Elevator Counterbalancing System Backlash Compensation
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Solution Overview
Problem
In counterbalancing systems, such as elevators, the transition from stationary to moving can cause rollback, vibrations, and noise due to the brief period between brake disengagement and motor activation, leading to discomfort for occupants and disturbances.
Innovation Solution
A method is introduced to determine the pre-torque direction and magnitude by applying torques in opposing directions while the brake is engaged, using an encoder to detect backlash and adjust the motor's torque accordingly, ensuring a smooth transition by pre-applying torque opposite to the load direction before brake release.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the brake is disengaged and motor is activated to resume motion, then the elevator cab can move to another floor, but rollback and vibrations occur during the transition period
Solution Approach 1:
The system performs preliminary action by detecting the load direction and magnitude before brake disengagement, then pre-applying torque in the opposite direction to counteract the impending rollback. This advance preparation eliminates the transition instability that would otherwise occur when the brake is released and motor activates.
Solution Approach 2:
The system applies preliminary anti-action by generating torque in the direction opposite to the load direction before brake disengagement. This counter-torque neutralizes the forces that would cause rollback and vibrations during the brake-to-motor transition, maintaining position stability throughout the motion resumption.
2Reliability
If the motor quickly catches the car to maintain stationary position after brake disengagement, then position is maintained, but auditory noises and vibrations are generated
Solution Approach 1:
The system performs preliminary action by calculating the appropriate torque magnitude and direction before brake disengagement. This pre-calculated torque is applied smoothly from the outset, eliminating the need for quick catching actions that generate noise and vibration while still maintaining reliable position holding.
Solution Approach 2:
The system changes parameters by dynamically adjusting torque magnitude and direction based on detected load conditions. By optimizing these parameters before brake disengagement, the system achieves reliable position holding with minimal noise and vibration, avoiding the harsh quick-catch scenario.
3Measurement precision
If external load weighing devices are used to determine load direction and magnitude, then accurate control is achieved, but installation and calibration costs increase
Solution Approach 1:
The system implements self-service by using the motor's own torque application and the encoder's position feedback to indirectly measure load direction and magnitude. This self-contained approach eliminates the need for external load weighing devices, achieving accurate load detection while reducing system complexity and costs.
Solution Approach 2:
The system uses an intermediary approach by employing the encoder and control system as mediators to infer load characteristics from motor torque application and position feedback. This indirect measurement method provides accurate load detection without requiring direct load weighing hardware, simplifying the overall system.
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
This approach minimizes rollback, vibrations, and noise, providing a smoother, quieter, and more consistent start for elevator movements without the need for external load weighing devices, reducing installation and calibration costs.
Implementation Method 1
This limited amount of movement may allow for determining the direction that the sheave is being pulled by activating an electric motor, with the brake engaged, to apply torques in opposing directions. There will be no movement in the direction that the sheave is being pulled, but there will be a limited amount of movement measurable in a direction opposite the direction that the sheave is being pulled due to backlash.
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A method and system for reducing -rollback in a counterbalancing system as a holding brake is released is disclosed. A limited amount of movement of a drive shaft is present in. the holding brake. A motor drive provides current to the motor with the holding brake set such that a torque is applied at the drive shaft. The current is controlled to generate torque in both directions. The limited amount of movement in the brake rnay be used to determine a direction and magnitude of torque required to support a mechanical load being applied to the motor. The motor drive then provides a current to generate the necessary torque required to support the load prior to releasing the holding brake.