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.

Extensible Continuum Manipulator Toward In-situ Explosive Ordnance Disposal

Abstract

Homemade bombs made by terrorists threaten seriously the social public security. Now, it is still a challenge to guarantee safety without destroying bombs. Compared with the destructive explosive disposal approach employing rigid robots, we proposed an in-situ explosive disposal method, which takes advantage of an extensible continuum manipulator to pass through obstacles and cut wires by end-effector. The spring-based continuum manipulator has six-degrees-of-freedom and is 400 mm in length but only 15 mm in diameter. Also, we have created only a 15 g end-effector that can cut 1-mm-diameter copper wire and embed a miniature camera. According to the experiment, a single continuum manipulator has around 2 mm repeatability accuracy and can carry a 50 g weight. Without special training, the operator can control the integrated explosive ordnance disposal (EOD) robot to complete a simulation mission in approximately five minutes. This paper broadens the application of the continuum manipulator and gives a unique solution for EOD robots.

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