An artificial 15 degrees of mobility direct drive hand, slightly bigger than a human hand, is presented. Advantages and limitations of a direct drive hand are given. The authors introduce the design of their hand and present a model for control of the hand. Finally the authors describe their experiments with the hand. The direct drive hand dynamics have been simulated and the control algorithm has been tested on the model.

Recent experimental and analytical evidence indicates that direct drive robots become very practical and economical at miniature and microscopic scales, so it is interesting to understand quantitatively the properties of direct drive robots under scaling transformations. This leads to a study of how screws and their dual co-screws behave under the group of similarity transforms. This group is the group of isometries together with dilations. Several different representations are found on the space of screws and complementary representations are found on the dual space of co-screws. From the electromagnetic theory of the force and torque on a magnet in a magnetic field, we derive the scaling properties of the electromagnetic wrench. Hence, these results can be directly applied to the scaling of direct drive motors (A. Haruhiko and K. Youcef-Toumi, 1986). We conclude by proposing a scale invariant measure for direct drive actuator performance.

We have developed miniature direct drive DC motor actuators for robotics. These actuators have low friction, small size, high speed, low construction cost, no gear backlash, operate safely without the use of limit switches and generate moderate torque at a high torque to weight ratio. Our initial experiments indicated the feasibility of constructing a variety of new high speed low cost actuators, for applications in camera pointing, robot hands, and robot legs. In this work we study some prototype devices in each of these categories.>

A pan-tilt mechanism is a computer-controlled actuator designed to point an object such as a camera sensor. For applications in active vision, a pan-tilt mechanism should be accurate, fast, small, inexpensive and have low power requirements. The authors have designed and constructed a new type of actuator meeting these requirements, which incorporates both pan and tilt into a single, two-degree-of-freedom device. The spherical pointing motor (SPM) consists of three orthogonal motor windings in a permanent magnetic field, configured to move a small camera mounted on a gimbal. It is an absolute positioning device and is run open-loop. The SPM is capable of panning and tilting a load of 15 grams, for example a CCD image sensor, at rotational velocities of several hundred degrees per second with a repeatability of .15/spl deg/. The authors have also built a miniature camera consisting of a single CCD sensor chip and miniature lens assembly that fits on the rotor of this motor. In this paper, the authors discuss the theory of the SPM, which includes its basic electromagnetic principles, and derive the relationship between applied currents and resultant motor position. The authors present an automatic calibration procedure and discuss open- and closed-loop control strategies. Finally, the authors present the physical characteristics and results of their prototype.>

The authors have developed a prototype miniaturized active vision system whose sensor architecture is based on a logarithmically structured space-variant pixel geometry. This system integrates a CCD sensor, miniature pan-tilt actuator, controller, general purpose processors and display. Due to the ability of space-variant sensors to cover large work-spaces yet provide high acuity with an extremely small number of pixels, space-variant active vision system architectures provide the potential for radical reductions in system size and cost. The authors describe a prototype space-variant active vision system which performs tasks such as moving object tracking and functions as a video telephone. The potential application domains for systems of this type include vision systems for mobile robots and robot manipulators, traffic monitoring systems, security and surveillance, and consumer video communications.>

An active vision system with a multiresolution sensor has the advantages of a wide visual field, high central resolution and low data rate. The authors use a special space-variant sensor based on complex log mapping to do character recognition in real scenes. The authors describe experiments with feature designs based on several statistical OCR methods: characteristic loci, partition and projection. The authors also examine several rotation-invariant feature designs based on the partition and projection methods. After studying the problem of recognizing strings in real scenes. The authors derive a rule based approach to solve the attention problem in the context of pattern recognition. Finally the authors describe an active vision system which successfully recognizes characters on a license plate in a real scene.>

The authors investigate two small robotic pan-tilt devices that differ from the conventional motor-on-motor design. The Platform Pantilt is based on a parallel linkage actuated by two small DC linear stepper motors. The spherical pointing motor (SPM) is a two-axis actuator built using three orthogonal motor windings. The SPM is controlled open-loop and is capable of panning and tilting a load of 15 grams, for example a CCD image sensor, at rotational velocities up to 600 degrees /sec. It is 4*5*6 cm and weight 160 grams. A subminiature camera consisting of a single CCD sensor chip and a lens assembly that fits on the rotor of this motor have also been built.>

Presents a robotic video telephone application of the Cortex-1 miniaturized space-variant active vision system. The embedded processor architecture of Cortex-1 enables it to implement a variety of functions not found in conventional video telephones, for example the camera tracks moving users with its pantilt mechanism. The authors also report an analog channel coding scheme to transmit logmap video images through band-limited analog channels such as the public switched telephone network (PSTN). The transmitter divides the frequency band into 768 channels, and modulates two values in quadrature on each channel. Some channels are reserved for special calibration signals enabling the receiver to recover both the phase and magnitude of the transmitted signal. The remaining channels carry pixel intensities.>

A two-step procedure that finds natural clusters in geometric point data is described. The first step computes a hierarchical cluster tree minimizing an entropy objective function. The second step recursively explores the tree for a level clustering having minimum description length. Together, these two steps find natural clusters without requiring a user to specify threshold parameters or so-called magic numbers. In particular, the method automatically determines the number of clusters in the input data. The first step exploits a new hierarchical clustering procedure called numerical iterative hierarchical clustering (NIHC). The output of NIHC is a cluster tree. The second step in the procedure searches the tree for a minimum-description-length (MDL) level clustering. The MDL formulation, equivalent to maximizing the posterior probability, is suited to the clustering problem because it defines a natural prior distribution.>

This paper present a color vision based robot road following program. The program uses an adaptive color model to classify pixels as road or shoulder features. To update the color statistics, the program tracks the shape of the road through the image sequence. As long as the program has either a reasonable color model from the previous image or a reasonable estimation of the expected road position it can steer a robot vehicle along a road reliably even in the presence of surface color variation, fluctuation of illumination conditions and deviation of sensor response. We present results from several test runs of a robot vehicle in a natural outdoor environment. The paper includes a discussion of failure modes of the program that have been catalogued and analyzed in order to guide future developments.

We report progress in visual road following by autonomous robot vehicles. We present results and work in progress in the areas of system architecture, image rectification and camera calibration, oriented edge tracking, color classification and road-region segmentation, extracting geometric structure, and the use of a map. In test runs of an outdoor robot vehicle, the Terregator, under control of the Warp computer, we have demonstrated continuous motion vision-guided road-following at speeds up to 1.08 km/hour with image processing and steering servo loop times of 3 sec.