Rotating Stage Assembly with Piezo Actuators for Position Error Correction
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Solution Overview
Problem
Achieving high three-dimensional positional precision in rotating stages is challenging due to random errors from bearings, spindle wobble, and thermal expansion in engineering materials, which is critical for applications like 3D x-ray imaging where precise rotation axis alignment is required.
Innovation Solution
A rotating stage assembly with five piezo actuators and corresponding capacitive sensors continuously corrects motor stage errors by adjusting the entire rotating motor and stage assembly relative to a reference frame, using a metrology disk made of low thermal expansion materials and a conductive coating for precise position and angle measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional bearings and spindles are used in rotating stages, then the device can operate with standard engineering materials, but random errors from bearing imperfections and spindle wobble cause degradation of rotational precision
Solution Approach 1:
The patent implements a feedback control system using capacitive sensors to continuously monitor the position of the rotation axis and piezoelectric actuators to apply real-time corrections. The control system processes sensor signals and adjusts actuator positions to compensate for bearing errors and spindle wobble, maintaining sub-nanometer rotational precision despite using conventional mechanical components.
2Manufacturing precision
If normal engineering materials are used in the stage assembly, then manufacturing is feasible, but thermal expansion characteristics cause dimensional variations and precision degradation
Solution Approach 1:
The patent uses piezoelectric actuators that respond to electrical voltage changes to actively compensate for thermal expansion effects. The capacitive sensors detect dimensional changes caused by temperature variations, and the control system adjusts actuator positions in real-time to counteract thermal drift, maintaining precise positioning despite temperature fluctuations.
3Measurement precision
If high precision correction systems are implemented, then position accuracy is improved, but the device complexity increases due to multiple actuators and sensors
Solution Approach 1:
The patent employs a multi-functional correction system where five piezoelectric actuators perform multiple functions: three actuators correct lateral position errors in the x and y directions, while the other two actuators correct rotational errors. The five capacitive sensors similarly perform multiple measurement functions by monitoring both position and orientation. This integrated approach achieves comprehensive error correction with a compact actuator-sensor configuration.
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
This solution ensures high precision position accuracy, correcting for mechanical and thermal anomalies, thereby enabling accurate tomographic data acquisition in 3D x-ray imaging by maintaining precise rotation axis alignment with sub-nanometer precision.
Implementation Method 1
five piezo actuators; one for translation in x, one for translation in y and three for both translational and angular motion of the z corrections
Implementation Method 2
five corresponding capacitive sensors for measuring the corrected positions
Data Source
AI summary
A rotating stage assembly performs high precision rotational angle and position error correction by continuous sensing and correcting motor stage assembly errors. It performs these corrections, to adjust for motor environmental and operational errors by sensing and correcting using five sensors placed to measure the adjustments of five corresponding actuators, which adjust the entire motor rotating stage and rotary motor assembly relative to a reference frame.