Latest Papers

ASME Journal of Mechanisms and Robotics

  • Integrated Wheel–Foot–Arm Design of a Mobile Platform With Linkage Mechanisms
    on March 20, 2024 at 12:00 am

    AbstractInspired by lizards, a novel mobile platform with revolving linkage legs is proposed. The platform consists of four six-bar bipedal modules, and it is designed for heavy transportation on unstructured terrain. The platform possesses smooth-wheeled locomotion and obstacle-adaptive legged locomotion to enhance maneuverability. The kinematics of the six-bar bipedal modules is analyzed using the vector loop method, subsequently ascertaining the drive scheme. The foot trajectory compensation curve is generated using the fixed-axis rotation contour algorithm, which effectively reduces the centroid fluctuation and enables seamless switching between wheels and legs. When encountering obstacles, the revolving linkage legs act as climbing arms, facilitating seamless integration of wheel, foot, and arm. A physical prototype is developed to test the platform on three typical terrains: flat terrain, slope, and vertical obstacle. The experimental results demonstrated the feasibility of the platform structure. The platform can climb obstacles higher than its own height without adding extra actuation.

A Novel Tunable Stiffness Mechanism Using Filament Jamming

Abstract

The jamming mechanism is a crucial method to tune the stiffness of soft-bodied machines to adapt to their surroundings. However, it is difficult for the present jamming structures to integrate them into systems with complicated shapes such as twist, cylinder, and spiral. This paper introduces a novel jamming mechanism termed a filament jamming technique, which varies stiffness using jamming of a cluster of tiny and compliant filaments. The jamming structure demonstrated various characteristics such as softness, shape compatibility, lightweight, and high stiffness. These feats can meet a variety of application scenarios that the traditional jamming one cannot afford. The experimental test was used to explore the jamming structure’s stiffness behavior and dynamic performance. The influence of the filament structure dimensions, material properties, and the vacuum pressure on the stiffness was revealed. With the negative pressure increasing, both the natural frequency and damping ratio increase due to the rigidity variation. It indicates that the filament jamming structure has excellent response rapidity and shock resistance. Our work demonstrated some versatile features of the filament jamming technology, like shape adaptation, shape-preserving, stiffness stability, and compliance. To demonstrate the advantage of the jamming technique, we constructed a soft gripper and a torsional actuator to illustrate how the mechanics of filament jamming can enhance real-world robotics systems’ performance. Therefore, the filament jamming mechanism provides various machines and structures with additional properties to increase forces transmitted to the environment and tune response and damping. This study aims to foster a new generation of mechanically versatile machines and structures with softness and stiffness.

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