Adaptive Gain Control for Laser Interferometer Tracking Stability
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Solution Overview
Problem
The optical axis tracking control system of a tracking-type laser interferometer is unstable due to excessive or insufficient feedback control gain, which is based on the absolute distance between the retro reflector and the laser interferometer, leading to unstable tracking control.
Innovation Solution
A feedback gain adjusting method and device that starts tracking control when return light reaches a detection range and adjusts feedback gain based on settling time and jumping out time to stabilize the optical axis tracking control without relying on absolute distance measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If feedback control is performed using optical axis offset and biaxial rotation mechanism, then tracking control is achieved, but the control gain becomes excessive or insufficient based on absolute distance
Solution Approach 1:
The patent applies dynamics by making the feedback gain adjustable and adaptive rather than fixed. The gain is dynamically modified based on the detected behavior of return light (settling time and jumping out time), allowing the control system to adapt to different operating conditions and distances without requiring manual intervention or absolute distance measurement.
Solution Approach 2:
The patent implements feedback by using the position sensitive detector to monitor the behavior of return light on the detector surface. The settling time (time to reach center from circumference) and jumping out time (time to exit detection range) are measured and fed back to adjust the feedback gain, creating a closed-loop adaptive control system that stabilizes tracking control.
2Measurement precision
If absolute distance between retro reflector and laser interferometer is entered, then feedback gain can be set, but the system requires additional input and setup complexity
Solution Approach 1:
The patent applies self-service by enabling the system to automatically determine the appropriate feedback gain without requiring external input of absolute distance. The position sensitive detector autonomously measures the behavior of return light (settling time and jumping out time), and the controller automatically adjusts the feedback gain based on these measurements, making the system self-configuring and eliminating the need for manual distance entry.
Solution Approach 2:
The patent replaces the mechanical/manual process of entering absolute distance with an optical/electronic measurement system. Instead of requiring user input or mechanical measurement tools, the system uses the position sensitive detector to optically track the return light behavior and electronically compute the appropriate gain settings, substituting a simpler automated optical-electronic system for the complex manual process.
3Reliability
If feedback gain is optimized based on return light behavior, then tracking control stability is improved, but the system requires real-time monitoring of light position
Solution Approach 1:
The patent applies preliminary action by pre-establishing the relationship between return light behavior characteristics (settling time and jumping out time) and the appropriate feedback gain values. The system is designed to directly measure these time parameters and immediately apply the corresponding gain adjustment, eliminating the need for complex real-time calculations or iterative tuning processes.
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 method stabilizes the optical axis tracking control system by dynamically adjusting feedback gain in response to the behavior of return light on the position sensitive detector, ensuring effective tracking control without requiring absolute distance information.
Implementation Method 1
an position sensitive detector detecting an offset of an optical axis of the laser interferometer
Implementation Method 2
a retro reflector reflecting reflected light in a direction parallel to incident light
Data Source
AI summary
A laser interferometer that includes a laser interferometer, an position sensitive detector detecting an offset of an optical axis of the laser interferometer, a biaxial rotator turning the laser interferometer toward an arbitrary direction, an angle sensor detecting a rotation angle of the biaxial rotator, a retro reflector reflecting reflected light in a direction parallel to incident light, and a controller performing feedback control of the biaxial rotator so as to track the retro reflector based on signals from the position sensitive detector and the angle sensor. The tracking-type laser interferometer starts tracking control when return light from the retro reflector is returned to a detection range of the position sensitive detector, and changes gain for the feedback control in accordance with a behavior for a position of the return light on the position sensitive detector due to the tracking control.