Closed-Loop Stylus Probe Control for Precision Profilometry
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Solution Overview
Problem
Stylus profilometry systems lack closed-loop feedback for force and position control, making them insensitive to environmental changes and temperature-induced drift, limiting their adaptability and measurement accuracy.
Innovation Solution
A closed-loop stylus profilometry system with a probe arm, control arm, torque coils, and a sensing subsystem, where a processor generates magnetic forces and measures rotational positions to precisely control the probe tip's position and force, using a servo loop integrator for feedback-based adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If open loop stylus profilometry system is used, then device complexity is reduced, but measurement precision and force control are degraded due to lack of feedback
Solution Approach 1:
The patent implements closed-loop feedback control by using a sensing subsystem to detect stylus position and feed this information back to the control system. The control system adjusts drive signals based on the feedback to maintain precise force control and position accuracy, resolving the contradiction between system complexity and measurement precision.
2Device complexity
If open loop system is used, then device complexity is reduced, but adaptability to environmental changes and temperature drift is worsened
Solution Approach 1:
The closed-loop feedback system continuously monitors stylus position and adjusts control signals to compensate for environmental changes and temperature drift. This feedback mechanism enables the system to adapt to varying conditions while maintaining measurement accuracy, resolving the contradiction between system complexity and environmental adaptability.
3Device complexity
If separate system configurations are used for force and position measurements, then device complexity is reduced, but measurement precision is worsened due to disconnected calibrations
Solution Approach 1:
The patent combines force control and position measurement into a single integrated closed-loop system. The sensing subsystem simultaneously provides feedback for both force and position control, eliminating the need for separate configurations and disconnected calibrations. This merging improves measurement precision while maintaining manageable 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
Enables precise and adaptive force and position control, improving measurement sensitivity and adaptability to different samples and environments, reducing wear and damage to the probe tip, and enhancing the ability to characterize smaller feature sizes.
Implementation Method 1
one or more torque coils disposed on opposite sides of the control arm. The one or more torque coils may be configured to cause rotation of the control arm about a pivot joint based on interaction with the internal magnet
Implementation Method 2
a sensing subsystem. The sensing subsystem may be configured to measure a rotational position of the control arm
Data Source
AI summary
The system includes a processor configured to energize a pair of torque coils with a force signal to generate a magnetic force between the pair of torque coils and an internal magnet of a control arm disposed between the pair of torque coils. The control arm is connected to a probe arm, and the magnetic force causes the control arm and the probe arm to rotate about a pivot joint and causes a probe tip of the probe arm to contact a surface of a sample. After energizing the sensing subsystem with an excitation signal, the processor receives a sensing signal difference from the sensing subsystem that is proportional to the rotational position of the control arm, which corresponds to a height of the probe tip relative to the surface of the sample.