Publications
46 results found
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.
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.
Ahmed JF, Franco E, Rodriguez Y Baena F, et al., 2024, A review of bioinspired locomotion in lower GI endoscopy, Robotica, ISSN: 0263-5747
Flexible endoscopy is the gold standard modality for diagnosis and therapeutic intervention of various colorectal conditions. A high bar is currently set for any new technology to replace the current modern colonoscope, but limitations do exist. For a robotic system to gain acceptance, ideally a clear advantage over the established standard needs to be demonstrated. The application of robotic technology inspired by locomotion observed in animals has been demonstrated in many fields including colonoscopy. A myriad of novel concepts has been proposed, which can overcome the anatomical and technical challenges. This review discusses novel and innovative examples of bioinspired robotic locomotion in the colon with a detailed comparison of studies alongside separating the discussion by animal sections of insect, marine and reptile locomotion. We also discuss the current advantages and challenges a bioinspired robot will bring to the colon. Bioinspired robotics in the colon is an exciting field of research with the potential to improve upon current existing high standards of practice in colonoscopy. By addressing areas that the conventional colonoscope is weaker in, studies are demonstrating improvement upon current limitations of standard practice and providing an insight into new methods of engineering and fabrication. Focus on the technological, mechanical and regulatory barriers is key to achieve acceptance into standard practice and will allow the aspiration of a safe, low discomfort, low cost and potentially fully autonomous robotic colonoscope to be not too distant in the future of colonoscopy.
Ferrandy V, Indrawanto, Ferryanto F, et 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.
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.
Runciman M, Franco E, Avery J, et al., 2023, Model based position control of soft hydraulic actuators, IEEE International Conference on Robotics and Automation, Publisher: IEEE, Pages: 1-7
In this article, we investigate the model based position control of soft hydraulic actuators arranged in an an-tagonistic pair. A dynamical model of the system is constructed by employing the port-Hamiltonian formulation. A control algorithm is designed with an energy shaping approach, which accounts for the pressure dynamics of the fluid. A nonlinear observer is included to compensate the effect of unknown external forces. Simulations demonstrate the effectiveness of the proposed approach, and experiments achieve positioning accuracy of 0.043 mm with a standard deviation of 0.033 mm in the presence of constant external forces up to 1 N.
Franco E, Aktas A, Treratanakulchai S, et 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.
Franco E, Astolfi A, 2023, Energy shaping control of a class of underactuated mechanical systems with high-order actuator dynamics, European Journal of Control, Vol: 72, Pages: 1-13, ISSN: 0947-3580
In this work we present some new results on energy shaping control for underactuated mechanical systems with high-order actuator dynamics. To this end, we propose an extension of the Interconnection and damping assignment Passivity based control methodology to account for actuator dynamics. This brings the following new results: i) a potential and kinetic energy shaping and damping assignment procedure that yields two alternative controllers; ii) a potential energy shaping and damping assignment procedure for a narrower class of underactuated mechanical systems. The proposed approach is illustrated with numerical simulations on three examples: an Acrobot system with a series elastic actuator; a soft continuum manipulator actuated by electroactive polymers; a two-mass-spring system actuated by a DC motor.
Treratanakulchai S, Franco E, Rodriguez y Baena F, 2023, Model-free position control of a soft continuum manipulator in cartesian space, International Conference on Control, Automation and Diagnosis, Publisher: IEEE, Pages: 1-6
This work investigates the position control in Cartesian space of a soft continuum manipulator with pneumatic actuation. To this end, we employ a feedback integral action initialized using an optimized mapping between pressure and tip position. This approach is detailed for a manipulator consisting of either a single actuated segment or of two actuated segments connected in series. Experiments are conducted on individual prototypes and with a teleoperation setup including a master unit from our track record.
Virdyawan V, Ayatullah T, Sugiharto A, et 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.
Alian A, Zari E, Wang Z, et al., 2023, Current engineering developments for robotic systems in flexible endoscopy, Techniques and Innovations in Gastrointestinal Endoscopy, Vol: 25, Pages: 67-81, ISSN: 2590-0307
The past four decades have seen an increase in the incidence of early-onset gastrointestinal cancer. Because early-stage cancer detection is vital to reduce mortality rate, mass screening colonoscopy provides the most effective prevention strategy. However, conventional endoscopy is a painful and technically challenging procedure that requires sedation and experienced endoscopists to be performed. To overcome the current limitations, technological innovation is needed in colonoscopy. In recent years, researchers worldwide have worked to enhance the diagnostic and therapeutic capabilities of endoscopes. The new frontier of endoscopic interventions is represented by robotic flexible endoscopy. Among all options, self-propelling soft endoscopes are particularly promising thanks to their dexterity and adaptability to the curvilinear gastrointestinal anatomy. For these devices to replace the standard endoscopes, integration with embedded sensors and advanced surgical navigation technologies must be investigated. In this review, the progress in robotic endoscopy was divided into the fundamental areas of design, sensing, and imaging. The article offers an overview of the most promising advancements on these three topics since 2018. Continuum endoscopes, capsule endoscopes, and add-on endoscopic devices were included, with a focus on fluid-driven, tendon-driven, and magnetic actuation. Sensing methods employed for the shape and force estimation of flexible endoscopes were classified into model- and sensor-based approaches. Finally, some key contributions in molecular imaging technologies, artificial neural networks, and software algorithms are described. Open challenges are discussed to outline a path toward clinical practice for the next generation of endoscopic devices.
Bastos G, Franco E, 2023, Dynamic tube model predictive control for a class of soft manipulators with fluidic actuation, International Journal of Robust and Nonlinear Control, ISSN: 1049-8923
Controlling soft continuum manipulators is a challenging task due to the structural compliance of these systems which results in underactuation. While a variety of control approaches have been proposed for regulation tasks, tracking control requires further investigation. To this end, a new dynamic tube-Model Predictive Control formulation is presented, which includes an ancillary control law constructed analytically with an energy-shaping approach. Two different models are considered: (i) a rigid-link model with direct-torque actuation, which is representative of miniature soft continuum manipulators supplied by digital pressure regulators; (ii) an extended model that includes the pressure dynamics of the fluid, which is representative of fluidic actuation by means of a variable flow rate. The effectiveness of the proposed algorithm is demonstrated with numerical simulations considering bounded external disturbances, either constant or time-varying.
Treratanakulchai S, Franco E, Garriga Casanovas A, et 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.
Franco E, Astolfi A, 2022, Energy shaping control of underactuated mechanical systems with fluidic actuation, International Journal of Robust and Nonlinear Control, Vol: 32, Pages: 10011-10028, ISSN: 1049-8923
Energy shaping is a remarkably effective control strategy which can be applied to a wide range of systems, including underactuated mechanical systems. However, research in this area has generally neglected actuator dynamics. While this is often appropriate, it might result in degraded performance in the case of fluidic actuation. In this work we present some new results on energy shaping control for underactuated mechanical systems for which the control action is mediated by a pressurized ideal fluid. In particular, we introduce an extended multi-step energy shaping and damping-assignment controller design procedure that builds upon the Interconnection-and-damping-assignment Passivity-based-control methodology in a modular fashion to account for the pressure dynamics of the fluid. Stability conditions are assessed with a Lyapunov approach, the effect of disturbances is discussed, and the case of redundant actuators is illustrated. The proposed approach is demonstrated with numerical simulations for a modified version of the classical ball-on-beam example, which employs two identical cylinders, either hydraulic or pneumatic, to actuate the beam.
Franco E, Donaire A, 2022, Energy shaping nonlinear control of underactuated needle insertion, Control Engineering Practice, Vol: 128, ISSN: 0967-0661
This work investigates the position control of an underactuated mechatronic system for straight needle insertions in soft tissues. The system consists of a pneumatic cylinder pushing a slender needle supported at the base and subject to external forces at the tip due to interactions with soft tissues. The system dynamics is described by a rigid-link underactuated model for controller design purposes. The main contribution of this work is a new energy shaping control law that: (i) does not rely on the analytical solution of partial differential equations, which is a major hurdle in energy shaping techniques, and does not require partial feedback linearization, which is known to be sensitive to model uncertainties; (ii) accounts for the work of the friction forces on the pneumatic cylinder and of the lateral forces acting on the needle tip, which are estimated adaptively with nonlinear observers. For comparison purposes, an alternative controller that employs feedback linearization is also presented. Simulations and experiments on silicone rubber phantoms using a needle with axial-symmetric tip indicate that the proposed controller can reduce the needle tip rotation and the corresponding deflection compared to a PID algorithm. In case of larger insertion forces, the controller can limit the insertion depth to prevent large needle deflections: this behavior can be influenced by acting on a specific tuning parameter, thus providing additional flexibility compared to previous implementations. Finally, the proposed solution is less sensitive to parameter uncertainties than the alternative controller.
Franco E, 2022, Model based eversion control of soft growing robots with pneumatic actuation, IEEE Control Systems Letters, Vol: 6, Pages: 2689-2694, ISSN: 2475-1456
This letter investigates the model based position control of soft growing robots with pneumatic actuation that extend according to the principle known as eversion. A dynamical model of the system which accounts for the energy of the ideal gas is presented by employing the port-Hamiltonian formulation. A new control law is constructed with an energy shaping approach. An adaptive observer is employed to compensate the effect of external forces, including that of gravity. Numerical simulations indicate that the proposed controller is superior to simpler energy shaping algorithms.
Franco E, Garriga Casanovas A, Tang J, et 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.
Garriga-Casanovas A, Treratanakulchai S, Franco E, et 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
Franco E, 2021, Energy shaping control of hydraulic soft continuum planar manipulators, IEEE Control Systems Letters, Vol: 6, Pages: 1748-1753, ISSN: 2475-1456
This letter investigates the model-based control of a class of soft continuum manipulators with hydraulic actuation that bend on a plane due to pressurization of one or more internal chambers. A port-Hamiltonian formulation is employed to describe the system dynamics, which includes the pressure dynamics of the hydraulic fluid. A new nonlinear control law is constructed with an energy-shaping approach, and it is combined with an adaptive observer to compensate the effect of unknown external forces. Stability conditions are investigated with a Lyapunov approach, and the effect of the tuning parameters and of key model parameters is discussed. The effectiveness of the controller is demonstrated with numerical simulations.
Caulcrick C, Huo W, Franco E, et al., 2021, Model predictive control for human-centred lower limb robotic assistance, IEEE Transactions on Medical Robotics and Bionics, Vol: 3, Pages: 980-991, ISSN: 2576-3202
Loss of mobility and/or balance resulting from neural trauma is a critical public health issue. Robotic exoskeletons hold great potential for rehabilitation and assisted movement. However, the synergy of robot operation with human effort remains a problem. In particular, optimal assist-as-needed (AAN) control remains unresolved given pathological variance among patients. We introduce a model predictive control (MPC) architecture for lower limb exoskeletons that achieves on-the-fly transitions between modes of assistance. The architecture implements a fuzzy logic algorithm (FLA) to map key modes of assistance based on human involvement. Three modes are utilised: passive, for human relaxed and robot dominant; active-assist, for human cooperation with the task; and safety, in the case of human resistance to the robot. Electromyography (EMG) signals are further employed to predict the human torque. EMG output is used by the MPC for trajectory following and by the FLA for decision making. Experimental validation using a 1-DOF knee exoskeleton demonstrates the controller tracking a sinusoidal trajectory with relaxed, assistive, and resistive operational modes. Results demonstrate rapid and appropriate transfers among the assistance modes, and satisfactory AAN performance in each case, offering a new level of human-robot synergy for mobility assist and rehabilitation.
Bastos Jr G, Franco E, 2021, Energy shaping dynamic tube-MPC for underactuated mechanical systems, Nonlinear Dynamics, Vol: 106, Pages: 359-380, ISSN: 0924-090X
This work investigates the tracking control problem for underactuated mechanical systems. To this end, we develop an extension of the dynamic tube Model Predictive Control (MPC) approach by combining an MPC design, an ancillary energy shaping controller constructed with the Interconnection and Damping Assignment Passivity-Based Control methodology, and an analytical expression of the dynamic tube. In addition, we extend the proposed approach by including the adaptive compensation of a class of unknown disturbances. The stability analysis is presented by employing a Lyapunov approach. The effectiveness of the proposed controller is demonstrated with simulations on two underactuated systems: a two-mass-spring-damper system with uncertain damping and either linear or nonlinear spring; an inertia-wheel-pendulum with unmodeled disturbances.
Franco E, Ayatullah T, Sugiharto A, et 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.
Franco E, Garriga Casanovas A, Tang J, et 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.
Franco E, Tang J, Garriga Casanovas A, et 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.
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.
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.
Franco E, Brown T, Astolfi A, et al., 2021, Adaptive energy shaping control of robotic needle insertion, Mechanism and Machine Theory, Vol: 155, ISSN: 0094-114X
This work studies the control of a pneumatic actuator for needle insertion in soft tissue without using axial rotation or additional needle supports. Employing a simplified rigid-link model description of an axial-symmetric tip needle supported at the base, two energy shaping controllers are proposed. The friction forces of the pneumatic actuator are compensated adaptively and the stability conditions for the closed-loop equilibrium are discussed. The controllers are compared by means of simulations and experiments on two different silicone rubber phantoms. The results indicate that the proposed controllers effectively compensate the actuator's friction, which is comparable to the insertion forces for the chosen pneumatic actuators. The first controller only depends on the actuator's position thus it achieves the prescribed insertion depth but results in a larger tip rotation and corresponding deflection. The second controller also accounts for the rotation of the needle tip on the bending plane, which can consequently be reduced by over 70% for this specific system. This is achieved by modulating the actuator force and, in case of harder phantoms, by automatically limiting the insertion depth.
Franco E, Rodriguez y Baena F, Astolfi A, 2020, Robust dynamic state feedback for underactuated systems with linearly parameterized disturbances, International Journal of Robust and Nonlinear Control, Vol: 30, Pages: 4112-4128, ISSN: 1049-8923
This article investigates the control problem for underactuated port‐controlled Hamiltonian systems with multiple linearly parameterized additive disturbances including matched, unmatched, constant, and state‐dependent components. The notion of algebraic solution of the matching equations is employed to design an extension of the interconnection and damping assignment passivity‐based control methodology that does not rely on the solution of partial differential equations. The result is a dynamic state‐feedback that includes a disturbance compensation term, where the unknown parameters are estimated adaptively. A simplified implementation of the proposed approach for underactuated mechanical systems is detailed. The effectiveness of the controller is demonstrated with numerical simulations for the magnetic‐levitated‐ball system and for the ball‐on‐beam system.
Meagher C, Franco E, Turk R, et al., 2020, New advances in mechanomyography sensor technology and signal processing: validity and intrarater reliability of recordings from muscle, Journal of Rehabilitation and Assistive Technologies Engineering, Vol: 7, ISSN: 2055-6683
IntroductionThe Mechanical Muscle Activity with Real-time Kinematics project aims to develop a device incorporating wearable sensors for arm rehabilitation following stroke. These will record kinematic activity using inertial measurement units and mechanical muscle activity. The gold standard for measuring muscle activity is electromyography; however, mechanomyography offers an appropriate alterative for our home-based rehabilitation device. We have patent filed a new laboratory-tested device that combines an inertial measurement unit with mechanomyography. We report on the validity and reliability of the mechanomyography against electromyography sensors.MethodsIn 18 healthy adults (27–82 years), mechanomyography and electromyography recordings were taken from the forearm flexor and extensor muscles during voluntary contractions. Isometric contractions were performed at different percentages of maximal force to examine the validity of mechanomyography. Root-mean-square of mechanomyography and electromyography was measured during 1 s epocs of isometric flexion and extension. Dynamic contractions were recorded during a tracking task on two days, one week apart, to examine reliability of muscle onset timing.ResultsReliability of mechanomyography onset was high (intraclass correlation coefficient = 0.78) and was comparable with electromyography (intraclass correlation coefficient = 0.79). The correlation between force and mechanomyography was high (R2 = 0.94).ConclusionThe mechanomyography device records valid and reliable signals of mechanical muscle activity on different days.
Franco E, Garriga Casanovas A, Rodriguez y Baena F, et 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.
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