Latest Papers

ASME Journal of Mechanisms and Robotics

  • Discrete Cosserat Method for Soft Manipulators Workspace Estimation: An Optimization-Based Approach
    by Walid A, Zheng G, Kruszewski A, et al. on August 11, 2021 at 12:00 am

    AbstractThis article investigates the workspace estimation of soft manipulators. Given a configuration of such a soft robot, with the bounded actuators, the discrete Cosserat method is adopted to deduce the mathematical model of soft manipulators, based on which an optimization-based approach is proposed to estimate the workspace. Implemented to various soft manipulators’ configurations, numerical simulations are provided to highlight the feasibility of the proposed methodology.

  • Design Control and Performance of a Cable-Driving Module With External Encoder and Force Sensor for Cable-Driven Parallel Robots
    by An H, Zhang Y, Yuan H, et al. on August 11, 2021 at 12:00 am

    AbstractCable-driven parallel robots (CDPRs) have the characteristic of easy deployment, which endows CDPRs with flexible workspace, freely configurable degrees-of-freedom (DOFs), and various configurations, greatly expanding their range of applications. Modular design provides excellent convenience and feasibility for deployment, which is a crucial issue of CDPR design. A highly integrated cable-driving module is designed in this paper, which includes the winding bobbin, servo motor, force sensor, external encoder, electromagnetic brake, as well as other devices. Experiments show that the maximum cable length control error is less than 0.16%, and the maximum cable tension control error is less than 8% in the back-and-forward rotation test. Furthermore, a CDPR with eight cables and six DOFs is constructed rapidly using the proposed module, whose dimension is 850 × 850 × 650 mm3. Results show that the robot’s trajectory errors are all less than 4.5 mm, and the root-mean-square-error (RMSE) is 2.1 mm. Besides, the compliance control experiments show that the robot’s tracking error in an impedance control mode is less than 2 mm, and the RMSE is 0.95 mm. Moreover, the dragging force in a teaching mode is less than 2.5 N. The proposed integrated cable-driving module could be helpful for the modular design and deployment of CDPRs.

  • A Modular Method for Mechanical Error Analysis of Planar Linkages Composed of Class II Assur Group Kinematic Chains
    by Hsu K, Chung J. on August 11, 2021 at 12:00 am

    AbstractThis paper presents a modular method for the mechanical error analysis of complex planar linkages. The topology of the linkage under investigation is decomposed into several class II Assur group kinematic chains (AGKCs) combined in a given sequence. Therefore, the mechanical error of the whole linkage can be analyzed by investigating the error propagations of adopted AGKCs in successive order. Because class II AGKCs are first served as modules, the mechanical error equations of these AGKCs in terms of each error in link lengths and joint variables can be pre-formulated and embedded in form of subroutines in any programmable language. Once the AGKCs constituting the linkage topology are identified, the corresponding subroutines are introduced to compute the error propagations in the linkage. Therefore, the presented modular approach can facilitate the analysis by concentrating on the topology decomposition instead of the algebraic derivation. Numerical examples are provided to illustrate the advantage and flexibility of the modular approach.

Analysis of Reachable Workspace for Spatial Three-Cable Under-Constrained Suspended Cable-Driven Parallel Robots


The workspace is an important reference for designs of cable-driven parallel robots (CDPRs). Most current researches focus on calculating the workspace of redundant CDPRs. However, few literature study the workspaces of under-constrained CDPRs. In this paper, the static equilibrium reachable workspaces (SERWs) of spatial 3-cable under-constrained CDPRs are solved numerically since expressions describing workspace boundaries cannot be obtained in closed forms. The steps to solve the SERWs are as follows. First, expressions that describe the SERWs and their boundaries are proposed. Next, these expressions are instantiated through a novel anchor points model composed of linear equations, quadratic equations, and tension limits in cables. Then, based on the reformulated linearization technique (RLT), the constraints system is transformed into a system containing only linear equality constraints and linear inequality constraints. Finally, the framework of the branch-and-prune (BP) algorithm is adopted to solve this system. The effect of the algorithm is verified by two examples. One is searching the SERWs boundaries of a special three-cable-driven parallel robot (CDPR) whose anchor points layouts both on the moving platform (MP) and on the base are equilateral triangles, followed by a method to extract the SERW boundary where cables do not interfere with each other. The other is searching the SERWs boundaries of a general three-cable CDPR with randomly selected geometry arrangement. The presented method in this paper is universal for calculating the SERWs of spatial three-cable CDPRs with arbitrary geometry parameters.
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