Parallel Link Actuation Control With Interpolated Position Correction
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Solution Overview
Problem
Existing link actuation devices with parallel link mechanisms face challenges in achieving desired positioning accuracy due to manufacturing and assembly errors, deflection of link mechanisms, and the impracticality of setting correction amounts for all positions using three-dimensional maps.
Innovation Solution
The proposed solution involves a link actuation device with a parallel link mechanism that includes a first and second link hub, at least three link mechanisms, a drive device with motors for each link mechanism, and a control device. The control device stores a map of drive command values for discrete positions and uses a polynomial curved surface formula to interpolate drive command values for positions not stored in the map, thereby improving positioning accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a three-dimensional map with correction amounts for all positions is used, then positioning accuracy is improved, but the amount of data required and the burden on operators increase enormously
Solution Approach 1:
The three-dimensional map is segmented into multiple two-dimensional maps, each corresponding to a specific link hub center position. This segmentation reduces the data complexity and makes it more manageable while maintaining positioning accuracy across the full workspace.
Solution Approach 2:
The patent transitions from a full three-dimensional map to multiple two-dimensional maps by fixing one dimension (link hub center position) and varying the other two dimensions (motor command values). This dimensional reduction significantly decreases data requirements while preserving essential correction information.
2Measurement precision
If the number of measurement points for generating the three-dimensional map is increased, then positioning accuracy is improved, but the time required for adjustment and the burden on operators increase enormously
Solution Approach 1:
The measurement and map generation process is segmented into multiple independent two-dimensional measurements rather than one comprehensive three-dimensional measurement. This allows for more efficient data collection and processing, reducing overall adjustment time.
Solution Approach 2:
Instead of measuring all possible positions in the three-dimensional space, the patent measures only the essential two-dimensional planes at key link hub positions. This partial measurement approach provides sufficient correction data without the exhaustive time commitment of full three-dimensional mapping.
3Device complexity
If a theoretical inverse kinematic function is used to calculate drive command values, then the device complexity is reduced, but positioning accuracy cannot be achieved due to manufacturing errors, assembly errors, and deflection
Solution Approach 1:
Correction maps are generated in advance through measurement and stored for later use. These pre-computed correction data account for manufacturing and assembly errors, allowing the system to compensate for inaccuracies without adding complex real-time calculation requirements.
Solution Approach 2:
The correction maps serve as an intermediary between the theoretical inverse kinematic function and the actual motor commands. They translate the ideal theoretical values into corrected practical values that account for real-world errors, maintaining simple control logic while improving accuracy.
Data Source
AI summary
A link actuation device includes a proximal link hub, a distal link hub, link mechanisms that couple the link hubs, an actuator, and a control device. The actuator includes motors provided for link mechanisms, respectively. The control device stores a map in which drive command values for each of the motors corresponding to a plurality of discrete positions within a movable range of the distal link hub are stored. Upon receipt of a command value for movement to a position that coincides with none of the plurality of positions within the movable range, the control device determines a drive command value for each of the motors by interpolating a region surrounded by four points at the plurality of positions on the map using a polynomial curved surface formula.