Articulated Measuring Arm Accuracy Feedback
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Solution Overview
Problem
Three-dimensional measuring machines face inaccuracies in coordinate acquisition due to factors like axial and radial play in arm joints, bending of segments, and encoder resolution, which increase with displacement amplitude, leading to overall measurement errors.
Innovation Solution
A method is introduced where an articulated measuring arm with a measuring head and rotary encoders provides an accuracy indicator to the operator, allowing them to adjust the measurement position to achieve precision beyond a predetermined threshold, using finite element modeling to simulate and optimize measurement positions for improved accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the measuring arm moves from one measurement point to another, then the measurement coverage is improved, but the measurement accuracy deteriorates due to accumulated errors from joint play, segment bending, and encoder resolution
Solution Approach 1:
The system calculates and provides feedback to the operator about the expected measurement accuracy for different arm positions. This feedback loop enables the operator to adjust the measurement strategy by selecting alternative positions or repeating measurements to maintain accuracy within acceptable tolerances while still achieving comprehensive measurement coverage.
Solution Approach 2:
The system dynamically adapts the measurement process by allowing repeated measurements at the same point with different arm positions. The operator can choose to remeasure points by moving the arm to different positions and then returning, thereby dynamically adjusting the measurement path to minimize accumulated errors while maintaining coverage.
2Length of moving object
If the amplitude of movement of measuring arm elements is increased, then the measurement range is improved, but the measurement error increases due to joint play and segment bending
Solution Approach 1:
Before performing the actual measurement, the system calculates the expected accuracy for various arm positions based on finite element modeling of the arm structure. This preliminary accuracy assessment allows the operator to plan the measurement path in advance, selecting positions that maintain accuracy while achieving the required measurement range.
Solution Approach 2:
The system changes the measurement parameters by allowing flexible repetition of measurements at different arm positions. Instead of following a fixed path, the operator can modify the measurement parameters by selecting alternative arm configurations and repeating measurements, thereby optimizing the balance between measurement range and precision.
Data Source
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AI summary
A method for measuring a part using an articulated measuring arm (1) comprising a measuring head (9) equipped with a pointing device and at least one joint equipped with at least one rotary encoder (12, 13, 14, 15), comprising the steps of: - pointing a first measuring point on the part, the measuring arm (1) assuming a first measuring position; - manipulating the measuring arm (1) to a second measuring position to point a second measuring point on the part in order to acquire a geometric characteristic of the part from the measuring points; - determining the accuracy of the acquired geometric characteristic as a function of the first and second measuring positions of the arm. An articulated measuring arm (1) adapted to implement the method of the invention.