Elevator Brake Control for Smooth Startup Torque
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Solution Overview
Problem
Elevators may shake during startup due to errors in weighing sensors, leading to inaccurate compensation torque output, which cannot maintain a stable state.
Innovation Solution
An elevator system with a brake control unit and torque control unit that gradually releases braking force and adjusts torque output to match the unbalance torque between the car and counterweight, using proportional integral control to minimize sharp torque changes and reduce shaking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the brake is released suddenly to start the elevator, then the startup time is reduced, but the car shakes due to abrupt torque changes
Solution Approach 1:
The brake control unit dynamically adjusts the braking force during the transition from stopped to moving state. The braking force is gradually reduced rather than abruptly released, allowing the car to accelerate smoothly while maintaining stability. This dynamic control resolves the contradiction by making the braking force adaptable to the real-time state of the elevator system.
Solution Approach 2:
The system changes the parameter of braking force from a fixed high value to a gradually decreasing value during startup. By continuously adjusting the braking force parameter in response to car movement, the system achieves both rapid startup and minimal shaking, resolving the contradiction between speed and stability.
2Reliability
If the compensation torque is increased to prevent car fall, then the safety is improved, but the car shakes upon starting due to torque error
Solution Approach 1:
The control unit receives feedback from the weighing sensor about the actual car weight and dynamically adjusts the compensation torque accordingly. This feedback mechanism ensures that the compensation torque accurately matches the actual unbalance torque, preventing both car fall and shaking. The system continuously monitors and adjusts the torque to maintain both safety and stability.
Solution Approach 2:
The brake control unit performs preliminary action by gradually reducing the braking force before the car fully starts moving. This preliminary adjustment of braking force, combined with the compensation torque, prevents sudden torque changes that would cause shaking while maintaining safety throughout the transition period.
3Measurement precision
If the weighing sensor is used to detect car weight, then the compensation torque can be determined, but sensor error causes inaccurate torque output and car shaking
Solution Approach 1:
The control unit uses feedback from the weighing sensor to continuously monitor the actual car weight and adjusts the compensation torque in real-time. This feedback loop compensates for sensor errors by dynamically adjusting the torque output to match the actual unbalance torque, thereby maintaining car stability despite measurement imperfections.
Solution Approach 2:
The brake control unit performs preliminary control by gradually reducing braking force based on anticipated weight conditions. This preliminary action, combined with real-time torque adjustment based on weighing sensor feedback, compensates for potential sensor errors before they can cause significant shaking.
Data Source
Figure 1
Figure 2
Figure 3(a)~3(d)
AI summary
The elevator includes a car (104), a drive unit for moving the car by rotating a rotary body connected to the car, a brake (102) for applying a braking force to the rotary body, an elevator control unit (2) for controlling an operation of the car, a brake control unit (20) for changing a brake torque of the brake stepwise for releasing upon reception of a start signal of the elevator from the elevator control unit (2), and a torque control unit (23) for controlling a torque of the drive unit to approximate the car speed to zero upon reception of the start signal of the elevator from the elevator control unit (2).