Coordinate Measuring Machine Active Damping for Dynamic Errors
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Solution Overview
Problem
Existing coordinate measuring machines (CMMs) face challenges in accurately measuring due to dynamic errors caused by vibrations and oscillations, which are not adequately addressed by current methods that primarily focus on static errors and simple speed-dependent calibration.
Innovation Solution
A method involving a dynamic state model and state-space controller, combined with a Kalman filter and observers, is used to estimate and actively damp vibrations and deformations, using actuators and frequency filters to manage natural frequencies and reject environmental disturbances, thereby improving measurement precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the frame structure is made of stone (granite) to increase static stiffness and measurement precision, then measurement precision is improved, but the machine weight increases and requires high forces for acceleration
Solution Approach 1:
The patent replaces passive mechanical stiffness (granite frame) with active dynamic compensation. A dynamic model predicts frame deflections caused by accelerations, and a controlling parameter compensates for these deflections in real-time, substituting the need for heavy rigid structures with intelligent control.
Solution Approach 2:
The patent changes the approach from static parameter optimization (frame material and geometry) to dynamic parameter adjustment. By continuously calculating compensating values based on actual acceleration and dynamic model parameters, the system adapts to varying operational conditions rather than relying on fixed mechanical properties.
2Productivity
If the frame structure is made lighter to reduce acceleration forces and improve speed, then productivity is improved, but vibrations and oscillations increase causing measurement errors
Solution Approach 1:
The patent substitutes mechanical vibration suppression (heavy damping structures) with a control system that actively compensates for dynamic errors. The dynamic model and controlling parameter allow lightweight structures to achieve measurement precision through software-based correction rather than physical mass.
Solution Approach 2:
The patent implements a feedback mechanism where actual accelerations are measured, fed into the dynamic model to predict frame deflections, and compensating values are applied to correct measurement errors. This closed-loop approach allows lightweight structures to maintain precision despite vibrations.
3Device complexity
If conventional static error analysis and speed-dependent calibration are used to correct measurement errors, then device complexity is kept simple, but dynamic errors from accelerations and vibrations are not adequately compensated
Solution Approach 1:
The patent performs preliminary action by pre-calculating and storing a dynamic model that represents the frame's dynamic behavior. This model is prepared in advance to predict deflections under various acceleration conditions, enabling real-time compensation without complex real-time calculations during measurement.
Solution Approach 2:
The patent introduces a dynamic model as an intermediary between the physical frame and the measurement system. This model acts as a mediator that translates acceleration inputs into predicted deflection outputs, which are then compensated, simplifying the control architecture while improving accuracy.
4Measurement precision
If measurements are taken at low accelerations to reduce dynamic measurement errors, then measurement precision is improved, but productivity decreases due to slower measurement speed
Solution Approach 1:
The patent uses feedback to maintain measurement precision at high speeds. By continuously measuring accelerations, predicting frame deflections through the dynamic model, and applying compensating values, the system achieves the accuracy of slow measurements while maintaining high measurement speeds.
Solution Approach 2:
The patent transitions from static error compensation to dynamic compensation. The system adapts to varying acceleration conditions in real-time using a dynamic model, allowing measurements to be taken at optimal speeds for each specific motion condition rather than requiring uniformly slow measurements.
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
This approach effectively reduces vibrations and oscillations, enhancing the accuracy and precision of CMMs by actively damping system frequencies and compensating for dynamic errors, allowing for higher moving speeds and reduced machine weight.
Implementation Method 1
Resonances or vibrations of machine parts when moving one frame component relative to another component are just two examples for dynamic errors
Implementation Method 2
active damping of a measuring device
Data Source
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Figure 4b~6
AI summary
Method for controlling via input-shaping applied to a driving unit the relative movement of at least two structural components of a measuring device such as a coordinate measuring machine, the relative movement being driven by means of said driving unit. The controlling signal driving the driving unit is filtered by a tunable frequency filter so as to reduce oscillations between the two structural components, whereby the filterable frequency range is continuously adapted according to at least one frequency region that is derived from at least one monitored variable physical property of one of the structural components, said property change influencing the relevant frequency range to be controlled. The variable property may be e.g. a position, a mass, an acceleration, a torque, a force, a stiffness and it is monitored by a sensor or by means of a dynamic model or an observer.