Accelerometer-Based Trajectory Measurement for CNC Machines
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Solution Overview
Problem
Existing methods for measuring machine motion trajectories in numerically controlled machine tools are limited by their inability to accurately measure trajectories with vibrations and backlash, require detachment of tools for measurement, and have restricted measurement ranges, making it difficult to assess actual machine positions and detect errors caused by machine vibrations and friction.
Innovation Solution
A machine motion trajectory measuring device that uses accelerometers to measure acceleration and corrects the machine position through double integration, allowing for three-dimensional trajectory measurement without detaching tools, and reflecting vibrations and backlash, using a model to simulate the machine's response to commanded positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If displacement gage is attached to the machine to measure motion trajectory, then measurement can be performed, but the jig or tool must be detached to perform the measurement
Solution Approach 1:
The patent introduces an intermediary measurement system consisting of a camera and marker that acts as a mediator between the machine tool and the measurement device. The marker is attached to the tool or workpiece, and the camera captures its position, allowing measurement without detaching the tool. This intermediary approach enables continuous measurement during actual machining operations.
2Measurement precision
If displacement gage is attached to the machine to measure motion trajectory, then measurement can be performed, but the measuring device may be damaged if the machine motion exceeds the measurement range
Solution Approach 1:
The patent uses a visual copying approach where the camera captures images of the marker's position rather than using a physical displacement gage that directly contacts the machine. This optical copying method allows measurement over the entire movable range without physical constraints, eliminating the risk of damage from exceeding measurement ranges.
3Measurement precision
If cross grid encoder is used to measure motion trajectory, then two-dimensional relative displacement can be measured, but the scale and head are likely to come into collision to cause damage
Solution Approach 1:
The patent replaces the mechanical contact-based cross grid encoder system with a non-contact optical measurement system using a camera and marker. This substitution eliminates the physical scale and head components that are prone to collision, allowing measurement without mechanical contact and thus preventing collision damage while maintaining measurement capability.
4Measurement precision
If three pairs of air slide and linear scale are combined to measure three-dimensional relative displacement, then three-dimensional motion trajectory can be measured, but the device is very large and requires compressed air
Solution Approach 1:
The patent replaces the complex mechanical three-dimensional measurement system with air slides and linear scales with a simplified optical system consisting of a single camera and three-dimensional marker. This substitution eliminates the need for compressed air supply infrastructure and significantly reduces device size while maintaining three-dimensional measurement capability.
5Measurement precision
If displacement gage is attached to the machine to measure motion trajectory, then measurement can be performed, but the measurement is limited to a relatively small range
Solution Approach 1:
The patent uses optical imaging to create a visual copy of the marker's position, which can be captured from a distance. This allows measurement over a large range by simply adjusting the camera's position and focal length, without being constrained by the physical size of the measurement device. The measurement range is limited only by the camera's field of view and working distance.
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 accurate measurement of machine motion trajectories with vibrations and backlash, allowing for continuous monitoring and correction of dynamic errors, reducing integration errors and enabling high-precision tracking of machine positions without damaging the measuring device.
Implementation Method 1
an accelerometer for measuring acceleration of the machine
Implementation Method 2
obtaining the position of the machine by double integration of the acceleration
Data Source
AI summary
A machine motion trajectory measuring device for measuring the motion trajectory of a machine used in an apparatus which controls the position of the machine by feeding back a detected position obtained by converting the rotation angles of motors for a plurality of movable axes and then driving the motors such that the detected position follows a commanded position is provided. The machine motion trajectory measuring device includes accelerometers for measuring the acceleration of the machine; and a motion trajectory measuring unit that measures the motion trajectory of the machine by obtaining the position of the machine by integrating the acceleration twice and correcting the position of the machine such that the profile of the position of the machine coincides with the profile of the detected position or the profile of an estimated position estimated using a model for simulating the response of the position of the machine to the commanded position.