Scanning Probe Contact Force Control for Complex Surfaces

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Solution Overview

Problem

Existing scanning methods are inefficient for complex surfaces in three dimensions, as they struggle to maintain a constant contact force while minimizing bending and inertia effects, leading to inaccurate measurements.

Innovation Solution

A method using a scanning probe on a coordinate measuring machine with drive means and control systems that adjust the contact force along a determined trajectory, maintaining the force within a predefined range by considering theoretical surface profiles and cinematic effects, allowing for flexible and accurate scanning of complex surfaces.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional straight-line scanning methods are used, then the machine can cover the whole scanning area, but the scanning speed is slow and measurement precision deteriorates due to acceleration and deceleration inertia forces

Engineering Contradiction:

Improvemeasurement precisionVSAvoidscanning speed

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The patent applies dynamic scanning trajectories that allow the probe to move along curved paths at relatively constant speed, eliminating acceleration and deceleration phases. The head can rotate about two orthogonal axes during scanning, enabling continuous contact with complex surfaces while maintaining constant velocity, thus avoiding inertia forces that compromise measurement precision.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent introduces additional rotational degrees of freedom (two orthogonal rotation axes) to the conventional three-axis linear movement system. This allows the probe to scan complex three-dimensional surfaces by combining linear translation with angular rotation, enabling constant speed operation while adapting to surface geometry variations.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Reliability

If heavy machine components are used for positioning, then the structure is stable, but inertia forces during acceleration and deceleration cause bending of positioning pieces and measurement errors

Engineering Contradiction:

Improvestructural stabilityVSAvoidmeasurement accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent converts the harmful effect of heavy components by eliminating the acceleration and deceleration phases entirely. By using continuous constant-speed scanning along curved trajectories with rotational degrees of freedom, the system avoids generating inertia forces that would cause bending and measurement errors, thereby neutralizing the problem caused by heavy structural components.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Adaptability or versatility

If the probe follows complex three-dimensional surface profiles, then scanning flexibility improves, but maintaining constant contact force becomes difficult due to varying surface orientations

Engineering Contradiction:

Improvescanning flexibilityVSAvoidcontact force stability

Core Design Contradiction:

Adaptability or versatilityVSForce

Solution Approach 1:

The patent employs a control system that receives feedback from force detectors measuring the contact force between the measurement stylus and the workpiece surface. Based on this feedback and knowledge of the theoretical surface profile, the control system adjusts the positioning in real-time to maintain contact force within a predetermined range, enabling consistent measurement quality across complex three-dimensional surfaces.

Inventive Principle:

Principle #23Feedback

4Adaptability or versatility

If additional rotational degrees of freedom are added to the probe, then scanning of complex surfaces becomes possible, but device complexity increases

Engineering Contradiction:

Improvescanning capabilityVSAvoidmechanical complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent integrates multiple functions into a single coordinated system: the head rotation about two orthogonal axes serves both to orient the probe for scanning complex surface geometries and to maintain constant contact force through the control system's force detection and adjustment mechanisms. This multi-functionality reduces the need for separate specialized components for each scanning challenge.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentEP1978328B1Oscillating scanning probe with constant contact force

Publication Date: 2015.02.18 HEXAGON METROLOGY A B (SE)

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AI summary

A method for scanning a surface of a workpiece using a scanning probe 2 mounted on a support 3 on a coordinate measuring machine 4. The support contains drive means 5,7 for actuating the movement of the scanning probe 2 relatively to the support 3. The method further involves detecting means 9 to measure a contact force F applied between the tip 10 of the probe and the surface 1, control means 13 coupled to the drive means, and memory means 14 for storing theoretical profiles 19 and coordinates 20 of the surface. This method is characterized by the fact that the control means 13 adjust the actuation of the drive means 5,7 along a scanning path 18 in order to maintain the contact force 11 within the defined range of values 15 during the whole scanning operation along the scanning path 18.