The paper presents an algorithm for the real-time evaluation of the actual end-effector orientation (pose) of general parallel spherical wrists. Conceptually, the method relies on the evidence that the pose of a rigid body is defined once the location of at least two linearly independent vectors attached to the body is known. The location of these vectors of the wrist end-effector is determined by the solution of the direct position analysis of some properly chosen kinematic chains (legs) of the manipulator. In order to accomplish this analysis, extra-sensors, which measure suitable non-actuated variables of the chosen legs, need to be placed in addition to the ones normally embedded in the servo motors, i.e. the sensors which measure the actuated variables. From a mathematical point of view, the algorithm is built on the Polar Decomposition of a matrix and has inherent least square features. Thus, together with measurement redundancy, i.e. more sensors (extra-sensors) than the mechanism degrees of freedom, the method also allows minimizing the influence of both round-off and measurement errors on the estimation of the location of the wrist end-effector. The method is general but, in order to prove its effectiveness, without loss of generality it has been customized to the solution of the (3-UPS)S fully parallel wrist architecture. Comparison of the proposed method, in both its general and specialized form, with others from the literature is provided.
- Design Engineering Division and Computers and Information in Engineering Division
Real-Time Direct Position Analysis of Parallel Spherical Wrists by Using Extra Sensor Data
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Vertechy, R, & Parenti-Castelli, V. "Real-Time Direct Position Analysis of Parallel Spherical Wrists by Using Extra Sensor Data." Proceedings of the ASME 2004 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. Volume 2: 28th Biennial Mechanisms and Robotics Conference, Parts A and B. Salt Lake City, Utah, USA. September 28–October 2, 2004. pp. 875-883. ASME. https://doi.org/10.1115/DETC2004-57340
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