Grid Plate Encoder Calibration for High-Accuracy Positioning
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Solution Overview
Problem
Existing grid plate encoder-based positioning systems face accuracy limitations due to manufacturing imperfections in the grid plate pattern, leading to signal imperfections and reduced positioning accuracy, especially in nano-scale manufacturing and inspection systems.
Innovation Solution
A grid plate encoder-based positioning system that includes a grid plate with optical sensors, a mapping unit to compute compensated coordinate data, and a feedback control unit to account for deviations caused by imperfections, using a compensation table or polynomial interpolation to achieve accurate positioning, and a calibration process with a mark sensor to determine true positions and compute calibration parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a grid plate with periodic pattern is used for positioning, then the positioning system can determine position in multiple degrees of freedom, but manufacturing imperfections in the grid plate pattern lead to signal imperfections and limit positioning accuracy
Solution Approach 1:
The system performs preliminary calibration by measuring the actual grid plate pattern at multiple positions and storing compensation data before actual positioning operations. This pre-characterization of the grid plate's manufacturing imperfections allows the system to compensate for them during positioning, resolving the contradiction between using a practical grid plate and achieving high accuracy.
Solution Approach 2:
The system implements feedback by comparing the encoder's raw position measurements with the pre-stored compensation data, then applying corrections based on the differences. This closed-loop approach allows the system to maintain high positioning accuracy despite manufacturing imperfections in the grid plate pattern.
2Measurement precision
If compensation for manufacturing imperfections is implemented, then positioning accuracy is improved, but system complexity increases due to additional calibration and computation requirements
Solution Approach 1:
The calibration process is performed once during system setup or periodic maintenance, and the compensation data is stored for reuse during normal positioning operations. This approach concentrates the complexity into a one-time preliminary action rather than requiring continuous complex computations during positioning, thus improving accuracy while limiting ongoing system complexity.
Solution Approach 2:
The system creates a digital copy or model of the grid plate's actual pattern characteristics through calibration measurements. This compensation map or lookup table stores the deviations and allows the system to correct positioning errors without needing to physically modify the grid plate or implement complex real-time calculations, thereby managing system complexity.
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 system provides improved accuracy in positioning elements by compensating for manufacturing imperfections in the grid plate, ensuring precise alignment even in the presence of pattern deviations, enhancing the reliability of nano-scale manufacturing and inspection processes.
Implementation Method 1
an encoder unit with one or more optical sensors for sensing a grid plate surface pattern of the grid plate surface
Data Source
AI summary
A grid plate encoder based positioning system (1) for positioning of an element is provided, the positioning system (1) comprisesa grid plate (2) with a grid plate surface (21);an encoder unit (3) with one or more optical sensors (31) for sensing a grid plate surface pattern (23) of the grid plate surface (21);an input (7) to receive coordinates (Xd, Yd) specifying a desired position of the element;a mapping unit (8) to compute compensated coordinate data (Xa, Ya) corresponding to estimated position data expected from the encoder unit (3) when the element is positioned at a desired position (Xd, Yd) specified by the setpoint coordinates;a feedback control unit (9) providing the compensated coordinate data (Xa, Ya) as a setpoint (Xs, Ys) to a positioning unit (12), with feedback control based on the estimated position data obtained from the encoder unit.Additionally, a grid plate encoder based positioning method and a method for computing compensation data are provided.