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.

Design of Torque-Compensated Mechanical Systems With Two Connected Identical Slider-Crank Mechanisms

Abstract

Balancing the torque of mechanisms designed to minimize the fluctuation of input shaft torque is an effective means of improving their dynamic performance. There are several ways of solving the problem: optimizing the distribution of the moving mass of the original mechanism; cam sub-systems that displace the balancing mass; cam-spring mechanisms; flywheels driven by noncircular gears; adding articulated dyads, linkages or redundant drivers. This paper addresses the problem of input torque compensation with the optimal connection of two identical slider-crank mechanisms. The acceleration and deceleration phases of the links of the slide-crank mechanism obviously change periodically, causing torque to fluctuate at the input shaft. The problem is how to connect two mechanisms in order to reduce the input torque. This is done by minimizing the root-mean-square value of the input torque of the combined linkages. Two schemes are considered: slider-crank mechanisms with sliders moving on the same side, and on opposite sides. The prime value of this study is that it proposes an analytically tractable solution for identifying the general dynamic properties of mechanisms. Based on the ratio of link lengths, the precise relations for optimal connection of identical slider-crank mechanisms, i.e., a connection that produces the minimum root-mean-square values of the input torque, are developed. The numerical simulations illustrate the efficiency of the suggested approach. Observations show that the best solutions from the point of view of input torque minimization are obtained for the value of the coupling angle of two mechanisms around 90 deg.

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