Research Information

Research Interests

  • Robotics: Medical Robotics, Haptics, Teleoperation, Design of Mechatronic Systems
  • Human-Machine Interfaces / Virtual Environments: Surgical Simulation, Haptic Interfacing to Virtual
    Environments, Physical Modeling for Simulation in Virtual Environments
  • Systems and Control: Modeling and Simulation of Complex Biological Systems

For a brief summary of my research activities, you can read my Research Statement.

Here is the list of my publications and my students (where you can find their theses as well).

Current Projects

For a list of my current research projects, please visit the web site of my research group:
Medical Robotics and Computer Integrated Surgery Laboratory.

MEDICAL ROBOTICS

VIRTUAL ENVIRONMENT BASED SURGICAL SIMULATION

HAPTICS AND TELEOPERATION

MODELING AND SIMULATION OF BIOLOGICAL SYSTEMS

 

Past Projects

Research Projects During Graduate and Postdoctoral Studies at UC Berkeley

My PhD thesis at UC Berkeley was "Telesurgery and Surgical Simulation: Design, Modeling, and Evaluation of Haptic Interfaces to Real and Virtual Surgical Environments." My PhD advisor was Prof. S. Shankar Sastry, and my co-advisor was Prof. Frank Tendick. After my PhD, I stayed as a postdoctoral researcher / specialist with the Medical Robotics group at UC Berkeley, Dept. of EECS. During my PhD and postdoctoral studies, I worked on the following projects:

 
Robotic Telesurgical System for Laparoscopy
  Minimally Invasive Surgery (MIS) is a revolutionary approach in surgery. In MIS, the operation is performed with instruments and viewing equipment inserted into the body through small incisions created by the surgeon, in contrast to open surgery with large incisions. This minimizes surgical trauma and damage to healthy tissue, resulting in shorter patient recovery time. Unfortunately, there are disadvantages due to the reduced dexterity, workspace, and sensory input to the surgeon which is only available through a single video image.

In this joint project between the Robotics and Intelligent Machines Laboratory of the University of California, Berkeley (UCB) and the Department of Surgery of the University of California San Francisco (UCSF), a robotic telesurgical workstation for laparoscop was developed. Our Robotic Telesurgical Workstation for Laparoscopy was a bimanual system with two 6 DOF manipulators instrumented with grippers, controlled by a pair of 6 DOF master manipulators.

With the telesurgical workstation, the conventional surgical tools are replaced with robotic instruments which are under direct control of the surgeon through teleoperation. The goal is to restore the manipulation and sensation capabilities of the surgeon which were lost due to minimally invasive surgery. A 6 DOF slave manipulator, controlled through a spatially consistent and intuitive master, will restore the dexterity, the force feedback to the master will increase the fidelity of the manipulation, and the tactile feedback will restore the lost tactile sensation.

Here you can find a video of the system in action (high resolution video [21MB], low resolution video [4MB]). You will need a DivX codec to view the videos.

My main roles in this project were the analysis of the manipulator, control design, tissue modeling, and evaluation of the system.

For more information please visit the UC Berkeley Medical Robotics Group web pages, and my related publications.

 
 

Workspace Analysis of Robotic Manipulators:

As part of this project, I have also developed a method to evaluate the kinematic ability of surgical robotic manipulators to perform the critical tasks of suturing and knot tying. The method uses open (i.e., non-MIS) surgical suturing motion data collected from experiments done with expert surgeons. One oft he goals ofrob otic telesurgical systems is to enable the surgeons to use open surgical techniques for suturing and knot tying in the MIS setting by having robotic tools with sufficient dexterity and a suitable user interface. Therefore, open surgical suturing motion data is used in the analysis. This way, it is possible to evaluate if the system can be used with the natural open surgical techniques, without the need of learning new ways to perform these tasks.

 

Bilateral Teleoperation
Minimally invasive surgery (MIS) can be of great benefit to the patient, but places great demands on the surgeon's perceptual motor skills. Teleoperation technology can restore some of the lost dexterity and sensation in MIS.

In this research project we studied teleoperation controller design for haptic exploration and telemanipulation of soft environments. Our research had three components: (a) experiments to determine human capability to discriminate changes in compliance displayed through a haptic interface, (b) analysis and design of teleoperator control algorithms to optimize the transmission of compliance, (c) experiments to evaluate operator performance using teleoperation systems in a task more representative of surgery, complementing the control design procedure. The paradigm used in all the cases is the ability to detect a change in compliance of a surface, as would occur due to a lesion or vessel embedded in soft tissue.

As part of this research project, I have proposed a new measure for fidelity in teleoperation which quantifies the teleoperation system's ability to transmit changes in the compliance of the environment. This sensitivity function also incorporates the experimentally measured frequency dependent compliance discrimination sensitivity of the human operator. The bilateral teleoperation controller design problem was then formulated in a task-based optimization framework as the optimization of this metric with constraints on free space tracking and robust stability of the system under environment and human operator uncertainties. We have also used this analysis to evaluate the effectiveness of using a force sensor in a teleoperation system.

Please refer to my related publications, Frank Tendick's web pages, and the UC Berkeley Medical Robotics Group web pages for more information.

 
Virtual Environments for Surgical Training
    Learning laparoscopic techniques is much more difficult for surgeons than learning open surgery procedures. Currently, surgeons are trained during actual operations or in the animal laboratory. Training in the operating room increases risk to the patient and slows the operation, resulting in greater cost. Animal training is expensive and cannot duplicate human anatomy. Computer-based training has many potential advantages. It is interactive, yet an instructor's presence is not necessary, so students may practice in their free moments. Any pathology or anatomical variation can be created. Simulated positions and forces can be recorded to compare with established performance metrics for assessment and credentialing. Students could also try different techniques and look at anatomy from perspectives that would be impossible during surgery.

In the context of this application, I have worked on the development of real-time finite element models of soft tissue behavior and high fidelity haptic interfacing to deformable object models simulated in virtual environments, to generate a realistic environment for training.

Please refer to Frank Tendick's Virtual Environments for Surgical Training and Augmentation (VESTA) page and my related publications for related information.

 
   
 

Haptic Interfacing to Virtual Environments

Haptic interaction is an increasingly common form of interaction in virtual environment (VE) simula-
tions. This medium introduces some new challenges. As part of my research, I have introduced a multirate simulation scheme which uses a local linear approximation to address the problem arising from the difference between the sampling rate requirements of haptic interfaces and the significantly lower update rates of the physical models being manipulated in surgical simulators.

Please refer to my publications for further information.
 

Open Source Modeling Framework for Biocomputation

The objective of this effort was to study organ level modeling and simulation for surgical applications. The point to the proposed research is to explore the feasibility of developing open source, open architecture models of different levels of granularity and spatio-temporal scale for a project that has been labeled the Digital Human project. While the emphasis on this program was on how the simulations that we develop will allow for the interconnections between individual organ simulations, and between different types of physical processes within a given organ, we developed our tools on a specific test bed application: the construction of a heart model for simulation of heart surgery.

This effort later evolved into the development of the GiPSi framework.
 

Development of an Echography Simulator with Force Feedback

While visiting the SHARP Group at the INRIA Rhone-Alpes Research Center in Grenoble, France, I worked on modeling the dynamics of human-thigh for development of an echography simulator with force feedback. We have developed a mass-spring model of the dynamics of a human thigh based on real data acquired. Using a force sensor mounted on a robot arm the deformation of the thigh with respect to an external force is measured. The stress-strain curves we obtained exhibit a strong non-linearity due to the incompressibility of the human tissue. Hence, we
propose a two-layer model of the thigh using both linear and non-linear visco-elastic springs to simulate the observed behaviour. The parameters of the springs are estimated using a least-squares minimisation method.

For further information, please refer to my publications.
Hybrid Systems
 

Force control and manipulation involving contacts are essentially hybrid control problems because of the inherent switching present in the dynamic behavior when the manipulator comes in contact with and leaves a surface. In this study, I used the game theoretic approach of hybrid control design is used to synthesize the least restrictive control law for a robotic manipulator to establish and maintain contact with a surface while keeping interaction forces within specified bounds.

Please refer to my publications for further information.

 

Undergraduate

My graduation project at METU was "Closed Loop Position and Force Control of Anthrobot III Robot Hand," which was supported by Ankara Electronics Research and Development Institute (now BILTEN) of Turkish Scientific and Technical Research Council, under project number 95-20-100.  My project advisor was Assoc. Prof. Dr. Aydan Erkmen.
Last updated: July 2007. MCC.