Stylus Probe Scanning Vector Calculation for Surface Measurement
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Solution Overview
Problem
Conventional shape measuring methods using a stylus to scan surfaces face challenges in achieving smooth scanning due to deviations from the measuring surface, leading to increased measurement errors and time, especially when the surface has arbitrary inclinations or angles less than a right angle.
Innovation Solution
The solution involves calculating a moving vector by rotating the stylus displacement vector by 90 degrees and adjusting it with a scalar value to detect the direction perpendicular to the measuring surface, allowing the stylus to move parallel to the surface despite frictional forces, maintaining a constant magnitude of displacement vector and enabling accurate scanning across arbitrary inclinations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the probe is moved in the direction perpendicular to the measuring force, then the measuring force can be detected, but the probe deviates from the measuring surface due to frictional force
Solution Approach 1:
Instead of moving the probe perpendicular to the measuring force (conventional approach), the invention moves the probe in the direction parallel to the measuring surface. The measuring force direction is used to determine the correct scanning direction by calculating the angle between the measuring force and the surface normal, then moving the probe perpendicular to this angle (i.e., parallel to the surface). This inversion of the conventional approach eliminates deviation caused by frictional force.
Solution Approach 2:
The invention continuously detects the measuring force acting on the stylus and uses this feedback to dynamically adjust the probe movement direction. By calculating the angle between the measuring force vector and the surface normal at each measurement point, the system adapts the scanning direction in real-time to maintain alignment with the measuring surface, ensuring smooth scanning even on arbitrarily inclined surfaces.
2Measurement precision
If the measuring force is corrected to a constant value, then measurement accuracy improves, but the probe moves on a sinusoidal track causing difficulty in performing smooth measurement
Solution Approach 1:
Rather than adjusting probe position to maintain constant measuring force (conventional method), the invention inverts the approach by moving the probe parallel to the measuring surface and allowing the measuring force to vary naturally. The constant velocity movement parallel to the surface eliminates sinusoidal tracking while maintaining measurement accuracy through proper force detection and angle calculation.
Solution Approach 2:
The invention dynamically adjusts the scanning direction based on the real-time measuring force direction, rather than maintaining a fixed scanning path. By continuously calculating the angle between the measuring force and surface normal and adapting the probe movement direction accordingly, the system achieves smooth scanning on arbitrarily inclined surfaces without sinusoidal oscillations.
3Device complexity
If the probe moves straight on extensions of straight lines linking measurement points, then the path is simple, but the measuring force exceeds limit values on curved surfaces
Solution Approach 1:
The invention uses real-time feedback from the measuring force detection to dynamically adjust the scanning direction. At each measurement point, the system detects the measuring force, calculates the angle between this force and the surface normal, and uses this information to determine the next scanning direction. This feedback mechanism ensures the probe follows the curved surface accurately while maintaining measuring force within acceptable limits.
Solution Approach 2:
Instead of forcing the probe to move in straight lines between measurement points (conventional approach), the invention inverts the approach by allowing the probe to move parallel to the measuring surface at each point, with the direction determined by the measuring force orientation. This results in smooth curved paths that naturally adapt to surface geometry while maintaining force control.
4Measurement precision
If the probe moves in the direction perpendicular to the extension upon detection of excess measuring force, then the force is corrected, but the probe needs to return to initial position and turn, resulting in unsmooth scanning measurement
Solution Approach 1:
Rather than correcting measuring force by moving perpendicular to the extension line (conventional method causing discontinuities), the invention inverts the approach by continuously moving the probe parallel to the measuring surface in the calculated scanning direction. This eliminates the need for corrective perpendicular movements and position returns, ensuring continuous smooth scanning while naturally maintaining force control through proper alignment with the surface.
Data Source
Figure 1A
Figure 1B
Figure 2
AI summary
A moving vector calculation unit calculates a moving vector M representing a quantity and a direction of movement of a probe on basis of a stylus displacement vector, a stylus displacement vector D, and a direction change angle θ of the stylus displacement vector D that is caused by a frictional force between a stylus 32 and the measuring surface 5a during scanning of the measuring surface 5a by the stylus 32. The stylus displacement vector D is a vector including a quantity and a direction of position displacement of the stylus 32 relative to the probe 5. Movement of an XY-stage 7 is controlled so that the probe 6 moves in accordance with the moving vector M.