-time detection of approaching instability conditions and triggers appropriate corrective actions, creating a closed-loop stability management system that balances performance and stability.
2Object-affected harmful factors
If the acceleration controller is activated to suppress vibrations, then passenger comfort is improved, but the risk of instability and resonance increases
Solution Approach 1:
The system monitors the RMS value of acceleration controller output in real-time to detect early signs of instability before resonance occurs. When threshold values are approached, the system preemptively deactivates the acceleration controller, preventing harmful resonance forces while maintaining vibration suppression during stable operation.
Solution Approach 2:
The system introduces an intermediary monitoring mechanism that measures the RMS value of controller output as an intermediate parameter. This intermediary measurement serves as an early warning indicator of approaching instability, allowing the system to take preventive action before actual resonance and harmful vibrations occur.
3Device complexity
If simple hardware or software components are used in the controller, then device complexity is reduced, but susceptibility to instability increases
Solution Approach 1:
The system implements a simple yet effective preliminary detection mechanism using RMS value calculation and threshold comparison. This straightforward monitoring approach requires minimal additional hardware or software complexity but provides robust detection of instability conditions, enabling preventive deactivation of the acceleration controller before instability occurs.
Solution Approach 2:
The system employs a feedback mechanism based on RMS value monitoring and threshold comparison that adds minimal complexity to the controller. This feedback loop continuously assesses controller output stability and triggers appropriate responses, providing reliable instability detection with simple computational operations.
Data Source
AI summary
The present invention automatically detects the onset of instability of an elevator active ride control system and activates a system shutdown if it occurs. As an elevator car is guided along rails by guide elements, a plurality of sensors mounted on the car measure vibration transverse to a direction of travel. The signals from the sensors are input to a controller which in turn produces a controller output signal. This signal is used to energize an actuator positioned between the car and the guide elements and thereby dampen the vibrations acting on the car. As instability sets in, a controller signal increases. The controller signal is monitored by a comparator such that the actuator is deactivated if the controller signal becomes greater than a predetermined value.