Peter J. Berkelman

A miniature microsurgical instrument tip force sensor for enhanced force feedback during robot-assisted manipulation

This paper reports the development of a new miniature force sensor designed to measure contact forces at the tip of a microsurgical instrument in three dimensions, and its application to scaled force feedback using a cooperatively manipulated microsurgical assistant robot. The principal features of the sensor are its small size of 12.5 mm in diameter and 15 mm in height, a novel configuration of flexure beams and strain gauges in order to measure forces isotropically at the instrument tip 40 mm from the sensor body, and sub-mN three-axis force-sensing resolution.

A compact, compliant laparoscopic endoscope manipulator

We have developed a cable-driven manipulator using pneumatic artificial muscle actuators to control the orientation and insertion depth of an endoscope during abdominal surgery. This manipulator enables a single surgeon to manipulate surgical instruments with both hands while the endoscope position is controlled to view an area of interest inside the abdomen. The surgeon may then control the endoscope by alternate methods such as voice commands, pedals, a joystick, or head movements. The advantages of our newly developed endoscope manipulator over those of commercially available robotic laparoscopic surgical systems are its low cost, simplicity, ease of setup and use, compliance, nonintrusiveness, and very small size and light weight, with the disadvantage of somewhat reduced absolute positioning accuracy. Multiple instruments may be manipulated simultaneously by the manipulators set close together. Experimental performance results of open-loop and feedback control methods are presented.

Interacting with virtual environments using a magnetic levitation haptic interface

A high-performance magnetic levitation haptic interface has been developed to enable the user to interact dynamically with simulated environments by holding a levitated structure and directly feeling its computed force and motion responses. The haptic device consists of a levitated body with six degrees of freedom and motion ranges of /spl plusmn/5 mm and /spl plusmn/3.5 degrees in all directions. The current device can support weights of up to 20 N and can generate a torque of 1.7 Nm. Control bandwidths of up to 50 Hz and stiffnesses from 0.01 to 23 N/mm have been achieved by the device using a digital velocity estimator and 1 KHz control on each axis. The response of the levitated device has been made successfully to emulate virtual devices such as gimbals and bearings as well as different dynamic interactions such as hard solid contacts, dry and viscous friction, and textured surfaces.

Development of miniaturized light endoscope-holder robot for laparoscopic surgery.

PURPOSE We have conducted experiments with an innovatively designed robot endoscope holder for laparoscopic surgery that is small and low cost. MATERIALS AND METHODS A compact light endoscope robot (LER) that is placed on the patients skin and can be used with the patient in the lateral or dorsal supine position was tested on cadavers and laboratory pigs in order to allow successive modifications. The current control system is based on voice recognition. The range of vision is 360 degrees with an angle of 160 degrees . Twenty-three procedures were performed. RESULTS The tests made it possible to advance the prototype on a variety of aspects, including reliability, steadiness, ergonomics, and dimensions. The ease of installation of the robot, which takes only 5 minutes, and the easy handling made it possible for 21 of the 23 procedures to be performed without an assistant. CONCLUSION The LER is a camera holder guided by the surgeons voice that can eliminate the need for an assistant during laparoscopic surgery. The ease of installation and manufacture should make it an effective and inexpensive system for use on patients in the lateral and dorsal supine positions. Randomized clinical trials will soon validate a new version of this robot prior to marketing.

LER: the light endoscope robot

LER is a compact surgical assistant robot for positioning of an endoscope and camera during minimally invasive surgery. In contrast to typical endoscope manipulators, LER is particularly compact and lightweight at 625 g and 110 mm in diameter, so that it is simple to set up and use, occupies no floor space, and does not limit access to the patient in any way. Our current prototype is fully sterilizeable by autoclave and is ready for clinical trials. It features a full motion range of 360/spl deg/ in rotation and inclination to 10/spl deg/ from the horizontal plane and is backdriveable for manual positioning. Actuation forces are limited for safety. LER may be held in place on the abdomen by adhesive strips or sutures, or attached to the sides of the table with elastic straps or clamps. We have implemented a variety of different user command interfaces for LER, including a miniature keypad, automatic optical instrument motion tracking, and voice command recognition. Experimental trajectory following results and performance parameters are given.

Virtual peg-in-hole performance using a 6-DOF magnetic levitation haptic device: comparison with real forces and with visual guidance alone

We describe two experiments using three testbeds (real, virtual and vision-only) for comparison of user performance during 3-D peg-in-hole tasks. Tasks are performed using a six-degree-of-freedom (6-DOF) magnetic levitation haptic device. The experimental design allows a user to experience real and virtual forces using the same device. The first experiment compares real and virtual tasks. In the virtual task, a peg and hole are rendered haptically and visually. During the real task, a physical peg is attached to the underside of the haptic device. A hole in a plate attached to a force/torque sensor receives the peg. The second experiment compares a virtual haptic task to one performed using vision alone. Preliminary results indicate increased task time, more variation in force and position, and more failures occur with the virtual task than with the real task. More variation in force and position, and more failures occur with the vision-only task than with the virtual task. Users apply similar strategies for virtual and real tasks. Virtual haptic display, while worse than reality, contributes significantly to task performance when compared to vision alone.

Interaction with a real time dynamic environment simulation using a magnetic levitation haptic interface device

A high performance six degree-of-freedom magnetic levitation haptic interface device has been integrated with a physically-based dynamic rigid-body simulation to enable realistic user interaction in real time with a 3-D dynamic virtual environment. The user grasps the levitated handle of the device to manipulate a virtual tool in the simulated environment and feels its force and motion response as it contacts and interacts with other objects in the simulation. The physical simulation and the magnetic levitation controller execute independently on separate processors. The position and orientation of the virtual tool in the simulation and the levitated handle of the maglev device are exchanged at each update of the simulation. The position and orientation data from each system act as impedance control setpoints for the other, with position error and velocity feedback on each system acting as virtual coupling between the two systems. The setpoints from the simulation are interpolated by the controller at the faster device control rate so that the user feels smooth sliding contacts without chattering due to the slower updates of the simulation. The simple feedback coupling between the two systems enables the overall stiffness and stability of the combined system to be tuned easily and provides realistic haptic user interaction. Sample task simulation environments have been programmed to demonstrate the effectiveness of the haptic interaction system.

Comparison of 3-D haptic peg-in-hole tasks in real and virtual environments

We describe an experimental arrangement for comparison of user performance during a real and a virtual 3D peg-in-hole task. Tasks are performed using a unique six-degree-of-freedom (6-DOF) magnetic levitation haptic device. The arrangement allows a user to exert and experience real and virtual forces using the same 6-DOF device. During the virtual task, a peg and hole are rendered haptically, and visual feedback is provided through a graphical display. During the real task, a physical peg is attached to the underside of the haptic device. Using only real forces/torques, the peg is inserted into a hole in a plate attached to a force/torque sensor, while positions/orientations are measured by the haptic device. positions/orientations and forces/torques are recorded for both modes. Preliminary results indicate increased task time, larger total forces and more failures occur with the virtual task. Recorded data reveal user strategies that are similar for both tasks. Quantitative analysis of the strategies employed should lead to identification of significant factors in haptic interface design and haptic rendering techniques.

Medical Image Computing and Computer-Aided Medical Interventions Applied to Soft Tissues: Work in Progress in Urology

Until recently, computer-aided medical interventions (CAMI) and medical robotics have focused on rigid and nondeformable anatomical structures. Nowadays, special attention is paid to soft tissues, raising complex issues due to their mobility and deformation. Mini-invasive digestive surgery was probably one of the first fields where soft tissues were handled through the development of simulators, tracking of anatomical structures and specific assistance robots. However, other clinical domains, for instance urology, are concerned. Indeed, laparoscopic surgery, new tumour destruction techniques (e.g., HIFU, radiofrequency, or cryoablation), increasingly early detection of cancer, and use of interventional and diagnostic imaging modalities, recently opened new challenges to the urologist and scientists involved in CAMI. This resulted in the last five years in a very significant increase of research and developments of computer-aided urology systems. In this paper, we propose a description of the main problems related to computer-aided diagnostic and therapy of soft tissues and give a survey of the different types of assistance offered to the urologist: robotization, image fusion, surgical navigation. Both research projects and operational industrial systems are discussed

Dynamic performance of a magnetic levitation haptic device

A new haptic interface device has been developed which uses Lorentz force magnetic levitation for actuation. With this device, the user grasps a floating rigid body to interact with the system. The levitated moving part grasped by the user contains curved oval wound coils and LEDs embedded in a hemispherical shell with a handle fixed at its center. The stationary base contains magnet assemblies facing the flotor coils and optical position sensors facing the flotor LEDs. The device is mounted in the top cover of a desk-side cabinet enclosure containing all the amplifiers, control hardware, microprocessing, and power supplies needed for operation. A network connection provides communication with a workstation to allow interaction with simulated 3D environments in real time. Ideally, the haptic interface device should reproduce the dynamics of the modelled or remote environment with such high fidelity that the user cannot distinguish interaction with the device from interaction with a real object in a real environment. In practice, this ideal can only be approached with a fidelity that depends on its dynamic properties such as position and force bandwidths, maximum forces and accelerations, position resolution, and realizable impedance range. The motion range of the moving part is approximately 25 mm and 15 - 20 degrees in all directions. A current of 0.75 A is required in three of the six coils to generate the vertical force to lift the 850 g levitated mass, dissipating only 13.5 W. Peak forces of over 50 N and torques of over 6 Nm are achievable with the present amplifiers without overheating the actuator coils. Other measured performance results include stiffness ranges from 0.005 N/mm to 25.0 N/mm and a position control bandwidth of approximately 75 Hz.