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.

TriRhino: A Five-Degrees-of-Freedom of Hybrid Serial–Parallel Manipulator With All Rotating Axes Being Continuous: Stiffness Analysis and Experiments

Abstract

This paper studies the stiffness and experiment of a five-degrees-of-freedom (DOF) hybrid, serial–parallel, manipulator, with all rotating axes being continuous: TriRhino. First, the motion principle of the hybrid manipulator is introduced and the structural design is presented. Next, the stiffness analysis of the hybrid manipulator is carried out. Specifically, a stiffness test, based on prototype and loading device, is performed, proving that the real stiffness is lower than that obtained by the finite element analysis. Following, the main geometric parameters, involving error, are determined, while the real values of the parameters with an error are identified, through performed calibration experiments. Finally, the measurement results show that the positioning accuracy of the manipulator is significantly improved, after kinematic calibration. Moreover, machining experiments on a workpiece show the great ability of the proposed manipulator, in machining parts with curved surface; thus, great application prospects, in the machining of structural parts with complex surfaces, are quite realistic.
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