Active Damping of Elevator Car Oscillations via Traction Sheave Control
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Solution Overview
Problem
Elevators experience disruptive vertical oscillations due to changes in load and stretching/contracting of belts or ropes, particularly in systems with large travel height and few ropes, affecting riding comfort and safety.
Innovation Solution
A system comprising a sensor and controller connected to a traction sheave that monitors and controls the rotation of the sheave to maintain a baseline angular position and velocity, using a brake to prevent oscillations by adjusting the motor's operation based on sensor signals, thereby actively damping vertical oscillations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the elevator car uses soft hitch springs and few ropes for large travel height, then the device complexity is reduced, but vertical oscillations are generated causing discomfort
Solution Approach 1:
The patent applies mechanical vibration principles by using the motor to generate controlled oscillations that counteract the harmful vertical oscillations. The motor creates vibrational forces through the traction sheave that actively cancel out the unwanted car movements caused by rope elasticity and load changes.
Solution Approach 2:
The patent implements feedback control by using sensors to detect the actual position of the elevator car and comparing it with the target position. The controller continuously adjusts the motor output based on this feedback signal to eliminate position deviations and dampen oscillations, creating a closed-loop control system.
2Use of energy by moving object
If the elevator car hovers at landing with motor disengaged, then energy consumption is reduced, but position stability deteriorates due to load changes
Solution Approach 1:
The patent applies dynamics by transitioning the system from a static hover state (motor disengaged) to a dynamic control state (motor actively adjusting). The motor provides continuous small adjustments to maintain position stability while consuming minimal energy, adapting the system's behavior to the operational requirements.
Solution Approach 2:
The patent changes the control parameter from complete motor disengagement to partial motor engagement with reduced torque output. This parameter change allows the motor to provide just enough force to counteract position deviations caused by load changes, maintaining stability while minimizing energy consumption.
3Manufacturing precision
If traditional position control with gain devices is used, then landing accuracy is achieved, but oscillations are not effectively damped during hovering
Solution Approach 1:
The patent uses mechanical vibration by generating controlled oscillations through the motor that are specifically designed to counteract and dampen the harmful oscillations during hovering. This vibration-based approach addresses the oscillation problem without compromising landing accuracy.
Solution Approach 2:
The patent employs feedback control to continuously monitor car position and adjust motor output accordingly. This feedback mechanism effectively damps oscillations during hovering while maintaining the precision required for accurate landing, as the same control loop serves both functions.
Data Source
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AI summary
A system and a method are provided for damping vertical oscillations of an elevator car hovering at an elevator landing. The system includes a sensor, a controller and an elevator machine connected to a traction sheave. The sensor is adapted to provide a sensor signal indicative of rotation of the traction sheave, wherein the rotation of the traction sheave corresponds to the vertical oscillations of the hovering elevator car. The controller is adapted to provide a control signal based on the sensor signal. The elevator machine is adapted to reduce the vertical oscillations of the hovering elevator car by controlling the rotation of the traction sheave based on the control signal.