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.

Planar Variable Structure Cable-Driven Parallel Robots for Circumventing Obstacles

Abstract

This article aims to address some of the current limitations of cable-driven parallel robots (CDPRs) by enabling regional changes in dynamic structure through collisions between cables and fixed objects placed in the work area (such as idler pulleys). This leads to the definition of a new class of robots referred to as variable structure cable-driven parallel robots (VSCRs). One of the major advancements from VSCRs is their ability to cover nonconvex reachable workspaces: a significant relaxation on the constraints of traditional CDPRs that is especially useful for circumventing obstacles and has implications for a wide range of applications. Specific examples of vertical farming and rehabilitation are demonstrated experimentally. It is shown that VSCRs can dramatically improve the reachability and accessible workspace of traditional CDPRs. In addition, an online method for solving the planar VSCR inverse kinematics problem is introduced, which is based on an extended cable model. The method is general and has been validated through experimental studies.
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