Murat Cenk Cavusoglu

A critical study of the mechanical and electrical properties of the PHANToM haptic interface and improvements for high-performance control

This paper presents a critical study of the mechanical and electrical properties of the PHANToM haptic interface and improvements to overcome its limitations for applications requiring high-performance control. Target applications share the common requirements of low-noise/granularity/latency measurements, an accurate system model, high bandwidth, the need for an open architecture, and the ability to operate for long periods without interruption while exerting significant forces. To satisfy these requirements, the kinematics, dynamics, high-frequency dynamic response, and velocity estimation of the PHANToM system are studied. Furthermore, this paper presents the details of how the unknown subsystems of the stock PHANToM can be replaced with known, high-performance systems and how additional measurement electronics can be interfaced to compensate for some of the PHANToMs shortcomings. With these modifications, it is possible to increase the maximum achievable virtual wall stiffness by 35, active viscous damping by 120, and teleoperation loop gain by 50 over the original system. With the modified system, it is also possible to maintain higher forces for longer periods without causing motor overheating.

A Virtual Environment Testbed for Training Laparoscopic Surgical Skills

With the introduction of minimally invasive techniques, surgeons must learn skills and procedures that are radically different from traditional open surgery. Traditional methods of surgical training that were adequate when techniques and instrumentation changed relatively slowly may not be as efficient or effective in training substantially new procedures. Virtual environments are a promising new medium for training. This paper describes a testbed developed at the San Francisco, Berkeley, and Santa Barbara campuses of the University of California for research in understanding, assessing, and training surgical skills. The testbed includes virtual environments for training perceptual motor skills, spatial skills, and critical steps of surgical procedures. Novel technical elements of the testbed include a four-DOF haptic interface, a fast collision detection algorithm for detecting contact between rigid and deformable objects, and parallel processing of physical modeling and rendering. The major technical challenge in surgical simulation to be investigated using the testbed is the development of accurate, real-time methods for modeling deformable tissue behavior. Several simulations have been implemented in the testbed, including environments for assessing performance of basic perceptual motor skills, training the use of an angled laparoscope, and teaching critical steps of the cholecystectomy, a common laparoscopic procedure. The major challenges of extending and integrating these tools for training are discussed.

Design of bilateral teleoperation controllers for haptic exploration and telemanipulation of soft environments

In this letter, teleoperation controller design for haptic exploration and telemanipulation of soft environments is studied. First, a new measure for fidelity in teleoperation is introduced which quantifies the teleoperation systems ability to transmit changes in the compliance of the environment. This sensitivity function is appropriate for the application of telesurgery, where the ability to distinguish small changes in tissue compliance is essential for tasks such as detection of embedded vessels. The bilateral teleoperation controller design problem is 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. The control design procedure is illustrated with a case study. The analysis is also used to evaluate the effectiveness of using a force sensor in a teleoperation system.

Intelligent Control Algorithms for Robotic-Assisted Beating Heart Surgery

This paper focuses on the development of control algorithms for intelligent robotic tools that assist off-pump coronary artery bypass graft (CABG) surgery. In the robotic-assisted CABG surgery, the surgeon operates on the beating heart using intelligent robotic instruments. Robotic tools actively cancel the relative motion between the surgical instruments and the point of interest on the beating heart, dynamically stabilizing the heart for the operation. This algorithm is called active relative motion canceling (ARMC). Here, a model-based intelligent ARMC algorithm employing biological signals, such as electrocardiogram, to achieve effective motion cancellation is proposed. Finally, experimental results of the algorithm on a 3-degree-of-freedom robotic test-bed system are reported.

A laparoscopic telesurgical workstation

In this paper, various aspects of robotic telesurgery are studied. After a general introduction to laparoscopic surgery and medical applications of robotics, the UC Berkeley/Endorobotics Inc./UC San Francisco Telesurgical Workstation, a master-slave telerobotic system for laparoscopic surgery, is introduced, followed by its kinematic analysis, control, and experimental results. Some conceptual and future issues on telesurgery are discussed, including teleoperation and hybrid control, focusing on the special requirements of telesurgery.

Human-machine interfaces for minimally invasive surgery

Increasing numbers of surgical procedures are performed using minimally invasive techniques, in which trauma to external tissue is minimized. Unfortunately, reduced access reduces dexterity, limits perception, increases strain and the likelihood of error, and lengthens procedure time. Surgical technology must improve the interface between task requirements and human abilities. This paper describes three projects to evaluate and improve the human interface in laparoscopic surgery, or minimally invasive surgery of the abdomen: (a) measurement of movement trajectories under different visual conditions to determine the effect of viewing geometry, (b) the development of virtual environments for training, and (c) the development of haptic interfaces and control algorithms for teleoperative surgery.

Multirate simulation for high fidelity haptic interaction with deformable objects in virtual environments

Haptic interaction is an increasingly common form of interaction in virtual environment simulations. This medium introduces some new challenges. In this paper we study 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. We propose a multirate simulation approach which uses a local linear approximation. The treatment includes a detailed analysis and experimental verification of the approach. The proposed method is also shown to improve the stability of the haptic interaction.

Workspace analysis of robotic manipulators for a teleoperated suturing task

An important missing piece in the medical robotics literature is the lack of systematic methods to quantitatively compare different manipulator designs, and to evaluate kinematic configurations chosen for telesurgical manipulators in application-critical tasks. Such a quantitative method is especially important during design stage to make an informed decision between various design alternatives. In the paper, a quantitative method to evaluate the kinematic ability of surgical manipulators to perform the critical tasks of suturing and knot tying is presented. The proposed method does not require a physical prototype. This is achieved by running typical tool motions during these tasks through the inverse kinematics of the manipulators and checking if the system can accommodate the desired motions. The system can perform a given motion if the whole trajectory lies continuously within the workspace of the manipulator. Open surgical suturing motion data collected from experiments done with expert surgeons is used as the set of desired tool motions used in the analysis. The method is applied to compare two different wrist configurations of telesurgical slave manipulators, intended for use in minimally invasive surgery, by looking at the requirements on joint ranges and wrist manipulability during these motions.

GiPSi: a framework for open source/open architecture software development for organ-level surgical simulation

This paper presents the architectural details of an evolving open source/open architecture software framework for developing organ-level surgical simulations. Our goal is to facilitate shared development of reusable models, to accommodate heterogeneous models of computation, and to provide a framework for interfacing multiple heterogeneous models. The framework provides an application programming interface for interfacing dynamic models defined over spatial domains. It is specifically designed to be independent of the specifics of the modeling methods used, and therefore facilitates seamless integration of heterogeneous models and processes. Furthermore, each model has separate geometries for visualization, simulation, and interfacing, allowing the model developer to choose the most natural geometric representation for each case. Input/output interfaces for visualization and haptics for real-time interactive applications have also been provided

Modeling the Dynamics of the Human Thigh for a Realistic Echographic Simulator with Force Feedback

This paper proposes 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. Finally, we discuss the feasibility of our model as part of a fully functional simulator coupled with a haptic interface to train practitioners for echographic exams.