Anti-Sway Control Using Frequency Filtering for Hoisting Loads
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Solution Overview
Problem
Existing anti-sway algorithms for hoisting appliances struggle to effectively control secondary sway phenomena, which have a higher frequency and are difficult to suppress, leading to reduced efficiency and productivity due to the need to stop the hoisting operation until the sway subsides.
Innovation Solution
A method and apparatus that utilize frequency domain analysis to identify primary and secondary sway frequencies, applying lowpass and highpass filters to isolate and reject secondary sway frequencies, allowing the anti-sway algorithm to focus on controlling primary sway, thereby enhancing the stability and productivity of hoisting operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing anti-sway algorithms are used to control primary sway, then primary sway is reduced, but secondary sway remains uncontrolled and reduces effectiveness
Solution Approach 1:
The patent segments the sway control problem into two distinct frequency components: primary sway (lower frequency) and secondary sway (higher frequency). By separating the control of these two phenomena, the system can address each independently. The segmentation is achieved through frequency domain analysis that identifies and processes different sway frequencies separately, allowing the anti-sway algorithm to focus on primary sway while filtering out secondary sway interference.
Solution Approach 2:
The patent extracts the harmful secondary sway frequency components from the measured angle signal using frequency domain analysis. By identifying the frequency spectrum of the sway signal and isolating the secondary sway frequencies, the system removes these harmful components through filtering before feeding the cleaned signal to the anti-sway algorithm. This extraction process eliminates the negative impact of secondary sway on control effectiveness.
2Reliability
If hoisting operation is stopped to wait for secondary sway to subside, then safety is maintained, but productivity decreases
Solution Approach 1:
The patent applies preliminary action by filtering out secondary sway frequencies from the measured angle signal before the anti-sway algorithm processes it. This preprocessing step ensures that the control system receives clean signal data without secondary sway contamination, enabling safe and continuous operation without needing to stop and wait for sway to subside naturally. The filtering action is performed in advance, allowing uninterrupted hoisting operations.
3Reliability
If frequency domain analysis and filtering are applied, then secondary sway is rejected, but system complexity increases
Solution Approach 1:
The patent replaces complex mechanical sway suppression mechanisms with signal processing-based frequency domain analysis and digital filtering. Instead of adding complex mechanical dampers or physical stabilization devices, the system uses computational methods to analyze the frequency spectrum of the sway signal and apply digital filters to remove secondary sway components. This substitution of mechanical complexity with computational processing achieves effective sway rejection while maintaining system simplicity.
Data Source
AI summary
For optimizing an anti-sway algorithm for the transport of a load by a hoisting appliance spanning a hoisting area and comprising a trolley, a reeving system and a tool handling the load, a control device is able to: record a time-domain signal representative of a measured angle of the load with respect to a vertical Z-axis during operation of the hoisting appliance; perform a frequency domain analysis on the recorded time-domain signal to estimate its frequency components; identify a primary sway frequency and a secondary sway frequency of the hoisting appliance among the estimated frequency components; filter the time-domain signal representative of a measured angle of the load with respect to a vertical Z-axis by a lowpass filter designed to reject the identified secondary sway frequency; and transport the load in the hoisting area by applying the anti-sway algorithm to the filtered signal.