Latest Papers

ASME Journal of Mechanisms and Robotics

  • Double-Layer Deployable Mechanical Network Constructed of Threefold-Symmetric Bricard Linkages and Sarrus Linkages
    by Song X, Guo H, Chen J, et al. on June 4, 2021 at 12:00 am

    AbstractThreefold-symmetric (TFS) Bricard linkages are known for their excellent deployment performance properties. This paper proposes a novel networking method of TFS Bricard linkages and a double-layer mechanical network. First, the angle relationship for parts of the TFS Bricard linkage is analyzed. Then, the angle relationship of two TFS Bricard linkages connected by a scissor mechanism is studied. The result suggests that when the twist angles of the two TFS Bricard linkages are equal, their corresponding planes are parallel, and the link lengths have no effect on the parallel relationship. A novel networking method of the TFS Bricard linkage is recommended according to these results. This mechanical network is constructed of two different sized units and can be plane deployed and be folded with a smaller height. We also propose a hybrid linkage constructed of the TFS Bricard linkage and Sarrus linkage. Two kinds of double-layer mechanical networks are suggested by applying the hybrid linkage to a smaller unit in the mechanical network and using the hybrid linkage as the interlayer pillar. The new networking method and the double-layer mechanical network provide convenience for the TFS Bricard linkage's engineering application.

  • Design of Robotic Motion Platform Utilizing Continuous Contact Skating
    by Kumar R, Gupta V, Agarwal S, et al. on June 4, 2021 at 12:00 am

    AbstractThe continuous contact-based skating technique utilizes the sideway movement of the two skates while changing the orientation of the two skates simultaneously. The skates remain in contact with the surface. A mathematical model mimicking a continuous skating technique is developed to analyze the kinematic behavior of the platform. Kinematic and dynamic equations of motion are derived for the nonholonomic constraints. Heuristic-based motion primitives are defined to steer the robotic platform. For the lateral movement of the platform, a creeping-based motion primitive is proposed. A prototype of the robotic platform is developed with three actuated degrees-of-freedom—orientation of two skates and distance between them. A multibody model of the platform is also developed in matlab. Analytical expressions are verified using simulation and experiments. The robotic platform follows the desired motion profiles. The motion profiles include straight-line motion, motion in a circular curve, and lateral creep-like motion of the platform. However, the initial deviation has been observed in both the simulations and experiments due to the slipping of the roller skate at the contact point with the surface. The platform can be effectively used in a structured environment.

  • Direct Kinematic Analysis of the Spatial Parallel Mechanism With 3-R(P)S Structure Based on the Point Pair Relationship
    by Zhu G, Wei S, Zhang Y, et al. on June 4, 2021 at 12:00 am

    AbstractThis paper demonstrates a novel geometric modeling and computational method of the family of spatial parallel mechanisms (PMs) with 3-R(P)S structure for direct kinematic analysis based on the point pair relationship. The point pair relationship, which is derived from the framework of conformal geometric algebra (CGA), consists of the relationship between the point and the point pair and two point pairs. The first research is on the distance relationship between the point and the point pair. Second, the derivation of the distance relationship between two point pairs is based on the aforementioned result, which shows the mathematical homogeneity. Third, two formulations for a point of the point pairs that satisfy the distance relationship between two point pairs are reduced. Fourth, the point pair relationship is applied to solve the direct kinematic analysis of the spatial parallel mechanism with 3-R(P)S structure. Finally, four numerical examples are provided to verify the validity of the proposed algorithm. Overall, the proposed method can be generalized for the direct kinematics of a series of spatial parallel mechanisms with 3-R(P)S structure.

Data-Driven Analysis of Locomotion for a Class of Articulated Mobile Robots

Abstract

In the recent past, the use of autonomous vehicles is becoming of relevant interest in several fields of application. In many cases, the use of articulated structures is preferred to single chassis robots for their peculiar modularity. Such vehicles are often built as an active front module and a rear one that is pulled passively or that can contribute to the vehicle traction when required. Understanding whether this contribution is convenient or not is the main matter of this paper. Two different mobile robots of different scales and purposes are taken into consideration. A dynamic model is presented and analyzed. An experimental validation of the model parameters is also presented in order to make it exploitable as a reliable analysis tool. At last, a simple yet effective actuation law is tested for both the considered robots to evaluate whether the contribution of the back module is beneficial or not to the whole machine maneuverability.
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