Steven C. Venema

Telerobotic remote handling of protein crystals

A combined university/industry team has developed a prototype system for handling protein crystals aboard the space station. This system uses a miniature direct drive robot, CCD television cameras, and a client-server computing system using Internet protocols to support the capture of protein crystals from aqueous growth solutions. The system was demonstrated between Huntsville AL. and Seattle WA. An operator in Huntsville controlled the mini robot by invoking predefined relative and absolute macro files. The operators observed results using video images sent through the Internet link using Cu-SeeMe video conferencing software. In 3 of 4 trials, the operators successfully captured 0.5 mm simulated protein crystals into a glass capillary. The system is a promising start for the development of a space-station based remote protein crystal analysis facility.

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.

Experiments in Fingertip Perception of Surface Discontinuities

In this paper, we present the results of experiments that explore the ability of the human fingertip to detect haptically simulated first-order and second-order surface discontinuities. A single finger, planar motion fingertip haptic display (FHD) developed at the University of Washington was used by multiple test operators to kinesthetically trace haptically simulated surfaces under a variety of treatment conditions. Experiment variables included the magnitude and type of discontinuity, as well as the stiffness and damping terms used in the haptic simulation algorithm. Test operators were asked to haptically locate a discontinuity on a simulated surface for each treatment condition with the location accuracy being used as the experiment performance metric. The results reveal how the surface discontinuity detection ability is degraded by control gains that are either too low or too high, indicating that a given haptic simulation system may have an optimum set of control gains that will yield the best performance for this type of task.

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>>

Kalman filter based calibration of precision motion control

A method is described and validated for the automatic calibration of analog sine-wave quadrature sensors, such as optical encoders, embedded in a functioning system. The algorithm uses a Kalman filter to estimate the true position of the direct-drive actuator joint using a model of its dynamics, an applied actuator command and measurements from the uncalibrated sensor. From the estimated true position, a lookup table is constructed which corrects sensor errors. Our results indicate that this method achieves accuracies typical of interferometric calibration, without requiring an external measurement device. The accuracy is surprisingly robust to modeling errors.

The anthroform neural controller: a system for detailed emulation of neural circuits

The authors describe a versatile parallel computing architecture for emulating the spinal circuits of the human nervous system. When used in conjunction with a dynamically realistic replica of the human arm, this controller will provide a versatile tool for studying human motor-sensory control. The design is based on the structural constraints of the nervous system, and consists of a special purpose digital bus which implements connections between simulated neurons running on TMS 320C30 digital signal processors (DSPs). The system supports up to 1024 individual neuron models, each connected to every other one at least once every millisecond. These neuron models may be distributed over as many as 256 processor circuit cards, each supporting an interface for high level control from a host and another for input and output functions.<<ETX>>

The anthroform neural controller: An architecture for spinal circuit emulation

Existing robotic manipulator and controller deigns compare unfavorably to the human arm when performing tasks in unstructured environment. Traditionally, “antropomorphic” designs have focused on replicating only the kinematic ot the human arm. In contrast, we describe a versatile parallel computing architecture for emulating the spinal circuit of te human nervous system in conjunction wit a dynamically ralistic actuated arm model. This deign is based on the structural constraints of the nervous system, and consists of a special purpose digital bus which implements connections between simulated neurn pls. The processing elements are circuit cards based an the TMS 320C30 digital signal procesing chip. The system may b expanded t 256 processor cards, supporting a total of 102 computational nodes that are interconnected every millisecond.

Telerobotic macros for remote handling of protein crystals

A combined University/Industry team has developed a prototype system for handling protein crystals aboard the space station. This system uses a miniature direct drive robot, CCD television cameras, and a client-server computing system using Internet protocols to support the capture of protein crystals from aqueous growth solutions. The system was demonstrated between Huntsville AL, and Seattle WA. An operator in Huntsville controlled the mini robot by invoking predefined relative and absolute macro files. A set of movement macros (a predefined sequence of multi-device movement commands) were developed to support precision motion between task locations in the glovebox. The operator can invoke the macros by clicking icons in the remote control interface. The system is a promising start for the development of a space-station based remote protein crystal analysis facility.

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.