35 results found
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
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
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.
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
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, 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.
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.
Franco E, Brown T, 2019, Energy shaping control for robotic needle insertion, 23rd International Conference on System Theory, Control and Computing (ICSTCC), Publisher: IEEE, Pages: 1-6
This work investigates the use of energy shaping control to reduce deflection in slender beams with tip load and actuation at the base. The ultimate goal of this research is a buckling avoidance strategy for robotic-assisted needle insertion. To this end, the rigid-link model of a flexible beam actuated at the base and subject to tip load is proposed, and an energy shaping approach is employed to construct a nonlinear controller that accounts for external forces. A comparative simulation study highlights the benefits of the proposed approach over a linear control baseline and a simplified nonlinear control.
Franco E, 2019, Energy-based design of elastic joints for inverted pendulum systems with input saturation, 27th Mediterranean Conference on Control and Automation, Publisher: IEEE
This work investigates the balancing control of underactuated inverted pendulum systems with input saturation. To this end, the design of elastic joints according to potential-energy shaping principles is combined with energy-shaping control. As a result, analytical design guidelines are synthesized and implemented fortwo classical examples: the inertia-wheel pendulum and the Acrobot system.Asimulation study demonstrates the effectiveness of the proposed approach in reducing control effort while preserving transient performance.
Franco E, 2019, IDA-PBC with adaptive friction compensation for underactuated mechanical systems, International Journal of Control, Vol: 94, Pages: 860-870, ISSN: 0020-7179
In this work the control of underactuated mechanical systems with dry friction on actuated and unactuated joints is investigated. A new interconnection-and-damping-assignment passivity-based-control (IDA-PBC) design is presented, which includes the adaptive estimation of the friction forces and the introduction of a nonlinear dissipative term in the closed-loop system dynamics. As a result, the traditional IDA-PBC is complemented with an additional matching condition and the control law is augmented with a new term that accounts for the Coulomb friction forces on all joints. Two adaptive control paradigms are considered for comparison purposes and stability conditions are discussed. The control design is detailed for two demonstrative examples: the disk-on-disk system; the Acrobot system. The effectiveness of the proposed design is demonstrated with numerical simulations.
Franco E, 2019, Adaptive IDA-PBC for underactuated mechanical systems with constant disturbances, International Journal of Adaptive Control and Signal Processing, Vol: 33, Pages: 1-15, ISSN: 0890-6327
This work investigates the control of nonlinear underactuated mechanical systems with matched and unmatched constant disturbances. To this end, a new control strategy is proposed, which builds upon the interconnection‐and‐damping‐assignment passivity‐based control, augmenting it with an additional term for the purpose of disturbance compensation. In particular, the disturbances are estimated adaptively and then accounted for in the control law employing a new matching condition of algebraic nature. Stability conditions are discussed, and for comparison purposes, an alternative controller based on partial feedback linearization is presented. The effectiveness of the proposed approach is demonstrated with numerical simulations for three motivating examples: the inertia wheel pendulum, the disk‐on‐disk system, and the pendulum‐on‐cart system.
Franco E, Rodriguez y Baena F, Astolfi A, 2018, Robust balancing control of flexible inverted-pendulum systems, Mechanism and Machine Theory, Vol: 130, Pages: 539-551, ISSN: 0094-114X
This work studies the balancing control problem for flexible inverted-pendulum systems and investigates the relationship between system parameters and robustness to disturbances. To this end, a new energy-shaping controller with adaptive disturbance-compensation for a class of underactuated mechanical systems is presented. Additionally, a method for the identification of key system parameters that affect the robustness of the closed-loop system is outlined. The proposed approach is applied to the flexible pendulum-on-cart system and a simulation study is conducted to demonstrate its effectiveness. Finally, the control problem for a classical pendulum-on-cart system with elastic joint is discussed to highlight the similarities with its flexible-link counterpart.
Franco E, 2018, Discrete-time IDA-PBC for underactuated mechanical systems with input-delay and matched disturbances, 2018 26th Mediterranean Conference on Control and Automation (MED), Publisher: IEEE, ISSN: 2473-3504
This work investigates the control problem of discrete-time underactuated mechanical systems with fixed input-delay and matched disturbances. A new control strategy is proposed, which builds upon a discrete-time implementation of the interconnection-and-damping-assignment passivity-based control (IDA-PBC) and extends it in two ways: the disturbances are estimated adaptively; the input-delay is compensated with a recursive algorithm. The resulting control law is constructed from IDA-PBC without solving any additional partial-differential-equation (PDE). Stability conditions are discussed and compared to alternative designs. Numerical simulations for the ball-on-beam system and for the Acrobot system demonstrate the effectiveness of the proposed approach.
Franco E, 2017, Immersion and invariance adaptive control for discrete-time systems in strict feedback form with input delay and disturbances, International Journal of Adaptive Control and Signal Processing, Vol: 32, Pages: 69-82, ISSN: 0890-6327
This work presents a new adaptive control algorithm for a class of discrete-time systems in strict-feedback form with input delay and disturbances. The immersion and invariance formulation is used to estimate the disturbances and to compensate the effect of the input delay, resulting in a recursive control law. The stability of the closed-loop system is studied using Lyapunov functions, and guidelines for tuning the controller parameters are presented. An explicit expression of the control law in the case of multiple simultaneous disturbances is provided for the tracking problem of a pneumatic drive. The effectiveness of the control algorithm is demonstrated with numerical simulations considering disturbances and input-delay representative of the application.
Burridge JH, Lee ACW, Turk R, et al., 2017, Telehealth, Wearable Sensors, and the Internet: Will They Improve Stroke Outcomes Through Increased Intensity of Therapy, Motivation, and Adherence to Rehabilitation Programs?, JOURNAL OF NEUROLOGIC PHYSICAL THERAPY, Vol: 41, Pages: S32-S38, ISSN: 1557-0576
Franco E, Rea M, Gedroyc W, et al., 2016, Control of a master-slave pneumatic system for teleoperated needle insertion in MRI, IEEE-ASME Transactions on Mechatronics, Vol: 21, Pages: 2595-2600, ISSN: 1083-4435
This paper presents the control of a pneumatically actuated master-slave system intended for teleoperated needle insertion in the liver under magnetic resonance imaging (MRI) guidance. It addresses the challenge of achieving accurate needle positioning and force feedback to the operator in the case of pneumatic actuation with significant friction. Using time-delay position control as the basis, we investigate force feedback via impedance control and admittance control. For impedance control, we propose a new adaptive friction compensation algorithm that only requires a single tuning parameter. Experiments on a 1-degree of freedom prototype system using silicone rubber phantoms with distinct densities highlight the differences between impedance control and admittance control, and demonstrate superior performance compared with a traditional impedance control scheme.
Franco E, Rea M, Gedroyc W, et al., 2016, Robot-Assistant for MRI-Guided Liver Ablation: a pilot study, Medical Physics, Vol: 43, ISSN: 0094-2405
Purpose:Percutaneous ablation under MRI-guidance allows treating otherwise inoperable liver tumors locally using a catheter probe. However, manually placing the probe is an error-prone and time consuming task that requires a considerable amount of training. The aim of this paper was to present a pneumatically actuated robotic instrument that can assist clinicians in MRI-guided percutaneous intervention of the liver and to assess its functionality in a clinical setting. The robot positions a needle-guide inside the MRI scanner bore and assists manual needle insertions outside the bore.Methods:The robot supports double oblique insertions that are particularly challenging for less experienced clinicians. Additionally, the system employs only standard imaging sequences and can therefore be used on different MRI scanners without requiring prior integration. The repeatability and the accuracy of the robot were evaluated with an optical tracking system. The functionality of the robot was assessed in an initial pilot study on two patients that underwent MRI-guided laser ablation of the liver.Results:The robot positioned the needle-guide in a repeatable manner with a mean error of 0.35 mm and a standard deviation of 0.32 mm. The mean position error corresponding to the needle tip, measured for an equivalent needle length of 195 mm over 25 fixed points, was 2.5 mm with a standard deviation of 1.2 mm. The pilot study confirmed that the robot does not interfere with the equipment used for MRI-guided laser ablation and does not visibly affect the MR images. The robot setup integrated seamlessly within the established clinical workflow. The robot-assisted procedure was successfully completed on two patients, one of which required a complex double oblique insertion. For both patients, the insertion depth and the tumor size were within the range reported for previous MRI-guided percutaneous interventions. A third patient initially enrolled in the pilot study and was considerably he
Franco E, 2016, Combined Adaptive and Predictive Control for a Teleoperation System with Force Disturbance and Input Delay, Frontiers in Robotics and AI, Vol: 3, ISSN: 2296-9144
This work presents a new discrete-time adaptive-predictive control algorithm for a system with force disturbance and input delay. This scenario is representative of a mechatronic device for percutaneous intervention with pneumatic actuation and long supply lines which is controlled remotely in the presence of an unknown external force resulting from needle-tissue interaction or gravity. The ultimate goal of this research is the robotic-assisted percutaneous intervention of the liver under Magnetic Resonance Imaging (MRI) guidance. Since the control algorithm is intended for a digital microcontroller, it is presented in the discrete-time form. The controller design is illustrated for a 1 degree-of-freedom system and is conducted with a modular approach combining position control, adaptive disturbance compensation, and predictive control. The controller stability is analyzed and the effect of the input delay and of the tuning parameters is discussed. The controller performance is assessed with simulations considering a disturbance representative of needle insertion forces. The results indicate that the adaptive-predictive controller is effective in the presence of a variable disturbance and of a known or variable input delay.
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