Cable Force Identification Algorithm for Semi-Rigid Constraints
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Solution Overview
Problem
Existing methods for calculating cable force in cable structures with semi-rigid constraints, such as cable net structures and suspension bridges, are inaccurate due to the complexity of boundary conditions, particularly when using string vibration theory, which assumes hinge constraints and fails to account for semi-rigid constraints at both ends.
Innovation Solution
A cable force identification algorithm that involves arranging acceleration sensors at the mid-span and ends of semi-rigid constrained cables to collect vibration signals, processing these signals to identify the first natural frequency and mode shapes, and simplifying the cable model to an equivalent single-degree-of-freedom system to calculate the generalized mass and stiffness, allowing for precise cable force determination under semi-rigid constraints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If string vibration theory is used to calculate cable force, then the calculation process is simple and convenient, but the accuracy deteriorates when boundary conditions are semi-rigid constraints instead of hinge constraints
Solution Approach 1:
The patent modifies the boundary condition parameters from hinge constraints to semi-rigid constraints by introducing rotational stiffness parameters (k1, k2) into the vibration frequency equation. This parameter change allows the string vibration theory to accurately reflect the actual boundary conditions of cable structures while maintaining the simplicity of the calculation method.
Solution Approach 2:
The patent dynamically adjusts the boundary condition characteristics by incorporating variable rotational stiffness parameters that can adapt to different working conditions. This dynamic approach enables the same calculation framework to handle both hinge and semi-rigid boundary conditions, improving accuracy without sacrificing operational simplicity.
2Measurement precision
If complex boundary conditions are considered in cable force calculation, then the accuracy of cable force identification improves, but the complexity of the calculation model increases
Solution Approach 1:
The patent segments the complex boundary condition problem into independent rotational stiffness components (k1 at left end, k2 at right end) that can be separately calculated and incorporated into the vibration frequency equation. This segmentation allows complex semi-rigid boundary conditions to be handled through a systematic, modular approach that maintains calculation simplicity.
Solution Approach 2:
The patent introduces intermediate parameters (generalized mass M*, overall stiffness K*, modified first natural frequency f1') as mediators between the complex boundary conditions and the final cable force calculation. These intermediate parameters simplify the relationship between boundary conditions and cable force, allowing accurate identification without directly solving complex boundary value problems.
3Productivity
If the cable model is simplified to equivalent single-degree-of-freedom system, then the calculation efficiency improves, but the accuracy may deteriorate due to model simplification
Solution Approach 1:
The patent creates a universal equivalent single-degree-of-freedom model that can accurately represent both hinge and semi-rigid boundary conditions through the generalized mass and stiffness parameters. This universal model maintains high accuracy across different boundary condition types while providing the computational efficiency of simplified single-degree-of-freedom analysis.
Solution Approach 2:
The patent incorporates feedback through the modified first natural frequency f1' that reflects the actual boundary conditions. By using the measured natural frequency of the semi-rigid constrained cable to calculate the generalized stiffness and mass parameters, the model continuously adjusts to match the actual system behavior, ensuring accuracy despite the simplification.
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 method enhances the accuracy of cable force identification, simplifies the analysis process, and is suitable for real-time monitoring, reducing errors associated with changing boundary mechanical properties, thus offering high efficiency and practicality for cable-stayed structures with semi-rigid constraints.
Implementation Method 1
collecting vibration signals of the cable under environmental excitation or artificial excitation
Implementation Method 2
arranging an acceleration sensor vertically at the mid-span and both ends of a semi-rigid constrained cable respectively, and collecting vibration signals
Data Source
AI summary
The present invention discloses a cable force identification algorithm considering semi-rigid constraints on both ends. The present invention only needs the basic parameters such as length and mass per unit length of a cable and then adopts a modal identification algorithm such as stochastic subspace method and frequency domain decomposition method to process signals collected by the acceleration sensor, and thus obtains the corresponding first natural frequency and mode shapes, and the cable force can be solved without obtaining any other data in advance. The present invention simplifies the cable to an equivalent single-degree-of-freedom system, modifies the first natural frequency of the cable through the mode shape of modal identification, avoids the cable force identification error caused by the change of the boundary mechanical characteristics of the cable, improves the efficiency and accuracy of cable force monitoring, has good application prospect in real-time monitoring of cable force of cable-stayed structure.