bluuebunny/crossref_metadata_2025 huggingface dataset:
The Hadley‐Apennine KREEP basalt igneous province
Authors: TAYLOR G. Jeffrey , MARTEL Linda M. V. , SPUDIS Paul D.
Published: May 2012

Abstract– We have studied 27 KREEP basalt fragments in six thin sections of samples collected from four Apollo 15 stations. Based on local geology and regional remote sensing data, these samples represent KREEP basalt lava flows that lie beneath the younger, local Apollo 15 mare basalts and under other mare flows north of the Apollo 15 site. Some of these rocks were deposited at the site as ejecta from the large craters Aristillus and Autolycus. KREEP basalts in this igneous province have a volume of 103–2 × 104 km3. Mineral and bulk compositional data indicate that the erupted magmas had Mg# [100 × molar Mg/(Mg + Fe)] up to 73, corresponding to orthopyroxene‐rich interior source regions with Mg# up to 90. Minor element variations in the parent magmas of the KREEP basalts, inferred from compositions of the most magnesian pyroxene and most calcic plagioclase in each sample, indicate small but significant differences in the concentrations of minor elements and Mg#, reflecting variations in the composition of lower crustal or mantle source regions and/or different amounts of partial melting of those source regions.
A Democracy Results Approach: The Present Debate and Growing Consensus Surrounding the Inter‐American Democratic Charter
Authors: Sample Kristen , Mariani Santiago
Published: May 2012

Renewed interest from Organization of American States (OAS) member states, academia, and civil society organizations in ways to make the implementation of the Inter‐American Democratic Charter (IADC) more effective marked its tenth anniversary year. Drawing on discussion in the sessions of the OAS Permanent Council and various parallel events, this article describes and reviews this auspicious dynamic, focusing on the close link between democracy and integral development reflected in descriptions of social elements in several of the charter's articles. The persistence of high rates of poverty, inequality, and indigence are among the most urgent and significant challenges to be addressed if the region's democracies are to become consolidated, according to a growing consensus reflected in these discussions. A social charter has been proposed as a possible tool to complement the IADC in the area of social inclusion. This discussion has gone hand in hand with an effort to build consensus about the importance of integral democracy as an opportunity for the Inter‐American System.
Comparison of an inertial sensor system of lameness quantification with subjective lameness evaluation
Authors: McCracken M. J. , Kramer J. , Keegan K. G. , Lopes M. , Wilson D. A. , Reed S. K. , LaCarrubba A. , Rasch M.
Published: May 2012

Reasons for performing study:Subjective evaluation of mild lameness has been shown to have poor interobserver reliability. Traditional methods of objective lameness evaluation require specialised conditions and equipment. Wireless inertial sensor systems have been developed to allow for simple, rapid, objective lameness detection in horses trotted over ground.

Objective:The purpose of this study was to compare the sensitivities of an inertial sensor system and subjective evaluation performed by experienced equine practitioners at detecting lameness in horses. We hypothesised that the inertial sensor system would identify lameness at a lower level of sole pressure than a consensus of 3 experienced equine veterinarians.

Methods:Fifteen horses were fitted with special shoes that allowed for lameness induction via sole pressure. Horses were simultaneously evaluated by 3 equine veterinarians and a wireless inertial sensor system. Horses were subjected to multiple trials: 1) before inserting the screw; 2) after inserting the screw to just touch the sole; and 3) after tightening the screw in half turn increments. The number of screw turns required for lameness identification in the correct limb by the inertial sensors and by consensus of 3 equine veterinarians was compared using the Wilcoxon test.

Results:The inertial sensor system selected the limb with the induced lameness after fewer screw turns than did the 3 veterinarians (P<0.0001). The inertial sensor system selected the correct limb before the 3 veterinarians in 35 trials (58.33%), the evaluators selected the correct limb before the inertial sensors in 5 trials (8.33%), and in 20 trials (33.33%) they selected the correct limb at the same time.

Potential relevance:The inertial sensor system was able to identify lameness at a lower level of sole pressure than the consensus of 3 equine veterinarians. The inertial sensor system may be an effective aid to lameness localisation in clinical cases.
The use of intrathecal analgesia and contrast radiography as preoperative diagnostic methods for digital flexor tendon sheath pathology
Authors: FISKE‐JACKSON A. R. , BARKER W. H. J. , ELIASHAR E. , FOY K. , SMITH R. K. W.
Published: May 2012

Reasons for performing study:The sensitivity of ultrasonography for the diagnosis ofmanica flexoria(MF) tears within the digital flexor tendon sheath (DFTS) is lower than for diagnosis of marginal tears of the deep digital flexor tendon (DDFT). Additional diagnostic tools would assist in appropriate decision making for either conservative or surgical management.

Objectives:To evaluate the improvement in lameness of horses with MF or DDFT tears following intrathecal analgesia and to assess the sensitivity and specificity of contrast radiography for the diagnosis of these tears.

Methods:The case records of horses presented to a referral clinic over a 7‐year period that underwent intrathecal diagnostic analgesia, or intrathecal analgesia and contrast radiography, of the DFTS with subsequent tenoscopy were examined.

Results:Fifty‐three limbs had intrathecal diagnostic analgesia performed and 23 contrast tenograms were assessed in horses undergoing DFTS tenoscopy. Horses with DDFT tears were significantly more likely to respond positively to intrathecal diagnostic analgesia than those with MF tears (P = 0.02). Using contrast radiography, tears of the MF were predicted with an overall sensitivity of 96% and specificity of 80%; marginal tears of the DDFT were predicted with an overall sensitivity of 57% and specificity of 84%.

Conclusions:The results of intrathecal analgesia of the DFTS in combination with contrast radiography have a high sensitivity for predicting MF tears. The sensitivity of contrast radiography for predicting tears of the DDFT is lower but the specificity remains high.

Potential relevance:Contrast radiography performed at the same time as intrathecal analgesia provides useful information regarding the presence of MF tears and DDFT tears, which can assist in the decision of whether to manage the lameness conservatively or with tenoscopic evaluation.
Investigation of the Tip Clearance Flow in a Compressor Cascade Using a Novel Laser Measurement Technique With High Temporal Resolution
Authors: Fischer Andreas , Büttner Lars , Czarske Jürgen , Gottschall Marcel , Vogeler Konrad , Mailach Ronald
Published: May 2012

The understanding of the tip clearance flow in axial compressors is a key issue for developing new compressors with enhanced efficiency and reduced noise for instance. However, necessary flow measurements in the blade tip region and within the tip clearance are challenging due to the small gap width. The application of a novel optical measurement technique named Doppler global velocimetry with laser frequency modulation is presented, which provides velocity field measurements of all three velocity components nonintrusively in the tip clearance flow of a linear cascade at near stall conditions. These array measurements have a high temporal resolution enabling turbulence analysis such as the evaluation of velocity standard deviations and turbulence spectra up to several kilohertz. Conventional pneumatic and hot-wire measurements in planes at the inlet and the outlet as well as on the blade surface were taken to complete the flow pattern and validate the data of the Doppler global velocimetry. Wake measurements identified a strong flow separation in the rear suction side dominating the transient character of the cascade flow. Towards the endwall this high loss region is reduced by the clearance flow and the resulting vortex, which is obviously not affected by the profile separation and the pulsating blockage frequency. Inside the blade passage and the tip clearance the Doppler global velocimetry measurements allowed a spatial assignment of the origin of the tip leakage flow and the downstream developing vortex. In addition, the tip clearance vortex could be resolved and identified successfully as the most dominant turbulence generating effect in the near endwall region at this high loading operating point of the blading.
Enhanced Design of Cross-Flow Microchannel Heat Exchanger Module for High-Performance Aircraft Gas Turbine Engines
Authors: Northcutt Brittany , Mudawar Issam
Published: May 2012

This study explores the design of highly compact air–fuel heat exchangers for high-performance aircraft turbine engines. The heat exchangers consist of a large number of modules that can be brazed together into a rectangular or annular outer envelope. Inside the module, fuel flows through parallel microchannels, while air flows externally perpendicular to the direction of the fuel flow over rows of short, straight fins. A theoretical model recently developed by the authors for a single module is both validated experimentally, by simulating aircraft fuel with water, and expanded to actual heat exchangers and JP-8 aircraft fuel. An optimization study of the module’s geometrical parameters is conducted for high-pressure-ratio engine conditions in pursuit of the highest heat transfer rate. These parameters are then adjusted based on such considerations as microfabrication limits, stress and rupture, and the need to preclude clogging of the fuel and air passage. Using the revised parameters, the analytical model is used to generate effectiveness plots for both rectangular and annular heat exchangers with one air pass and one, two, or three fuel passes. These results demonstrate both the effectiveness of the module design and the versatility of the analytical tools at designing complex heat exchangers for high-performance aircraft gas turbine engines.
Mixture Preparation Effects on Distributed Combustion for Gas Turbine Applications
Authors: Khalil Ahmed E. E. , Gupta Ashwani K. , Bryden Kenneth M. , Lee Sang C.
Published: May 2012

Distributed combustion is now known to provide significantly improved performance of gas turbine combustors. Key features of distributed combustion include uniform thermal field in the entire combustion chamber for significantly improved pattern factor and avoidance of hot-spot regions that promote thermal NOx emissions, negligible emissions of hydrocarbons and soot, low noise, and reduced air cooling requirements for turbine blades. Distributed combustion requires controlled mixing between the injected air, fuel, and hot reactive gasses from within the combustor prior to mixture ignition. The mixing process impacts spontaneous ignition of the mixture to result in improved distributed combustion reactions. Distributed reactions can be achieved in premixed, partially premixed, or nonpremixed modes of combustor operation with sufficient entrainment of hot and active species present in the combustion zone and their rapid turbulent mixing with the reactants. Distributed combustion with swirl is investigated here to further explore the beneficial aspects of such combustion under relevant gas turbine combustion conditions. The near term goal is to develop a high intensity combustor with ultralow emissions of NOx and CO, and a much improved pattern factor and eventual goal of near zero emission combustor. Experimental results are reported for a cylindrical geometry combustor for different modes of fuel injection with emphasis on the resulting pollutants emission. In all the cases, air was injected tangentially to impart swirl to the flow inside the combustor. Ultra low NOx emissions were found for both the premixed and nonpremixed combustion modes for the geometries investigated here. Results showed very low levels of NO (∼10 ppm) and CO (∼21 ppm) emissions under nonpremixed mode of combustion with air preheats at an equivalence ratio of 0.6 and a moderate heat release intensity of 27 MW/m3-atm. Results are also reported on lean stability limits and OH* chemiluminescence under different fuel injection scenarios for determining the extent of distribution combustion conditions. Numerical simulations have also been performed to help develop an understanding of the mixing process for better understanding of ignition and combustion.
A Simplified Micromechancial Model for Analyzing Viscoelastic–Viscoplastic Response of Unidirectional Fiber Composites
Authors: Jeon Jaehyeuk , Muliana Anastasia
Published: May 2012

This study introduces a simplified micromechanical model for analyzing a combined viscoelastic–viscoplastic response of unidirectional fiber reinforced polymer (FRP) composites. The micromechanical model is derived based on a unit-cell model consisting of fiber and matrix subcells. In this micromechanical model, a limited spatial variation of the local field variables in the fiber and matrix subcells is considered in predicting the overall time-dependent response of composites. The constitutive model for the polymer matrix is based on Schapery’s viscoelastic and Perzyna’s viscoplastic models. An incremental stress–strain relation is considered in solving the time-dependent and inelastic response. A linearized prediction and iterative corrector scheme are formulated to minimize errors from the linearization within the incremental stress–strain relation such that both the micromechanical constraints and the nonlinear constitutive equations are satisfied. The goal is to provide the accurate effective stress–strain relations of the composites and the corresponding viscoelastic and viscoplastic deformation in the polymeric matrix. The micromechanical model is verified by comparing the time-dependent response of the glass FRP composites having several off-axis fiber orientations with experimental data available in the literature.
Kinematics of a Fully-Decoupled Remote Center-of-Motion Parallel Manipulator for Minimally Invasive Surgery
Authors: Kuo Chin-Hsing , Dai Jian S.
Published: May 2012

A crucial design challenge in minimally invasive surgical (MIS) robots is the provision of a fully decoupled four degrees-of-freedom (4-DOF) remote center-of-motion (RCM) for surgical instruments. In this paper, we present a new parallel manipulator that can generate a 4-DOF RCM over its end-effector and these four DOFs are fully decoupled, i.e., each of them can be independently controlled by one corresponding actuated joint. First, we revisit the remote center-of-motion for MIS robots and introduce a projective displacement representation for coping with this special kinematics. Next, we present the proposed new parallel manipulator structure and study its geometry and motion decouplebility. Accordingly, we solve the inverse kinematics problem by taking the advantage of motion decouplebility. Then, via the screw system approach, we carry out the Jacobian analysis for the manipulator, by which the singular configurations are identified. Finally, we analyze the reachable and collision-free workspaces of the proposed manipulator and conclude the feasibility of this manipulator for the application in minimally invasive surgery.
Spinal Implant Development, Modeling, and Testing to Achieve Customizable and Nonlinear Stiffness
Authors: Dodgen Eric , Stratton Eric , Bowden Anton , Howell Larry
Published: May 2012

The spine naturally has a nonlinear force-deflection characteristic which facilitates passive stability, and thus there is a need for spinal implants that duplicate this behavior to provide stabilization when the spine loses stiffness through injury, degeneration, or surgery. Additionally, due to the complexity and variability in the mechanics of spinal dysfunction, implants could potentially benefit from incorporating a customizable stiffness into their design. This paper presents a spinal implant with contact-aided inserts that provide a customizable nonlinear stiffness. An analytical model was utilized to optimize the device design, and the model was then verified using a finite element model. Validation was performed on physical prototypes, first in isolation using a tensile tester and then using cadaveric testing on an in-house spine tester. Testing confirmed the performance of the implant and it was observed that the device increased mechanical stability to the spinal segment in flexion-extension and lateral-bending.
Comparative Study in Predicting the Global Solar Radiation for Darwin, Australia
Authors: Kean Yap Wai , Karri Vishy
Published: May 2012

This paper presents a comparative study in predicting the monthly average solar radiation for Darwin, Australia (latitude 12.46 deg S longitude 130.84 deg E). The city of Darwin, Northern Territory (NT), has the highest and most consistent sunshine duration among all the other Australian states. This unique climate presents an opportunity for photovoltaic (PV) applications. Reliable and accurate predictions of solar radiation enable potential site locations, which exhibit high solar radiations and sunshine hours, to be identified for PV installation. Three predictive models were investigated in this study—the linear regression (LR), Angstrom–Prescott–Page (APP), and the artificial neural network (ANN) models. The mean global solar radiation coupled with the climate data (mean minimum and maximum temperatures, mean rainfall, mean evaporation, and sunshine fraction) obtained from the Australian Bureau of Meteorology (BoM) formed the basis of the dataset. Using simple and easily obtainable climate data presents an added advantage by reducing model complexity. Predictive results showed the root mean square errors (RMSEs) obtained were 6.72%, 13.29%, and 8.11% for the LR, APP, and ANN models, respectively. The predicted solar exposure from the LR model was then compared with the satellite-derived data to assess the accuracy of the LR method.
Measurement of Multi-segment Foot Joint Angles During Gait Using a Wearable System
Authors: Rouhani Hossein , Favre Julien , Crevoisier Xavier , Aminian Kamiar
Published: May 2012

Usually the measurement of multi-segment foot and ankle complex kinematics is done with stationary motion capture devices which are limited to use in a gait laboratory. This study aimed to propose and validate a wearable system to measure the foot and ankle complex joint angles during gait in daily conditions, and then to investigate its suitability for clinical evaluations. The foot and ankle complex consisted of four segments (shank, hindfoot, forefoot, and toes), with an inertial measurement unit (3D gyroscopes and 3D accelerometers) attached to each segment. The angles between the four segments were calculated in the sagittal, coronal, and transverse planes using a new algorithm combining strap-down integration and detection of low-acceleration instants. To validate the joint angles measured by the wearable system, three subjects walked on a treadmill for five minutes at three different speeds. A camera-based stationary system that used a cluster of markers on each segment was used as a reference. To test the suitability of the system for clinical evaluation, the joint angle ranges were compared between a group of 10 healthy subjects and a group of 12 patients with ankle osteoarthritis, during two 50-m walking trials where the wearable system was attached to each subject. On average, over all joints and walking speeds, the RMS differences and correlation coefficients between the angular curves obtained using the wearable system and the stationary system were 1 deg and 0.93, respectively. Moreover, this system was able to detect significant alteration of foot and ankle function between the group of patients with ankle osteoarthritis and the group of healthy subjects. In conclusion, this wearable system was accurate and suitable for clinical evaluation when used to measure the multi-segment foot and ankle complex kinematics during long-distance walks in daily life conditions.
Numerical Study Optimal Timing of the Axial Piston Pump
Authors: Zhang Shusen , Manring Noah D. , Mehta Viral S.
Published: May 2012

In this paper, the theoretical optimal timing of the axial piston pump is first derived to confirm the analysis published by Professor Kevin Edge [1]. It is discovered that the optimal discharge port delay is different from the optimal inlet port delay. The dimensional analysis also shows that higher shaft angular velocity indicates less delay required in both discharge port and inlet port. Numerical studies show that optimal timing can reduce the dynamic pressure ripple greatly, but since it does not affect the kinematic component, it will not eliminate the entire pressure ripple. The optimal timing could also induce an increase in efficiency where the baseline pump design has cross-porting. However, there is certain tradeoff between pressure ripple reduction and efficiency consideration. Actual design consideration to affect independent timing of the portplate is not studied in this work.
Study on Working Characteristics of Expansion Energy Used Booster
Authors: Shi Yan , Cai Maolin
Published: May 2012

Boosters are widely used to obtain high-pressure air. In order to obtain a higher output flow of high-pressure air, a new kind of booster is proposed, namely, the Expansion Energy Used booster (EEU booster). Output flow is improved by utilizing the expansion power of the compressed air to accelerate the piston’s movement. A mathematical model of the booster is constructed and analyzed to obtain the piston’s movement characteristics, variations of air pressure in the boosting and driving chamber as well as the characteristics of the output flow. Evaluation of simulation and experimental flow characteristics shows that the derived model corresponds well to experimental results. For a source and output air pressure of 0.6Mpa and 0.8MPa respectively, the output flow of the booster rises as the Convergent Pressure in the driving chamber increases. At a certain point, the output flow stabilizes and remains at a near constant. For an output pressure of 0.8MPa at the Optimum Work State, the output flow declines with a rise in the boosting ratio. This research lays the foundation for future work on the optimization of the EEU booster.
Force-Based ABS Control Using Lateral Force Measurement
Authors: Gerard Mathieu , Corno Matteo , Verhaegen Michel , Holweg Edward
Published: May 2012

In this paper a hybrid force-based Anti Locking Braking System (ABS) is presented. The proposed control system directly considers the lateral tyre behaviour during heavy braking. In this way it is possible to guarantee drivability and stability also when braking on surfaces without a clear tyre characteristic peak. The goal of the paper is to show the potentialities of load-based vehicle dynamics control. It is shown that, thanks to the availability of the lateral and longitudinal tyre force measurements, a stable braking can be achieved with a minimal increase of complexity of the algorithm in conditions that are critical for traditional ABS. The general control concept is that of reducing the longitudinal slip if the measured lateral force is smaller than a desired minimum. Two different ways of computing the minimum lateral forces are presented: one for the front axle with the objective of guaranteeing steerability and one for the rear axle to guarantee stability. Simulations on a nonlinear vehicle simulator confirm that the controller can maintain the desired steering behaviour and vehicle yaw stability in case of heavy braking.
Gearshift Controller Design for Automatic Transmission
Authors: Liu Zhiyuan , Gao Jinwu , Zheng Quan
Published: May 2012

A gearshift controller for automatic transmission is developed in this paper, which regulates turbine speed to track the desired trajectory and suppresses the output shaft oscillation at the same time by single clutch pressure control. In order to achieve this task, the proposed controller is designed, by integrating backstepping technique and sliding mode output feedback control theory. Simulation of 1–2 upshift is illustrated to verify the validity of the proposed gearshift controller.
Modeling Dynamic Ankle Mechanical Impedance in Relaxed Muscle
Authors: Lee Hyunglae , Hogan Neville
Published: May 2012

This paper presents identification and modeling of dynamic ankle mechanical impedance in relaxed muscles. A multi-variable estimation method using a wearable therapeutic robot enabled clear interpretation of dynamic ankle impedance both in the sagittal and frontal planes. Estimation results showed that dynamic ankle behavior apparently cannot be reconciled with a simple 2nd order model. Measurements in a seated and standing position verified that ankle impedance changes substantially depending on lower-limb posture. Identification results were fitted with a modified Hill model with a mass between the muscle and tendon elements. When coupled with foot inertia, either singly or antagonistically, this model successfully captured the dynamic behavior of the ankle impedance both in the seated and standing positions up to 20 Hz. At least a 4th order model having 2 complex zero and 1 complex pole pairs was required to describe relaxed ankle impedance either in the sagittal or frontal plane up to 20Hz. In the seated position, a 6th order model was slightly better than the 4th order model but with the expense of complexity, and a 8th order model might be used to describe dynamic ankle behavior up to 30∼40Hz.
A Virtual-Cam Control Methodology for Free-Piston Engines
Authors: Yong Chao , Barth Eric J.
Published: May 2012

In conventional internal combustion engines, valves are opened and closed using a cam surface. The cam is kinematically related to the piston positions through the crankshaft and timing belt. In contrast, there is no crankshaft or kinematic cam surface in a free-piston engine to physically realize this mechanism. As a consequence, a free-piston engine has variable stroke lengths, which presents a challenge for active piston motion and precise stroke length control. This paper presents a virtual-cam based approach to relate free-piston motion to actuated engine valve control within a clear and familiar intuitive physical context. The primary functionality of the virtual cam control framework is to create a variable index, which is adjustable from cycle to cycle, for the exhaust/injection valves and spark timing similar to the function of physical cams in conventional engines. Since the cam is virtually created, it can be dynamically rebuilt to comply with cycle-to-cycle variations such as amount of the air/fuel supply, engine load and stroke length. This index rebuilding process is based on a cycle-to-cycle adaptive control method that uses the knowledge obtained from previous cycles to adjust the cam parameters. Preliminary experimental results are presented for a novel liquid-piston free-piston engine intended as a compact and efficient energy source for untethered power dense pneumatic systems such as untethered robots.
Optimized Pulse Modulation: A Novel Idea of a Digital Control Method for On/Off Valves
Authors: Schepers Ingo , Weiler Daniel , Weber Juergen
Published: May 2012

This article describes how on/off valves can be used in the closed loop control. After studying different industrial hydraulic applications typical requirements will be compiled. From these requirements a basic on/off valve architecture will be derived. In this article the number of parallel connected on/off valves per control edge is limited to one valve. So the typical digital hydraulics with a high number of parallel connected valves is not considered. The on/off valves could not be controlled like normal directional valves. To control on/off valves digital control methods are common to use. The digital control methods are not optimized for the hydraulic on/off valves, because the origins of the digital control methods will be found in the electrical engineering. The novel idea for the digital control methods is the optimized pulse control which eliminates the disadvantages of the common digital control methods. How the optimized pulse control works is described in this article.
Stabilization of Nonlinear Strict-Feedback Systems With Time-Varying Delayed Integrators
Authors: Bekiaris-Liberis Nikolaos , Krstic Miroslav
Published: May 2012

We consider nonlinear systems in the strict-feedback form with simultaneous time-varying input and state delays, for which we design a predictor-based feedback controller. Our design is based on time-varying, infinite-dimensional backstepping transformations that we introduce, to convert the system to a globally asymptotically stable system. The solutions of the closed-loop system in the transformed variables can be found explicitly, which allows us to establish its global asymptotic stability. Based on the invertibility of the backstepping transformation, we prove global asymptotic stability of the closed-loop system in the original variables. Our design is illustrated by a numerical example.
Experimental Analysis for Wind Induced Disturbance Rejection on Bridge Crane Structures
Authors: Pasternack Julia , Thayer Dan , Bansal Rohan , Maleki Ehsan , Tao Greg , Kim Kevin , Singhose William
Published: May 2012

This paper describes the development of a feedback controller for rejecting wind disturbances on a crane payload. The goal of this research is to perform in-situ parameter sensitivity testing that is specific to a given crane structure. Through experimentation, this paper evaluates the robustness of a closed-loop controller that implements station keeping on a bridge crane. A set of general trends were developed to describe how altering system parameters and operating conditions affected controller performance. Such findings are not limited to single parameter characterization and can be extended to multiple variables given specific system specifications.
From Canonical Hamiltonian to Port-Hamiltonian Modeling: Application to Magnetic Shape Memory Alloys Actuators
Authors: Calchand Nandish , Hubert Arnaud , Le Gorrec Yann , Maschke Bernhard
Published: May 2012

This paper presents the modelling of an actuator based on Magnetic Shape Memory Alloys (MSMA). The actuation principle relies on the ability of the material to change its shape under the application of a magnetic field. Previous models proposed by authors were based on canonical (symplectic) Hamiltonian modeling and thermodynamics of irreversible processes. These models, though physically cogent, are non-minimal differential algebraic dynamical models and hence less adapted for control purposes. This paper therefore proposes a modified and system-oriented modeling procedure which lends itself naturally to a port-Hamiltonian model. The latter is found to be a minimal realization of the above whereby interconnection between subsystems is clearly visible. Using Lagrange multipliers, constraints which arise due to causality and interconnection are expressed. In the last section, Differential Algebraic Equations (DAE) resulting from previous models are reduced to Ordinary Differential Equations (ODE) and by using coordinate transformations, constraints are decoupled from the system input/output. The resulting model is well-suited for control.
Design and Development of a 2-DOF Miniature Force Sensor for Surgical Procedures
Authors: Tan U-Xuan , Desai Jaydev P.
Published: May 2012

Force sensing is an important component for a number of surgical procedures as it can help to prevent undesirable damage to the tissue and at the same time provides the surgeons with a better “feel” of the tool-tissue interaction. However, most of the current commercially available multi-DOF force sensors are relatively large in size and it is a challenge to incorporate them into the surgical tool. Hence, a multi-DOF miniature force sensor is desired and this paper presents the design and development of a miniature 2-DOF force sensor. In order to achieve a miniature force sensor, microfabrication technique is used and the proposed force sensor is a capacitive-based sensor. The proposed force sensor can be used in a number of percutaneous procedures as well as catheter-based procedures. This paper presents the design and microfabrication process of the proposed miniature force sensor.
Oxygen Concentration Dynamic Model Through a Diesel Engine Aftertreatment System
Authors: Chen Pingen , Wang Junmin
Published: May 2012

This paper presents a control-oriented model describing the dynamics of oxygen concentration through a Diesel engine aftertreatment system that includes a Diesel oxidation catalyst (DOC) and a Diesel particulate filter (DPF). Exhaust gas oxygen concentration is important for catalysts such as NOx conversion efficiencies of selective catalytic reduction (SCR) systems and lean NOx traps (LNT). In the presence of low-pressure loop exhaust gas recirculation (EGR), the exhaust gas oxygen concentration after-DPF also influences combustion. Due to the chemical reactions occurring inside DOC and DPF, the exhaust gas oxygen concentration considerably varies through the aftertreatment systems. Directly measuring the exhaust gas oxygen concentrations at different locations through the exhaust gas aftertreatment system is costly and unreliable. A dynamic model is thus needed in order to design model-based observers to estimate the exhaust gas oxygen concentrations at various locations. The oxygen-related reactions within a DOC and a DPF are investigated in this study. A lumped-parameter, control-oriented DOC-DPF oxygen concentration dynamic model was developed by a multi-objective optimization method and validated with experimental data obtained on a medium-duty Diesel engine equipped with full aftertreatment systems. Experimental results show that the model can well capture the oxygen dynamics across the Diesel engine aftertreatment systems.
A Comparative Study of Permanent Magnet Linear Alternator and Hydraulic Free-Piston Engines
Authors: Sadighi Ali , Li Ke , Sun Zongxuan
Published: May 2012

This paper presents a comparative study of two possible power-generating units for the free-piston engine (FPE): Permanent-magnet linear alternator (PMLA) and linear hydraulic pump. The FPE discussed in this paper is a linear, opposed-piston, opposed-cylinder (OPOC) engine that operates with a homogenous charge compression ignition (HCCI) combustion. Lack of crankshaft in the FPE allows lower friction loss, variable compression ratio, and higher modularity compared to a conventional engine. Also the OPOC configuration enables high-frequency operation of the FPE, which results in high power density. The FPE is also well suited for HCCI operation, which offers improved fuel efficiency and emissions. The chemical power released in the combustion chambers can be transformed to fluid or electric power. This could be done via a hydraulic pump or a linear alternator. In this paper these two systems are studied and compared as the power-generating device for the FPE.
Decentralized Charging of Plug-In Electric Vehicles
Authors: Li Chiao-Ting , Ahn Changsun , Peng Huei , Sun Jing
Published: May 2012

Plug-in electric vehicles (PEVs) are equipped with sizable batteries to replace fossil fuel with electric energy. The electric grid may be stressed when a large number of PEVs charge their batteries, especially during peak hours. This paper presents a PEV charging control algorithm, which achieves balance between the system-level objective (valley filling) and individual-level objective (full battery charging). In addition, grid frequency regulation is achieved through a two-level control algorithm, which ensures robustness and reduces reliance on conventional ancillary services. This two-level control algorithm is scalable because it is designed for decentralized implementation. In other words, the algorithm works with indefinite numbers of PEVs as long as the load is within the grid capacity.
Design and Control of a Compact and Flexible Pneumatic Artificial Muscle Actuation System: Part One—Design Process
Authors: Waycaster Garrett , Wu Sai-Kit , Driver Tad , Shen Xiangrong
Published: May 2012

This paper describes the design and control of a compact and flexible pneumatic artificial muscle (PAM) actuation system for bio-robotic systems. The entire paper is divided into two parts, with the first part covering the mechanism design and the second part covering the corresponding controller design. This novel system presented in this part incorporates two new features, including a variable-radius pulley based PAM actuation mechanism, and a spring-return mechanism to replace the PAM in the “weak” direction. With the pulley radius as a function of the joint angle, this new feature enables the designer to freely modulate the shape of the torque curve, and thus achieves a significantly higher flexibility than the traditional configuration. The other new feature, the spring-return mechanism, is inspired by the fact that a large number of bio-robotic systems require a significantly larger torque in one direction than the other.
Anti-Windup LPV Control Design of MR Dampers for Structural Vibration Suppression
Authors: Meisami-Azad Mona , Shirazi Farzad A. , Grigoriadis Karolos M.
Published: May 2012

Magneto-rheological (MR) dampers that belong to the family of semi-active devices are widely used for vibration attenuation in space and civil engineering structures. In this paper, we study the use of MR dampers for seismic protection of a model two-story structure. A modified Bingham model of the MR damper is considered for linear parameter varying (LPV) modeling and control of the system. The main contribution of the paper is the design and experimental validation of an LPV anti-windup compensator to tackle the effect of actuator saturation on control design performance. The designed LPV anti-windup control scheme is advantageous from the implementation standpoint because it can be considered as an addition to the existing control system. Experimental results demonstrate the effective vibration suppression of the structure in the presence of the seismic excitation inputs by utilizing an LPV control strategy. An inner/outer loop control strategy is further developed and implemented considering the actuator saturation effect to reduce the control effort and saving the MR damper power consumption.
Real-Time and Robust Estimation of Biodiesel Blends Using NOx Sensor
Authors: Mirheidari S. , Franchek M. A. , Grigoriadis K. M. , Mohammadpour J. , Wang Y. Y. , Haskara I.
Published: May 2012

Biodiesel as a renewable alternative fuel produces lower exhaust emissions with the exception of nitrogen oxides (NOx) when compared to the conventional diesel fuel. Reducing nitrogen oxides produced from engines running on biodiesel is a challenging task to be able to meet the emission requirements. Knowledge of fuel blend could be very helpful for control and adaptation purposes to tune the engine control system parameters leading to lower NOx emission and improved engine performance. Proposed in this paper is a NOx sensor-based biodiesel blend estimation strategy. This strategy is fitted in a robust adaptive estimation structure for achieving a robust estimation. Sensitivity analysis has been done to check the robustness of the estimators against measurement errors.
Electrochemical Li-Ion Battery Modeling for Control Design With Optimal Uneven Discretization
Authors: Lee Tae-Kyung , Filipi Zoran S.
Published: May 2012

This paper proposes a reduced Li-ion battery model for design optimization and control design by implementing the electrode-averaged diffusion dynamics and uneven discretization of the particle radius for fast computation and accurate prediction of the Lithium intercalation dynamics. First, the unevenly discretized dynamics model is constructed from the ordinary differential equation (ODE) derived in the electrode-averaged battery model. Then, constrained optimization problems with multi-objectives are formulated to find the optimal uneven discretization. The cost function is evaluated under the wide battery operation data sets constructed by Latin hypercube sampling (LHS) to reduce the total number of cases. The optimally determined unevenly discretized model can predict the battery electrochemical dynamics with much smaller number of discretization steps compared to the evenly discretized electrode-averaged battery model without loss of physical interpretation of the diffusion dynamics in the electrode solid particles.
Generating a Racing Line for an Autonomous Racecar Using Professional Driving Techniques
Authors: Theodosis Paul A. , Gerdes J. Christian
Published: May 2012

During a race, professional drivers follow a racing line using specific maneuvers that allow them to utilize as much of the car’s tire force as possible. These lines could be used to create trajectories for obstacle avoidance in autonomous vehicles if they could be analytically defined. In fact, many of the techniques described by professional drivers can be expressed by a family of simple curves including straights, clothoids, and constant radius arcs. By comparing different members of this family of curves, different racing techniques can be examined. In particular, the differences between two phase and three phase corners described by professional drivers can be easily captured and analyzed in a single parameter. Experimental results on an autonomous race-car highlight the advantages of two phase cornering over three phase cornering and demonstrate the types of comparisons that can be made with this approach.
Improved Modeling of a Dynamic Mirror With Antagonistic Piezoelectric Stack Actuation
Authors: Mynderse James A. , Whitney Ann M. , Chiu George T. C.
Published: May 2012

An enhanced model of a dynamic mirror actuator (DMA) for laser beam steering is presented. The DMA is driven by an antagonistic pair of piezoelectric stack actuators (PESA). The proposed model of the DMA employs explicit PESA charging dynamics and an adjustable PESA shunt circuit to address the frequency-dependent effective mechanical compliance term in several previous models from literature. The proposed DMA model with shunt circuit accurately predicts the first damped natural frequency of the DMA with a shunt circuit across each PESA. Simulation and experimental data are presented. Good agreement is shown between the predicted and measured damped first natural frequencies.
Linearization and Model Reduction of Contact Dynamics Simulation
Authors: Liang Jianxun , Ma Ou , Liu Caishan
Published: May 2012

Finite element methods are widely used for simulations of contact dynamics of flexible multibody systems. Such a simulation is computationally very inefficient because the system’s dimension is usually very large and the simulation time step has to be very small in order to ensure numerical stability. A potential solution to the problem is to apply a model reduction method in the simulation. Although many model reduction techniques have been developed, most of them cannot be readily applied due to the high nonlinearity of the involved contact dynamics model. This paper presents a solution to the problem. The approach is based on a modified Lyapunov balanced truncation method. A numerical example is presented to demonstrate that, by applying the proposed model reduction method, the simulation process can be significantly speeded up while the resulting error caused by the model reduction is still within an acceptable level.
Development of Diagnostic Algorithms for an Air Brake System: Theory and Implementation
Authors: Dhar Sandeep , Darbha Swaroop , Rajagopal K. R.
Published: May 2012

In this paper, we consider the problem of designing an algorithm for estimating the stroke of a pushrod of the air brake system. The stroke of pushrod directly relates to the braking force available at the wheels and also affects the response time. The longer the stroke, the volume available for expansion is larger and correspondingly, the response is slower. The stroke depends on the clearance between the brake pad and the drum, which can vary due to variety of factors such as thermal expansion of drum and mechanical wear. Typical safety inspections of air brakes include the measurement of the stroke of the pushrod of each brake chamber. Regulations on trucks such Federal Motor Vehicle Safety Standard (FMVSS) 121 require the inspection to be carried out at 90 psi supply pressure and at full brake application. The evolution of the brake pressure depends on the stroke of the pushrod and the area of the treadle valve, which is controlled by the driver. The treadle valve meters compressed air from the supply reservoir to the brake chamber. The proposed scheme requires the measurement of pressure and a model for predicting the evolution of brake chamber pressure in response to full application of the brake (brake pedal is fully depressed). We experimentally corroborate the effectiveness of the proposed algorithm.
LQR Control Design of Discrete-Time Networked Cascade Control Systems With Time Delay
Authors: Belapurkar Rohit K. , Yedavalli Rama K.
Published: May 2012

Series cascade control systems, in which, the output of one process drives a second process are studied extensively in literature. Traditional control design methods based on transfer function approach are used for design of cascade control systems with disturbances in inner loop and time delays in outer loop process. Design of current turboshaft engine control systems are based on cascade control system framework. Next generation aircraft engine control systems are based on distributed architecture, in which, communication constraints like time delays can degrade control system performance. Stability of networked cascade control systems for turboshaft engines in a state space framework is analyzed in the presence of time delays. Two architectures of networked cascade control systems are presented. Stability conditions for discrete-time cascade control systems are presented for each of the architecture with time delays which are more than the sampling time.
Two Dimensional Modeling and Simulation of a Tethered Airfoil System for Harnessing Wind Energy
Authors: Das Tuhin K. , Mukherjee Ranjan , Sridhar Rahulram , Hellum Aren
Published: May 2012

A novel wind machine is described in which an airfoil-like kite is tethered to a moving base; the non-conservative nature of the wind loads over a cycle of the kite allows energy to be extracted at the base. A dynamic model for the kite-tether system is derived which models the tether as a series of point masses connected by massless rods. The lift and drag characteristics of the kite are determined from airfoil calculations. The system has been found to be stable via simulation at several wind speeds of interest. A sample base motion which extracts energy from the oncoming wind is also presented.
Optimal Control of PEV Charging Based on Residential Base Load Prediction
Authors: Gong Qiuming , Midlam-Mohler Shawn , Marano Vincenzo , Rizzoni Giorgio
Published: May 2012

Due to the characteristics of electric power generation, transmission and distribution in the U.S., experts have identified local distribution as a likely component of the chain to be adversely affected by unregulated PEV (Plug-in Hybrid Electric Vehicle/Electric Vehicle) charging. This paper studied the optimal control of PEV charging considering the loss of life of residential distribution transformer based on the prediction of residential base load. The prediction was studied using an autoregressive moving average (ARMA) model. A dynamic thermal model was used for prediction of the transformer hot-spot temperature with the information on power load and ambient temperature. The loss of life model including the dynamic thermal model was integrated into the optimization problem. The objective of the optimal control is to minimize the loss of life of transformer. Finally, a genetic algorithm (GA) was used for searching the optimal solution of PEV charging based on the predicted base load.