Q. M. Jonathan Wu

A hybrid sequential deposition fabrication technique for micro fuel cells

Micro fuel cell systems have elicited significant interest due to their promise for instantly rechargeable, longer duration and portable power. Most micro fuel cell systems are either built as miniaturized plate-and-frame or silicon-based microelectromechanical systems (MEMS). Plate-and-frame systems are difficult to fabricate smaller than 20 cm3. Existing micro fuel cell designs cannot meet the cost, scale and power requirements of some portable power markets. Traditional MEMS scaling advantages do not apply to fuel cells because the minimum area for the fuel cell is fixed by the catalyst area required for a given power output, and minimum volume set by mass transport limitations. We have developed a new hybrid technique that borrows from both micro and macro machining techniques to create fuel cells in the 1–20 cm3 range, suitable for cell phones, PDAs and smaller devices.

A fast two dimensional image based grasp planner

This research concerns a grasp-planning algorithm that is fast and capable of determining grasp points for planar nondegenerate objects. We use a novel representation of the target and a quadtree based sampling scheme to generate a set of candidate grasps which are evaluated using a cost function. This function returns the first acceptable grasp point it finds. The resulting system has an execution time of seconds and is suitable for a large number of planar grasp planning problems.

An imaging system with structured lighting for on‐line generic sensing of three‐dimensional objects

This paper focuses on the design of an inexpensive and accurate range scanner for automatic acquisition of a CAD model of a manufactured part by using two‐dimensional images to determine a digitized three‐dimensional shape. In the developed approach, the object is passed at a speed of 4 cm/s through a single linear laser stripe and forty continuous images are captured into the frame memory of the host computer for subsequent processing. A major problem that is encountered in the design of laser stripe scanner is the specula reflection, which can be mitigated by the developed approach. Six center‐locating algorithms are described, which are central to the developed approach. These algorithms are able to achieve sub‐pixel accuracy. The center of mass algorithm that uses three points, gives the best repeatability over the other algorithms. The center of mass algorithm that uses intensity threshold, provides the best linearity over the other algorithms.

A HYBRID STEREO FEATURE MATCHING ALGORITHM FOR STEREO VISION-BASED BIN PICKING

Stereo vision-based bin picking systems require accurate 3D information to be recovered from 2D stereo images. To achieve this goal, we have developed a hybrid coarse-to-fine algorithm for stereo feature matching, which is based on the 2D six-parameter affine transformation and local similarity evaluation. With this algorithm, the coarse matching is performed by the 2D six-parameter affine transformation to get rough feature matches, imposing a strong constraint to further search instead of the traditional epipolar constraint. To obtain precise matches, the perspective effect is dealt with fine stereo feature matching by performing local similarity evaluation on the attribute vectors of features. Experimental results proving the performance of the stereo feature matching algorithm are also presented.

A Pyramid Approach to Motion Tracking

This paper presents a multiresolution approach to visual motion tracking. In the approach, the foveation mechanism of the human visual system is used to model the multiresolution information perception algorithms of a Transputer-based pyramid visual tracking system. The video images of a moving target are transformed into pyramidal data structures, each of those images consists of multiple image layers with different resolutions by a Gaussian pyramid generation algorithm. The tracking of a moving target over an image sequence is accomplished by performing a foveal search that is based on an iterative intensity pattern correlation along the multiple resolution levels of the Gaussian pyramids of two successive images. Analyses are given as to the efficiency and accuracy of our tracking algorithm, showing that the algorithm is over 160 times faster than conventional mono-resolution tracking methods, with the tracking error within one pixel. To demonstrate the superiority of the multiresolution tracking algorithm in the connection to parallel computation, a scheme for mapping the tracking algorithm into a Transputer-based pyramidal parallel computing structure is proposed in the paper. Experimental results demonstrate good performance of the proposed approach.

An Optimized Micromixer with Patterned Grooves

With the development of microfluidic systems, there is a growing interest in micro scale laminar flow mixing. In this work, the fluid rotating angle and mixing efficiency in a micromixer with patterned grooves are studied as a function of the dimensions of the microstructure by numerical simulation. We found that mixing efficiency does not always increase with higher fluid stream rotation in the microchannel. High groove aspect ratios are not advantageous to fluid rotation. Experiments on mixture of two fluids were done on a micromixer fabricated in PDMS by replica molding. An 85% mixing efficiency was obtained in a 30mm long mixing channel with two dyed liquids.

Dynamic Switching of Fuzzy Resolution in Knowledge-Based Self-Tuning Control

Self-tuning of a control system may be effectively carried out by means of a properly designed, fuzzy, decision-making system. Optimization of the operation of such knowledge-based systems requires consideration of several factors including proper selection of fuzzy resolution, shape of the membership functions of fuzzy variables, and the level of overlap among various fuzzy states of a variable. This article studies the effect of fuzzy resolution on the processing speed and response accuracy of a fuzzy logic based control or tuning system. First, the underlying analytical concepts are presented, and on that basis, experiments are carried out to study this effect of fuzzy resolution. Response of the experimental system is studied at different levels of fuzzy resolution. Next, the concept of resolution switching is introduced and incorporated into the experimental system. The results obtained with and without resolution switching are comparatively studied to demonstrate the effectiveness of resolution switching.

An intelligent vision guided telerobotic system for file manipulation and office automation

Describes a vision-guided telerobotic system that enables people with disabilities to perform clerical or office tasks. By adding a light-duty robot to the office workspace, the operator can manipulate files and perform other work-related tasks. To increase the effectiveness of the robot, vision can be used to verify that the robot is correctly positioned. In addition, vision can be be coupled with the telerobotic system to allow the user more intuitive control over the robot. Visual servoing and traditional computed kinematics actions are inappropriate for this application because visual servoing requires an excessive number of iterations and computed kinematics requires accurate calibration. To counteract these difficulties and to provide user functionality, we have designed a hybrid computed-kinematics telerobotic system with an initial coarsely-calibrated computed-kinematics step followed by a more accurate visual-servoing step. We show that there are significant performance benefits from this approach. Finally, we describe how the hybrid system may be utilized in an office environment.

ACTIVE HEAD TRACKING BASED ON CHROMATIC SHAPE FITTING

This paper presents a method for tracking a human head based on the integration of camera saccade and chromatic shape fitting, which are implemented as functional modules in an active tracking system. Head motion is detected in the saccade module by extracting edges from two successive images. The position of the head in the current image is approximated as the centroid of the apparition formed by the moving edges of the target. A visual position cue is used to drive a pan/tilt camera to perform real-time saccade keeping the target in the foveal area in the image. The shape-fitting module is invoked to extract more information from the target. The shape of the target is modeled as an ellipse whose position, orientation and size are dynamically determined by shape fitting, and implemented with a color registration technique. In the proposed method, quasi real-time pursuit is achieved using a Pentium II computer in an uncontrolled environment with arbitrary relative motion between the target and camera.

An efficient real-time system for active video conferencing

This paper describes a new approach for implementation of an efficient real-time system proper for using in active video conferencing sessions. A camera tracks presenter’s head and its movements and orientations in an unconstrained environment automatically by its pan and tilt actions. Head or face is modeled by an ellipse using least square ellipse fitting algorithm. Linear Kalman filter is employed effectively, in addition to a measurement model based on bimodal color information. Experimental results demonstrate the effectiveness of the proposed system in overcoming challenges that trackers are facing in real world environments.