Reduced-order modeling of soft robots

Abstract

We present a general strategy for the modeling and simulation-based control of soft robots. Although the presented methodology is completely general, we restrict ourselves to the analysis of a model robot made of hyperelastic materials and actuated by cables or tendons. To comply with the stringent real-time constraints imposed by control algorithms, a reduced-order modeling strategy is proposed that allows to minimize the amount of online CPU cost. Instead, an offline training procedure is proposed that allows to determine a sort of response surface that characterizes the response of the robot. Contrarily to existing strategies, the proposed methodology allows for a fully non-linear modeling of the soft material in a hyperelastic setting as well as a fully non-linear kinematic description of the movement without any restriction nor simplifying assumption. Examples of different configurations of the robot were analyzed that show the appeal of the method.

Fast, Generic, and Reliable Control and Simulation of Soft Robots Using Model Order Reduction

“…To keep the method numerically efficient in the case of nonlinear material behaviour, some hyperreduction method [26], [25], [27], [28] are used to reduce that computation. Some notable contributions in the idea of using model order reduction technique for fast FE simulations can be found for a simple soft robot example using Proper Generalised Decomposition (PGD) [29], or in the context of computer animations [30], [31] or material design [32]. These latter methods generate the reduced basis by computing vibration modes and their derivatives to account for large deformations.…”

Model-based dynamic feedback control of a planar soft robot: trajectory tracking and interaction with the environment

“…For some hybrid soft–rigid systems the rigid part is dynamically dominant, which allows the soft dynamics to be neglected in the control design (Deutschmann et al, 2017a,b; Skorina et al, 2015). Moving to a more general scenario, finite element methods are commonly used in the mechanical design of soft robots (Chenevier et al, 2018; Polygerinos et al, 2015). However, their high dimensionality limits the practical use of these models for feedback control.…”

Dynamic simulation of articulated soft robots

“…Previous efforts to simulate soft robots have focused on Finite Element Method [11][12][13][14][15][16] , voxel-based discretization 17,18 , and modeling of slender soft robot appendages using Cosserat rod theory [19][20][21] . Drawing inspiration from simulation techniques based on discrete differential geometry (DDG) that are widely used in the computer graphics community 22 , we introduce a DDG-based numerical simulation tool for examining the locomotion of limbed soft robots.…”