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.

Modeling of Flexible-Link Manipulators Under Uncertain Parameters Based on Stochastic Finite Element Method

Abstract

This paper presents a novel approach to obtain the dynamic model of flexible-link manipulators based on the stochastic finite element method. The links and elements of flexible manipulators are affected by uncertainties. The main sources of uncertainties include the variation of mechanical properties. The present research study conveys the following contributions: (i) modeling the uncertain parameters such as the stiffness of the links as an extension of the finite element method based on stochastic fields and the stochastic finite element method, (ii) numerical method to simulate the dynamic response of flexible manipulation with uncertain parameters in the links based on the Monte Carlo simulation (MCS), and (iii) numerical application of the proposed method to the one-link flexible manipulator and two-link flexible manipulator. Numerical simulations illustrate the proposed approach in terms of joint responses and frequency response functions subject to uncertain parameters.

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