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 Novel Reconfigurable Parallel Manipulator With Kirigami-Inspired Bennett Plano-Spherical Linkages and Angular Pouch Motors

Abstract

Drawing inspiration from kirigami, this article first presents the crease pattern of a kirigami model which is kinematically equivalent to a Bennett plano-spherical linkage. In terms of the screw theory, distinct closed-loop motion branches of the linkage are revealed. This article then introduces a new reconfigurable parallel manipulator with three hybrid kinematic limbs. Each limb consists of closed-loop subchain, the Bennett plano-spherical linkage, and a R(RR) serial chain. Constraints provided by the hybrid limb are explored by analyzing constraint screws of serial limbs kinematically equivalent to the hybrid limb in different motion branches. The analysis reveals motion characteristics of the moving platform when the parallel manipulator is in different motion branches. The kinematic model provides a unified mapping between joint inputs and outputs of the reconfigurable manipulator in all three motion branches. This article further presents a new inflatable angular pouch motor and fabricated a prototype using a rectangular tile origami base and adhesive fabric. The pouch motors are then integrated with 3D printed prototypes of the Bennett plano-spherical linkage and the parallel manipulator for the purpose of reconfiguring motion branches.
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