Shaking Force Optimization for Accurate Frequency Response Testing
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Solution Overview
Problem
The use of highly accurate accelerometers and multiple exciters for modal experiments in large structures increases costs, and applying strong excitation forces leads to nonlinearity in frequency response functions, making it difficult to obtain accurate results.
Innovation Solution
An excitation force optimization system and method that includes an exciter, accelerometers, and an arithmetic device to derive and control the excitation force stepwise, discarding non-reproducible or excessive frequency response functions to achieve an accurate frequency response function.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a modal exciter applies a strong excitation force to a large structure, then the excitation force is sufficient for measurement, but nonlinearity appears in the frequency response function making it difficult to obtain accurate results
Solution Approach 1:
The patent divides the single large excitation force into multiple smaller excitation forces by using multiple exciters simultaneously. Each exciter applies a small excitation force to different locations on the structure, and the combined effect achieves sufficient excitation without causing nonlinearity in the frequency response function.
Solution Approach 2:
The patent combines the effects of multiple exciters by synchronizing their operations. The vibration responses from multiple exciters are merged through coherent addition, achieving the equivalent effect of a single strong excitation force while maintaining linearity and avoiding nonlinearity in the frequency response function.
2Measurement precision
If multiple exciters with small excitation force are used to avoid nonlinearity, then accurate frequency response function can be obtained, but the cost increases due to need for highly accurate accelerometers and multiple exciters
Solution Approach 1:
The patent segments the excitation task across multiple exciters, allowing each to operate at low power levels that avoid nonlinearity. This segmentation enables the use of standard, lower-cost accelerometers and exciters rather than requiring highly accurate expensive equipment.
Solution Approach 2:
The patent employs feedback control where the measured vibration responses are used to adjust and synchronize the excitation signals to the multiple exciters. This feedback mechanism ensures coherent addition of responses while allowing the use of simpler, less expensive equipment.
3Ease of operation
If impulse hammer is used for modal experiment, then the setup is simple, but attenuation becomes large for large structures making it extremely difficult to measure accurate frequency response function
Solution Approach 1:
The patent combines multiple small excitation forces from multiple exciters to achieve the cumulative effect needed for large structures. This merging of multiple weak excitations overcomes the attenuation problem that plagues single-point impulse hammer testing of large structures.
Solution Approach 2:
The patent uses controlled periodic excitation from multiple exciters rather than random impulse hammer strikes. This periodic action allows for better signal-to-noise ratio and more reliable frequency response function measurement, especially for large structures where impulse responses decay rapidly.
Data Source
AI summary
A excitation force optimization system (1) includes an exciter (10) that excites a structure (40), one or more accelerometers (20) that are installed in the structure (40) and measure vibration of the structure (40) every time the structure (40) is excited, and an arithmetic device (30) that derives a frequency response function on the basis of a measurement value of vibration of the structure (40) and controls an excitation force of the exciter (10) on the basis of the frequency response function.