Models and Analysis of Locomotion and Gripping in Soft Robots

Recent designs of soft robots and nano robots feature locomotion mechanisms thatentail orchestrating changes to intrinsic curvature or length to enable the robot’s limbs toeither stick, adhere, or slip on the robot’s workspace. The resulting locomotion mechanismhas several features in common with peristaltic locomotion that can be found in the animalworld. One of the purposes of this dissertation is to examine the feasibility of, and designguidelines for, a locomotion mechanism that exploits the control of intrinsic curvature ona rough surface featuring stick, slip, and adhesion interaction. Our work complements theever-increasing body of work on soft robots that is primarily focused on the design andfabrication of these systems. Modeling and analyzing these robots is challenging becauseof the difficulties in faithfully modeling the flexible nature of their components.The study of locomotion presented in this dissertation is composed of two parts. First,we consider the simplest possible model for a soft robot. The resulting model is a lumpedparameter system featuring a pair of mass particles and a spring with a variable naturallength. By appropriately varying the natural length as a function of time ℓ0(t), we showhow locomotion can be achieved and examine the energy efficiency for a variety of choicesof ℓ0(t). We then take the lessons gained from this model and use them to understandthe locomotion of a block that is propelled on a rough surface with the aid of a flexiblearm. Our analysis of the rod-based model for this system focuses on the development of astructurally stable mechanism to move the block. This analysis exploits recent results onstability of adhered rods that we supplement with a new discretized stability criterion.Beyond locomotion, soft robots have the ability to gently grip and maneuver objectswith open-loop kinematic control. Guided by several recent designs and implementationsof soft robot hands, we exploit our earlier works on locomotion and analyze a rod-basedmodel for the fingers in the hand of a soft robot. We show precisely how gripping isachieved and how the performance can be affected by varying the system’s parameters. Thedesigns of interest feature pneumatic control of the soft robot and we model this actuationas a varying intrinsic curvature profile of the rod. Our work provides a framework for thetheoretical analysis of the soft robot and the resulting analysis can also be used to developsome design guidelines