Quasi-static modeling of a novel growing soft-continuum robot

Soft-continuum robots attract researchers owing to their advantages over rigid-bodied robots such as adaptation of the flexible structure to tortuous environments, and compliant contact mechanics. The need for new modeling methods to attain precise control for such systems has emerged from the recent rapid progress in soft robotics. This article presents a quasi-static model for a growing soft-continuum robot that is propelled via thin-walled inflated tubes, and steered by the difference between tube lengths. Therefore, the robot shaft is modeled as a series of inflated beams under deformation. A quasi-static model coupled with a kinematic model is developed to accurately position the end effector while accounting for the inflated beam stiffness and end-effector loads. The proposed model calculates control parameters, namely tube lengths and tendon tensions required to maintain the end effector at a certain position. Tip deflection due to end-effector loading is calculated and kinematic model inputs are updated to correct positioning error caused by shaft deformation. The model is simulated for the soft-continuum robot moving on a path to show the change in model parameters for various end-effector positions. Results demonstrate the significance of including pressurized tube stiffness in the model for growing robots of similar type. Second, the need for tendons in addition to pneumatic actuation is emphasized for accurate positioning of the end effector under loading. The proposed model offers a potential method for simulation and control of similar growing soft-continuum robots presented in the literature.