Design, modeling and control of a SMA-actuated biomimetic robot with novel functional skin

Traditional colonoscopy requires highly trained personnel to be performed. Additionally, current devices may cause discomfort and carry the risk of perforating the bowel wall. In this paper, a soft three modular section robot is designed, modeled, controlled and tested. Each of the robotic sections has three degrees of freedom, one translation and two rotations. The robot uses a peristaltic motion to translate, inspired by the motion generated by the bowel. The robot uses nine independently controlled Shape Memory Alloy (SMA) springs as its actuators and a novel silicone rubber skin provides the passive recovery force to expand the springs to their original state. It also incorporates three air tubes, one for each section, to provide forced convection reducing the cooling time of the SMA springs. A parametric study on the skin curvature and thickness using Finite Element Analysis (FEA) is performed to maximize traction while providing enough recovery force. A multi-input multi-output (MIMO) controller based on fuzzy control is designed and implemented for each of the sections allowing the robot to achieve any orientation between −90° and +90° in both pitch and roll in less than 4 seconds with near zero steady state error. Both the peristaltic motion and the orientability of the robot are tested. The robot is able to perform a peristaltic motion with maximum speed of 4 mm/s (24 cm/min) and an average speed of 2.2 cm/min. Each section is also able to follow, with less than 2% overshoot and near zero steady-state error, periodic multi-input squared signals of 25° of amplitude.