Abstract
In this paper, we present a new method for the control of soft robots with elastic behavior, piloted by several actuators. The central contribution of this work is the use of the Finite Element Method (FEM), computed in real-time, in the control algorithm. The FEM based simulation computes the nonlinear deformations of the robots at interactive rates. The model is completed by Lagrange multipliers at the actuation zones and at the end-effector position. A reduced compliance matrix is built in order to deal with the necessary inversion of the model. Then, an iterative algorithm uses this compliance matrix to find the contribution of the actuators (force and/or position) that will deform the structure so that the terminal end of the robot follows a given position. Additional constraints, like rigid or deformable obstacles, or the internal characteristics of the actuators are integrated in the control algorithm. We illustrate our method using simulated examples of both serial and parallel structures and we validate it on a real 3D soft robot made of silicone.
Highlights
Traditional robots are based on articulated rigid structures and the design usually aims at finding the best trade off between a high stiffness and a large workspace of these rigid robots
We propose to use a real-time implementation of the Finite Element Method (FEM) in order to accurately model the deformations that are the cause of this mechanical coupling
Effector and contact models rely on setting constraints, we will get a measure of the mechanical compliance between them based on the FEM model
Summary
Traditional robots are based on articulated rigid structures and the design usually aims at finding the best trade off between a high stiffness and a large workspace of these rigid robots. High stiffness of the structure is often a goal so that vibration and/or deformations will not deviate the robot from its prescribed motion This high stiffness leads to a natural use of rigid bodies in the kinematic and mechanical models of the robot. Soft robots are adapted to exploration and manipulation in a fragile environment Their natural compliance allows to tolerate collision while reducing the risks for the robot and the environment. The number of degrees of freedom (dof) of soft robots is infinite This makes their control tricky: On the one hand, it seems natural to use a large number of actuators, to be able to impose a deformation everywhere. A study of the computation time performance of the control method is presented before the conclusion and the perspectives of this work
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