Surgical Robotics Group
My Ph.D. thesis deals with the control structure design for the eye surgery training haptic system. Due to the interaction between the users in the dual user haptic systems, the decision of each user is affected by the other user. However, most of the related studies use a general teleoperation architecture which is not customized for surgery training. In addition, most of the research reported in the literature are based upon linearity of the system which is an unrealistic assumption. Hence, it is highly beneficial to develop a control architecture based on special requirements of surgery training and analyze its stability as a nonlinear system. This is the objective of my thesis.
In my thesis design and implementation of a dual user surgery training framework, is discussed. One of the users is a novice surgeon who is learning the procedure by watching and feeling the movements that the other user, which is an expert surgeon, is doing. The training system consists of two identical haptic devices which are connected to each other via a fast and reliable communication channel. The embedded system that is managing the communication can control either of the haptic devices according to a predefined training routine. Three virtual fixture based cooperative control schemes are proposed and compared, and the stability of each is analyzed using passivity and ISS approaches. Moreover, the design and implementation process of the embedded system is discussed and the results for implementing one of the abovementioned approaches are presented.
Skill assessment in eye surgery is one of the important considerate goals in surgery training and evaluation. ARAS Haptic System for Eye Surgery Training (ARASH: ASiST) has implemented and developed in Surgical Robotic group of ARAS lab. These haptic devices can measure position and insertion force of tool that can be very useful in practical skill assessment. Based on eye surgery, especially vitrectomy, there are some important and necessary skills for novices like path length, tool’s speed in the entry point, depth perception, motion smoothness, applied forces and etc. I am studying some kinematic and dynamic parameters that can describe the movements well and they were reliable and valid in a practical skills assessment.
3. Eagle Eye
|Control Synthesis and ISS Stability Analysis of Dual-User Haptic Training System Based on S-Shaped Function||The controller design and stability analysis of dual user training haptic system is studied. Most of the previously proposed control methodologies for this system have not simultaneously considered special requirements of surgery training and stability analysis of the nonlinear closed loop system which is the objective of this paper. In the proposed training approach, the trainee is allowed to freely experience the task and be corrected as needed, while the trainer maintains the task dominance. A special S-shaped function is suggested to generate the corrective force according to the magnitude of motion error between the trainer and the trainee. The closed loop stability of the system is analyzed considering the nonlinearity of the system components using the Input-to-State Stability (ISS) approach. Simulation and experimental results show the effectiveness of the proposed approach.||2019||Journal|
|A Dual-User Teleoperated Surgery Training Scheme Based on Virtual Fixture||The widespread use of minimally invasive surgery (MIS) demands an appropriate framework to train novice surgeons (trainees) to perform MIS. One of the effective ways to establish a cooperative training system is to use virtual fixtures. In this paper, a guiding virtual fixture is proposed to correct the movements of the trainee according to trainer hand motion performing a real MIS surgery. The proposed training framework utilizes the position signals of trainer to modify incorrect movements of the trainee which leads to shaping the trainee's muscle memory. Thus, after enough training sessions the trainee gains sufficient experience to perform the surgical task without any further help from the trainer. The passivity approach is utilized to analyze the stability of system. Simulation results are also presented to demonstrate the effectiveness of the proposed method.||2018||Conference|
|An Observer-Based Force Reflection Robust Control for Dual User Haptic Surgical Training System||This paper investigates the controller design problem for the dual user haptic surgical training system. In this system, the trainer and the trainee are interfaced together through their haptic devices and the surgical operations on the virtual environment is performed by the trainee. The trainer is able to interfere into the procedure in the case that any mistakes is made by the trainee. In the proposed structure, the force of the trainer's hands is reflected to the hands of the trainee to give necessary guidance to the trainee. The force signal is obtained from an unknown input high gain observer. The position of the trainee and the contact force with the environment are sent to the trainer to give him necessary information regarding the status of surgical operations. Stabilizing control laws are also designed for each haptic device and the stability of the closed loop nonlinear system is proven. Simulation results are presented to show the effectiveness of the proposed controller synthesis.||2017||Conference|
|Adaptive Control of Dual User Teleoperation with Time Delay and Dynamic Uncertainty||This technical note aims at proposing an adaptive control scheme for dual-master trilateral teleoperation in the presence of communication delay and dynamic uncertainty in the parameters. The majority of existing control schemes for trilateral teleoperation systems have been developed for linear systems or nonlinear systems without dynamic uncertainty or time delay. However, in the practical teleoperation applications, the dynamics equations are nonlinear and contain uncertain parameters. In addition, the time delay in the communication channel mostly exists in the real applications and can affect the stability of closed loop system. As a result, an adaptive control methodology is proposed in this paper that to guarantee the stability and performance of the system despite nonlinearity, dynamic uncertainties and time delay. Simulation results are presented to show the effectiveness of the proposed adaptive controller methodology.||2016||Conference|
|Robust H-Infinity Control of a 2RT Parallel Robot For Eye Surgery||This paper aims at designing a robust controller for a 2RT parallel robot for eye telesurgery. It presents two robust controllers designs and their performance in presence of actuator saturation limits. The nonlinear model of the robot is encapsulated with a linear model and multiplicative uncertainty using linear fractional transformations (LFT). Two different robust control namely, H ? and ?-synthesis are used and implemented. Results reveal that the controllers are capable to stabilize the closed loop system and to reduce the tracking error in the presence of the actuators saturation. Simulation results are presented to show that effectiveness of the controllers compared to that of conventional controller designs. Furthermore, it is observed that ?-synthesis controller has superior robust performance.||2016||Conference|
|Particle Filters for Non-Gaussian Hunt-Crossley Model of Environment in Bilateral Teleoperation||Optimal solution for nonlinear identification problem in the presence of non-Gaussian distribution measurement and process noises is generally not analytically tractable. Particle filters, known as sequential Monte Carlo method (SMC), is a suboptimal solution of recursive Bayesian approach which can provide robust unbiased estimation of nonlinear non-Gaussian problem with desire precision. On the other hand, Hunt-Crossley is a widespread nonlinear model for modeling telesurgeries environment. Hence, in this paper, particle filter is proposed to capture most of the nonlinearities in telesergerie environment model. An online Bayesian framework with conventional Monte Carlo method is employed to filter and predict position and force signals of environment at slave side respectively to achieve transparent and stable bilateral teleoperation simultaneously. Simulation results illustrate effectiveness of the algorithm by comparing the estimation and tracking errors of sampling importance resampling (SIR) with extended Kalman filter.||2016||Conference|
|Adaptive Control for Force-Reflecting Dual User Teleoperation Systems||The aim of this paper is to develop an adaptive force reflection control scheme for dual master nonlinear teleoperation systems. Having a sense of contact forces is very important in applications of dual master teleopreation systems such as surgery training. However, most of the previous studies for dual master nonlinear teleoperation systems are limited in the stability analysis of force reflection control schemes. In this paper, it is assumed that the teleopreation system consists of two masters and a single slave manipulator. In addition, all communication channels are subject to unknown time delays. First, adaptive controllers are developed for each manipulator. Next, Input-to-State Stability (ISS) approach is used to analyze the stability of the closed loop system. Through simulation results, it is demonstrated that the proposed methodology is effective in a nonlinear teleopreation system.||2016||Conference|
|An Observer-Based Adaptive Impedance-Control for Robotic Arms: Case Study in SMOS Robot||In this paper an adaptive output-feedback impedance control is proposed to be used in environment-machine interaction applications. The proposed control is designed to achieve a desired robot impedance in the presence of possible dynamical parameter uncertainties. A high-gain observer is utilized in the control structure to achieve this objective by using only position feedback of robot joints, which in turn, reduces implementation costs and eliminates additional sensor requirements. Stability of the overall system is analyzed through input to state stability analysis. Finally, to evaluate the presented structure, computer simulations are provided and the scheme effectiveness is verified.||2016||Conference|
|Kinematic and Workspace Analysis of DIAMOND: An Innovative Eye Surgery Robot||This paper presents a new robot for eye surgeries, referred to as DIAMOND. It consists of a spherical mechanism that has a remote center of motion (RCM) point and is capable of orienting the surgical instrument about this unique point. Using the RCM as the insertion point of the surgery instruments makes the robot suitable for minimally invasive surgery applications. DIAMOND has two pairs of identical spherical serial limbs that form a closed kinematic chain leading to high stiffness. The spherical structure of the mechanism is compatible with the human head and the robot may perform the surgery upon the head without any collision with the patient. Furthermore, dexterity and having a compact size is taken into account in the mechanical design of the robot. The workspace of the robot is a complete singularity free sphere that covers the region needed for any eye surgeries. In this paper, a comparison between different types of existing eye surgery robots is presented, the structure of the mechanism is described in detail and kinematic analysis of the robot is investigated.||2015||Conference|
|Eye-RHAS Manipulator: From Kinematics to Trajectory Control||One of the challenging issues in the robotic technology is to use robotics arm for surgeries, especially in eye operations. Among the recently developed mechanisms for this purpose, there exists a robot, called Eye-RHAS, that presents sustainable precision in vitreo-retinal eye surgeries. In this work the closed-form dynamical model of this robot has been derived by Gibbs-Appell method. Furthermore, this formulation is verified through SimMechanics Toolbox of MATLAB. Finally, the robot is simulated in a real time trajectory control in a teleoperation scheme. The tracking errors show the effectiveness and applicability of the dynamic formulation to be used in the teleoperation schemes.||2015||Conference|
|Vision-Based Kinematic Calibration of Spherical Robots||In this article, a method to obtain spatial coordinate of spherical robot's moving platform using a single camera is proposed, and experimentally verified. The proposed method is an accurate, flexible and low-cost tool for the kinematic calibration of spherical-workspace mechanisms to achieve the desired accuracy in position. The sensitivity and efficiency of the provided method is thus evaluated. Furthermore, optimization of camera location is outlined subject to the prescribed cost functions. Finally, experimental analysis of the proposed calibration method on ARAS Eye surgery Robot (DIAMOND) is presented; In which the accuracy is obtained from three to six times better than the previous calibration.||2015||Conference|
|Sliding Impedance Control for Improving Transparency in Telesurgery||This paper describes a novel control scheme for teleoperation with constant communication time delay and soft tissue in environment of slave side. This control scheme combine fidelity criteria with sliding impedance. Fidelity is a measure for evaluating telesurgical system when environment at slave side contains soft tissues. Sliding impedance is used to stabilize the teleoperating system with constant time delays and improve tracking performance in the presence of uncertainties in slave dynamics. The control system contains impedance and sliding impedance control in master and slave manipulators, respectively. Parameters of sliding impedance controller are obtained from fidelity optimization problem while parameters of master impedance controller are determined such that to guarantee stability of the entire teleopertaion system. Simulation results demonstrate suitable performance of position and force tracking of the telesurgical system.||2014||Conference|
|Analytical Passivity Analysis for Wave-based Teleoperation with Improved Trajectory Tracking||In wave based teleoperation, although passivity is ensured for any time delay, tracking performance is usually distorted due to the bias term introduced by wave transmission. To improve the position tracking error, one way is to augment the forward wave with a corrective term and achieve pas-sivity by tuning the band width of a low pass filter in the forward path. However, this filter fails to meet the passivity condition in contact to stiff environments, especially at steady state. In this paper a new method is proposed and an analytical solution for passivity at steady state and a semi analytical solution for all other frequencies are represented. This method significantly reduces the complexity of the closed-loop system, ensures passivity in contact to the stiff environments, and improves trajectory tracking. Simulation results are presented to show the effectiveness of the pro-posed method.||2011||Conference|
|Force Control of Intelligent Laparoscopic Forceps||Actuators play an important role at the end-effectors of Minimally Invasive Surgery (MIS) robots. Having local, lightweight and powerful actuators would increase dexterity of surgeons. Shape Memory Alloy (SMA) actuators are considered as good candidates and presented significant behaviors in producing the force needed for grasping. Most of the current MIS systems provide surgeons with visual feedback. However, in many operations this information could not help surgeons to diagnose the manipulated tissue accurately. Therefore, having force and tactile information is also necessary. In order to have this information, local sensors are needed to give force feedback. This would also help to have control over the wire tension and prevent exceeding force causing tissue damages. In this paper a novel design of forceps that uses antagonistic SMA actuators is presented. This configuration helps to increase force and speed and also eliminates the bias spring used in similar works. Moreover, this antagonistic design makes it possible to place the force sensors at the back part of the forceps instead of attaching them to the jaws which results in a smaller forceps design. To control the exerted force, analytical model of system and a force control method are also presented. This enhanced design seems to address some of the existing shortcomings of similar models and remove them effectively.||2011||Journal|
|Identification and Robust H-Infinity Control of the Rotational/Translational Actuator System||The Rotational/Translational Actuator (RTAC) benchmark problem considers a fourth-order dynamical system involving the nonlinear interaction of a translational oscillator and an eccentric rotational proof mass. This problem has been posed to investigate the utility of a rotational actuator for stabilizing translational motion. In order to experimentally implement any of the model-based controllers proposed in the literature, the values of model parameters are required which are generally difficult to determine rigorously. In this paper, an approach to the least-squares estimation of the parameters of a system is formulated and practically applied to the RTAC system. On the other hand, this paper shows how to model a nonlinear system as a linear uncertain system via nonparametric system identification, in order to provide the information required for linear robust H-Infinity control design. This method is also applied to the RTAC system, which demonstrates severe nonlinearities due to the coupling from the rotational motion to the translational motion. Experimental results confirm that this approach can effectively condense the whole nonlinearities, uncertainties, and disturbances within the system into a favorable perturbation block.||2005||Journal|