Multibody system dynamics for bio-robotic design and simulation based on inching-locomotion caterpillar's gait: MBD-ILAR method.

Abstract

Inching-locomotion caterpillars (ILAR) inspire the design of "inch-worm" robots with biomimicry features, that can be adapted to different environments, such as natural, man-made, or other planets. Therefore, this work defines a novel mathematical method called Multi-Body Dynamics for Inching-Locomotion Caterpillar Robots (MBD-ILAR) to standardize the gait simulation of this type of machines, including a payload over the head to carry an object. The method is composed of 3 steps: (i) setting the model, where the input data is defined by: the phases of walk-stride (PHAWS) based on the bioinspired robotic design (BIROD) method, linkage dimensions of insect's morphology based on the geometrical kinematic analysis (GEKINS) algorithm, the joint types, the link's mass and center of mass, and the gravity constant. Then, (ii) kinematic analysis: to solve the orientation, velocity, and acceleration; and (iii) dynamic analysis: to obtain the joint forces, attachment forces to the ground, motor's torque, and mechanical power. The method was applied in a case study adapting the dimensions of a real specimen - Geometridae sp. (35000 species), for that purpose, a graphical user interface (GUI) was developed in order to get the biomechanical results that guarantee the robot's actuator selection: (a) attachment mechanisms: vacuum pumps with suction cups (SC) or electromagnets (EM), and (b) joints: electromechanical rotary servomotors. Finally, to validate the numerical approach of MBD-ILAR, we performed an influence study of model parameters: link's length, link's mass, and gravity on the behavior of the attachment forces to the ground, torque, and mechanical power. The future method's application is expected to be useful to complete the phase of the computational robotic design before the physically mechatronic implementation; in addition, it could be adapted to other arthropods.