Soft Robotics and Applied Control

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• Journal article
  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.

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• Journal article
  Burridge JH, Lee ACW, Turk R, Stokes M, Whitall J, Vaidyanathan R, Clatworthy P, Hughes A-M, Meagher C, Franco E, Yardley Let 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
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• Journal article
  Franco E, Rea M, Gedroyc W, Ristic Met 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.

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• Journal article
  Franco E, Rea M, Gedroyc W, Ristic Met 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

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• Journal article
  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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• Journal article
  Franco E, Ristic M, 2016,

  Needle-guiding robot for laser ablation of liver tumors under MRI guidance

  , IEEE-ASME Transactions on Mechatronics, Vol: 21, Pages: 931-944, ISSN: 1083-4435

  This paper presents the design, control and experimental evaluation of a needle-guiding robot intended for use in laser ablation (LA) of liver tumors under guidance by Magnetic Resonance Imaging (MRI). The robot provides alignment of a needle guide inside the MRI scanner bore and employs manual needle insertion. In order to minimize MR-image deterioration, the robot is actuated using plastic pneumatic cylinders and long pipes connecting to control valves located outside the MRI scanner room. A new Time Delay Control scheme (TDC) was employed to achieve high position accuracy without requiring pressure or force measurements in the MRI scanner. The control scheme was compared with experiments to a previously developed Sliding Mode Controller (SMC). A marker localization method based on the convolution theorem of Fourier transform was employed to register the robot in the MRI scanner coordinate system and to verify the position of the needle guide before the manual needle insertion. Experiments in a closed-bore MRI scanner showed a variation in SNR below 5%. A phantom study indicates that the targeting error in robot-assisted needle insertions is below 5 mm and suggest a potential time saving of 30 minutes compared to the manual MRI-guided LA procedure.

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• Journal article
  Franco E, Aurisicchio M, Ristic M, 2015,

  Design and control of 3-DOF needle positioner for MRI-guided laser ablation of liver tumours

  , International Journal of Biomechatronics and Biomedical Robotics, Vol: 3, ISSN: 1757-6792

  This article presents the design and control of a pneumatic needle positioner for laser ablation of liver tumours under guidance by magnetic resonance imaging (MRI). The prototype was developed to provide accurate point-to-point remote positioning of a needle guide inside an MR scanner with the aim of evaluating the potential advantages over the manual procedure. In order to minimise alterations to the MR environment, the system employs plastic pneumatic actuators and 9 m long supply lines connecting with the control hardware located outside the magnet room. An improved sliding mode control (SMC) scheme was designed for the position control of the device. Wireless micro-coil fiducials are used for automatic registration in the reference frame of the MR scanner. The MRI-compatibility and the accuracy of the prototype are demonstrated with experiments in the MR scanner.

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• Conference paper
  Franco E, Ristic M, 2015,

  Adaptive control of a master-slave system for teleoperated needle insertion under MRI-guidance

  , 23rd Mediterranean Conference on Control and Automation (MED), Publisher: IEEE, Pages: 61-67, ISSN: 2325-369X

  This paper presents the control of a master-slave system for teleoperated needle insertion under guidance by Magnetic Resonance Imaging (MRI). The primary aim of our research is the robot-assisted laser ablation of liver tumors. The master-slave system consists of a master unit that sits next to the operator, outside the scanner room, and of a slave unit located inside the cylindrical MRI scanner. The needle insertion force is measured with a specially designed fiber optic force sensor mounted on the slave unit. Pneumatic actuation is employed in both master and slave in order to minimize the interference with the MRI environment. Accurate position control of the slave unit is achieved with a Time Delay Control scheme (TDC). Differently from previous designs, the force feedback on the master unit is provided by an adaptive controller that compensates the friction of the pneumatic actuator. The advantages over a baseline force controller are demonstrated with experiments on silicone rubber phantoms.

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• Conference paper
  Franco E, Ristic M, 2014,

  Design and control of needle positioner for MRI-guided laser ablation of the liver

  , IEEE/ASME 10th International Conference on Mechatronic and Embedded Systems and Applications (MESA), Publisher: IEEE

  This paper presents the design and control of a pneumatic needle positioner for laser ablation of liver tumors under guidance by Magnetic Resonance Imaging (MRI). The prototype was developed to provide accurate point-to-point remote positioning of a needle guide inside an MR scanner with the aim of evaluating the potential advantages over the manual procedure. In order to minimize alterations to the MR environment the system employs plastic pneumatic actuators and 9 m long supply lines connecting with the control hardware located outside the magnet room. An optimized Sliding Mode Control (SMC) scheme was designed for the position control of the device. Wireless micro-coil fiducials are used for automatic registration in the reference frame of the MR scanner. The MRI-compatibility and the accuracy of the prototype are demonstrated with experiments in the MR scanner.

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• Conference paper
  Franco E, Ristic M, 2014,

  Time delay controller for the position control of a MRI-compatible pneumatic actuation with long supply lines

  , IEEE/ASME International Conference on Advanced Intelligent Mechatronics (AIM), Publisher: IEEE, Pages: 683-689, ISSN: 2159-6255

  Pneumatic actuation with long supply lines is widely employed in robotic devices operating in the Magnetic Resonance Imaging (MRI) environment because it produces minimum alteration to the magnetic field. However the high friction of the cylinders and the delay introduced by the pipes make accurate position control challenging. This work presents design and control of an MRI-compatible pneumatic actuation that employs a commercially available, plastic cylinder and long supply lines connecting with the control hardware located outside the magnet room. The system has been designed to actuate a MRI-compatible needle-guiding robot intended for MRI-guided intervention of liver tumors. Accurate position control is achieved with a new Time Delay Control (TDC) scheme that includes a saturation function. The controller requires limited knowledge of the system's parameters and does not rely on pressure or force measurements. Simulation results and experiments demonstrate the advantages of the proposed controller over existing TDC schemes. The MRI-compatibility of the pneumatic actuation is verified in a 3T MRI scanner.

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