<p>Biomimetic locomotive mechanisms can replace human workers when conditions are no longer safe. Such mechanisms have been designed using rigid bodies moving along a horizontal rail or combining soft links. The design of the locomotive systems highly depends on the actuation type and body structure as the preponderance of the existing designs in the literature have either complex actuation or design. In our previous work, we designed a biomimetic locomotive mechanism incorporating five carts sliding on a rail and connected each other through rigid arm-flexure hinge-rigid arm (RFR) springs. Each cart combining the first and the fifth sliders were equipped with two servo motor to control the translational motion of the locomotive mechanism. Since friction has a critical role in the speed and behavior of the compliant locomotive mechanism, each rigid portion of the compliant springs was mounted on the carts at an eccentricity with respect to the two ends of the RFR.</p><p>In this study, we present a novel, single-pieced designed, compliant locomotive mechanism actuated by only two motors. The locomotive system is comprised of three carts connected through horizontally aligned translational springs and compliant springs to actuate the carts on the front and back without the need for a rail. Two servo motors are mounted on the middle cart and the friction acting on each cart is controlled by both adjusting the masses and eccentricities of the pin locations. Two servos are actuated by Arduino while the positions of the carts are recorded through laser displacement sensors. Since the locomotive mechanisms require spring effects, the compliant members serve as springs in our single-pieced designed compliant locomotive mechanism. The two main springs are the rigid-flexure-rigid compliant links used to transfer the input torque thereby pushing and pulling the carts and the translational springs employed to orient the carts through tension/compression for the forward motion and bending for rotation. The stiffnesses of each compliant member are obtained from flexible body analysis performed in multi-body Adams simulations. Since the springs are nonlinear, polynomials are fitted to the strain energy vs displacement curves exported from Adams. The dynamical model of the mechanism is derived using vector closure loop equations and D’Alembert’s Method and the simulations are performed in Matlab Simulink. While the compliant locomotive mechanism is 3D printed using polyethylene terephthalate glycol (PETG) filament, the rigid-flexure-rigid arms are 3D printed thermoplastic polyethylene (TPU) to allow more deformation without yielding. Mechanism successfully followed forward and backward motion once the RFR links actuated at a constant angular velocity in opposite and same directions.</p>

Development of Single Piece Designed Compliant Locomotive Mechanism

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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