Latest Papers

ASME Journal of Mechanisms and Robotics

  • Stable Inverse Dynamics for Feedforward Control of Nonminimum-Phase Underactuated Systems
    on January 25, 2023 at 12:00 am

    AbstractAn enhanced inverse dynamics approach is here presented for feedforward control of underactuated multibody systems, such as mechanisms or robots where the number of independent actuators is smaller than the number of degrees of freedom. The method exploits the concept of partitioning the independent coordinates into actuated and unactuated ones (through a QR-decomposition) and of linearly combined output, to obtain the internal dynamics of the nonminimum-phase system and then to stabilize it through proper output redefinition. Then, the exact algebraic model of the actuated sub-system is inverted, leading to the desired control forces with just minor approximations and no need for pre-actuation. The effectiveness of the proposed approach is assessed by three numerical test cases, by comparing it with some meaningful benchmarks taken from the literature. Finally, experimental verification through an underactuated robotic arm with two degrees of freedom is performed.

Actuation Arrangement of Rigid Foldable Waterbomb Origami

Abstract

A novel approach is proposed to arrange the actuations of rigid foldable waterbomb origami with multiple facet loops such that the number of actuations equaled the degrees-of-freedom (DOF) of the origami. In this approach, the rigid waterbomb origami was regarded as a combination of three types of six-crease origami units, which is equivalent to spherical 6R mechanisms with three DOF. Then, clear, target, and arrangement parts were created to define the facets of the origami pattern in the proposed extrapolation method. The actuation arrangement for a waterbomb origami pattern, which extended outwards circumferentially from a six-crease origami unit, was completed, and adams software was used to verify the correctness of the arrangement. Finally, an intuitive mathematical method was used to arrange the actuations for this type of waterbomb origami. The proposed approach provided DOF for the rigid foldable waterbomb origami and facilitated an actuation design such that the origami exhibits unique motion and can be normally actuated.

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