Imperial College London

DrArnauGarriga Casanovas

Faculty of EngineeringDepartment of Mechanical Engineering

Visiting Researcher







City and Guilds BuildingSouth Kensington Campus





Publication Type

21 results found

Ferrandy V, Indrawanto, Ferryanto F, Sugiharto A, Franco E, Garriga-Casanovas A, Mahyuddin AI, Rodriguez Y Baena F, 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

Fiber winding reinforcement is widely used in soft robotic manipulators actuated by pressurized fluids. However, the specific effect of each type of winding on the bending motion of a tubular soft robotics manipulator with three chambers has not been explored widely. We present the development of precise finite element (FE) simulations and investigate the effect of helical fiber winding parameters on the bending motion of a two-degree-of-freedom manipulator with three internal chambers. We first show the development of an FE simulation that optimizes convergence and computational time and precisely matches the behavior of soft robots in practice. Compared to single-chamber robots, simulating three-chamber designs is more challenging due to the complex geometry. We then apply our FE model to simulate all the parameter variations. We show that for helical winding with a constant pitch, the closer the center of a chamber is to the intersection of the windings, the lower the bending stiffness of the chamber is. To minimize bending stiffness variation in different bending directions, the optimal angle between the center of the first chamber and the intersection of the two helical windings are 0° and 12°. Reducing the pitch of the helical windings or using other types of windings (i.e., ring winding or six helical winding) reduces the stiffness variation across different bending directions. The FE simulations are compared with experiments showing that the model can capture complex bending behaviors of the manipulator, even though the estimation tends to be less accurate at higher bending angles.

Journal article

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.

Conference paper

Virdyawan V, Ayatullah T, Sugiharto A, Franco E, Garriga Casanovas A, Mahyuddin AI, Rodriguez y Baena F, Indrawantoet al., 2023, Design and manufacturing of an affordable soft robotic manipulator for minimally invasive diagnosis, International Conference on Robotics and Automation Engineering (ICRAE), Publisher: IEEE

Soft robotic manipulators are inherently compliant thus they are ideally suited for minimally invasive diagnosis and intervention. In addition, soft robotics allows for affordable manufacturing, thus it could be adopted in low and middle-income countries where conventional robotics is prohibitively expensive. In this work, the design, manufacturing, and actuation strategy of an affordable soft robotic manipulator is presented. The manufacturing process does not rely on sophisticated technologies, and the pneumatic actuation does not require digital pressure regulators. Instead, a low-cost solution consisting of a needle valve operated by a servo motor is employed. The prototype is assessed with experiments that demonstrate its functionality.

Conference paper

Treratanakulchai S, Franco E, Garriga Casanovas A, Hu M, Kassanos P, Rodriguez y Baena Fet al., 2022, Development of a 6 DOF soft robotic manipulator with integrated sensing Skin, International Conference on Intelligent Robots and Systems (IROS 2022), Publisher: IEEE, Pages: 6944-6951

This paper presents a new 6 DOF soft roboticmanipulator intended for colorectal surgery. The manipulator,based on a novel design that employs an inextensible tube tolimit axial extension, is shown to maximize the force exertedat its tip and the bending angle, the latter being measuredwith a soft sensing skin. Manufacturing of the prototypeis achieved with a lost-wax silicone-casting technique. Thekinematic model of the manipulator, its workspace, and itsmanipulability are discussed. The prototype is evaluated withextensive experiments, including pressure-deflection measure-ment with and without tip load, and lateral force measurementswith and without the soft sensing skin to assess hysteresis. Theexperimental results indicate that the prototype fulfils the keydesign requirements for colorectal surgery: (i) it can generatesufficient force to perform a range of laparoscopic tasks; (ii) theworkspace is commensurate with the dimensions of the largeintestine; (iii) the soft sensing skin only results in a marginalreduction of the maximum tip rotation within the range ofpressures and external loads relevant for the chosen application.

Conference paper

Yung K, Garriga-Casanovas A, Khalili P, Cegla Fet al., 2022, Visually encoded contact inspection system for EMATs, Journal of Nondestructive Evaluation, Vol: 41, Pages: 1-9, ISSN: 0195-9298

Contact inspections are commonly performed in industry to check for defects and degradation, such as corrosion or cracks. Non-destructive evaluation (NDE) probes are being deployed with increasing frequency using autonomous robots, especially in harsh environments or in areas where access is restricted and difficult. Together with the NDE measurement, it is important to capture the 3D position of the probe so that the location where the data originated is known. This allows for the generation of 3D maps of the inspection, which ensure full scan coverage, and can be used for inspection reports and to generate digital twins of the structure for asset management. In this paper, a full inspection system integrating a robot mountable stereo camera system together with an electromagnetic acoustic transducer (EMAT) probe and a wireless NDE data acquisition system is presented. The system is capable of capturing and merging 3D positional data of the probe as it is scanned and NDE data. The system design in terms of hardware and software is described in this paper. A set of tests to evaluate its performance on relevant structural components are also presented, and the results are reported and discussed.

Journal article

Franco E, Garriga Casanovas A, Tang J, Rodriguez y Baena F, Astolfi Aet al., 2022, Adaptive energy shaping control of a class of nonlinear soft continuum manipulators, IEEE-ASME Transactions on Mechatronics, Vol: 27, Pages: 280-291, ISSN: 1083-4435

Soft continuum manipulators are characterized by low stiffness which allows safe operation in unstructured environments but introduces under-actuation. In addition, soft materials such as silicone rubber, which are commonly used for soft manipulators, are characterized by nonlinear stiffness, while pneumatic actuation can result in nonlinear damping. Consequently, achieving accurate control of these systems in the presence of disturbances is a challenging task. This paper investigates the model-based adaptive control for soft continuum manipulators that have nonlinear uniform stiffness and nonlinear damping, that bend under the effect of internal pressure, and that are subject to time-varying disturbances. A rigid-link model with virtual elastic joints is employed for control purposes within the port-Hamiltonian framework. The effects of disturbances and of model uncertainties are estimated adaptively. A nonlinear controller that regulates the tip orientation of the manipulator and that compensates the effects of disturbances and of model uncertainties is then constructed by using an energy shaping passivity-based approach. Stability conditions are discussed highlighting the beneficial role of nonlinear damping. The effectiveness of the controller is assessed with simulations and with experiments on a soft continuum manipulator prototype.

Journal article

Garriga-Casanovas A, Treratanakulchai S, Franco E, Zari E, Ferrandy V, Virdyawan V, Baena FRYet al., 2022, Optimised Design and Performance Comparison of Soft Robotic Manipulators, 7th International Conference on Mechanical Engineering and Robotics Research (ICMERR), Publisher: IEEE, Pages: 129-136

Conference paper

Franco E, Ayatullah T, Sugiharto A, Garriga Casanovas A, Virdyawan Vet al., 2021, Nonlinear energy-based control of soft continuum pneumatic manipulators, Nonlinear Dynamics, Vol: 106, Pages: 229-253, ISSN: 0924-090X

This paper investigates the model-based nonlinear control of a class of soft continuum pneumatic manipulators that bend due to pressurization of their internal chambers and that operate in the presence of disturbances. A port-Hamiltonian formulation is employed to describe the closed loop system dynamics, which includes the pressure dynamics of the pneumatic actuation, and new nonlinear control laws are constructed with an energy-based approach. In particular, a multi-step design procedure is outlined for soft continuum manipulators operating on a plane and in 3D space. The resulting nonlinear control laws are combined with adaptive observers to compensate the effect of unknown disturbances and model uncertainties. Stability conditions are investigated with a Lyapunov approach, and the effect of the tuning parameters is discussed. For comparison purposes, a different control law constructed with a backstepping procedure is also presented. The effectiveness of the control strategy is demonstrated with simulations and with experiments on a prototype. To this end, a needle valve operated by a servo motor is employed instead of more sophisticated digital pressure regulators. The proposed controllers effectively regulate the tip rotation of the prototype, while preventing vibrations and compensating the effects of disturbances, and demonstrate improved performance compared to the backstepping alternative and to a PID algorithm.

Journal article

Franco E, Garriga Casanovas A, Tang J, Rodriguez y Baena F, Astolfi Aet al., 2021, Position regulation in Cartesian space of a class of inextensible soft continuum manipulators with pneumatic actuation, Mechatronics, Vol: 76, Pages: 1-21, ISSN: 0957-4158

This work investigates the position regulation in Cartesian space of a class of inextensible soft continuum manipulators with pneumatic actuation subject to model uncertainties and to unknown external disturbances that act on the tip. Soft continuum manipulators are characterised by high structural compliance which results in a large number of degrees-of-freedom, only a subset of which can be actuated independently or instrumented with sensors. External disturbances, which are common in many applications, result in uncertain dynamics and in uncertain kinematics thus making the control problem particularly challenging. We have investigated the use of integral action to model the uncertain kinematics of the manipulators, and we have designed a new control law to achieve position regulation in Cartesian space by employing a port-Hamiltonian formulation and a passivity-based approach. In addition, we have compared two adaptive laws that compensate the effects of the external disturbances on the system dynamics. Local stability conditions are discussed with a Lyapunov approach and are related to the controller parameters. The performance of the controller is demonstrated by means of simulations and experiments with two different prototypes.

Journal article

Franco E, Tang J, Garriga Casanovas A, Rodriguez y Baena F, Astolfi Aet al., 2021, Position control of soft manipulators with dynamic and kinematic uncertainties, 21st IFAC World Congress, Publisher: Elsevier, Pages: 9847-9852, ISSN: 2405-8963

This work investigates the position control problem for a soft continuum manipulator in Cartesian space intended for minimally invasive surgery. Soft continuum manipulators have a large number of degrees-of-freedom and are particularly susceptible to external forces because of their compliance. This, in conjunction with the limited number of sensors typically available, results in uncertain kinematics, which further complicates the control problem. We have designed a partial state feedback that compensates the effects of external forces employing a rigid-link model and a port-Hamiltonian approach and we have investigated in detail the use of integral action to achieve position regulation in Cartesian space. Local stability conditions are discussed with a Lyapunov approach. The performance of the controller is compared with that achieved with a radial-basis-functions neural network by means of simulations and experiments on two prototypes.

Conference paper

Franco E, Garriga Casanovas A, Donaire A, 2021, Energy shaping control with integral action for soft continuum manipulators, Mechanism and Machine Theory, Vol: 158, ISSN: 0094-114X

This paper investigates the control problem for soft continuum manipulators that operate on a plane and that are subject to unknown disturbances. In general, soft continuum manipulators have more degrees-of-freedom than control inputs and are characterised by nonlinear dynamics. Thus, achieving high position accuracy with these systems in the presence of disturbances is a challenging task. In this paper we present the design of a new partial-state feedback controller by using the port-Hamiltonian formulation and we develop a variation of the Integral Interconnection and Damping Assignment Passivity Based Control methodology for a class of soft continuum manipulators. The system dynamics on the bending plane is described by using a rigid-link underactuated model with elastic virtual joints. The proposed control law regulates the tip rotation to the desired value while compensating unmodelled disturbances and only depends on the tip rotation, which is measurable, hence it is implementable. The effectiveness of the controller is demonstrated with simulations and with experiments on a soft continuum manipulator prototype that employs pneumatic actuation.

Journal article

Franco E, Garriga Casanovas A, 2021, Energy shaping control of soft continuum manipulators with in-plane disturbances, International Journal of Robotics Research, Vol: 40, Pages: 236-255, ISSN: 0278-3649

Soft continuum manipulators offer levels of compliance and inherent safety that can render thema superior alternative to conventional rigid robotsfor a variety of tasks, such as medical interventions or human-robot interaction. However, the ability of soft continuum manipulators to compensate external disturbances need to be further enhanced to meet the stringent requirements of many practical applications.In this paper, we investigate the control problem forsoft continuum manipulators that consist of one inextensible segmentof constant section, which bends under the effect of the internal pressure and is subject to unknown disturbances acting in the plane of bending. A rigid-link model of the manipulatorwith a single input pressureis employed for control purposes and an energy-shaping approach isproposedto derive thecontrol law. A method for the adaptive estimation of disturbances is detailed and a disturbance compensation strategy is proposed.Finally, the effectiveness of the controlleris demonstrated with simulations and with experiments on an inextensible soft continuum manipulator that employs pneumatic actuation.

Journal article

Garriga Casanovas A, Khalili P, Cegla F, 2020, Development of a new, wireless acquisition system for EMATs compatible with the robotics operating system, IEEE Sensors Journal, Vol: 20, Pages: 12783-12790, ISSN: 1530-437X

The deployment of transducers to perform in situ inspections of industrial components can be complicated, and in many cases is still performed manually by a team of operators, which involves significant costs and can be dangerous. Robots capable of deploying probes in difficult to access locations are becoming available. Electromagnetic acoustic transducers (EMAT) are well suited to be used with robots since they are noncontact transducers that do not require a coupling medium, and can easily perform scans. However, existing acquisition systems for EMATs are generally not suitable to be directly mounted on robots. In this paper, a new wireless acquisition system for EMATs is presented. The system is standalone, it transmits the inspection data over WiFi, and is compatible with the robotics operating system (ROS). In addition, it is designed to be modular, small and lightweight so that it can be easily mounted on robots. The system design in terms of hardware and software is described in thispaper. The resulting performance of the system is also reported.

Journal article

Franco E, Garriga Casanovas A, Rodriguez y Baena F, Astolfi Aet al., 2020, Model based adaptive control for a soft robotic manipulator, 58th IEEE Conference on Decision and Control, Publisher: IEEE, Pages: 1019-1024

The application of model based adaptive control to an underactuated system representative of a class of soft continuummanipulators is investigated. To this end, a rigid-linkmodel with elastic joints is employed and an energy shaping controller is designed. Additionally, model uncertainties and external disturbances, both matched and unmatched, are compensated with an adaptive algorithm. This results in a control law that only depends on the orientation and on the angular velocity of the distal link and it is therefore independent of the number of links. Finally, stability conditions are discussed and the effectiveness of the controller is verified via simulations.

Conference paper

Ivan V, Garriga-Casanovas A, Merkt W, Cegla FB, Vijayakumar Set al., 2020, Autonomous non-destructive remote robotic inspection of offshoreassets, ISSN: 0160-3663

Offshore assets suffer from material degradation over their lifetimes. Regular inspections are necessaryto prevent failures and to reduce the cost of maintenance. These often require downtime of the asset andcan involve risk to human workers who have to be sent to the offshore location. In this work, we presenta non-destructive (NDE) system in conjunction with a robotic platform, which can perform inspectionsof the thickness of a component, for example from the outside of a tank or a pressure vessel. The NDEsystem consists of a digital acquisition system and an electromagnetic acoustic transducer (EMAT). TheEMAT generates an acoustic wave, which reflects from the internal features of the component. The wave isreceived by the same device. The received signal is then processed by the acquisition system to determine thethickness of the component. The NDE system is integrated with a robotic platform that can autonomouslyor semi-autonomously perform scans of the asset. The robot platform presented in this work uses sensorfusion, machine vision and state of the art motion planning techniques to build a map of the material qualityin 3D. This is achieved by exploiting the precise movement of the robot end-effector along the surface ofthe asset and then integrating the position of the NDE sensor. The collected data is then presented to theremote operator in a user-friendly way, which allows them to evaluate the state of the asset. We validate thissystem using material samples with known defects. We performed experiments in a controlled environment,and we demonstrate the system in a case study at a testing facility operated by our industrial partners.

Conference paper

Garriga Casanovas A, Rodriguez y Baena F, 2019, Kinematics of continuum robots with constant curvature bending and extension capabilities, Journal of Mechanisms and Robotics, Vol: 11, ISSN: 1942-4302

Continuum robots are becoming increasingly popular due to the capabilities they offer, especially when operating in cluttered environments, where their dexterity, maneuverability, and compliance represent a significant advantage. The subset of continuum robots that also belong to the soft robots category has seen rapid development in recent years, showing great promise. However, despite the significant attention received by these devices, various aspects of their kinematics remain unresolved, limiting their adoption and obscuring their potential. In this paper, the kinematics of continuum robots with the ability to bend and extend are studied, and analytical, closed-form solutions to both the direct and inverse kinematics are presented. The results obtained expose the redundancies of these devices, which are subsequently explored. The solution to the inverse kinematics derived here is shown to provide an analytical, closed-form expression describing the curve associated with these redundancies, which is also presented and analyzed. A condition on the reachable end-effector poses for robots with six actuation degrees-of-freedom (DOFs) is then distilled. The kinematics of robot layouts with over six actuation DOFs are subsequently considered. Finally, simulated results of the inverse kinematics are provided, verifying the study.

Journal article

Garriga Casanovas A, Collison I, Rodriguez y Baena F, 2018, Towards a common framework for the design of soft robotic manipulators with fluidic actuation, Soft Robotics, Vol: 5, Pages: 622-649, ISSN: 2169-5172

Soft robotic manipulators with fluidic actuation are devices with easily deformable structures that comprise a set of chambers that can be pressurized to achieve structural deflection. These devices have experienced a rapid development in recent years, which is not least due to the advantages they offer in terms of robustness, affordability, and compliance. Nowadays, however, soft robotic manipulators are designed mostly by intuition, which complicates design improvement and hampers the advancement of the field. In this paper, a general study of the the design of soft robotic manipulators with fluidic actuation is presented, using an analytical derivation. The study relies on a novel approach that is applicable to a general design, and thus provides a common framework for the design of soft robots. In the study, two design layouts of interest are first justified, which correspond to extending and contracting devices. Design principles for each of the layouts are subsequently derived, both for planar and 3D scenarios, and considering operation to support any external loading and to provide any desired deflection. These principles are found to agree with the main design trends in literature, although they also highlight the potential for improvement in specific aspects of the design geometry and stiffness distribution. The principles are used to identify the most suitable design for both extending and contracting devices in 2D and 3D, and extract insight into their behavior.. To showcase the use of these design principles, a prototypical scenario in minimally invasive surgery requiring a manipulator segment capable of bending in any direction is defined, where the objective is to maximize its lateral force. The principles are applied to determine the most suitable design. These also highlight the need for numerical analysis to optimize two design parameters. Finite element simulations are developed, and their results are reported.

Journal article

Garriga Casanovas A, ’Athif Mohd Faudzi A, Hiramitsu T, Rodriguez y Baena F, Suzumori Ket al., 2018, Multifilament pneumatic artificial muscles to mimic the human neck, IEEE International Conference on Robotics and Biomimetics, 2017, Publisher: IEEE

Pneumatic Artificial Muscles (PAMs) are actuators that resemble human muscles, and offer an attractive performance in various aspects including robustness, simplicity, high specific power and high force for a given volume. These characteristics render them good candidates for use in humanoid robots. The use of traditional PAMs to closely mimic human structures, however, is difficult due to their relatively large size and relatively fixed designs. The recent development of multifilament PAMs enables the realization of humanoid robots that more closely mimic the human anatomy. In this paper, the application of multifilament PAMs to mimic the human neck is presented. First, the main structures of the human neck anatomy in terms of bones, ligaments and muscles are identified and detailed. The design to mimic each of these structures is subsequently described, together with the most relevant parts of the manufacturing process. The integrated neck is then presented, and the method to actuate it is outlined. The results of motion of the artificial neck when actuating different groups of muscles that mimic those in the human anatomy are reported, confirming a motion that is equivalent to that of the human neck. The results also indicate a range of motion of the robot neck somewhat lower than that of its human counterpart, and the reasons for this are discussed. Finally, future directions for improved motion range, stability, durability and efficiency are outlined.

Conference paper

Garriga Casanovas A, Rodriguez y Baena F, 2018, Complete follow-the-leader kinematics using concentric tube robots, International Journal of Robotics Research, Vol: 37, Pages: 197-222, ISSN: 0278-3649

Concentric tube robots offer the capability of follow-the-leader motion, which is desirable when navigating in cluttered environments, such as in minimally invasive surgery or in-situ inspections. The follow-the-leader capabilities identified in the existing literature, however, are limited to trajectories with piecewise constant-curvature segments or piecewise helical segments. A complete study of follow-the-leader kinematics is, therefore, relevant to determine the full potential of these robots, and clarify an open question. In this paper, a general analysis of follow-the-leader motion is presented, and a closed-form solution to the complete set of trajectories where follow-the-leader is possible under the assumption of no axial torsion of the tubes composing the robot is derived. For designs with constant-stiffness tubes, the precurvatures required are found to be either circumference arcs, helices, or deformed helices with exponentially varying curvature magnitude. The analysis developed also elucidates additional motions of interest, such as the combination of follow-the-leader motion in a robot segment with general maneuvers in another part. To determine the applicability of the assumption regarding the tubes’ torsion, the general equilibrium of the robot designs of interest is considered, and a closed-form solution to torsion in two-tube robots with helical precurvatures is derived. Criteria to select a desired torsional behavior are then extracted. This enables one to identify stable trajectories where follow-the-leader is possible, for potential application to minimally invasive surgery. An illustrative case study involving simulation and experiment is conceived using one of these trajectories, and the results are reported, showcasing the research.

Journal article

Garriga-Casanovas A, Faudzi AAM, Hiramitsu T, Rodriguez y Baena F, Suzumori Ket al., 2017, Multifilament Pneumatic Artificial Muscles to Mimic the Human Neck, IEEE International Conference on Robotics and Biomimetics (ROBIO), Publisher: IEEE, Pages: 809-816

Conference paper

Liu F, Garriga-Casanovas A, Secoli R, Baena FRYet al., 2016, Fast and adaptive fractal tree-based path planning for programmable bevel tip steerable needles, IEEE Robotics and Automation Letters, Vol: 1, Pages: 601-608, ISSN: 2377-3766

Steerable needles are a promising technology for minimally invasive surgery, as they can provide access to difficult to reach locations while avoiding delicate anatomical regions. However, due to the unpredictable tissue deformation associated with needle insertion and the complexity of many surgical scenarios, a real-time path planning algorithm with high update frequency would be advantageous. Real-time path planning for nonholonomic systems is commonly used in a broad variety of fields, ranging from aerospace to submarine navigation. In this letter, we propose to take advantage of the architecture of graphics processing units (GPUs) to apply fractal theory and thus parallelize real-time path planning computation. This novel approach, termed adaptive fractal trees (AFT), allows for the creation of a database of paths covering the entire domain, which are dense, invariant, procedurally produced, adaptable in size, and present a recursive structure. The generated cache of paths can in turn be analyzed in parallel to determine the most suitable path in a fraction of a second. The ability to cope with nonholonomic constraints, as well as constraints in the space of states of any complexity or number, is intrinsic to the AFT approach, rendering it highly versatile. Three-dimensional (3-D) simulations applied to needle steering in neurosurgery show that our approach can successfully compute paths in real-time, enabling complex brain navigation.

Journal article

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