Soft Robot Employing a Series of Pneumatic Actuators and Distributed Balloons: Modeling, Evaluation, and Applications

Tasks involving exploration and inspection of narrow environments demand a robot to have a flexible body. Such a robot is especially preferred if the integrity of its surrounding is crucial, as in endoscopy procedures. We propose the design of a small, self-propelled soft robot that can operate in a constrained environment. By periodic activation of a series of pneumatic actuators fabricated using a casting technique, sinusoidal locomotion is achieved. The wave-like locomotive strategy with an additional support mechanism enabled movement in multiple scenarios, including traveling horizontally and vertically in environments of different characteristics. Two analytical models are presented to highlight the design characteristics. The first predicts the velocity of the robot in relation to the working conditions, while the second calculates the force that the robot body exerts on its surroundings. Its mobility was tested in simple and complex routes under rigid and elastic environments. The resulting percent errors for the predictions of velocity and lateral force are 7.89% and 16.86%, respectively. In terms of performance, the robot can move horizontally in rigid tubes even if the walls are lubricated, and can achieve a peak speed of 40.11 mm/s, or 0.171 Body-Length/s (BL/s). With the addition of a tail balloon, the robot also successfully ascended a vertical tube with a maximum speed of 9.22 mm/s (or 0.039 BL/s). The presented work is expected to pave the way toward feasible robotic applications, such as pipe inspection.