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.

Design of a Novel Flexible Robotic Laparoscope Using a Two Degrees-of-Freedom Cable-Driven Continuum Mechanism With Major Arc Notches


This article presents the design, development, and motion control of a novel flexible robotic laparoscope (FRL). The main structure of the FRL includes a two degrees-of-freedom (DOFs) continuum mechanism driven by two pairs of cable-pulley-driven systems, which are actuated by four miniature linear actuators. A constant-curvature model is employed on the kinematics modeling and analysis of the continuum mechanism with designed major arc notches. The bending control strategy of the continuum mechanism is proposed and realized based on its kinematics model and a feedforward compensation method considering its nonlinearity motion calibration with a suitable initial tension of the driven cables. Besides, the continuum mechanism is made of elastic nylon material through 3D printing technology. An experimental prototype is developed to test the effectiveness and feasibility of the FRL. The experimental results indicate that the FRL has good positioning accuracy and motion performance with potential applications in robot-assisted laparoscopic surgery.

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