Latest Papers

ASME Journal of Mechanisms and Robotics

  • Measurement Configuration Optimization and Kinematic Calibration of a Parallel Robot
    by Huang C, Xie F, Liu X, et al. on December 10, 2021 at 12:00 am

    AbstractThis paper presents the kinematic calibration of a four-degrees-of-freedom (4DOF) high-speed parallel robot. In order to improve the calibration effect by decreasing the influence of the unobservable disturbance variables introduced by error measurement, a measurement configuration optimization method is proposed. Configurations are iteratively selected inside the workspace by a searching algorithm, then the selection results are evaluated through an index associated with the condition number of the identification Jacobian matrix; finally, the number of optimized configurations is determined. Since the selection algorithm has been shown to be sensitive to local minima, a meta-heuristic method has been applied to decrease this sensibility. To verify the effectiveness of the algorithm and kinematic calibration, computation validations, pose error estimations, and experiments are performed. The results show that the identification accuracy and calibration effect can be significantly improved by using the optimized configurations.

Design and Analysis of a Multisegment Shape Morphing Mechanism

Abstract

This article presents a novel design of a multisegment shape morphing mechanism that combines a lockable reconfigurable variable geometry truss manipulator (VGTM) with an active parallel compliant mechanism. The structure of the VGTM is in a parallel-serial structure, and its hyper-redundant degree-of-freedom (DOF) can be fully controlled by using two active flexible panels and some lockable joints. This mechanism is suitable for aerospace applications that require light and compact structure with high load-carrying ability as well as achieve multiple DOFs for large-scale shape deformation. To make shape morphing process simple and efficient, the mobility and topological configuration of the mechanism are analyzed first. Then, a control strategy combining the approximate motion mode and the exact motion mode is proposed. The kinematic models for different motion modes are established and solved analytically. It has been found that, under the exact motion mode, two approaches could be realized for the pose control under external loads for each segment. The one with the shorter moving path is selected in this article. Finally, a prototype was constructed to demonstrate the feasibility of this structure and to verify the proposed kinematic model.
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