Bridge Displacement Measurement Using Geophone Frequency Compensation

The patent replaces optical measurement systems (laser, radar interferometer) with a mechanical vibration-based measurement system using geophone sensors. The geophone detects bridge vibrations mechanically, and displacement is derived through signal processing, eliminating the need for expensive high-power lasers while maintaining measurement capability.

The patent employs inexpensive geophone sensors instead of expensive laser systems. The geophone is a low-cost device that can be easily replaced or moved to different measurement positions, providing an economical solution for displacement measurement through vibration analysis.

The patent replaces the complex radar interferometer system with a simple mechanical vibration detection system using geophone sensors. The measurement is achieved through mechanical vibration detection and mathematical integration rather than complex radar interference patterns, significantly reducing device complexity.

The patent extracts only the essential measurement function from complex systems. Instead of using full radar interferometer systems with their complex hardware and software, the invention extracts the core displacement measurement capability through simple vibration detection and integration, removing unnecessary complexity.

The patent changes the measurement parameter from acceleration (prone to error propagation) to velocity by using geophone sensors that directly measure velocity through their high-pass filter characteristics. This parameter change eliminates the need for double integration and reduces error propagation, improving measurement precision while maintaining low device cost.

Instead of measuring acceleration and integrating twice to obtain displacement (which amplifies errors), the patent inverts the approach by measuring velocity directly with geophones and integrating once. This inverted measurement strategy reduces error propagation while keeping device costs low.

The patent converts the geophone's high-pass filter characteristic, which was traditionally seen as a limitation causing attenuation at low frequencies, into a beneficial feature. By designing the system to work with this characteristic and using appropriate signal processing, the geophone's resonance behavior is utilized to achieve accurate displacement measurements without requiring expensive compensated geophones or complex digital filters.

The patent uses standard, inexpensive geophone sensors without requiring expensive compensated versions. The simple geophone design is sufficient when paired with the appropriate signal processing approach, providing a cost-effective solution that maintains measurement precision.