Experiments on Oscillation Control of a Continuum Soft Robotic Manipulator

In this paper, the results of several experiments made on the control of oscillations of a single module of the I-Support manipulator are presented. The I-Support is a soft continuum robotic manipulator composed of several similar modules, designed and built for assisting disabled users during a showering task. For these experiments, a single module is pneumatically actuated by three sets of bellow-like actuators, that allow controlled bending in any direction and also controlled extension. The actuators are made of latex and braided polyester components that, when pressurized, make up the load-carrying structure of the module. As motion control of even a single module is a complex non-linear problem, a stepwise approach was followed where several signal based control techniques were tested for feasibility. These techniques focus on the oscillation control itself, meaning that it is assumed that the inverse kinematics problem—the definition of the input signals that will allow the robot to reach a specified equilibrium position—is dealt with elsewhere. Results show that pre-filtering the input commands significantly reduces overshoot and settling time for a task in three-dimensional space. Also, closed-loop control based on feeding back the error from the equilibrium position showed promising results but has for now only been applied to one-dimensional problems.