Articulated Arm CMM Tilt Compensation Without Encoder Recalibration
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Solution Overview
Problem
Conventional coordinate measuring machines (CMMs) face challenges in achieving high accuracy, reliability, durability, ease of use, and low cost, particularly in terms of encoder calibration and tilt compensation during measurement processes.
Innovation Solution
The implementation of an articulated arm CMM with an absolute encoder and a tilt sensor, allowing for partial power-off of encoders without recalibration and automatic tilt compensation, along with modular features like counterbalance systems and feature packs for enhanced functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If conventional incremental encoders are used in articulated arm CMM, then the device can operate with lower cost and simpler structure, but the encoder requires recalibration after power-off which reduces productivity and increases loss of time
Solution Approach 1:
The patent replaces incremental encoders with absolute encoders that provide absolute position information without requiring continuous power or recalibration. This substitution eliminates the recalibration step after power-off, resolving the contradiction between energy saving and productivity.
2Measurement precision
If the articulated arm CMM base is rigidly fixed to prevent tilting, then measurement accuracy is improved, but the portability and ease of operation deteriorates
Solution Approach 1:
The patent uses tilt sensors to detect base orientation and feeds this information back to the measurement system. The system then compensates for tilt effects through coordinate transformation, allowing the base to remain portable while maintaining measurement accuracy.
Solution Approach 2:
The patent changes the measurement parameters by introducing tilt angle measurements and using these to transform coordinate systems. This allows accurate measurements even when the base is tilted, resolving the contradiction between portability and precision.
3Measurement precision
If tilt compensation features are added to the articulated arm CMM, then measurement accuracy under tilted conditions is improved, but device complexity increases
Solution Approach 1:
The patent introduces tilt sensors as intermediary devices that measure base orientation and enable software-based compensation. This approach adds minimal hardware complexity while achieving the goal of improved measurement accuracy under tilted conditions.
4Reliability
If absolute encoders are used instead of incremental encoders, then reliability is improved by eliminating recalibration requirements, but manufacturing cost increases
Solution Approach 1:
The patent replaces incremental encoders with absolute encoders, accepting the higher manufacturing cost in exchange for significantly improved reliability and elimination of recalibration requirements. This substitution is particularly valuable in portable applications where the device may be frequently powered on and off.
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 efficient and accurate coordinate measurement with reduced power consumption, improved durability, and modular flexibility, addressing the limitations of existing CMMs by allowing instant data acquisition without recalibration and providing real-time tilt compensation.
Implementation Method 1
The tilt sensor can be rigidly connected to the base such that the tilt sensor can detect a tilting angle of the base
Data Source
AI summary
A method of operating an articulated arm CMM is provided. One or more coordinates on an object can be measured with the articulated arm CMM. At least one of the encoders can then be at least partially powered-off. The encoder can then be powered on and one or more coordinates on the same object can be measured without recalibrating the encoder.