Design and Development of a Growing Pneumatic Soft Robot.

Soft continuum robots are getting more popular in areas such as minimally invasive surgery, search and rescue, and inspection due to their inherent compliance and flexibility. However, most of the conventional continuum robots still lack the ability to significantly change size and length. Growth as a means of robotic locomotion is a novel actuation method that can be used to overcome this disadvantage. In this study, we introduce a growing pneumatic soft robot made up of pressurized thin-walled tubings that can move in three-dimensional space with an extension ratio only limited by manufacturing capabilities. Besides the ability to grow from the tip, this design provides active steering by controlling the speed of each tubing separately, controllable stiffness that can be changed during motion, and capability to carry a tool channel. We present models to estimate tip force and position and experimentally verify the force model and robot kinematics. Open-loop speed controller has an overall root mean square error of 2.69% for speeds between 20 and 300 mm/s. The position controller based on the kinematic model has a mean positioning error of 13.9 mm at 100 mm and 22.6 mm at 200 mm longitudinal distance. Robot can produce a tip force of 20.1 N at 150 kPa tubing pressure and reach a maximum speed of 1490 mm/s at 100 kPa. We also demonstrate the navigation capabilities of the robot both in open field and in constrained environments.