Ver-vite: dynamic and experimental analysis for inchwormlike biomimetic robots

The intent of this work was to design an innovative robot to imitate inchworm locomotion. The prototype built demonstrates successful implementation of using only friction and variable masses to generate the motion. The theoretical model was simulated using working model and validated experimentally. The computer simulation shows the dynamic and kinetic effects on inchworm mobility, providing a complete understanding of the design concept. The experimental results compare well with the theoretical model, although the exact coefficient of friction during the experiment was not measured. Theoretical and experimental results both indicate a slight backward motion of the robot during the contractile phase of the cycle of motion. Although the results are similar, the theoretical model fails to include such phenomena as the friction in the revolute joints and the vibration produced by the pump and servos. The theoretical model will be used in future work to optimize the design of the robot for dynamic performance.

Fundamentals of Inchworm Motion

Worms are members of the phylum Annelida (which means segmented worms). Inchworms move by a process known as peristaltic contraction; a worm's body is a fluid-filled tube, divided into separate segments. There are circular muscles that surround each segment and longitudinal muscles running from segment to seg-ment for the length of the worm. Contraction of the longitudinal muscles shortens and widens the segments of the worm body. Circular muscle contraction lengthens and narrows the segments. By alternating these processes in waves down its entire body length, the worm crawls forward or backward. Inside its tunnel, the widening of several segments serves to anchor that part of the body against the tunnel walls. The leading end segments are then elongated by circular muscle contraction (squeezing), pushing that end forward, and the trailing end is drawn up by longitudinal muscle contraction [1]. This type of locomotion is important because of the adaptation to the surrounding environment. The inchworm does not need the whole body to move. Because it uses just a small part of its body to have enough frictional resistance along the surface, it can adapt easily to difficult terrains. Although locomotion of biologic inchworms is neither fast nor efficient, it is very flexible because it moves on rough surfaces, creeps into tubes, or crosses obstacles.