Latest Papers

ASME Journal of Mechanisms and Robotics

  • Design of Reconfigurable Articulated Walking Mechanisms for Diverse Motion Behaviors
    on March 20, 2025 at 12:00 am

    AbstractLegged robots are able to move across irregular terrains and those based on 1-degree-of-freedom planar linkages can be energy efficient but are often constrained by a limited range of gaits which can limit their locomotion capabilities considerably. This article reports the design of novel reconfigurable parallel linkages that not only produce different walking patterns but also realize behaviors beyond locomotion. Experiments with an implemented wearable device able to guide the lower extremity through multiple human-like walking trajectories are presented and the preliminary results validate the proposed approach.

  • Modeling, Kinematics, and Dynamics of a Rigid-Flexible Coupling Spring-Cable-Driven Parallel Robot
    on March 20, 2025 at 12:00 am

    AbstractConventional parallel robots are made of rigid materials for the purpose of fast and accurate localization, exhibiting limited performance in large-scale operations. Inspired by the softness and natural compliance of biological systems, this article proposes a rigid-flexible coupling cable-driven parallel robot. The concept of flexible cable and spring hybrid and working principle are introduced. The kinematics of single module and multiple modules connected in series are analyzed and equations are given, and the Lagrange equation is used to establish dynamic models. Finally, two methods are used to validate the kinematics and dynamics. One is to draw the specific structure with the posture of the end-effector and measure the cable length to compare it with the analytical solution in the kinematic model. The other is to build the structure and joint characteristics in simulink, given the posture of the end-effector and the external force/torque, the cable length and the force applied are compared with those obtained from the dynamic model. The reasonableness of the mechanism and the feasibility of the kinematic and dynamic models are verified.

Dynamics Modeling and Control Strategy Research on Multi-Joint Soft Lower Limb Assistive Exoskeletons

Abstract

In response to elderly individuals and stroke patients with weakened lower limb muscle strength, this study proposes a multi-joint soft lower limb assistive exoskeleton designed to assist hip and knee joint flexion and extension during human walking. To achieve smooth control of the flexible exoskeleton, a hardware control system based on STM32 is constructed. The study establishes the theoretical dynamics model and motion characteristic equations for the soft exoskeleton. To minimize assistive errors, a control strategy is designed based on the proportional derivative iterative learning control methods, and control algorithm simulations are performed. For precise assistance of the soft exoskeleton, a mean prediction method is employed to forecast the gait cycle of the human body. To validate the correctness of the dynamic model and the practicality of the soft exoskeleton, tracking experiments with a dummy and walking assistance experiments with human subjects are conducted separately. The dummy tracking experiment results indicate that the percentage errors of peak assistive values for hip and knee joint flexion are 4.77% and 5.81%, respectively, while for extension, the percentage errors are 8.94% and 9.13%. The human walking assistance experiment results show that the peak assistive values provided by the soft exoskeleton for hip joint flexion and extension reach 152.46 N and 150.26 N, respectively, while for knee joint flexion and extension, the peak assistive values are 107.64 N and 106.13 N, respectively.

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