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.

A Snake-Inspired Swallowing Robot Based on Hoberman’s Linkages

Abstract

To solve the problems of existing swallowing robots, such as low load capacity, small deploy/fold ratio, and small swallowing space, this article presents a new snake-inspired swallowing robot (SSR) that can synchronously deploy and fold both axially and radially. The SSR is composed of multiple modules, each of which includes two end disk mechanisms (EDMs) and three connecting backbone mechanisms (CBBMs). The EDM is designed based on Hoberman’s linkages to achieve a radial deployment and a folding motion, while the CBBM is designed to realize the axial deployment and the folding movement and connect the EDMs. In addition, the driving device is designed. Then, to achieve the maximum deploy/fold ratio of the SSR and meet the requirements of assembly, the length of the rods is optimized on the basis of the kinematics analysis of the SSR. The final deploy/fold ratio reached up to 2.2459. The ratio of the maximum to the minimum swallowing space is 28.2754. In the end, experiments are conducted to evaluate the ability to swallow and store one object and multiple objects.

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