Kevin Stanley

Design consideration of micro thin film solid-oxide fuel cells

Miniaturized planar solid-oxide fuel cells (SOFCs) and stacks can be fabricated by thin film deposition and micromachining. Serious thermal stresses, originating in fabrication and during operation, cause thermal–mechanical instability of the constituent thin films. In this paper, the effect of thin film geometry on thermal stress and mechanical stability is evaluated to optimize the structure of a thin film. A novel design of thin circular electrolyte films for SOFCs is presented by using corrugated structures, with which small thermal stresses and a broad design range of structure parameters can be obtained. Thermal transfer analysis shows that heat loss by solid conduction is serious in thin films with a small radius. But thermal convection and radiation dominate heat loss in large thin films with a radius of several millimetres. Scale-dependent thermal characteristics show the importance of film size and packaging in optimization of thermal isolation for micro SOFCs. A novel flip-flop stack configuration for micro SOFCs is presented. This configuration allows multiple cells to share one reaction chamber, helps to obtain uniform flow fields, and simplifies the flow field network for micro fuel cell stacks.

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.

Implementation of sensor selection and fusion using fuzzy logic

Different sensors may contain degrees of uncertainty and may be only reliable in particular situations, therefore sensor fusion and validation can be critical in complex redundant systems. This paper proposed a generic fuzzy logic algorithm for validation and fusion of uncertain sensor data. The system degrades marginal sensor data elegantly, while still removing obviously questionable data. Sensor data is represented as Gaussian curves. The sensor fusion problem is presented as determining a fused mean and standard deviation for the Gaussian of the output abstract sensor. Four variants of the fuzzy sensor fusion and validation system are presented and examined.

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.

Implementation of vision-based planar grasp planning

This research describes the implementation of a vision-based algorithm that is capable of rapidly determining robotic grasp points for planar objects. A representation of the target and a quadtree expansion generate candidate grasps that are compared using a cost function. The approach returns the first acceptable grasp point at a given tree resolution. The system has an execution time on the order of seconds and it is suitable for a large number of planar or near planar objects.

Fabrication of a micromachined direct methanol fuel cell

Small electronic devices require small, compact and lightweight power supplies. Direct methanol fuel cells (DMFCs) offer the potential for double the lifetime of lithium ion batteries. We have designed a process for micromachining direct methanol fuel cells using traditional micromachining techniques and macroassembly. Direct methanol fuel cells oxidize methanol through a catalytic reaction producing carbon dioxide and hydrogen. Hydrogen is further oxidized into hydrogen ions through a second catalytic reaction, producing electrons. We have micromachined flow fields and current collectors for the anode (methanol) side in both <100> and <110> silicon. Using laser ablation, we have opened fluidic channels through the back of the wafer for attaching fluid feed tubes. Aluminum is deposited as a current collector. The fuel cell is assembled using a commercial membrane electrode assembly (MEA), which contains the solid polymer proton exchange membrane (PEM) and catalysts. Sealing is provided using an epoxy. Simulated and actual results are presented.

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.

Neural network-based vision guided robotics

An essential problem of image based visual servoing is evaluating the inverse Jacobian which, relates changes in image features to the change in robot position. Neural networks can learn to approximate the inverse feature Jacobian. In addition, neural networks have been used in dimensionality reduction of image input. We show that it is possible to use neural networks for both feature extraction using compression and for feature Jacobian approximation in the visual servoing problem. In our system, we consider the following feature extraction methods: geometric features, averaging compression, vector quantization, and principal component extraction.

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.

An intelligent dual mode vision guided robotic system

Industrial robotics have looked to vision systems for flexibility. This promise has largely been unrealized because existing systems are either too slow or too inaccurate. Both visual servoing and traditional look and move are insufficient because visual servoing requires too much bandwidth, and look and move requires very accurate calibration. To mitigate these effects, we have designed a hybrid system. Our hybrid system is composed of a roughly calibrated look-and-move system using a linear approximation, and a gain scheduled PD controller which performs visual servoing. The system performs markedly better than visual servoing or look-and-move techniques in isolation. This system have many potential applications including bin-picking, sorting, and tele-operation.