bluuebunny/crossref_metadata_2025 huggingface dataset:
CO2 Capture and Removal System for a Gas-Steam Combined Cycle
Authors: Desideri Umberto , Proietti Stefania
Published: May 2008

This paper presents the study of a natural gas fired power cycle which includes a carbon dioxide capture plant based on an absorption and scrubbing system. The interest in this integration is due to the widespread use of combined cycles in the power generation sector because of their high energy conversion efficiency. Energy consumption of the capture and removal system and its influence on the energetic performance of the power plant have been calculated. Mass and heat balance calculations are carried out by using the software tools GateCycle for the combined cycle and Aspen+ Software for the absorption process. Results of plant performance calculations, including compression of the captured carbon dioxide, are presented. The results, compared to the combined cycle power plant with no carbon dioxide capture, have also been compared to the more commonly known carbon dioxide capture process based on atmospheric absorption with MEA.
On Evaluating Efficiency of a Combined Power and Cooling Cycle
Authors: Vijayaraghavan Sanjay , Goswami D. Yogi
Published: May 2008

A combined power and cooling cycle is being investigated. The cycle is a combination of the Rankine cycle and an absorption refrigeration cycle. Evaluating the efficiency of this cycle is made difficult by the fact that there are two different simultaneous outputs, namely power and refrigeration. An efficiency expression has to appropriately weigh the cooling component in order to allow comparison of this cycle with other cycles. This paper develops several expressions for the first law, second law and exergy efficiency definitions for the combined cycle based on existing definitions in the literature. Some of the developed equations have been recommended for use over others, depending on the comparison being made. Finally, some of these definitions have been applied to the cycle and the performance of the cycle optimized for maximum efficiency. A Generalized Reduced Gradient (GRG) method was used to perform the optimization. The results of these optimizations are presented and discussed.
Advancing Fuel Cells Technology via Analogous Heat Exchanger Design Principles
Authors: Haynes Comas , Melbourne Vaughn , Rooker William
Published: May 2008

Fuel cells and heat exchangers have numerous similarities. Both technologies are used to produce an “energy-in-transit.” Heat exchangers foster thermal transport (heat) as a result of thermal potential differences between streams; fuel cells foster charge transport across electrodes (current leading to power) as a result of electrochemical/electric potential differences between the reactant streams and fuel cell electrodes. Additional analogs include series resistance formulations, active regions for transport phenomena and pertinent capacity rates. These similarities have motivated the extension of heat exchanger design philosophies to fuel cells development. Pilot simulations have been done wherein solid oxide fuel cell geometries and process settings are being optimized via electrochemical pinch points, electroactive area optimization (patterned after optimal UA allocation within heat exchangers), and electrode “fins” for diminished polarization. The prevailing theme has been to bridge methodologies from the mature field of heat exchanger design to improve fuel cell design practices.
Application of a Decomposition Strategy to the Optimal Synthesis/Design of a Fuel Cell Sub-System
Authors: Oyarza´bal Borja , von Spokovsky Michael R. , Ellis Michael W. , Mun˜oz J. Ricardo , Georgopoulos Nikolaos G.
Published: May 2008

The application of a decomposition methodology to the synthesis/design optimization of a stationary cogeneration fuel cell sub-system for residential/commercial applications is the focus of this paper. To accomplish this, a number of different configurations for the fuel cell sub-system were considered. The most promising candidate configuration, which combines features of different configurations found in the literature, is chosen for detailed thermodynamic, geometric, and economic modeling both at design and off-design. The case is then made for the usefulness and need of decomposition in large-scale optimization. The types of decomposition strategies considered are conceptual/time and physical decomposition. Specific solution approaches to the latter, namely Local-Global Optimization (LGO) are outlined in the paper. Conceptual/time decomposition and physical decomposition using the LGO approach are applied to the fuel cell sub-system. These techniques prove to be useful tools for simplifying the overall synthesis/design optimization problem of the fuel cell sub-system. Finally, the results of the decomposed synthesis/design optimization of the fuel cell sub-system indicate that this sub-system is more economical for a relatively large cluster of residences (i.e. 50). To achieve a unit cost of power production of less than 10 cents/kWh on an exergy basis requires the manufacture of more than 1500 fuel cell sub-system units per year. In addition, based on the off-design optimization results, the fuel cell sub-system is unable by itself to satisfy the winter heat demands. Thus, the case is made for integrating the fuel cell sub-system with another sub-system, namely, a heat pump, to form what is called a total energy system.
CHP for Buildings: The Challenge of Delivering Value to the Commercial Sector
Authors: Cowie M. , Marantan A. , Garland P. W. , Rademacher R.
Published: May 2008

The commercial sector has historically not seen the same level of investment in Combined Cooling, Heating and Power (CHP) as the industrial sector. The average commercial building has smaller and more diverse energy requirements than would be expected at a typical industrial site. Consequently, even though the electrical requirements of the commercial and industrial sectors are very similar there is nine times more installed industrial CHP capacity than commercial CHP in the U.S. However, the advent of microturbines and increasing commercial viability of fuel cells promises generator sizes much more suitable for use in the commercial sector. There are many possible uses for the waste heat in a commercial building, depending upon geographic location, occupant requirements and the energy cost structures of both fuel and grid electricity. Possible waste heat technologies include absorption chillers, humidifiers, desiccant dehumidifiers, steam generators, hot water heating, space heating and thermal storage. Several of these could be combined with a generator to produce a commercial CHP for Buildings package. A well-designed and operated package should deliver energy and environmental savings as well as significant cost savings to the customer. Other potential value streams are improved indoor air quality, peak shaving to reduce demand charges, enhanced power reliability, tradable environmental credits or grid independence. This presentation is a broad discussion of the challenges that CHP faces when competing in the commercial sector and the technologies and strategies that will help overcome them.
Design, Construction and Heat Transfer Analysis of a Thermoacoustic Refrigeration System
Authors: Nsofor Emmanuel C. , Gurijala Phani R. , Jiang Zhan
Published: May 2008

The thermoacoustic processes resulting from pressure and temperature oscillations and their interactions with boundaries are utilized in thermoacoustic refrigeration systems. This technology offers benefits that include absence of significant moving parts (implying reduced maintenance), use of environmentally safe working fluids, quiet operation, and continuous capacity control. The flow of the thermoacoustically oscillating gas and heat transport in the stack were studied. Results indicate that there is a critical value of ΔT outside of which the work and heat transfer will increase for a given drive ratio. The system was designed and constructed. In order to achieve high thermal conductivity across the thickness of the stack and low thermal conductivity axially, a thermoplastic material with holes filled with carbon fiber was used for the stack. The fiber is in the direction perpendicular to the thickness of the plate thus increasing the heat transfer in this direction. Since thermoplastics have very low thermal conductivity, the dissipative heat transfer through the stack material by conduction from the hot heat exchanger to the cold one (the direction opposite to the heat pumping) is minimized. When thermoplastic materials are used for the stack in place of stainless steel there is a significant drop in Qlosses for the range of values studied.
Emerging Role for Absorption Chillers in Integrated Energy Systems in America
Authors: Foley Gearoid , Sweetser Richard
Published: May 2008

President Bush’s National Energy Policy, Clear Skies and the Global Climate Change Initiatives form a comprehensive roadmap to a secure, clean, reliable, and affordable energy supply for the future. These far reaching policy proposals rely heavily on the development of distributed energy systems. The cornerstone of distributed energy systems is the emergence of Integrated Energy Systems (IES), which will permit consulting engineers to substantially improve energy efficiency. Thermally Activated Technologies, in general, and absorption chillers, in particular, are increasingly being viewed as an important element to effectively apply IES designs to the American building stock. This paper will examine testing, demonstration projects and commercial applications of combining absorption chiller equipment with microturbines, engines, combustion turbines and thermal solar systems. Technical challenges of coupling absorption chillers to prime mover exhaust streams will be explored. Application specific integration of coincident power generation and thermal energy supply to satisfy building loads will yield economic metrics that will determine which combinations of prime mover and absorption chiller will succeed in the market place today and which combinations require more research and development.
Field Evaluation of Hotel/Motel Through-the-Wall HVAC Systems Supervisory Controller
Authors: Baskin Evelyn
Published: May 2008

Several potential energy-savings devices are available for through-the-wall HVAC (heating, ventilation, and air-conditioning) systems but independent test data quantifying their savings are sparse. This field evaluation and demonstration study quantifies the potential energy savings and assesses the impacts on occupants and staff of using a supervisory HVAC controller in the lodging industry. The supervisory controller operates according to the occupancy status of each room in a hotel or motel. The controller is a plug-in device installed between a wall outlet and the room HVAC unit. Preliminary tests in laboratory simulated environmental conditions suggest that energy savings ranging from 50% to 80% are possible in unoccupied lodging rooms employing the controller (Fisher, 1999). The field study objective was to quantify and verify these estimates and to identify impacts on occupant comfort. The controller was developed as a tool for reducing energy consumption and lowering operating costs in the lodging industry. This paper describes results from a field evaluation of the performance of a supervisory HVAC controller. During the test period, the uncontrolled rooms HVAC energy consumption averaged 2632.2 kWh monthly while the controlled rooms HVACs consume an averaged 1684.6 kWh, which equates to the uncontrolled rooms HVAC consuming an averaged of 947.6 kWh (56.3%) more energy than the units in the controlled room monthly. Due to intermittent inoperability of the controllers and other energy loads (controllers controlled approximately 50% of the hotel’s conditioned space), comparison analysis of the energy cost over a three-year period for the entire hotel does not reveal any discrete savings during the test period over prior years.
Condensation Heat Transfer of R22 and R410A in Horizontal Smooth and Microfin Tubes
Authors: Kim Man-Hoe , Lim Byung-Han , Shin Jeong-Seob
Published: May 2008

An experimental investigation of condensation heat transfer in 9.52 mm horizontal copper tubes was conducted using R22 and R410A. The test rig had a straight, horizontal test section with an active length of 0.92 m and was cooled by the heat transfer fluid (cold water) circulated in a surrounding annulus. Constant heat flux of 11.0 kW/m2 was maintained throughout the experiment and refrigerant quality varied from 0.9 to 0.1. The condensation test results at 45°C were reported for 40–80 kg/h mass flow rote. The local and average condensation coefficients for seven microfin tubes were presented compared to those for a smooth tube. The average condensation coefficients of R22 and R410A for the microfin tubes were 1.7–3.19 and 1.7–2.94 times larger than those in smooth tube, respectively.
Gibbs Systems Dynamics: A Simple But Powerful Tool for Process Analysis, Design and Optimization
Authors: Neveu Pierre , Mazet Nathalie
Published: May 2008

Dynamic process modeling by the mean of Equivalent Gibbs systems is described here. It allows to model a large number of processes and only requires standard engineering knowledge. This method is issued from thermodynamics of irreversible processes, initiated by I. Prigogine, but applied here to process engineering. First, an Equivalent Gibbs System (EGS) is defined for each component involved in the process. In such system, mass, energy and entropy are linked through Gibbs equation and entropy production can easily be expressed according to fluxes and their related forces. Assuming linear phenomenological laws, phenomenological coefficients can be calculated from common engineering correlations, or evaluated from technical data if available. As an example, a conventional vapor compression chiller is simulated. Three control modes are analyzed on an exergy basis: on/off control with constant or floating condensing pressure, PID control with variable compressor speed.
Numerical Simulation of Fluid Flow and Solid Structure in Screw Compressors
Authors: Kovacevic Ahmed , Stosic Nikola , Smith Ian K.
Published: May 2008

Screw compressor performance is usually predicted by thermodynamic and fluid flow calculations based on a dimensionless flow model. However factors, which affect the power consumption, delivery and reliability of these machines, such as dynamic flow losses, leakage and oil flow drag, are not estimated accurately by such procedures. By the use of 3-D numerical modelling of the compressor fluid flow and structure deformation, these factors can be predicted more precisely and hence losses within the machine can be minimized at the design stage. The authors have developed a CAD-CCM (Computer Aided Design to Computational Continuum Mechanics) interface program to transfer the screw compressor geometry directly into a commercial numerical solver, which simultaneously solves the compressor fluid flow and structural deformation of its parts. All necessary initial and boundary conditions, a procedure for moving of the mesh and additional functional features of the commercial solver are introduced through the user functions automatically generated by the interface program. Results have been obtained for an oil-flooded screw compressor and some of them are presented in this paper. They are presented as overall compressor parameters in the form of power and volume flow. Additionally, pressure-time diagrams of the compression process, flow and pressure patterns in the compressor chambers and rotor deformation are illustrated.
A Study on Running Reliability of Scroll Compressor in Heat Pump System
Authors: Zhao Yuanyang , Li Liansheng , Shen Jiang , Shu Pengcheng , Pu Gaoxuan , Shao Yukong
Published: May 2008

Scroll type of compressor has been used in heat pump & refrigeration system because of its compact size, high efficiency, low vibration and noise level, and excellent running reliability. In the refrigeration cycle the scroll compressor runs smoothly and perfectly, but in the heat pump cycle some troubles appear because its working condition becomes worse. The effect of different factors such as atmospheric condition, electric voltage fluctuation, structure of scroll compressor etc. on running reliability of heat pump system are discussed in this paper. The thermodynamic and aerodynamic behaviors will be emphasized. Some basic design concepts for the running reliability of scroll compressor in the heat pump system are pointed out.
Description of a High-Efficiency Floating-Piston Expander for a Miniature Cryocooler
Authors: Smith J. L. , Brisson J. G. , Traum M. J. , Hannon C. , Gerstmann J.
Published: May 2008

A cryogenic expander employing low-temperature helium is under development. This expander employs a floating piston operating between a warm variable volume and a cold variable volume to expand the working fluid. The piston’s position is dynamically regulated through an active control routine that actuates electromechanical valves. These valves control helium flow in and out of the variable volumes. Throttling through the warm-end valves regulates the piston’s velocity. The cold-end valves, operating at cryogenic temperatures, are of novel design to achieve system miniaturization and high efficiency at range of operating points.
Computer Aided Analysis of Results Obtained From Testing Compressors
Authors: Vaisman Igor B. , Cuirrier Chadwick
Published: May 2008

The goal of the paper is to present software providing computer-aided analysis of results obtained from testing compressors. References on compressor testing facilities have been reviewed. A fully automated compressor performance test rig realizing a thermodynamic cycle with partial condensation has been presented. Control strategies, instrumentation, and the data acquisition system are shown. Uncertainty analysis is provided. The software providing computer-aided analysis of test results as an integral part of the testing facility has been discussed. Conclusions have been given.
New Sorption Cycles for Heat and/or Cold Production Adapted for Long Distance Heat Transmission
Authors: Spinner B. , Stitou D. , Mazet N.
Published: May 2008

The analysis of the combinations of dipoles, linked by a gas transfer between an endothermic element and an exothermal element, through an exothermal physical-chemical process in thermal contact with an other endothermic process, is the basis of a new process for the transmission at long distance of heat/cold production. The yield of such cycles is identified through the values of the unused exergy, the untapped exergy and the exergy which is produced in excess by the process.
Development of Corrosion Inhibitors for Absorption Heat Pumps
Authors: Hannon C. L. , Gerstmann J. , Mansfeld F. B. , Sun Z.
Published: May 2008

This paper describes the results of a research project to develop a non-toxic corrosion in hibitor for the protection of carbon steel surfaces of ammonia-water absorption heat pumps through the use of rare earth metal salt (REMS) compounds. Chromate compounds are currently used as corrosion inhibitors in these systems, but are toxic, environmentally harmful, and their use is being phased out. Corrosion concerns in ammonia-water absorption systems are primarily those of non-condensable (NC) gases generated by corrosion reactions impeding the heat and mass transfer processes in the system. The research focused on the development of a dual-protection REMS based strategy of applying a cerium-oxide/hydroxide coating to the metal surface in a process called cerating, in conjunction with a cerium-sulfate solution-based inhibitor. A laboratory test was conducted in test rigs designed to simulate the conditions of temperature and ammonia concentration found in the desorber component of advanced ammonia-water absorption systems. The test compared the NC gas generation rate in a rig with cerated steel surfaces to a rig using sodium chromate as a solution based inhibitor. The cerated test rig demonstrated an NC gas generation rate about 3 times lower than that of the chromate protected rig. Neither rig showed any indications of significant corrosion activity. This work has shown that cerating can provide superior suppression of NC gas generation in ammonia-water absorption systems compared to sodium chromate, in a process that is simple and readily applicable to the commercial manufacture of equipment.
Stress States and Interference in Double Adhesive Layer Scarf and Butt Joints
Authors: Teli Samar , Sancaktar Erol
Published: May 2008

The stress interference effects adhesively bonded scarf and butt joints were investigated when an additional adhesive layer was incorporated in overall joint design. Finite element models were developed and analyzed to compare interfacial stress states and peak stresses on the double adhesive layer joints with those on the single adhesive layer joints with respect to the scarf angle, adhesive layer separation (ALS) and adhesive modulus. This comparison was done in terms of stress ratio calculated as a ratio of interfacial peak stress on double adhesive layer joint to that an single adhesive layer joint. The tensile task results were correlated with the finite element analysis (FEA) results in terms of load ratio calculated as a ratio of failure load on single adhesive layer joint to that on double adhesive layer joint. Six scarf angles (15°, 30°, 45°, 60°, 75° and 90°), three ALS and adhesives were analyzed for this study.
Indirect Neural Network Adaptive Robust Control of Linear Motor Drive System
Authors: Gong J. Q. , Yao Bin
Published: May 2008

In this paper, an indirect neural network adaptive robust control (INNARC) scheme is developed for the precision motion control of linear motor drive systems. The proposed INNARC achieves not only good output tracking performance but also excellent identifications of unknown nonlinear forces in system for secondary purposes such as prognostics and machine health monitoring. Such dual objectives are accomplished through the complete separation of unknown nonlinearity estimation via neural networks and the design of baseline adaptive robust control (ARC) law for output tracking performance. Specifically, recurrent neural network (NN) structure with NN weights tuned on-line is employed to approximate various unknown nonlinear forces of the system having unknown forms to adapt to various operating conditions. The design is actual system dynamics based, which makes the resulting on-line weight tuning law much more robust and accurate than those in the tracking error dynamics based direct NNARC designs in implementation. With a controlled learning process achieved through projection type weights adaptation laws, certain robust control terms are constructed to attenuate the effect of possibly large transient modelling error for a theoretically guaranteed robust output tracking performance in general. Experimental results are obtained to verify the effectiveness of the proposed INNARC strategy. For example, for a typical point-to-point movement, with a measurement resolution level of ±1μm, the output tracking error during the entire execution period is within ±5μm and mainly stays within ±2μm showing excellent output tracking performance. At the same time, the outputs of NNs approximate the unknown forces very well allowing the estimates to be used for secondary purposes such as prognostics.
Damping Characteristics of Mechanical Structures Assembled by Bonding: A Beam in Which Two Steel Strips Are Faced and Joined to Small Butt Straps by an Adhesive
Authors: Nakano Yuichi , Kobayashi Takashi
Published: May 2008

Machine structures assembled by adhesive bonding are expected to possess a high damping capacity because of the high damping capacity of the adhesive. In this study, the damping characteristics of a beam in which two steel strips are faced and joined to small butt straps by an adhesive have been investigated. The primary aim of this study was to clarify the damping characteristics of adhesively bonded structures and to establish an estimation method for the damping capacity. In the analysis, strain energy distributions in the adhesively bonded beam is derived using the strain energies and damping ratios of the two materials, i.e. the steel strips and the adhesive, which were obtained beforehand in independent experiments. The validity of the proposed estimation method for the damping capacity and the effects of the lengths of the butt straps and vibration modes on the damping capacity were confirmed by experiments. The estimated values of the damping capacity of the beam were shown to be consistent with the experimental results.
A Control Design Method for Switching Systems With Application to Pneumatic Servo Systems
Authors: Barth Eric J. , Goldfarb Michael
Published: May 2008

The motivation for this work is to formulate a control design method for a pneumatic system with discrete input values (resulting from the use of binary or three-position solenoid valves) that addresses the time-delay that is often associated with the flow state of solenoid on/off valves. This method is shown to be applicable to a general class of nonlinear, non-autonomous systems subject to possibly discontinuous governing dynamics. This method is then extended for time-delayed systems and applied to the case of LTI models with a finite number of allowed input values possessing a pure time delay. A pneumatic inertial positioning system employing binary solenoid valves exhibiting a time delay is modeled, and the control design method proposed is applied. An experimental implementation of the resulting control law for accurate position tracking utilizing only position feedback demonstrates the effectiveness of the method.
B-Spline Based Adaptive Control of Shape Memory Alloy Actuated Robotic Systems
Authors: Eren Yavuz , Mavroidis Constantinos , Nikitczuk Jason
Published: May 2008

In this paper we present a novel controller for Shape Memory Alloy (SMA) actuated robotic systems. The new controller, called BAC (B-spline based Adaptive Control), is based on a hybrid combination of gain scheduling, B-spline approximation, variable structure control and integral control. The proposed controller shows excellent positioning accuracy and speed throughout the full range of motion of a SMA actuated robotic system in large-scale applications. To demonstrate the validity of BAC, a novel anthropomorphic SMA Actuated forearm/wrist mechanism is utilized in real-time PC based control experiments. BAC is experimentally compared to PID and integral variable structure controllers and it is shown that its performance is superior.
Intelligent System Identification Using Neural Networks and Genetic Algorithms of an Ultrasonic Positioning System
Authors: Unnikrishnan Nishant , Mahajan Ajay
Published: May 2008

This paper presents an intelligent system identification methodology for the identification of a realistic model of an ultrasonic position estimation system that uses the difference in the time of arrivals of waves from a transmitter to various receivers. Even though a linearized formulation for the 3D system exists and is currently being used to estimate the position of the transmitter, its accuracy can still be improved further. A neural network approach is developed to train the system based on training sets obtained from the actual system, and it is proposed to use the final trained system to estimate the 3D position in real time. The weights of the neural network are obtained from an innovative procedure using genetic algorithms. Results for a simplified 1D system are presented as proof of concept. The performance of the identified 1D system using genetic algorithms is shown to be comparable to the one using the analytical model. Further, the identified system using genetic algorithms is also shown to be superior to the one using the traditional back propagation method for finding the weights for the neural networks. This work has significant applications in the identification of complex non-linear systems.
Implementation of a Deadlock Avoidance Policy for Multipart Reentrant Flow Lines Using a Matrix-Based Discrete Event Controller
Authors: Mireles Jose , Lewis Frank L. , Gu¨rel Ayla
Published: May 2008

A deadlock avoidance supervisory controller for Discrete Event (DE) Systems is implemented. The DE controller uses a novel rule-based matrix dispatching formulation (US patent received). This matrix formulation makes it direct to write down the DE controller from standard manufacturing tools such as the bill of materials or the assembly tree. It is shown that the DE controller’s matrix form equations plus the Petri Net marking transition equation together provide a complete dynamical description of DE systems. Deadlock-free dispatching rules are derived by performing circular wait analysis (CW) for possible deadlock situations. We analyze the so-called critical siphons, certain critical subsystems and resources to develop a DE controller that guaranties deadlock-free dispatching by limiting the work-in-progress in the critical subsystems associated with each CW. This is the least-restrictive dispatching policy that avoids deadlock. The deadlock-free dispatching rules are implemented by the DE controller on a three-robot, two machine reentrant flow line, the Intelligent Material Handling cell at the Automation and Robotics Research Institute of UTA. Technical information given includes the development of the deadlock-free controller in LabVIEW®.
Genetic Algorithm Based PD Control and Fuzzy Logic Control of a Two Link Robot
Authors: Garg Devendra P. , Kumar Manish
Published: May 2008

This paper presents two schemes for the control of robotic manipulator systems. The first method is based on proportional plus derivative (PD) control with the PD controller gain parameters optimized via Genetic Algorithm (GA). The cost function (or performance index) to be minimized is the time taken by the system to achieve a final desired position. The second scheme is a fuzzy PD controller whose inputs are error and derivative of error. The fuzzy rules have been formulated with common behavior of the system under certain input conditions and defuzzification has been carried out to obtain crisp joint torque values. The configuration considered in the present paper is a two robotic link system.
Stress Analysis of Combination Joints of Adhesive With Tap Bolt Under External Tensile Loads
Authors: Sawa Toshiyuki , Moriuchi Akira
Published: May 2008

The stress distributions in a combination joint of an adhesive with a tap bolt under external tensile loadings are analyzed in elasto-plastic deformation using a finite element method. The FEM code employed is MARC. The effects of the initial clamping force (preload), external loadings and the position of engagement screw thread on the interface stress distributions are analyzed. In addition, the stress distribution in the combination joints of the adhesive with the tap bolt is compared with that in tap bolted joint without an adhesive and the adhesive joints without the tap bolt. As the results, it is found that the stress distribution (compression) in the combination joint is less than that of bolt joints. In addition, the experiments were carried out to measure the strain of the combination joint under external tensile loads using strain gauges. Furthermore, the joint strengths under external loadings were measured. Fairly good agreements are observed between the numerical and the measured results. In addition, the usefulness of the combination joints is demonstrated in comparison with the bolted joints and the adhesive joints.
Time Optimal and Time-Energy Optimal Control of Satellite Attitude Using Genetic Algorithms
Authors: Boonlong Kittipong , Chaiyaratana Nachol , Kuntanapreeda Suwat
Published: May 2008

This paper presents the use of genetic algorithms for solving time optimal and time-energy optimal control problems in a satellite attitude control system. The satellite attitude control system is a multi-input/multi-output non-linear system at which its continuous attitude-related states are driven by discrete-valued command torque input. The problems investigated cover the time optimal control with two-state input (−u, +u) and three-state input (−u, 0, u) and the time-energy optimal control with three-state input. With the use of two-state input, the control problem has been formulated as a multi-objective optimisation problem where the decision variables are composed of the time where an input-state switching occurs while the objectives consist of the final state errors and the trajectory time. A multi-objective genetic algorithm (MOGA) has been successfully used to obtain the time optimal solution which is superior to that generated by linearising the system and utilising a bang-bang control law. In contrast, with the use of three-state input, the control problems are reduced to single-objective optimisation problems. In the case of time optimal control, the objective is the trajectory time while a time-energy cost is used as the search objective in the time-energy optimal control. A single-objective genetic algorithm has been successfully used to generate the optimal control solutions for both problems. In addition, the effects of diversity control on the genetic algorithm performances in the control problems have also been identified.
Analytical Dynamic Model and Experimental Robust and Optimal Control of Shape-Memory-Alloy Bundle Actuators
Authors: Lee Chunhao Joseph , Mavroidis Constantinos
Published: May 2008

In this paper, the analytical dynamic model derivation and the robust and optimal position control of Shape Memory Alloy (SMA) bundle actuators using the LQR and H2 techniques are presented. SMA bundle actuators, composed of multiple SMA wires placed in parallel, have been recently proposed as a means to considerably increase the lifting capabilities of SMA actuators. Robust and optimal linear controllers could provide the desired robustness in the performance of these non-linear and highly sensitive actuators combined with the simplicity of these control schemes. The novel contributions of the present research are: a) the derivation of a generic, linearized, time-invariant analytical system model for SMA Bundle actuators that is used in the design of the LQR and H2 based controllers; b) the development of a new improved estimator in discrete-time H2 optimal control design based on the Kalman Filter predictor form for use in the control of SMA bundle actuators; c) the experimental study of two control design methods using state-space models, LQR and H2 Optimal Design, in discrete-time domain, using an experimental SMA bundle actuator consisting of 48 Flexinol™ SMA wires and able to apply up to 100 lbs. (445 N). As demonstrated in the experiments, the designed controllers provide satisfactory results in accuracy, stability and speed.
Axisymmetrical FEM Analysis and Estimation of the Sealing Performance in Pipe Flange Connections Combining Metallic Gasket With Adhesive Subjected to Internal Pressure and Temperature Change
Authors: Katsuo Masahide , Sawa Toshiyuki
Published: May 2008

This study deals with the stress analysis and the estimation of the sealing performance of the pipe flange connections combining a metallic gasket with an adhesive subjected to an internal pressure and a temperature change. Stress distributions at the interface between the adherends and the adhesive in the connections are analyzed by using the finite element method (FEM). From the numerical calculations, the following results are obtained: (1) the stress distributes uniformly at the interface except near the edges, (2) the stress increases as Young’s modulus of an adhesive decreases, (3) the stress becomes singular at the edges of the interfaces. In the experiments, the pipe flange connections consisting of dissimilar circular gaskets with an adhesive were manufactured, and the leakage tests of the connections were carried out by applying an internal pressure and a temperature change to the connections. From the experimental results, the following results were obtained: (1) the sealing performance increased as the width of a gasket decreased and the initial clamping stress increased, and (2) the sealing performance of the pipe flange connections subjected to a temperature change increased under a moderately high temperature.
Development of an Intelligent Automatic Generation Control System for Electrical Power Plants
Authors: Hoffner Benjamin , Shoureshi Rahmat A. , Kramer R. A.
Published: May 2008

The United States electric grid is a complex structure that requires high precision control of frequency and tieline power flows among different generation areas. Highly varying loads introduce a major challenge for the present automatic generation control systems. Arc furnaces, rolling mills and other large motors can create large demands on the system which result in an unsatisfactory area control error (ACE). Recent studies have shown that very-short term load prediction can be incorporated into control schemes which are then able to compensate for the highly varying demand. Using a neural network prediction of the area load a new fuzzy logic controller has been developed that adjusts the set point of the area generation to attempt to match the upcoming changes on the system. Performance of the neural-fuzzy controller in a two-area tie-line model with actual load data from a collaborating utility is demonstrated and compared with the present AGC system through simulations.
A Novel Mathematical 3-D Procedure to Evaluate the Interfacial State of Stress in Adhesively Bonded Scarf Joints: The General Case of Parabolic Scarf Surface
Authors: Ma Weijian , Sancaktar Erol
Published: May 2008

A mathematical procedure is developed to utilize the complementary energy method, by minimization, in order to obtain an approximate analytical solution to the 3-D stress distributions in bonded interfaces of dissimilar materials. In order to incorporate the effects of surface topography, the interface is expressed as a general surface in Cartesian coordinates, i.e., F(x, y, z) = 0. In this paper, the parabolic interface problem, i.e., y = x2 surface is considered.
Information Theoretic Analysis for Input Vector Selection in Black Box Modeling
Authors: Martin Brett , Meckl Peter H. , Zwissler Benjamin J.
Published: May 2008

When developing a black box model, the precise functional relationship between inputs and output is unknown. Engineers and scientists have turned to various regression tools in order to effectively capture the relationship based on past data observations. When modeling this data, however, it is important to only use inputs that provide information about the output. This paper presents a method of selecting the most informational input vectors for use in regression model building. This information-theoretic analysis for input vector selection requires only past data observations. Experimental results show that models built on the most informational input vectors produce less mean squared error on both training and validation data sets.
On the Design of an Intelligent Suspension for Controlling Passenger Vehicle Roll Stability
Authors: Simon David E. , Ahmadian Mehdi
Published: May 2008

This paper will address the design, laboratory testing, and road testing of a semiactive suspension system for controlling the roll stability of a sport utility vehicle. Four magneto-rheological dampers, specially designed and built for the purpose of this testing, are described along with the vehicle test setup in the laboratory. Additionally, results from a series of tests conducted on the vehicle equipped with magneto-rheological dampers operated according to different control policies are documented. Displacement and velocity-based skyhook control techniques are evaluated among the methods that are implemented on the test vehicle. The test results indicate that neither velocity nor displacement based skyhook control are particularly better than the stock passive suspension (for the system inputs tested in the laboratory). In order to realize any significant performance improvements in practice, it may be necessary to augment the skyhook control methods with additional information, such as the steering angle. The results of this study further indicate that the performance potential of various skyhook control policies is heavily dependent on the tuning of both the controllable damper and the control strategy itself. Additionally, it was shown that velocity based skyhook control exhibits improved performance relative to displacement based skyhook control. It is worth noting that the results presented in this study are greatly affected by the class of vehicle as well as the specific dampers that are used for testing. Testing with a different class of vehicle or with a different type of dampers could result in significantly different conclusions.
Energy Management Strategy for a Parallel Hybrid Vehicle
Authors: Won Jong-Seob , Langari Reza , Ehsani Mehrdad
Published: May 2008

An energy management strategy – torque distribution and charge sustaining control – for a parallel hybrid electric vehicle with continuously variable transmission is proposed in this study. The torque distribution control problem is formulated as a multi-objective nonlinear optimization problem. In order to facilitate the implementation of the proposed approach in real time, the aforementioned multi-objective nonlinear optimization problem is recast as a single objective linear optimization problem by linearization of the objective functions and by introducing an equivalent energy consumption rate for the fuel flow rate. Furthermore, a charge sustaining strategy is proposed and incorporated as part of optimal torque distribution strategy resulting in the establishment of the unified framework for energy management. In addition, the proposed approach incorporates a continuously variable transmission (CVT), where the gear selection strategy of the CVT is coupled with torque distribution and charge sustaining control. Computer simulation is performed to evaluate the proposed energy management strategy. The simulation results reveal that the approach proposed in this study offers significant computational advantage for real-time application without impacting the optimization results. Finally, through sensitivity analysis, the robustness of the solution to changes in the parameters of the objective functions is investigated.
Motion Planning for Dynamic Systems Using First-Order Logic
Authors: Yan Lei , Krishnamurthy K.
Published: May 2008

The problem of motion planning for a class of dynamic systems is considered in this study. A knowledge-based approach is used to determine the initial conditions that will yield a certain desired state of the dynamic system. The search space is limited by using a set of rules because reasoning about dynamic systems is basically searching an infinite space. In this study, first-order logic is used for knowledge representation and reasoning. The methodology is applied to playing a pool game. The dynamics of the motion of the balls are complicated and significant expertise is required to know how to strike the balls. Simulated results presented show how the rules help in finding the appropriate strategies for playing the game.
In-Situ Delamination Studies Using X-Ray Microtomography
Authors: Pyrz Ryszard , Nygaard Jens V.
Published: May 2008

Considering existing microscopical techniques to study microstructures of materials, one can find that non-destructive information from the internal structure of an object in natural conditions can be obtained by transmission X-ray microscopy. Combination of X-ray transmission technique with tomographical reconstruction allows to get three-dimensional information about the internal microstructure. In this case any internal area can be reconstructed as a set of flat cross sections which can be used to analyse the two- and three-dimensional morphological parameters. For X-ray methods the contrast in the images is a mixed combination of density and compositional information which provides means for non-destructive reconstruction of the internal structure. The paper presents experimental results of crack propagation and fibre bridging glass fibre epoxy samples that were collected in-situ during loading in a X-ray scanner.
Towards Failure-Free Design: Reducing Dimensionality in Function-Failure Similarity Analysis for Large Databases
Authors: Tumer Irem Y. , Stone Robert B. , Roberts Rory A.
Published: May 2008

When designing products, it is crucial to assure failure and risk-free operation in the intended operating environment. Failures are typically studied and eliminated its much as possible during the early stages of design. The few failures that go undetected result in unacceptable damage and losses in high-risk applications where public safety is of concern. Published NASA and NTSB accident reports point to a variety of components identified as sources of failures in the reported cases. In previous work, data from these reports were processed and placed in matrix form for all the system components and failure modes encountered, and then manipulated using matrix methods to determine similarities between the different components and failure modes. In this paper, these matrices are represented in the form of a linear combination of failures modes, mathematically formed using Principal Components Analysis (PCA) decomposition. The PCA decomposition results in a low-dimensionality representation of all failure modes and components of interest, represented in a transformed coordinate system. Such a representation opens the way for efficient pattern analysis and prediction of failure modes with highest potential risks on the final product, rather than making decisions based on the large space of component and failure mode data. The mathematics of the proposed method are explained first using a simple example problem. The method is then applied to component failure data gathered from helicopter accident reports to demonstrate its potential.
The Onset of Gas Entrainment From a Stratified Two-Phase Region Through a Single Side-Oriented Branch
Authors: Ahmed M. , Lenard K. , Hassan I. , Esmail N.
Published: May 2008

A new theoretical investigation has been conducted for the prediction of the critical height at the onset of gas entrainment during single discharge from a stratified two-phase region through a branch installed on an inclined flat wall. Two models have been developed; a simplified point-sink model and a more-accurate finite-branch. The predicted critical height at the onset of gas entrainment was proven to be a function of Froude number (Fr) and density ratio of the interface fluids. The results of the predicted critical height at the onset of gas entrainment, at low values of Fr (<10), were found to be more accurate when using the finite-branch analysis compared to the results found using the pink-sink analysis. Whereas, with increasing Fr, the predicted values of both models converged to the same value. Furthermore, the point-sink analysis was demonstrated to be independent of wall inclination angle, while the finite-branch analysis showed a slight decrease in the value of the critical height with increasing wall inclination angle. Three different experimental data sets at wall inclination angles of zero, 45 and 90 degrees (i.e. side, inclined and bottom branches) were used in the following study for the comparisons between the experimental and theoretically predicted results. A good concurrence was illustrated between the experimental and theoretical values.