Hawkeye H. I. King

The RAVEN: Design and Validation of a Telesurgery System

The collaborative effort between fundamental science, engineering and medicine provides physicians with improved tools and techniques for delivering effective health care. Minimally invasive surgery (MIS) techniques have revolutionized the way a number of surgical procedures are performed. Recent advances in surgical robotics are once again revolutionizing MIS interventions and open surgery. In an earlier research endeavor, 30 surgeons performed 7 different MIS tasks using the Blue Dragon system to collect measurements of position, force, and torque on a porcine model. This data served as the foundation for a kinematic optimization of a spherical surgical robotic manipulator. Following the optimization, a seven-degree-of-freedom cable-actuated surgical manipulator was designed and integrated, providing all degrees of freedom present in manual MIS as well as wrist joints located at the surgical end-effector. The RAVEN surgical robot system has the ability to teleoperate utilizing a single bi-directional UDP socket via a remote master device. Preliminary telesurgery experiments were conducted using the RAVEN. The experiments illustrated the system’s ability to operate in extreme conditions using a variety of network settings.

Raven-II: An Open Platform for Surgical Robotics Research

The Raven-II is a platform for collaborative research on advances in surgical robotics. Seven universities have begun research using this platform. The Raven-II system has two 3-DOF spherical positioning mechanisms capable of attaching interchangeable four DOF instruments. The Raven-II software is based on open standards such as Linux and ROS to maximally facilitate software development. The mechanism is robust enough for repeated experiments and animal surgery experiments, but is not engineered to sufficient safety standards for human use. Mechanisms in place for interaction among the user community and dissemination of results include an electronic forum, an online software SVN repository, and meetings and workshops at major robotics conferences.

Portable surgery master station for mobile robotic telesurgery

We describe a system that provides a low-cost, portable control station for experimentation in mobile robotic telesurgery. The software and hardware implementation of our system are described in detail. The device mapping between the Haptic Interface Devices (HID) and the surgical robot that enable the surgeon to effectively teleoperate the surgical robot are explained along with our communication protocols for telesurgery. We have also provided our initial results from extensive field testing of our system in different hardware and software configurations and challenging locations. We focus on working under sub-optimal network conditions for field operation in remote environments, and the importance of interoperability and distribution among networked surgical technologies.

Perceptual thresholds for single vs. Multi-Finger Haptic interaction

This paper presents experiments measuring psychophysical thresholds for multi-finger single point interaction with small haptic effects. Subjects used the UW Multi-Finger Haptic Display to interact with small haptic icons in a virtual environment. A forced-choice adaptive thresholding method is used to find a minimum detectable force magnitude. First, studies are performed to evaluate the consistency of our test apparatus across the four fingertips and to compare our application of the adaptive thresholding method to the prior work. Next, force detection thresholds for individual fingers are collected and compared to the force detection threshold using four fingers simultaneously. The results show comparable force detection levels between index, middle, pinkie and multi-finger interaction (33.5, 32.1, 33.5, 28.9 mN respectively) but less sensitivity with the ring finger (mean threshold of 43.6 mN). Repeated measures analysis of variance and t-tests with Bonferroni correction supports these conclusions. Most importantly, we show that the multi-finger threshold is not significantly lower than the threshold of the individual fingers. The implication for device design is that the relevant multi-finger device parameters are no more stringent than for single finger devices.

Teleoperation of a Surgical Robot via Airborne Wireless Radio and Transatlantic Internet Links

Robotic assisted surgery generates the possibility of remote operation between surgeon and patient. We need better understanding of the engineering issues involved in operating a surgical robot in remote locations and through novel communication links between surgeon and surgery site. This paper describes two recent experiments in which we tested the RAVEN, a new prototype surgical robot manipulation system, in field and laboratory conditions. In the first experiment, the RAVEN was deployed in a pasture and ran on generator power. Telecommunication with the surgical control station was provided by a novel airborne radio link supported by an unmanned aerial vehicle. In the second experiment, the RAVEN was teleoperated via Internet between Imperial College in London and the BioRobotics Lab at the University of Washington in Seattle. Data are reported on surgeon completion times for basic tasks and on network latency experience. The results are a small step towards teleoperated surgical robots which can be rapidly deployed in emergency situations in the field.

Application of Unscented Kalman Filter to a cable driven surgical robot: A simulation study

Cable driven power transmissions are used in applications such as haptic devices, surgical robots etc. The use of flexible cable based power transmission often causes relative motion between the motor actuator and mechanism joint during operation due to the elasticity of the cable. State-space control methods can be used to improve performance, but may require state estimates. For nonlinear systems, the Unscented Kalman Filter (UKF) provides a computationally efficient way to obtain state estimates. The UKF is applied here to a simulation of a minimially invasive surgical robot, to study the state estimation for a cable driven system with nonlinear dynamics. State estimates from the UKF are compared with the known states available from the simulation. These state estimates are also utilized by two different controllers interacting with the simulation to test the UKF performance under closed loop control. We tested the UKF performance with error perturbations in the system models cable stiffness parameter.

Acceleration compensation for vehicle based telesurgery on earth or in space

Current telesurgical robotic systems are designed to be used exclusively in stationary environments. The ability of a robotic master and slave system to monitor and correct for acceleration induced movement errors would enable conduct of delicate medical procedures onboard moving vehicles. Such operations, without compensation, would be complicated by unintended movement of the surgeonpsilas hands and master controls, causing potentially dangerous response of the surgical robot manipulators. In caring for astronauts on long haul interplanetary missions, it is essential to compensate for alterations in gravitational acceleration when delivering telesurgical or autonomous robotic therapy in the microgravity of space or on non-terrestrial planetary surfaces. This paper introduces new work focused on compensating for unintended master and slave manipulator motion resulting from accelerations of the environment within which they are operated. Experimental results from vehicular operation show how induced motion can be reduced by introduction of dynamic electronic balancing of the master manipulator device and the addition of variable damping proportional to vehicle acceleration. A surgical master console and robot were operated in the micro-gravity and variable gravity of the NASA C-9 airborne parabolic laboratory. Robot kinematics data and surveys of surgeon and astronaut users show that compensating for different gravitational conditions improves usability of the system. Further experiments using an elevator as a motion platform demonstrate the effectiveness of acceleration compensation.

Effects of thermal protection methods on haptic perception

Electric DC motors that convert electric current to torque are the most common type of actuators used in haptic interfaces. However, high currents necessary to deliver large haptic forces can generate heat in the electromagnetic coils, and in the extreme can cause malfunctions due to overheating. It is therefore necessary to add thermal protection mechanisms to limit the output current. While this is a common feature of haptic devices, it is not clear what makes a superior current limiting method or what effect such limits have on haptic perception.

Experimental evaluation of guidance and forbidden region virtual fixtures for object telemanipulation

Telerobotic task performance cannot compare to direct object manipulation with the hands. However, the computer in-the-loop offers the potential to give assistance to a human operator. The present work studies a class of computer assistance functions known as haptic virtual fixtures (VF). The objective is to use practical human trials to discover the ways VFs impact task execution.

Multi-finger Haptic Displays for Characterization of Hand Response

This chapter will describe some properties of multi-finger haptic interaction and two devices which support it. Multi-finger haptic interaction can involve many contacts with the environment, but can also involve only one contact point when mediated by a tool such as a pen. As multiple fingers interact with the environment, their individual biomechanics and their sensory properties interact to form the net mechano-sensory properties of the interaction. This chapter will look at such interactions in two particular cases, spatially varying stiffness of the pen grasp, and sensory thresholds of multi-finger versus single finger interaction with haptic features. To characterize the stiffness of the pen-like grasp in various directions, we describe experiments in which force steps (randomized in amplitude and direction) were applied to subjects’ pen-like tools in the plane tangential to the tip. From these, the stiffness ellipse could be identified. A dynamical model of the fingers positioned similarly to the user’s grasp was used to predict the stiffness ellipsoids with similar results. The ellipsoids were shown to be a function of the squeezing force with which the subjects performed the grasps. Much of the research on sensitivity and sensory thresholds is based on measurements with a single finger. We developed a multi-finger haptic device (MFHD) to allow two high quality degrees of freedom for each of four fingers in a natural pose. With this device we could compare the sensory thresholds between single finger and multiple finger haptic exploration.