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.

Energy-Based Footstep Planning of Biped on Uneven Deformable Terrain Using Nonlinear Inverted Pendulum

Abstract

In this work, the motion of a nonlinear inverted pendulum (NIP) on deformable terrain due to foot contact forces is used for energy analysis and footstep placement. In order to include the linear and rotational motions of the NIP, the mass moment of inertia of the body is also considered in the center of mass (CoM) model. The terrain deformation is modeled using a spring-damper contact model, and based on the rigid body dynamics of the NIP, its motion is generated. The energy analysis of the system provides the regions of possible foot placement. Based on the loss of potential energy due to ground deformation, the limits of terrain stiffness are also obtained for walking on uneven deformable terrain.

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