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.

Shape-Adaptive Electrostatic Soft Gripper With Transform Mechanism for Multifunctional Grips

Abstract

This paper proposes a shape-adaptive electroadhesion dielectric elastomer actuator (EA-DEA) pad gripper that can actively adapt to the shape of curved objects and quickly handle various objects by combining an EA pad and a multi-layered DEA driven by electrostatic force. This gripper has a rapid release function capable of detaching thin and light objects in less than 0.2 s with bending motion of multi-layered DEA and reverse polarity voltage. Moreover, combined with a transform mechanism that changes the posture of the EA-DEA pad gripper, a multifunctional gripper handling various objects from thin to irregularly shaped objects is implemented. The high voltage controller is configured to generate the variable and reversible voltages required for the control of the developed gripper. To verify the performance and practicality of the proposed multifunctional gripper system, we demonstrate the gripping task in three modes formed by controlling the EA-DEA pad gripper and the transform mechanism to adapt to the object shape. According to the experimental results, this gripper can reliably and rapidly pick and place various objects, such as thin film, hexahedron, cylinders, spheres, irregular shaped, deformable, and fragile objects corresponding to each mode.

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