Robust Fractional-Order Control Using a Decoupled Pitch and Roll Actuation Strategy for the I-Support Soft Robot

Jorge Muñoz,Concepción A Monje,Francesco Piqué,Egidio Falotico

doi:10.3390/math9070702

Abstract

Tip control is a current open issue in soft robotics; therefore, it has received a good amount of attention in recent years. The desirable soft characteristics of these robots turn a well-solved problem in classic robotics, like the end-effector kinematics and dynamics, into a challenging problem. The high redundancy condition of these robots hinders classical solutions, resulting in controllers with very high computational costs. In this paper, a simplification is proposed in the actuation setup of the I-Support soft robot, allowing the use of simple strategies for tip inclination control. In order to verify the proposed approach, inclination step input and trajectory-tracking experiments were performed on a single module of the I-Support robot, resulting in zero output error in all cases, including those where the system was exposed to disturbances. The comparative results of the proposed controllers, a proportional integral derivative (PID) and a fractional order robust (FOPI) controller, validate the feasibility of the proposed approach, showing a clear advantage in the use of the fractional robust controller for the tip inclination control of the I-Support robot compared to the integer order controller.

Highlights

The difference in overshoot percent values will show the system robustness, with the results showing similar overshoot percentages in both output signals being more robust. An example of this first experiment for target angles α = 10 and β = 30 is shown in Figure 10 for the fractionalorder proportional integral controller (FOPI) and IOPI controllers
A robust control for the I-Support soft robot tip orientation is proposed in this paper through the use of a FOPI controller, and compared to a similar proportional integral derivative (PID) controller in terms of performance and robustness
Given the simplifications made in the model, a robust controller is proposed to deal with the parameter variations and neglected dynamics

Summary

Introduction

Soft robotics is a growing research field which aims to incorporating softness in robotic bodies or in novel end effectors, enabling safe and adaptive interactions [1]. Soft robotics is bio-inspired, since it tries to reproduce the abilities of certain animals, such as worms, snakes or the octopus [2], to move without a rigid skeleton or exoskeleton, exploiting their softness in order to squeeze, and adapt to unstructured environments. Soft robotics finds application in tasks where safety and adaptability to unstructured environments is of paramount importance [1]. Such tasks include delicate food handling, medical procedures, and assistive tasks

Methods

Results

Conclusion