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Soft Robotics and Applied Control

Soft and flexible robotic systems for affordable healthcare.

Head of Group

B414B Bessemer Building
South Kensington Campus

What we do

Our research investigates fundamental aspects of control of soft and flexible robots for surgery. These include harnessing the intrinsic compliance of soft robots, rejecting disturbances that characterise the surgical environment, and complying with stringent safety requirements. Our ambition is to provide affordable robotic solutions for a range of surgical applications, including endoscopy, percutaneous intervention, and multi-handed surgery.

Why it is important?

Robotics for healthcare is one of the fastest growing segments in the global robotics market. However, conventional surgical robots are unaffordable in low-resource settings. Harnessing the potential of soft and flexible robots can contribute to making surgery safter, more accurate, and more accessible in low-middle income countries. These are pressing needs due to the aging population, and to the growing workforce crisis in the healthcare market.

How can it benefit patients?

Our work aims to improve accuracy, reduce the risk of injury, and reduce discomfort in percutaneous interventions such as biopsy, in diagnostic and interventional endoscopy, and in multi-handed surgery.

Dr Enrico Franco
Lecturer

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Journal article
Garriga-Casanovas A, Shakib F, Ferrandy V, Franco Eet al., 2024,
Hybrid Control of Soft Robotic Manipulator
, Actuators, Vol: 13
Soft robotic manipulators consisting of serially stacked segments combine actuation and structure in an integrated design. This design can be miniaturised while providing suitable actuation for potential applications that may include endoluminal surgery and inspections in confined environments. The control of these robots, however, remains challenging, due to the difficulty in accurately modelling the robots, in coping with their redundancies, and in solving their full inverse kinematics. In this work, we explore a hybrid approach to control serial soft robotic manipulators that combines machine learning (ML) to estimate the inverse kinematics with closed-loop control to compensate for the remaining errors. For the ML part, we compare various approaches, including both kernel-based learning and more general neural networks. We validate the selected ML model experimentally. For the closed-loop control part, we first explore Jacobian formulations using both synthetic models and numerical approximations from experimental data. We then implement integral control actions using both these Jacobians, and evaluate them experimentally. In an experimental validation, we demonstrate that the hybrid control approach achieves setpoint regulation in a robot with six inputs and four outputs.
- Abstract
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- Citations: 2
Journal article
Franco E, Arpenti P, Donaire A, Ruggiero Fet al., 2024,
Integral IDA-PBC for underactuated mechanical systems subject to matched and unmatched disturbances
, IEEE Control Systems Letters, Vol: 8, Pages: 568-573, ISSN: 2475-1456
This letter presents a new formulation of the integral interconnection and damping-assignment passivity-based control methodology for underactuated mechanical systems subject to both matched and unmatched disturbances, either constant or position-dependent. The new controller is also applicable to systems with non-constant input matrix. Simulations results on two examples demonstrate its effectiveness.
Journal article
Franco E, Fulvio F, 2024,
Integral controlled lagrangians for underactuated mechanical systems subject to position-dependent matched disturbances
, IEEE Control Systems Letters, Vol: 8, Pages: 466-471, ISSN: 2475-1456
This letter investigates the dynamic extension of the Controlled Lagrangians methodology for underactuated mechanical systems subject to matched disturbances that depend on the generalized position. A new passivity-preserving controller design procedure is presented for a class of underactuated mechanical systems. An interpretation of the dynamic extension as first-order low-pass filter is proposed. Simulations results on a inertia-wheel pendulum with various types of disturbances demonstrate the effectiveness of the new controller.
Journal article
Franco E, Arpenti P, Donaire A, 2024,
Integral passivity-based control of underactuated mechanical systems with state-dependent matched disturbances
, International Journal of Robust and Nonlinear Control, Vol: 34, Pages: 3565-3585, ISSN: 1049-8923
This work investigates the energy shaping control of a class of underactuated mechanical systems subject to state-dependent linearly parameterized matched disturbances. To this end, a new integral interconnection and damping-assignment passivity-based design is proposed. The controller design is developed for systems subject to either momenta-dependent disturbances or position-dependent disturbances or to both simultaneously. The effectiveness of the proposed approach is demonstrated with numerical simulations on three examples: an Acrobot system with nonlinear friction; a ball-on-beam system with constant and position-dependent disturbances; a disk-on-disk system with a complete set of state-dependent disturbances. In all examples, the proposed controller shows better performance compared to previous implementations.
Journal article
Aktas A, Franco E, 2024,
A force-limiting mechanism for needle insertions
, IEEE Transactions on Medical Robotics and Bionics, Vol: 6, Pages: 362-365, ISSN: 2576-3202
Needle bending is a significant cause of error in biopsies, leading to lesion missampling and consequent cancer misdiagnosis. This paper presents the design of a new mechanism that detects the needle bending as soon as it occurs and immediately reduces the insertion force. Importantly, this is achieved without employing external sensors or electromechanical actuators. Experiments on a silicone-rubber phantom indicate that the proposed device can help to avoid deep insertions with bent needles, thus potentially reducing the associated risks and improving patient safety in biopsies and percutaneous interventions.
Journal article
Ahmed JF, Franco E, Y Baena FR, Darzi A, Patel Net al., 2024,
A review of bioinspired locomotion in lower GI endoscopy
, ROBOTICA, ISSN: 0263-5747
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Conference paper
Treratanakulchai S, Garriga-Casanovas A, Borvorntanajanya K, Franco E, Baena FRet al., 2024,
A Novel Soft Robotic Manipulator Design with Zig-zag Chamber Geometry
, Pages: 12-17
The development of soft robots has advanced rapidly in recent years. However, most designs present significant non-linearities and deviate from the desired bending direction in an unpredictable manner. This makes accurate control more difficult. In this paper, we present a novel design of a soft robotic manipulator with zig-zag partition walls, which minimize those deviations. We first outline the design and describe a lost wax manufacturing process for complex geometries. We then report experiments to evaluate the bending characteristics, force, and repeatability of the prototype, and we compare it against an existing design. The results show a significant improvement in bending consistency with minimal deviations.
- Abstract
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- Citations: 1
Journal article
Ferrandy V, Indrawanto, Ferryanto F, Sugiharto A, Franco E, Garriga-Casanovas A, Mahyuddin AI, Baena FRY, Mihradi S, Virdyawan Vet al., 2023,
Modeling of a two-degree-of-freedom fiber-reinforced soft pneumatic actuator
, ROBOTICA, Vol: 41, Pages: 3608-3626, ISSN: 0263-5747
- Cite
Journal article
Franco E, 2023,
Integral passivity-based control of underactuated mechanical systems with actuator dynamics and constant disturbances
, International Journal of Robust and Nonlinear Control, Vol: 33, Pages: 10024-10045, ISSN: 1049-8923
This work investigates the energy shaping control of a class of underactuated mechanical systems with first-order actuator dynamics and subject to both matched and unmatched constant additive disturbances. To this end, a new nonlinear control law which includes two independent integral actions is presented. The controller design is outlined for systems with first-order actuator dynamics, and also for systems with direct actuation. The effectiveness of the proposed approach is demonstrated with numerical simulations on an inertia wheel pendulum and on a ball-on-beam system, both actuated by electric DC motors and subject to constant disturbances.
Conference paper
Franco E, Aktas A, Treratanakulchai S, Garriga Casanovas A, Donder A, Rodriguez y Baena Fet al., 2023,
Discrete-time model based control of soft manipulator with FBG sensing
, ICRA 2023, Publisher: IEEE, Pages: 567-572
In this article we investigate the discrete-time model based control of a planar soft continuum manipulator with proprioceptive sensing provided by fiber Bragg gratings.A control algorithm is designed with a discrete-time energyshaping approach which is extended to account for control-related lag of digital nature. A discrete-time nonlinear observer is employed to estimate the uncertain bending stiffness of the manipulator and to compensate constant matched disturbances. Simulations and experiments demonstrate the effectiveness of the controller compared to a continuous time implementation.

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