Multi body mechanisms linked with translational or torsional springs can perform locomotive motion such as running, jumping and swimming. There is an ongoing effort in the design of locomotive multibody mechanisms imitating the motion seen in nature since those robots can replace human beings to serve as rescue robots in rough terrains. Various types of legged jumping and hopping robots have been studied however it’s still been of interest as the technology advances.

In this study, we present the design and development of a compliant multi-link hopping mechanism actuated by two DC motor couple together. Two main design goals are to have a single piece designed main body for the jumping robot and a passive stabilizer to allow consecutive jumps. Mechanism consists of monolithically designed large deflecting main body incorporating the gears and initially curved flexure hinge. Due to the limitations of the design goal, revolute motion between top and bottom legs on the main body are realized by a compliant flexible links which replaces the need of ball bearings. Also, continuous energy store and release during jumping is ensured by the same flexure hinges.  Passive self-righting cage is attached to the bottom of the main body to maintain upright position both in landing and takeoff. Mechanism parts including the cage are 3D printed using PETG. One half-tooth gear engages to the two gears that are on the tip of the main body. As the motors are actuated, the main body compresses due to the bending on the flexures while storing the potential energy. As the half-tooth gear disengages from the connected gears, potential energy stored in the flexures will be released and the main body jumps in the air. During jumping, the mass center moves from the bottom to the top since the body changes its configuration. The cage allows the center of mass to stay in the vertical plane to prevent tilting. During landing, cage absorbs the impact and allows the main body to roll to its initial configuration so that the robot can complete jumping. Maximum height the robot can achieve, and the takeoff velocity are obtained from the video recording of the experimental testing. Design optimization of the body parts including the rigid legs and flexure hinges are analyzed both experimentally and analytically. Finite element analysis is performed to calculate the equivalent stiffness and natural frequency of the jumping robot and simplified mathematical model is derived using rigid body dynamics and simulation outputs are compared with the experimental data.


Design of a Compliant Jumping Robot With Passive Stabilizer

Division / Sponsors: 
Aerospace, Bioengineering, Applied Mechanics, Design Engineering Division, Advanced Energy Systems, Manufacturing Engineering Division, Noise Control and Acoustics, Nondestructive Evaluation, Diagnosis, and Prognosis (NDPD), Nuclear Engineering Division, Process Industries Division, Fluids Engineering, Heat Transfer, Materials, Microelectromechanical Systems, Safety Engineering and Risk Analysis, Computers & Information in Engineering


Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2020/volume/84478

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