Elevator Cable Sway Reduction via Motion Profile Control
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Solution Overview
Problem
Elevator cable sway caused by external disturbances such as wind-induced building deflection and vibrations leads to cable tangling and structural weakening, which existing passive damping systems attempt to mitigate but at the cost of increased system complexity and reduced flexibility.
Innovation Solution
The elevator car's vertical movement is strategically controlled to induce dynamical terms that counteract cable sway, using a motion profile defined by changes in the length, velocity, and acceleration of the elevator rope to minimize sway without external actuators, with predetermined motion profiles simplifying computational requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If passive damping mechanical systems are added to the elevator shaft to reduce cable sway, then cable vibration is reduced, but system cost and complexity increase
Solution Approach 1:
The elevator car itself is used to generate counteracting vibrations through controlled motion profile adjustments, eliminating the need for external damping devices. The car's movement serves dual purposes: transporting passengers and actively reducing cable sway through self-generated counter-vibrations.
Solution Approach 2:
The motion profile parameters of the elevator car (acceleration, velocity, position over time) are dynamically adjusted to generate counter-vibrations. By changing the temporal parameters of car movement, the system creates opposing vibrational forces that cancel out harmful cable sway without adding mechanical damping components.
2Object-affected harmful factors
If passive damping mechanical systems are added to the elevator cables to reduce vibrations, then cable oscillation is dampened, but system flexibility is reduced
Solution Approach 1:
The motion profile of the elevator car is dynamically adjusted in real-time based on operational conditions to generate appropriate counter-vibrations. This dynamic control approach allows the system to adapt to varying cable sway conditions while maintaining full system flexibility and avoiding rigid mechanical damping structures.
Solution Approach 2:
The elevator car's motion control system actively compensates for cable oscillations by generating counter-vibrations through programmed motion profile adjustments, preserving system flexibility while eliminating the need for rigid passive damping mechanisms that would constrain system adaptability.
3Object-affected harmful factors
If complex motion profiles are used to reduce cable sway, then sway reduction effectiveness improves, but computational requirements increase
Solution Approach 1:
Motion profiles that generate counter-vibrations are pre-calculated and stored in memory before operation. During elevator operation, the controller simply retrieves and executes these pre-computed profiles rather than performing complex real-time calculations, thereby achieving effective sway reduction with minimal computational burden during actual operation.
Solution Approach 2:
The counter-vibration motion profiles utilize periodic motion patterns with specific frequencies and durations that are pre-determined to effectively counteract cable sway. These periodic profiles simplify computational requirements compared to continuous complex control algorithms, as they rely on repeating predetermined sequences rather than real-time iterative calculations.
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 effectively reduces cable sway by optimizing the elevator car's motion profile, minimizing computational complexity and system costs, while ensuring safe and efficient elevator operation.
Implementation Method 1
vertical movement of the elevator car induces an extra dynamical terms in the cable equations, that counteracts the cable sway due to external disturbances on the building
Data Source
AI summary
An elevator system includes an elevator car supported by an elevator rope wrapped around a sheave, such that a rotation of the sheave changes a length of the elevator rope between the sheave and the elevator car thereby controlling a movement of the elevator car within an elevator shaft of the elevator system. An elevator cable is connected to the elevator car and the elevator shaft to carry electrical signals to the elevator car. The operation of the elevator system is controlled in response to receiving a call for a movement of the elevator car requesting a change of the length of the elevator rope. A motion profile of the elevator car causing the requested change of the length of the elevator rope that minimizes the sway of the cable is determined according to a model of a cable relating a sway of the cable to a motion profile. Next, the motion of the elevator car is controlled according to the determined motion profile.