Feedforward Vibration Isolation to Prevent Feedback Sensor Saturation
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Solution Overview
Problem
Existing active vibration-isolation systems often saturate in noisy environments, leading to inadequate performance and the need for costly hardware changes or redesigns to maintain effective vibration reduction for precision instruments.
Innovation Solution
The implementation of a feedforward control system using a less sensitive motion sensor mounted on the base, which processes signals to drive actuators and reduce intermediate mass motion, allowing the feedback system to operate effectively in noisier conditions without altering existing hardware.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a feedback system with high-sensitivity motion sensors is used to detect and counteract vibrations, then vibration reduction performance is improved, but the system saturates in noisy environments and becomes inoperative
Solution Approach 1:
The system segments the vibration detection function into two separate sensor systems: feedforward sensors mounted on the base that detect incoming vibrations before they reach the payload, and feedback sensors mounted on the payload that detect residual vibrations. This segmentation allows each sensor type to be optimized for its specific function and operating range, preventing saturation of the feedback sensors by dividing the detection burden.
Solution Approach 2:
The feedforward control system performs preliminary action by detecting base vibrations before they are transmitted to the payload and generating counteracting actuator commands in advance. This proactive approach reduces the amplitude of vibrations reaching the payload, keeping them within the measurable range of feedback sensors and preventing feedback sensor saturation.
2Device complexity
If passive motion dampers are used to reduce vibrations, then system complexity is reduced, but adequate vibration isolation cannot be achieved for precision instruments requiring high levels of isolation
Solution Approach 1:
The system implements active feedback control where motion sensors on the payload detect residual vibrations, the control circuit processes these signals, and actuators generate counteracting forces to eliminate detected vibrations. This closed-loop feedback mechanism enables precision instruments to achieve vibration isolation levels that passive dampers alone cannot provide.
Solution Approach 2:
The control circuit acts as an intermediary that receives signals from both feedforward and feedback sensors, processes them through filtering and integration algorithms, and generates appropriate actuator commands. This intermediary processing layer combines information from multiple sources to optimize the counter-vibration signal, achieving superior isolation performance.
3Device complexity
If the feedback system operates alone without feedforward assistance, then hardware requirements remain simple, but the system cannot handle environments with high levels of external vibration
Solution Approach 1:
The system merges feedforward control and feedback control into a unified hybrid system. Feedforward sensors detect incoming vibrations at the base level, generate preliminary counteracting commands, which are then refined and supplemented by feedback sensors detecting actual payload vibrations. The combined control signals drive the actuators to achieve vibration reduction across a broader range of environmental conditions than either system alone.
Data Source
AI summary
Apparatus and methods to reduce unwanted motion in precision instruments are described. An active vibration-isolation system may include a feedback loop that senses motion of an intermediate mass. In noisy environments, where the feedback loop would otherwise fail or provide inadequate isolation, feedforward control can be implemented to sense floor vibrations and reduce motion of the intermediate mass that would otherwise be induced by the floor vibrations. The feedforward control can reduce motion of the intermediate mass to a level that allows the feedback loop to operate satisfactorily.