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.

Kinetostatic Analysis of Pneumatic Bending Soft Actuator Coupling With Revolute Joint

Abstract

This paper presents the kinetostatic analysis of pneumatic bending soft actuator coupling with revolute joint, aimed to discover the bending performance of soft actuator wearing on physical joint of human body as exoskeleton. First, a new pneumatic bidirectional bending soft actuator is designed and its mechanical characteristic is obtained by experimental tests. Then, the kinetostatic analysis based on the principle of virtual work is conducted on the proposed soft actuator in the cases of bending alone and coupling with revolute joint. Finally, the kinetostatic equations are solved, and thus the bending performance of the soft actuator bending alone or coupling with revolute joint is obtained. This research mainly reveals the influence of coupling constraint on bending motions of soft actuator and lays a theoretical foundation for the pneumatic bending soft actuator to be applied in assist exoskeletons.

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