Hoist Motor Speed Control via Cable Force Position Derivative
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Solution Overview
Problem
Existing speed-controllable hoist drives face challenges in reducing impact loads during lifting, as methods based on monitoring the time derivative of cable force are not well-suited for controlling rotation speeds effectively across a range of lifting speeds.
Innovation Solution
The method involves using the position derivative of the cable force to control the rotation speed of the motor, where the hoist controller determines the position derivative of the cable force and adjusts the final speed instruction to prevent excessive impact loads by monitoring changes in cable force relative to the position of the hoisting member.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the lifting speed is kept low when removing the load from the ground, then the impact load is reduced, but the productivity is decreased
Solution Approach 1:
The hoist controller performs preliminary detection of the load state by monitoring cable force and its derivatives before the load is fully lifted. When the load is detected to be airborne, the controller proactively reduces the lifting speed to prevent impact load, rather than waiting for the impact to occur. This preliminary action allows smooth load removal while maintaining high productivity during stable lifting phases.
Solution Approach 2:
The system continuously monitors cable force and calculates its time and position derivatives to provide real-time feedback on the load state. Based on this feedback, the hoist controller dynamically adjusts the lifting speed - reducing it when the load is airborne and maintaining higher speeds when the load is stable. This closed-loop feedback control resolves the contradiction by enabling speed optimization at different lifting stages.
2Object-affected harmful factors
If the time derivative of cable force is monitored to control lifting speed, then the impact load is reduced, but the control effectiveness is insufficient for speed-controllable hoist drives with variable lifting speeds
Solution Approach 1:
The control system transitions from static speed control to dynamic speed control by introducing position-dependent derivative monitoring. The hoist controller calculates the derivative of cable force with respect to position (dF/dz) in addition to the time derivative (dF/dt). This dynamic approach adapts to varying lifting speeds because the position derivative provides speed-independent information about load state changes, making the control effective across the entire speed range of speed-controllable hoist drives.
Solution Approach 2:
The invention changes the control parameter from solely time-based (dF/dt) to include position-based measurement (dF/dz). The position derivative of cable force serves as a more robust indicator of load state transitions regardless of lifting speed. By using this transformed parameter, the system maintains accurate load detection and speed control adaptability across varying operating conditions.
Data Source
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AI summary
A method according to the invention of controlling a rotation speed of a motor of a speed-controllable hoist drive comprises receiving a lift speed instruction (?'m )\ forming a final speed instruction (?m ) by using initial information con- taining the lift speed instruction (?'m ); and using the final speed instruction (?m ) as a speed instruction for the rotation speed of the motor of the speed- controllable hoist drive. The method further comprises monitoring a position derivative of an actual value of a cable force (dF/dz). The initial information for forming the final speed instruction (?m ) comprises the position derivative of the actual value of the cable force (dF/dz).