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.

Locomotion Identification Method of One-Degree-of-Freedom Six-Bar for Jumping Robot

Abstract

Exploring the locomotion of creatures is a challenging task in bionic robots, and the existing iterative design methods are mainly based on one or two characteristics to optimize robots. Here, we introduce the thinking of system identification theory to bionic robots, bypassing the exploration of the dynamics and reducing the difficulty of design greatly. A one-degree-of-freedom (DOF) six-bar mechanism (Watt I) was designated as the model to be identified, and it was divided into two parts, i.e., a one-DOF four-bar linkage and a three-DOF series arm. Then, we formed constraints and a loss function. The parameters of the model were identified based on the kinematic data of a jumping marmoset, an animal chosen for its unusually high mass-specific power output. As a result, we obtained the desired model. Then, a prototype derived from the model was fabricated, and the experiments verified the effectiveness of the method. Based on the success of our experiments, we believe our method can be applied to emulate other motions as well.

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