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Publisher DOI: 10.3390/robotics8030072
Title: Performance evaluation of a sensor concept for solving the direct kinematics problem of general planar 3-RPR parallel mechanisms by using solely the linear actuators’ orientations
Language: English
Authors: Schulz, Stefan 
Keywords: direct kinematics problem;parallel robots;linear actuators’ orientations;assembly modes;general planar 3-RPR parallel mechanism;inertial measurement units;Cramér-Rao lower bound;static and dynamic experiments
Issue Date: 16-Aug-2019
Publisher: Multidisciplinary Digital Publishing Institute
Source: Robotics 8 (3): 72 (2019)
Journal or Series Name: Robotics 
Abstract (english): In this paper, we experimentally evaluate the performance of a sensor concept for solving the direct kinematics problem of a general planar 3-RPR parallel mechanism by using solely the linear actuators’ orientations. At first, we review classical methods for solving the direct kinematics problem of parallel mechanisms and discuss their disadvantages on the example of the general planar 3-RPR parallel mechanism, a planar parallel robot with two translational and one rotational degrees of freedom, where P denotes active prismatic joints and R denotes passive revolute joints. In order to avoid these disadvantages, we present a sensor concept together with an analytical formulation for solving the direct kinematics problem of a general planar 3-RPR parallel mechanism where the number of possible assembly modes can be significantly reduced when the linear actuators’ orientations are used instead of their lengths. By measuring the orientations of the linear actuators, provided, for example, by inertial measurement units, only two assembly modes exist. Finally, we investigate the accuracy of our direct kinematics solution under static as well as dynamic conditions by performing experiments on a specially designed prototype. We also investigate the solution formulation’s amplification of measurement noise on the calculated pose and show that the Cramér-Rao lower bound can be used to estimate the lower bound of the expected variances for a specific pose based exclusively on the variances of the linear actuators’ orientations.
DOI: 10.15480/882.2381
Other Identifiers: doi: 10.3390/robotics8030072
Institute: Laser- und Anlagensystemtechnik G-2 
Type: (wissenschaftlicher) Artikel
Funded by: Deutsche Forschungsgemeinschaft (DFG)
Project: Open Access Publizieren 2018 - 2019 / TU Hamburg 
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