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.

Twist-Coupled Flapping Mechanism for Bird-Type Flapping-Wing Air Vehicles

Abstract

In flapping-wing air vehicles, the flapping mechanism is directly related to the movement of the wing making it one of the major factors in determining aerodynamic performance. In this study, a method to increase aerodynamic performance using the flapping mechanism is discussed. This paper presents a twist-coupled mechanism that can increase thrust by combining twisting motion with flapping motion. The proposed mechanism generates twisting motion by the 4-bar planar link mechanism and flapping motion by the 4-bar spatial link mechanism. The mechanism can be driven by only one actuator by connecting two crankshafts with a pair of gears and rotating them at once. Here, we define the design parameters and constraints and search for the optimal design parameters to maximize aerodynamic force. Optimization is carried out by a genetic algorithm, a global optimization algorithm, combining kinematic and aerodynamic analyses. We then search for the design parameters that maximize thrust. Based on our optimization results, the proposed mechanism has the figure-of-eight wingtip trajectory motion like the flying animals. The aerodynamic efficiency of the proposed mechanism was validated by an aerodynamic measurement test comparing a reference mechanism that can only generate flapping motion without twisting motion. For comparative validation, prototypes of the proposed mechanism and the reference mechanism were designed and fabricated. Thrust and lift were measured by the wind tunnel test. From the wind tunnel test, it is confirmed that the proposed mechanism can generate aerodynamic loads more efficiently than the reference mechanism.

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