Linear Motion Stage Control Apparatus Position-Dependent Filter Adaptation
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Solution Overview
Problem
Conventional control systems for linear motion stages face instability due to varying inherent oscillation frequencies with driven positions, leading to unstable operations and inadequate filtering across the operational range.
Innovation Solution
A control apparatus that adjusts cut-off frequencies and damping rates of filters based on driven positions using correction tables, employing interpolation methods to ensure accurate filtering and control responses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single representative cut-off frequency of a filter is employed, then the filter design is simple, but the filter cannot properly perform its function over the whole operational range of the linear motion stage, resulting in unstable frequency amplification
Solution Approach 1:
The patent applies dynamics by making the filter cut-off frequency variable rather than fixed. The control apparatus dynamically adjusts the cut-off frequency of the filter based on the current position of the linear motion stage, allowing the system to adapt to position-dependent oscillation characteristics and maintain stability across the entire operational range.
Solution Approach 2:
The patent changes the parameter of cut-off frequency from a constant value to a variable value that depends on stage position. By storing multiple cut-off frequency values in a lookup table and selecting the appropriate value based on current position, the system optimizes filter performance for each operational condition without requiring complex real-time calculations.
2Adaptability or versatility
If the inherent oscillation frequency varies with driven position, then the system reflects real physical characteristics, but a fixed cut-off frequency filter cannot eliminate oscillation components, resulting in mixed oscillation in control response
Solution Approach 1:
The patent changes the filter parameter (cut-off frequency) according to the stage position to match the position-dependent oscillation characteristics. This allows the filter to effectively suppress oscillation components at each position while maintaining accurate control response, resolving the contradiction between adapting to physical characteristics and achieving precision.
Solution Approach 2:
The system uses position feedback from the linear encoder to determine which cut-off frequency value to apply. The current position information feeds back to the control apparatus, which selects the appropriate filter parameter from the lookup table, ensuring the filter always operates at the optimal setting for the current operational condition.
3Measurement precision
If interpolation methods are used to determine cut-off frequencies between adjacent driven positions, then filtering accuracy is improved, but calculation complexity increases
Solution Approach 1:
The patent applies partial action by using simple linear interpolation between discrete position points rather than implementing complex continuous mathematical models. This approach provides sufficient filtering accuracy for practical applications while keeping the calculation complexity manageable, avoiding unnecessary over-engineering.
Data Source
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AI summary
The present invention relates to a control apparatus of a linear motion stage, which comprises: a first filter for filtering the frequency of a signal received from a linear encoder of the linear motion stage; an adder for adding an input signal representing a command position and a negative of an output signal of the first filter; a control for generating a control signal for controlling the linear motion stage based on an output signal of the adder; and a second filter for filtering the frequency of the control signal, wherein each of the input terminals of the first and second filters has a correction table for storing cut-off frequencies and damping rates measured according to the driven positions of the linear motion stage, thereby applying the correction table so as to determine the cut-off frequencies of the first and second filters and the damping rates according to the driven positions of the linear motion stage.