Torsional Vibration Damping in Lifting Device Tethers
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Solution Overview
Problem
Existing lifting devices, such as cranes, face challenges in effectively damping torsional vibrations about the vertical axis, which hinder rapid and precise load manipulation due to the complexity and cost of existing solutions, as well as the requirement for precise geometric and mechanical models.
Innovation Solution
A method that identifies model parameters of torsional vibrations using an identification method at specific lifting heights, allowing for damping without manual controller parameter setting, utilizing hydraulic or electric actuators and camera systems for precise angle measurement, and employing a state controller with anti-wind-up protection to adjust actuator positions and speeds for effective damping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a slewing gear is arranged between the load-receiving element and the tethers to compensate for torsional vibrations, then the torsional vibrations can be compensated, but the device complexity increases and the payload is reduced by the weight of the slewing gear
Solution Approach 1:
The patent replaces the mechanical sleving gear system with an active control system using actuators on tethers. Instead of using a complex mechanical device to physically rotate the load-receiving element, the invention uses controlled length adjustments of the tethers to achieve the same torsional vibration compensation effect, thereby eliminating the need for heavy mechanical components
Solution Approach 2:
The actuators originally designed for positioning the load-receiving element are made to serve dual functions: both positioning and torsional vibration compensation. This multi-functionality eliminates the need for separate dedicated vibration compensation mechanisms, reducing overall device complexity while maintaining effective vibration control
2Measurement precision
If conventional control methods are used to compensate for angle errors, then the angular deviations can be compensated, but torsional vibrations cannot be compensated as the dynamics are not taken into account
Solution Approach 1:
The patent implements a feedback control system where measured angular deviations and their derivatives (velocity, acceleration) are continuously fed back to the controller. This feedback loop enables the system to not only compensate for static angle errors but also dynamically respond to and suppress torsional vibrations by adjusting actuator commands based on real-time vibration state
Solution Approach 2:
The controller calculates setpoint values for the actuators based on measured angular deviations and their derivatives, anticipating the needed compensation before full vibration occurs. By using derivative information (angular velocity and acceleration), the system can proactively counteract developing vibrations rather than merely reacting to completed movements
3Productivity
If rapid movement processes are used to increase profitability, then goods handling speed increases, but undesirable vibrations of the load handling element build up which delay the manipulation process
Solution Approach 1:
The vibration compensation system operates continuously during rapid movement processes, ensuring that vibration suppression is active throughout the entire manipulation cycle. This continuous action allows rapid movements to proceed without interruption from vibration-induced delays, maintaining both high speed and high precision throughout the process
Data Source
Figure 1~2b
Figure 3
Figure 4~5
AI summary
A method for damping torsional vibrations of a load-bearing element (7) of a lifting device (1) is provided, wherein at least one controller parameter is determined on the basis of a torsional vibration model of the load-bearing element (7) as a function of the lifting height (IH) and wherein, in order to dampen the torsional vibration of the load-bearing element (7) at an arbitrary lifting height (IH), the at least one controller parameter is adapted to this lifting height (IH).