Continuous Growth in Plant-Inspired Robots Through 3D Additive Manufacturing

This paper presents a new material deposition strategy for developing a growing robot capable of building its own body. The growing robot is inspired by plant growth and is based on a 3D printer-like mechanism. The plotting of a filament near the tip allows the forward movement of the robot and results in building a tubular body. A material deposition process is introduced to perform a straight continuous growth as well as a turning behavior in order to permit the navigation of the robot in the environment. Bending is achieved by controlling the filament height in each position of the plotting, lowering or increasing plotting velocity with a position PID control algorithm. We demonstrate that the continuous deposition of the filament allows to obtain homogeneous and robust structures, with a significant improvement of the robot's performance compared to our previous version of the system (i.e., more than 100 N pulling force and 200 N shear force). The current version of the robot can sustain its weight, move efficiently by growing in the environment - both air and soil - and penetrate hard medium (up to 60kPa).