Force-Feedback Seismometer Control Circuit for Low Noise
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Broadband seismometers with force-feedback systems face challenges in measuring weak ground motion at low frequencies due to high electronic noise, and require additional mass centering adjustments for tilt and temperature compensation, increasing size, cost, and reducing reliability.
Innovation Solution
A broadband seismometer design with a control circuit and forcing transducer that generates a feedback force sufficient to counterbalance constant accelerations, incorporating a sensing transducer to measure displacement and produce a signal for maintaining the mass at rest, with a self-noise component that reduces spectral density to achieve low noise performance without mechanical adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If strong electronic force feedback is used in short-period seismometers, then the seismometer can balance effects of tilt and temperature as well as inertial forces, but this causes noise that makes the seismometer unable to measure weak ground motion at low frequencies
Solution Approach 1:
The patent implements dynamic feedback control where the feedback gain is automatically adjusted based on operating conditions. The control circuit monitors the position of the inertial mass and dynamically modifies the feedback force strength, allowing the system to maintain reliability across varying tilt and temperature conditions while minimizing noise generation during quiet periods
Solution Approach 2:
The patent changes the parameters of the feedback system by using a control circuit that adjusts feedback gain and filtering characteristics based on detected ground motion levels and environmental conditions. This allows the seismometer to adapt between high-gain mode for stability and low-gain mode for low-noise operation
2Object-generated harmful factors
If electronic force feedback is made weaker in broadband seismometers to improve noise performance, then low frequency measurement capability is improved, but an additional mass centering adjustment mechanism is required which adds to size and cost and impairs reliability
Solution Approach 1:
The patent implements a self-adjusting feedback system where the control circuit automatically compensates for tilt and temperature effects through electronic means, eliminating the need for manual mass centering adjustment mechanisms. The system self-regulates by monitoring inertial mass position and applying appropriate feedback forces, thereby reducing mechanical complexity while maintaining noise performance
Solution Approach 2:
The patent replaces mechanical mass centering adjustment mechanisms with an electronic feedback control system. The control circuit uses sensing transducers to detect position and generates electronic feedback signals that produce forces to counteract gravitational and thermal effects, substituting mechanical adjustment with electronic control
3Reliability
If mass centering adjustment mechanism is added to broadband seismometers, then tilt and temperature compensation is improved, but the size and cost of the seismometer increase
Solution Approach 1:
The patent integrates multiple functions into the feedback control system. The same feedback transducers and control circuit that maintain inertial mass position during seismic events also automatically compensate for tilt and temperature effects. This multi-functionality eliminates dedicated mechanical adjustment mechanisms, reducing overall system size and cost
4Adaptability or versatility
If mass centering adjustment mechanism is added to broadband seismometers, then internal mechanics can be adjusted for environmental changes, but reliability is impaired due to additional adjustment requirements
Solution Approach 1:
The patent creates a self-adjusting system where the feedback control circuit continuously monitors and compensates for environmental changes without requiring manual intervention. The system automatically adapts to tilt and temperature variations through electronic feedback, eliminating reliability issues associated with mechanical adjustment mechanisms that require periodic manual servicing
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
The solution allows for accurate measurement of weak ground motion across a range of tilt and temperature without mechanical adjustments, reducing the size and cost of the seismometer while maintaining low noise performance, suitable for field service.
Implementation Method 1
a frame capacitor plate operatively connected to the frame and oriented parallel to the mass capacitor plate and spaced apart from the mass capacitor plate by a perpendicular distance
Implementation Method 2
a forcing transducer for applying a feedback force in a predetermined direction to the mass
Data Source
AI summary
A broadband weak-motion seismometer includes: a frame, a mass, a suspension means for movably connecting the mass to the frame, a sensing transducer for measuring displacement of the mass with respect to the frame and for generating a sensing transducer output signal, which is a function of the measured displacement, a forcing transducer for applying a feedback force in a predetermined direction to the mass, and a control circuit. The control circuit receives the sensing transducer output signal and generates a forcing transducer input signal that includes a self-noise component. The forcing transducer input signal is processed by the forcing transducer to apply the feedback force to maintain the mass at rest with respect to the frame. The feedback force is sufficient to counterbalance a constant acceleration of the frame of at least 0.2 m/s2 in the predetermined direction of the feedback force. The self-noise component of the forcing transducer input signal, when processed by the forcing transducer, produces variable acceleration of the mass with spectral density less than −150 dB with respect to 1 m2/s3 at 0.01 Hz.