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.

Topological Reconfiguration Planning for a Variable Topology Truss

Abstract

This paper introduces a new class of self-reconfigurable robot: the variable topology truss (VTT), which is an extension of an existing class of robots: the variable geometry truss (VGT). Variable topology trusses have the additional capability to change the topology of the truss through self-reconfiguration by merging and splitting the nodes of the truss. We first introduce a hardware platform that enables this reconfigurability. We give a procedure to compute all possible distinct reconfiguration actions for a given robot topology. We show that 18 members are required for a minimal reconfigurable VTT, and we exhaustively enumerate all possible reconfigurable topologies for VTTs up to 29 members. Lastly, we introduce the topology network, which describes the relationship between these reconfigurable topologies. The topology network concept enables some high-level planning and provides insights into the design of truss topologies.
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