Manuel Moreyra

Computerized Endoscopic Surgical Grasper

We report a computerized endoscopic surgical grasper with computer control and a force feedback (haptic) user interface. The system uses standard unmodified grasper shafts and tips. The device can control grasping forces either by direct surgeon control, via teleoperation, or under software control. In this paper, we test an automated palpation function in which the grasper measures mechanical properties of the grasped tissue by applying a programmed series of squeezes. Experimental results show the ability to discriminate between the normal tissues of small bowel, lung, spleen, liver, colon, and stomach. We anticipate applications in telesurgery, clinical endoscopic surgery, surgical training, and research.

Computer-controlled motorized endoscopic grasper for in vivo measurement of soft tissue biomechanical characteristics.

Accurate biomechanical characteristics of tissues are essential for developing realistic virtual reality surgical simulators utilizing haptic devices. Surgical simulation technology has progressed rapidly but without a large database of soft tissue mechanical properties with which to incorporate. The device described here is a computer-controlled, motorized endoscopic grasper capable of applying surgically relevant levels of force to tissue in vivo and measuring the tissues force-deformation properties.

A practical measure of dynamic response of haptic devices

A method is described to characterize and experimentally measure the dynamic performance of haptic display devices. The method characterizes the response to impulse inputs of various frequencies characteristic of simulating hard contacts in virtual environments. By comparing the experimentally measured velocity just after the impulse with the actual velocity, a dimensionless measure of structural distortion is derived. The method is easy to apply because no additional sensors or test fixtures are required. This paper presents a derivation of the structural deformation ratio for the single degree of freedom case, generalization to N-DOF spatial devices, and experimental results for a single axis of a rugged haptic device in our laboratory.

Scaling of direct drive robot arms

This article studies the ways that the performance of direct drive (DD) serial robots changes as system size is changed. We are particularly interested in the physical laws for scaling down direct drive arms to small sizes. Using theoretical scaling analysis, we show that there is a net physical performance advantage to small direct drive arms. A key factor for direct drive robot performance is the torque-to-mass ratio of the actuators, U. We show how U varies with the scale of DD actuators, and we also calculate how the dynamic performance varies with scale and U. We compare our calculations with experimental measurements of actuators of various sizes taken from small hard disk drives and compare them with published data for larger motors. Finally, we describe a prototype, five- axis, direct drive serial arm having a reach of 10 cm and a work volume of about 136 cm3. Some potential applications are briefly discussed.

A 5-axis mini direct drive robot for time delayed teleoperation

A previously developed 3 axis mini direct drive robot has been enhanced with two additional direct drive axes for general positioning and orientation of an axially symmetric tool. The arm has a work volume of about 50 cc and will have 5-10 micron or better resolution and repeatability. The arm forms an initial prototype for the NASA/University of Washington MicroTrex flight telerobotics experiment. The contemplated terrestrial applications include handling sub-microliter liquid samples for electrophoresis, and micro-manipulation with scaled force reflection.<<ETX>>

A 5-Axis Mini Direct Drive Robot for Teleoperation and Biotechnology

Publisher Summary In recent years, teleoperation has greatly expanded its scope of applications from its beginnings in the nuclear industry and its early expansion into undersea operations. Space and terrestrial biomedical applications are now attracting increasing attention. In both of these areas, in addition to the desirability of removing humans from sources of physical risk, there is increasing interest in miniaturization. In space, economic and other pressures are shifting the emphasis from relatively heavy, high-cost and complex systems, toward low-mass, low-cost systems with fewer functions and higher launch frequency. In surgery, similar pressures are encouraging replacement of traditional operations with endoscopic ones, which are much less invasive. In both space and medical applications, communication links and time delays will play a key role in the overall system design. The design of the UW mini direct-drive robot has been described. The mechanics and electronics are now complete, and closed-loop control of each axis, employing the analog encoder signals, has been demonstrated. Three-axis mini direct-drive robot has been enhanced with two additional direct-drive axes for general positioning and orientation of an axially symmetric tool. The arm has a work volume of about 120 cm 3 and 5-10 μm or better resolution and repeatability. The arm forms an initial prototype for the NASA/University of Washington MicroTrex flight-telerobotics experiment. The contemplated terrestrial applications include handling sub-microliter liquid samples for electrophoresis and micromanipulation with scaled force reflection.