Tracking Laser Interferometer Servo Mechanism Vibration Control
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Solution Overview
Problem
Conventional tracking type laser interferometers experience increased tracking deviation with higher moving speeds of the retroreflector, limiting tracking control and speed due to vibration modes in the tracking control system.
Innovation Solution
A servo mechanism is introduced that calculates an estimated displacement of the retroreflector by multiplying relative angular displacement by a nominal conversion factor and applying a compensation gain, generating a compensation signal to reduce tracking deviation independently of the tracking control system gain, and includes a vibration control compensator to suppress vibration modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the gain of the tracking control system is increased to decrease tracking deviation, then tracking precision is improved, but vibration modes in the mechanism portion restrict further gain increase, limiting tracking speed
Solution Approach 1:
The invention introduces a feedback mechanism where the actual angular displacement of the carriage is detected and fed back to the controller. The controller calculates the difference between the target angular displacement and actual angular displacement, then adjusts the carriage rotation accordingly. This closed-loop feedback system enables precise tracking without requiring excessive gain that would excite vibration modes, thus resolving the contradiction between tracking precision and tracking speed.
Solution Approach 2:
The invention replaces pure mechanical tracking control with a combination of optical detection and computational control. Position detectors detect the position of the retroreflector, and the controller computationally determines the required carriage rotation based on target position and actual position differences. This substitution of mechanical control with optical-mechanical-computational integration allows for smoother, more precise control that avoids mechanical vibrations while maintaining high tracking precision and speed.
2Productivity
If the moving speed of the retroreflector is increased, then productivity is improved, but tracking deviation increases and may exceed the detection range of the position detector
Solution Approach 1:
The invention implements dynamic tracking control where the carriage rotation speed and position are continuously adjusted based on the real-time position of the retroreflector. The controller calculates the required angular displacement dynamically using the positions of both the retroreflector and carriage, enabling the system to track high-speed moving targets while maintaining the laser beam within the detection range of the position detector. This dynamic adaptation allows high productivity without sacrificing tracking precision.
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 servo mechanism effectively reduces tracking deviation by up to (1 - Kf) times, allowing for increased tracking speed without further increasing the tracking control system gain, and further suppresses vibrational behaviors.
Implementation Method 1
interference of the laser beam reflected in a returning direction by the retroreflector 10 is utilized to detect a displacement of the retroreflector 10
Implementation Method 2
laser beam reflected in a returning direction by the retroreflector 10
Data Source
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AI summary
There is provided a tracking type laser interferometer in which a laser beam is irradiated to a retroreflector 10, or an object to be measured, from a laser interferometer 24 mounted on a carriage 22 arranged so as to rotate around a turning center which is fixed and placed, interference of the laser beam reflected in a returning direction by the retroreflector 10 is utilized to detect a displacement of the retroreflector 10 and a tracking deviation detected as positional change of an optical axis of the laser beam is used to carry out tracking, thereby controlling the rotation of the carriage 22, and the tracking type laser interferometer is provided with a servo mechanism having means for adding a tracking deviation ΔLf to a signal obtained by multiplying a relative angular displacement Θa of the carriage 22 by a nominal value Kmn of a conversion factor Km, thereby calculating an estimated value Lc* of displacement of the retroreflector 10, means for multiplying the estimated value Lc* of displacement of the retroreflector 10 by a compensation gain Kf which is given as 0 < Kf < 1 and differentiating the same to generate a compensation signal Vf of a target speed of the carriage 22, and means for adding a compensation signal Vf to a signal obtained by multiplying the tracking deviation ΔLf by a gain Kp of the tracking control system to generate a target speed Var of the carriage 22, thereby increasing a tracking speed of the tracking type laser interferometer.