Spherical Tool Adaptor for Fast Robot TCP Calibration
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Solution Overview
Problem
Calibration of articulated robots with multiple rotary joints is challenging due to cumulative positional errors, and existing methods like laser tracking are expensive and slow, while other techniques require complex parametric modeling and multiple poses, making them inefficient.
Innovation Solution
A method involving a pivot pose and a length-measuring device to determine new model parameters by measuring separation between target and pivot points, with an adaptable system for various tools, and a kit including an adaptor and inserts for precise calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If laser tracking is used for calibration, then measurement precision is improved, but cost and calibration time increase significantly
Solution Approach 1:
The patent replaces expensive laser tracking equipment with inexpensive, simple measuring devices such as ballbars or distance meters. These simple devices, while less sophisticated than laser trackers, provide sufficient accuracy for robot calibration when used with the optimized measurement method, dramatically reducing cost while maintaining acceptable calibration precision.
Solution Approach 2:
The patent extracts the essential calibration function from complex laser tracking systems and implements it using minimal equipment. By focusing only on the critical measurements needed for calibration (using a pivot pose and targeted distance measurements), the system eliminates unnecessary complexity and time-consuming procedures while retaining adequate accuracy.
2Measurement precision
If complex parametric modeling and multiple poses are used for calibration, then measurement precision is improved, but device complexity and calibration time increase
Solution Approach 1:
The patent extracts the essential calibration information from complex parametric models and obtains it through a simplified approach. By using a pivot pose and measuring distances from a fixed pivot point to the tool center point in various configurations, the method directly determines TCP coordinates without requiring complex parametric modeling, reducing system complexity while maintaining calibration accuracy.
Solution Approach 2:
The calibration process is segmented into distinct, manageable steps: establishing a pivot pose, measuring distances in different configurations, and calculating TCP coordinates. This segmentation breaks down the complex calibration task into simple, sequential operations that reduce overall system complexity and make the process more manageable.
3Measurement precision
If traditional calibration methods are used, then measurement precision is improved, but ease of operation deteriorates due to extensive setup requirements
Solution Approach 1:
The patent performs preliminary action by establishing a pivot pose and fixing a reference point before conducting measurements. This preliminary setup creates a stable reference framework that simplifies subsequent measurements and calculations, making the overall calibration process easier to operate while maintaining accuracy through the pre-established geometric relationships.
Data Source
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AI summary
An adaptor 24 is described which is adapted to fit onto and/or around an element 4 on or for a coordinate positioning machine. The element 4 has a point of interest 8, and the adaptor 24 comprises an at least part-spherical bearing surface 20 having a centre point 28 which, when fitted onto and/or around the element 4, substantially coincides with the point of interest 8. The element 4 may be a tool and the point of interest 8 may be a tool centre point (TCP) of the tool 4. With this adaptor 24, each point on the bearing surface 20 is substantially equidistant from the point of interest (e.g. TCP) 8 of the element (e.g. tool) 4 to which the ball adaptor 24 is attached, when the adaptor 24 is in place. The measurement point of a measuring device (e.g. ballbar) that bears against the at least part spherical bearing surface 20 of the adaptor 24 is then substantially coincident with the point of interest (e.g. TCP) 8 at all times during a measurement operation. In this way, the measuring device (e.g. ballbar) is effectively "addressing" the point of interest (e.g. TCP) 8 directly, almost as if the measuring device (e.g. ballbar) is connected directly to the point of interest (e.g. TCP) 8.