The surgical robotics group aims at developing new robotics-based technologies for robot-assisted surgery and surgery training applications. This includes design and integration of mechanical and electrical components as well as development of innovative control structures for these systems. These robotic systems will enhance the safety and efficiency of medical surgeries which leads to more satisfaction in all of the people dealing with the healthcare systems specially the patients, the surgeons, and the residents. This group has enjoyed the collaboration and consultation of several national and international partners in the fields of engineering and medical science.
The general applications of teleoperation systems has been considered as a research interest in the ARAS laboratory from 2008. Our major focus from 2008 to 2011 was control structure development, improvement of transparency, and stability analysis for bilateral teleoperation systems. From 2012, our group have become interested in development of a robotic-assisted eye surgery system based on bilateral teleoperation systems, including several aspects such as mechanical design and construction and controller development and implementation. From 2014, our collaboration with the Farabi eye hospital is started and our team members had the opportunity to attend the surgical room and visit several eye surgeries. Our extensive meetings and consultations with notable ophthalmologists have led to proposing a haptic system for eye surgery training which is currently the major research project of our group.
Haptic system for eye surgery training
In spite of the recent advances in the equipment and techniques of surgical operations, teaching surgery to the residents and fellows is still an important task for the trainer surgeons, for which limited assistive equipment is being used. Indeed, any unexpected mistake made by the trainee, increase the risk of intra-operative and post-operative complications for the patient. Furthermore, the possibility of occurrence of the unwanted complications in eye surgery is more than other surgeries owing to the higher accuracy requirement in eye surgery.Intraocular eye surgery may be performed on anterior or posterior segment of the eye. The most commonly performed type of anterior segment eye surgery is Cataract , which is also proven to be one of the most common surgeries. On the other hand, Vitrectomy is a common posterior segment eye surgery. Concept photos of these two types of surgeries are depicted here. Although these two surgeries are performed on different segments of eye, they have two similar features. First, a small and delicate sector of the eye should be cut in both. Besides, both surgeries are mostly performed by Minimally Invasive Surgery (MIS) method. That is, instruments enter the eye through one or more small incisions. The required accuracy for these surgeries is about one tenth of a millimeter which becomes achievable for the surgeons after many years of practice. As a result, the current method of surgery training might lead to disastrous complications for the patient. Posterior Capsule Opacity (PCO) for cataract surgery and damage to the retina for Vitrectomy surgery are among the many other inevitable complications may be caused in the current method of training.
In order to reduce the adverse events and facilitate surgery training, it is proposed to harness robotic technology through a haptic system. Haptic technology creates the sense of touch by applying forces to the operators. Utilizing this technology, two surgeons are able to cooperatively perform a surgery. As an illustration, one surgeon may directly perform the surgery, whereas the other may be following the motion of first surgeon hand through the haptic system. In fact, the role of the haptic system is to recreate the sense of touch to the second surgeon.
Note that, two approaches may be considered about performing the real surgery. In the first scenario, the commands of the surgeons are sent to a slave robot whose role is to perform the surgery. This system is known as dual master teleoperation system in the literature. An important fact is that the robotics-based eye surgery is not a common surgery method at the current stage due to technical, technological, and cultural concerns. Therefore we propose using the second approach, in which the surgical tool is connected to one of the master consoles; hence, the surgery is directly performed by one of the surgeons. The aim of the first approach is robotic surgery training, whereas the purpose of the second approach is to train the traditional direct surgery. Owing to the more applicability, the second approach is the subject of this project.
Our collaboration with the professors, and surgeons in Farabi Eye Hospital, the Center of Excellence in Ophthalmology, is a valuable and constructive asset for this project. This project is the output of several hours of attendance in the surgical room and numerous meetings with distinguished surgeons. This project has been funded by National Institute for Medical Research Development and Research Network in Ophthalmology . This project is highly benefited from the collaboration with several domestic and international partners especially professor Keyvan Hashtrudi-Zaad, from the Queen’s University and professor Seyed Farzad Mohammadi, from the Farabi Eye Hospital.
Figure 1: Cataract Surgery
Figure 2 : Vitrectomy Surgery
Application of teleoperation systems in robot-assisted eye surgery
Robot-assisted eye surgery with a master-slave teleoperation system is investigated in this research. The actual surgery is performed by the slave robot utilizing the commends applied by the surgeon on the master robot. Robotic assisted surgery has the following advantages over the manual surgery
- Filtering Tremor
- Scaling of Position and Force
- Enhanced sensitivity through haptic feedback
- providing the surgeon an ergonomic body posture
Since the slave robot is designed to perform Minimally Invasive Surgeries, the Remote Center of Motion (RCM) is provided by the mechanical solutions. Most of the eye surgery robotic systems such as Preceyes, Steady-Hand, etc have utilized parallelogram mechanism to provide RCM. However, a different methodology based on the spherical mechanism is followed in this research to provide RCM. The capstan drive mechanism is utilized to provide a backdrivable transmission mechanism with high accuracy and zero backlash.
Another aspect of this project is designing the control architecture for the teleoperation system. It can be verified that control of teleoperation systems is complicated due to a lot of challenges. The dynamics of master and slave robots are often nonlinear and subjected to uncertainty. Another cause of difficulty is the uncertainty presents in the interaction of these robots with unknown and widely varying operator and environment dynamics. Finally, the communication time delay in telerobotic applications is the main obstacle to maintain both transparency and stability of the system. Communication time delay causes a trade-off between stability and transparency.
Several approaches are followed to design the controller. One methodology is to design sliding mode impedance controller and analyze its stability by the Lyapunov theory. In this method, the sliding mode impedance controller is utilized to achieve a desired impedance in the presence of various uncertainties in the dynamics of the system. The stability analysis in the presence of time delay is proved via Input-to-State Stability (ISS) methodology. Another approach is to utilize a Model Mediated Teleoperation (MMT) framework. This technique facilitates combining sources of knowledge and provides the opportunity of accessing whole information of model parameters. This approach is completely beneficial in the tele-surgery applications. In this method, the parameters of environment dynamic are identified using Bayesian approaches. The full probability distribution is obtained from the whole existing knowledge. These hyper parameters are passed to the master virtual model through communication channel to render the local environment dynamic. Controller parameters are tuned based on probabilistic robust, minimizing the risk of instability and violation of performance index. Several projects have been conducted based on the two mentioned approaches with experimental validation.
1- P. Agand, M. Motaharifar, H. D. Taghirad, Decentralized Robust Control for Teleoperated Needle Insertion with Uncertainty and Communication Delay. Mechatronics, 2017.
2- P. Agand, M. Motaharifar, H. D. Taghirad, Teleoperation with Uncertain Environment and Communication Channel: an H∞ Robust Approach. Iranian Conference on Electrical Engineering, Tehran, Iran, 2017.
3- A. Bataleblu, M. Motaharifar, E. Abedlu, H. D. Taghirad. Robust H∞ control of a 2RT parallel robot for eye surgery, International Conference on Robotics and Mechatronics, Tehran, Iran, 2016.
4- S. Abkhofte, M. Motaharifar, H. D. Taghirad, Adaptive control for force-reflecting dual user teleoperation systems, International Conference on Robotics and Mechatronics (ICROM), Tehran, Iran, 2016.
5- M. Motaharifar, A. Bataleblu, H. D. Taghirad, Adaptive control of dual user teleoperation with time delay and dynamic uncertainty. Iranian Conference on Electrical Engineering, Shiraz, Iran, 2016.
6- E. Abedloo, S. Gholami, and H. D. Taghirad. “Eye-rhas manipulator: From kinematics to trajectory control.” International Conference on Robotics and Mechatronics, Tehran, Iran, 2015..
7- S. Khosravi, A. Arjmandi, and H. D. Taghirad. “Sliding impedance control for improving transparency in telesurgery.” International Conference on Robotics and Mechatronics, Tehran, Iran, 2014.
Figure 3 : Robotic arm designed in ARAS graduate lab
Surgery Training Haptic System
My PhD thesis deals with 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.
Modle Mediated Teleoperation (MMT)
Currently, I am working on environment dynamic identification and its application in telesurgeries in Modle Mediated Teleoperation (MMT) framework. I have great tendency to focus on probability framework while dealing with such problems to prepare the appropriate base to utilize learning concepts in system identification problems. This procedure facilitates combining sources of knowledge and provides the opportunity of accessing whole information of model parameters.
Increasing transparency in eye telesurgery
My researches could be counted as the first steps of getting into eye telesurgery in the ARAS. During these researches, I found out that interacting with soft tissues is the integral part in the eye telesurgery, although the accuracy of position tracking between master and slave have to be considered as well. Therefore, I decided to organize my thesis so that it can increase transparency in such eye surgeries. I have employed impedance control either master or slave robot in order to deal with this problem. In this structure, the parameters of the controllers have been determined by optimizing a problem whose cost function is fidelity criteria. To achieve robust stability of closed loop control, small gain constraints have been applied on the optimization problem. Additionally, the stability of closed loop in the presence of variable delay in communication channel has been guaranteed by input to state stability.
Finally, this structure has been evaluated by implementing it on the haptic Omni as master and a developed virtual reality SMOS robot as slave robot in the ARAS. The SMOS robot has been developed in C++ programming language. It used Ogre and Bullet libraries to form its graphic. The inspiration of this robot was our researches on eye robot surgeries which introduce the SMOS as the first robot has been utilized for this purpose. Different scenarios such as free and constrained motion with constant and variable delay have been designed to show the excellent performance of this structure.
A dexterous haptic device for surgery training system
My master thesis deals with the design and fabrication of a three degrees of freedom (DoF) haptic device for a dual haptic eye surgery training system. This haptic device has two rotational and one translational DoF corresponding to the required movements in the eye surgery. Remote center of motion (RCM), which is necessary for this type of surgery, is satisfied using the parallelogram mechanism in the device structure. The mass and inertia of device is significantly reduced by applying strict considerations. Fully static balancing is applied using counterweight, and hence, the operator does not feel gravitational force at all. All the three DoF of the haptic device is actuated using capstan-drive transmission systems. The cable routings and cable transmission systems, in addition to the suitable transmission ratio with no backlash, caused the two main motors of the device be grounded. Suitable performance of the haptic device is evaluated by some practical experiments.
A parallel spherical robot for eye-surgery
My master project was implementation of ARES parallel spherical robot for eye-surgery. In this project, two most popular eye surgeries which are cataract and vitroretinal surgeries are carefully observed and requirements for these surgeries are derived. Based in the requirements, ARES which is designed in ARAS group has been selected for further research and implementation. In this project, the kinematic is derived. An adaptive impedance controller with high gain observer is implemented on SimMechanics model. The end-effector of the robot with the goal of compact and precise instrument with the feasibility of further development is designed and implemented. Impedance control of this instrument is developed using ESCON32 driver and a control board. The achieved results are promising for further implementations. This project is a teamwork in ARAS group that is conducting with Farabi hospital which is the most equipped center of ophthalmology in Iran.
A 2RT parallel robot for eye tele-surgery
Currently, I am working on design and implementation of a 2RT parallel robot for eye tele-surgery as the slave robot in a master-slave teleoperation system. The actual surgery is performed by the slave robot using commands applied by the surgeon on the master robot. Since the slave robot is designed to perform Minimally Invasive Surgeries (MIS), the Remote Center of Motion (RCM) is provided by the mechanical solutions. In this regard, unlike most of the eye surgery robots such as Eye-Rhas, Steady-Hand, etc. which utilize parallelogram mechanism to provide RCM, spherical mechanism is followed in this research to provide RCM. Based on the need of the power transfer system analysis, design and building of the Capstan drive system (Cable driven sectorial rotary actuator) as the actuators of the robot is done which leads to a back-drivable transmission mechanism with high accuracy and zero backlash.