CMM Movement Control via Variable Acceleration and Jerk
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Solution Overview
Problem
Coordinate measuring machines and machine tools face challenges in maintaining measurement accuracy due to vibrations caused by movement, which are exacerbated by the position and orientation of machine parts, leading to difficulties in achieving both speed and precision.
Innovation Solution
The method involves controlling the movement of machine parts by varying the maximum acceleration and jerk based on the position and orientation of the machine part, with higher values allowed in non-critical areas and reduced in susceptible regions to minimize vibrations, using a controller that adjusts parameters dynamically according to a characteristic map or curve.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If higher maximum values for acceleration and jerk are specified to reduce measurement time, then productivity is improved, but measurement precision deteriorates due to increased vibrations
Solution Approach 1:
The patent applies dynamics by making the maximum acceleration and jerk values variable rather than constant. The control system dynamically adjusts these parameters based on the current position and orientation of the machine part, using pre-determined characteristic curves that define state-dependent maximum values. This allows the system to operate at higher accelerations in stable regions while reducing accelerations in vibration-prone regions, thereby improving productivity without sacrificing measurement precision.
Solution Approach 2:
The patent changes the parameters of maximum acceleration and jerk from fixed values to state-dependent variable values. By using characteristic curves that define maximum values as functions of machine part position and orientation, the system optimizes the balance between speed and accuracy. The control system continuously monitors the state and adjusts parameters accordingly, allowing faster operation in stable configurations while maintaining precision in sensitive configurations.
2Measurement precision
If lower maximum values for acceleration and jerk are specified to maintain measurement accuracy, then measurement precision is improved, but productivity deteriorates due to longer measurement times
Solution Approach 1:
The system dynamically adjusts acceleration and jerk limits based on real-time position and orientation data. Rather than using conservative low values throughout the entire measurement space, the control system identifies regions where high dynamics are acceptable and regions where they must be limited, optimizing the trade-off between speed and accuracy for each specific state of the machine part.
Solution Approach 2:
The patent transforms fixed safety margins into adaptive parameter settings. By establishing characteristic curves that map state variables to maximum permissible acceleration and jerk values, the system eliminates unnecessary conservatism in stable regions while maintaining appropriate caution in unstable regions, thereby reducing overall measurement time without compromising accuracy where it matters.
3Device complexity
If fixed maximum values for acceleration and jerk are used throughout the measuring volume, then device complexity is reduced, but measurement precision deteriorates in vibration-prone regions
Solution Approach 1:
The patent applies preliminary action by pre-determining and storing characteristic curves that define maximum acceleration and jerk values for various positions and orientations before actual measurement begins. This preparation work creates a lookup table or reference data structure that the control system can efficiently query during operation, avoiding the need for complex real-time calculations while still providing state-dependent parameter adjustment.
Solution Approach 2:
While maintaining relatively simple control logic, the system achieves dynamic parameter adjustment by referencing pre-computed characteristic curves. The control system's complexity remains manageable because it only needs to determine current state, query the appropriate maximum values from stored curves, and apply them - avoiding the need for complex vibration analysis or real-time simulation while still providing adaptive control.
Data Source
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AI summary
The invention relates to a method for operating a coordinate measuring machine (11) or a machine tool, wherein a movement of a machining part (41) is controlled in such a way that during the movement of the machine part (41) a predetermined maximum acceleration and/or a predetermined maximum jerk (P) is not exceeded, the maximum acceleration and/or the maximum jerk being varied depending on the position of the machine part (41) and/or depending on the alignment of the machine part.