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Soft robot shape estimation with IMUs leveraging PCC kinematics for drift filtering

Stella, F. (author), Della Santina, C. (author), Hughes, Josie (author)

The control possibilities for soft robots have long been hindered by the need for reliable methods to estimate their configuration. Inertial measurement units (IMUs) can solve this challenge, but they are affected by well-known drift issues. This letter proposes a method to eliminate this limitation by leveraging the Piecewise Constant...

journal article 2024

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Physics-Informed Neural Networks to Model and Control Robots: A Theoretical and Experimental Investigation

Liu, J. (author), Borja, Pablo (author), Della Santina, C. (author)

This work concerns the application of physics-informed neural networks to the modeling and control of complex robotic systems. Achieving this goal requires extending physics-informed neural networks to handle nonconservative effects. These learned models are proposed to combine with model-based controllers originally developed with first...

journal article 2024

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Input Decoupling of Lagrangian Systems via Coordinate Transformation: General Characterization and its Application to Soft Robotics

Pustina, P. (author), Della Santina, C. (author), Boyer, Frederic (author), De Luca, Alessandro (author), Renda, Federico (author)

Suitable representations of dynamical systems can simplify their analysis and control. On this line of thought, this article aims to answer the following question: Can a transformation of the generalized coordinates under which the actuators directly perform work on a subset of the configuration variables be found? We not only show that the...

journal article 2024

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Model and Control of R-Soft Inverted Pendulum

Caradonna, Daniele (author), Pierallini, M. (author), Della Santina, C. (author), Angelini, Franco (author), Bicchi, Antonio (author)

Soft robots enable safe and robust operations in unstructured environments. However, the nonlinearities of their continuum structure complicate the accomplishment of classic robotic tasks, such as pick and place. In this work, we propose the R-Soft Inverted Pendulum, a Soft Inverted Pendulum (SIP) actuated only by a revolute joint at the base...

journal article 2024

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P-satI-D Shape Regulation of Soft Robots

Pustina, P. (author), Borja, Pablo (author), Della Santina, C. (author), De Luca, Alessandro (author)

Soft robots are intrinsically underactuated mechanical systems that operate under uncertainties and disturbances. In these conditions, this letter proposes two versions of PID-like control laws with a saturated integral action for the particularly challenging shape regulation task. The closed-loop system is asymptotically stabilized and...

journal article 2023

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Robust Jumping with an Articulated Soft Quadruped via Trajectory Optimization and Iterative Learning

Ding, J. (author), Sels, Mees A.van Loben (author), Angelini, Franco (author), Kober, J. (author), Della Santina, C. (author)

Quadrupeds deployed in real-world scenarios need to be robust to unmodelled dynamic effects. In this work, we aim to increase the robustness of quadrupedal periodic forward jumping (i.e., pronking) by unifying cutting-edge model-based trajectory optimization and iterative learning control. Using a reduced-order soft anchor model, the...

journal article 2023

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On the stability of the soft pendulum with affine curvature: open-loop, collocated closed-loop, and switching control

Trumic, Maja (author), Della Santina, C. (author), Jovanovic, Kosta (author), Fagiolini, Adriano (author)

This letter investigates the stability properties of the soft inverted pendulum with affine curvature - a template model for nonlinear control of underactuated soft robots. We look at how changes in physical parameters affect stability and equilibrium. We give conditions under which zero dynamics corresponding to a collocated choice of the...

journal article 2023

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A Provably Stable Iterative Learning Controller for Continuum Soft Robots

Pierallini, M. (author), Stella, F. (author), Angelini, Franco (author), Deutschmann, Bastian (author), Hughes, Josie (author), Bicchi, Antonio (author), Garabini, Manolo (author), Della Santina, C. (author)

Fully exploiting soft robots' capabilities requires devising strategies that can accurately control their movements with the limited amount of control sources available. This task is challenging for reasons including the hard-to-model dynamics, the system's underactuation, and the need of using a prominent feedforward control action to...

journal article 2023

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Experimental Closed-Loop Excitation of Nonlinear Normal Modes on an Elastic Industrial Robot

Bjelonic, Filip (author), Sachtler, Arne (author), Albu-Schaffer, Alin (author), Della Santina, C. (author)

Adding elastic elements to the mechanical structure should enable robots to perform efficient oscillatory tasks. Still, even characterizing natural oscillations in nonlinear systems is a challenge in itself, which nonlinear modal theory promises to solve. Therein eigenmanifolds generalize eigenspaces to mechanical systems with non-Euclidean...

journal article 2022

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Feedback Regulation of Elastically Decoupled Underactuated Soft Robots

Pustina, P. (author), Della Santina, C. (author), De Luca, Alessandro (author)

The intrinsically underactuated and nonlinear nature of continuum soft robots makes the derivation of provably stable feedback control laws a challenging task. Most of the works so far circumvented the issue either by looking at coarse fully-actuated approximations of the dynamics or by imposing quasi-static assumptions. In this letter, we...

journal article 2022

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An experimental validation of the polynomial curvature model: identification and optimal control of a soft underwater tentacle

Stella, F. (author), Obayashi, Nana (author), Della Santina, C. (author), Hughes, Josie (author)

The control possibilities for soft robots have long been hindered by the lack of accurate yet computationally treatable dynamic models of soft structures. Polynomial curvature models propose a solution to this quest for continuum slender structures. Nevertheless, the results produced with this class of models have been so far essentially...

journal article 2022

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Piston-Driven Pneumatically-Actuated Soft Robots: modeling and backstepping control

Stölzle, Maximilian (author), Della Santina, C. (author)

Actuators’ dynamics have been so far mostly neglected when devising feedback controllers for continuum soft robots since the problem under the direct actuation hypothesis is already quite hard to solve. Directly considering actuation would have made the challenge too complex. However, these effects are, in practice, far from being negligible....

journal article 2021

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Putting Back Actuation in Pneumatically Actuated Soft Robots: modeling and backstepping control

Stölzle, Maximilian (author), Della Santina, C. (author)

abstract 2021

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Actuating Eigenmanifolds of Conservative Mechanical Systems Via Bounded or Impulsive Control Actions

Della Santina, C. (author), Calzolari, Davide (author), Giordano, Alessandro Massimo (author), Albu-Schaffer, Alin (author)

Eigenmanifolds are two-dimensional submanifolds of the state space, which generalize linear eigenspaces to nonlinear mechanical systems. Initializing a robot on an Eigenmanifold (or driving it there by control) yields hyper-efficient and regular oscillatory behaviors, called modal oscillations. This letter investigates the possibility of...

journal article 2021

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Efficient and Goal-Directed Oscillations in Articulated Soft Robots: the Point-to-Point Case

Bonacchi, Luigi Bono (author), Roa, Maximo A. (author), Sesselmann, Anna (author), Loeffl, Florian (author), Albu-Schaffer, Alin (author), Della Santina, C. (author)

Introducing elasticity in the mechanical design can endow robots with the ability of performing efficient and effective periodic motions. Yet, devising controllers that can take advantage of such elasticity is still an open challenge. This letter tackles an instance of this general problem, by proposing a control architecture for executing...

journal article 2021

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PD-like Regulation of Mechanical Systems with Prescribed Bounds of Exponential Stability: the Point-to-Point Case

Calzolari, Davide (author), Della Santina, C. (author), Albu-Schaffer, Alin (author)

This letter discusses an extension of the famous PD regulator implementing point to point motions with prescribed exponential rates of convergence. This is achieved by deriving a novel global exponential stability result, dealing with mechanical systems evolving on uni-dimensional invariant manifolds of the configuration space. The...

journal article 2021

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Exciting efficient oscillations in nonlinear mechanical systems through Eigenmanifold stabilization

Della Santina, C. (author), Albu-Schaeffer, Alin (author)

Nonlinear modes are a well investigated concept in dynamical systems theory, extending the celebrated modal analysis of linear mechanical systems to nonlinear ones. This letter moves a first step in the direction of combining control theory and nonlinear modal analysis towards the implementation of hyper-efficient oscillatory behaviors in...

journal article 2021

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Covid-19 and Flattening the Curve: a Feedback Control Perspective

Di Lauro, Francesco (author), Kiss, Istvan Zoltan (author), Rus, Daniela (author), Della Santina, C. (author)

Many of the policies that were put into place during the Covid-19 pandemic had a common goal: to flatten the curve of the number of infected people so that its peak remains under a critical threshold. This letter considers the challenge of engineering a strategy that enforces such a goal using control theory. We introduce a simple formulation...

journal article 2021

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Editorial: On the Planning, Control, and Perception of Soft Robotic End-Effectors

Averta, Giuseppe (author), Della Santina, C. (author), Ficuciello, Fanny (author), Roa, Maximo A. (author), Bianchi, Matteo (author)

contribution to periodical 2021

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Adaptive Control of Soft Robots Based on an Enhanced 3D Augmented Rigid Robot Matching

Trumic, Maja (author), Della Santina, C. (author), Jovanovic, Kosta (author), Fagiolini, Adriano (author)

Despite having proven successful in generating precise motions under dynamic conditions in highly deformable soft-bodied robots, model based techniques are also prone to robustness issues connected to the intrinsic uncertain nature of the dynamics of these systems. This letter aims at tackling this challenge, by extending the augmented rigid...

journal article 2021