bluuebunny/crossref_metadata_2025 huggingface dataset:
New scoring system for predicting relapse after lamivudine‐induced hepatitis B e‐antigen loss in chronic hepatitis B patients
Authors: Song Byung‐Cheol , Cui Xiu Ji , Cho Yoo‐Kyung , Choi Eun Kwang , Hyun Soyoung , Song Hyun Joo , Kim Heung Up
Published: July 2009

Aim:  In endemic areas of hepatitis B virus (HBV) infection, lamivudine‐induced hepatitis B e‐antigen (HBeAg) loss is not durable. We developed a scoring system to predict the relapse after lamivudine‐induced HBeAg loss.

Methods:  Of 93 HBeAg‐positive chronic hepatitis B patients receiving lamivudine therapy, we studied the 30 patients who achieved HBeAg loss. Qualitative polymerase chain reaction assays for HBV DNA were performed after HBeAg loss; if results were negative on two consecutive occasions, lamivudine treatment was stopped. Serum HBV DNA levels at the time of HBeAg loss were determined using stored serum by the Cobas Amplicor HBV Monitor Kit.

Results:  Cumulative relapse rates were 44%, 55.8% and 59.8%, after 1, 2 and 5 years, respectively. Univariate analysis showed that the risk factors for relapse were age (≥ 30 years), HBV DNA level (≥ 60 IU/mL) at the time of HBeAg loss and liver cirrhosis. Independent risk factors for relapse were age (odds ratio [OR], 4.3; 95% confidence interval [CI], 1.2–17.6) and serum HBV DNA level at the time of HBeAg loss (OR, 5.1; 95% CI, 1.3–21.6). We developed a scoring system based on these independent risk factors. No relapse was observed for patients with a risk score of 0. For patients with a risk score of 1, the relapse rates were 41%, 49% and 56% at 1, 2 and 5 years, respectively. All patients with a risk score of 2 relapsed (P = 0.01).

Conclusion:  Our new scoring system may be useful for predicting relapses in patients with lamivudine‐induced HBeAg loss. Treatment strategies should be individualized according to risk score.
Clock Mechanism Fundamentals for Education: Modeling and Analysis
Authors: Wagner John , Huey Cecil , Knaub Katie
Published: July 2009

Time keeping devices have been designed, fabricated, and widely deployed throughout history to regulate daily functions including commerce and transportation. In addition, horology offers a catalog of mankind’s innovation and demonstrates important scientific and engineering concepts. The investigation and analysis of clock systems from a mechatronics perspective illustrates the evolution of gear systems, feedback control, and transformation of energy for time measurement. In this paper, the operational behavior of an eight day mechanical clock has been studied through mathematical models, numerical simulation, and computer animation. The classroom exploration of time keeping mechanisms offers practical applications of physical principles.
Fault Diagnosis for a Three Mass Torsion Oscillator Using a Bank of Fault Models
Authors: Baehr Joachim , Isermann Rolf
Published: July 2009

A fault diagnosis method for a three mass torsion oscillator is considered which is subject to different additive faults. By using a bank of fault models three faults of different type are detected, isolated and identified in size and time of occurrence. The bank of fault models is formed by a model of each considered fault. Comparison of simulated fault model outputs and measured signals leads to fault isolation. Fault size and time of occurrence are identified by a parity equation approach and used as fault model parameters. The method is capable to perform the tasks with use of one actuator and one sensor signal. It is shown that common approaches for fault isolation can not be used due to the small number of measured signals.
A PMN-PT/PDMS Vibrational Energy Harvester: Modeling and Experiments
Authors: Mathers Alex , Moon Kee , Yi Jingang
Published: July 2009

In this paper, we present design, modeling analysis, and experimental study of a vibration-based energy harvester. The energy harvester is made of a composite cantilever of a single crystal relaxor ferroelectric material (PMN-PT), and a polydimethyl-siloxane (PDMS) base layer. A PDMS proof mass is constructed at the tip of the composite cantilever beam. The use of the PMN-PT piezo-material and an interdigited electrodes (IDE) design improves the energy conversion efficiency. The PDMS base layer prevents the possible damage to the fragile PMN-PT layer. A dynamic systems approach is employed to analyze the responses and the performance of the harvester design. The experiments have demonstrated that a prototype of the harvester with a size of 7.4 mm × 2 mm × 110 μm can produce a maximum output voltage of 10 V (0.3 mW power) under a vibration excitation with a peak-to-peak amplitude of 1 mm, and the power density can reach 4.15 mW/cm3 under short circuit conditions.
Control of Exoskeletons Inspired by Fictitious Variable Gain in Human
Authors: Kong Kyoungchul , Tomizuka Masayoshi
Published: July 2009

A human wearing an exoskeleton-type assistive device results in a parallel control system that includes two controllers: the human brain and a digital exoskeleton controller. Unknown and complicated characteristics of the brain dynamically interact with the exoskeleton controller which makes the controller design challenging. In this paper, the motion control system of a human is regarded as a feedback control loop that consists of a brain, muscles and the dynamics of the extended human body. The brain is modeled as a control algorithm amplified by a fictitious variable gain. The variable gain compensates for characteristic changes in the muscle and dynamics. If a human is physically impaired or subjected to demanding work, the exoskeleton should generate proper assistive forces, which is equivalent to increasing the variable gain. In this paper, a control algorithm that realizes the fictitious variable gain is designed and its performance and robustness are discussed for single-input single-output cases. The control algorithm is then verified by simulation results.
A Hydraulic Actuated Automotive Thermal Management System: Theory and Experiment
Authors: Frick Peyton , Wagner John , Mehta Parikshit
Published: July 2009

The performance of engine cooling systems can be improved by replacing the traditional mechanical driven radiator fan and water pump assemblies with computer controlled components. The power requirements for electric servo-motors increase with larger cooling demands which necessitate larger motors and/or a distributed configuration. One solution may be the use of hydraulic-based components due to their high power density and compact size. This paper investigates a thermal management system that features a computer controlled hydraulic actuated automotive fan and water pump. A mathematical model was derived for the hydraulic and thermal system components. To experimentally study the concept, a hydraulic driven fan and coolant pump were integrated with electric immersion heaters and radiator to emulate a vehicle cooling system. The dynamic model exhibited a strong correlation with the experimental test data. For a series of operating profiles, the servo-solenoid proportional control valves successfully tracked prescribed temperature set points to demonstrate that a hydraulic cooling system can maintain engine operating conditions.
Computationally Efficient Nonlinear H∞ Control Designs for a Rigid Body Spacecraft
Authors: Zheng Qian , Wu Fen
Published: July 2009

In this paper, we consider nonlinear control of a symmetric spacecraft about its axis of symmetry with two control torques. Using a computationally efficient ℋ∞ control design procedure, attitude regulation and trajectory tracking problems of the axi-symmetric spacecraft were solved. Resorting to higher order Lyapunov functions, the employed nonlinear ℋ∞ control approach reformulates the difficult Hamilton-Jacobian-Isaacs (HJI) inequalities as semi-definite optimization conditions. Sum-of-squares (SOS) programming techniques are then applied to obtain computationally tractable solutions, from which nonlinear control laws will be constructed. The proposed nonlinear ℋ∞ designs will be able to exploit the most suitable forms of Lyapunov function for spacecraft control and the resulting controllers will perform better than existing nonlinear control laws.
Intelligent Kalman Filtering for Fault Detection on an Active Magnetic Bearing System
Authors: Noel Nana K. , Tammi Kari , Buckner Gregory D. , Gibson Nathan S.
Published: July 2009

One of the challenges of condition monitoring and fault detection is to develop techniques that are sufficiently sensitive to faults without triggering false alarms. In this paper we develop and experimentally demonstrate an intelligent approach for detecting faults in a single-input, single-output active magnetic bearing. This technique uses an augmented linear model of the plant dynamics together with a Kalman filter to estimate fault states. A neural network is introduced to enhance the estimation accuracy and eliminate false alarms. This approach is validated experimentally for two types of fabricated faults: changes in suspended mass and coil resistance. The Kalman filter alone is shown to be incapable of identifying all fault cases due to modeling uncertainties. When an artificial neural network is trained to compensate for these uncertainties, however, all fault conditions are identified uniquely.
Parameter Adaptation by Parameter Signature Isolation in the Time-Scale Domain
Authors: Danai Kourosh , McCusker James R.
Published: July 2009

It is shown that delineation of output sensitivities with respect to model parameters in dynamic models can be enhanced in the time-scale domain. This enhanced differentiation of output sensitivities then provides the capacity to isolate regions of the time-scale plane wherein a single output sensitivity dominates the others. Due to this dominance, the prediction error can be attributed to the error of a single parameter at these regions so as to estimate each model parameter error separately. The proposed Parameter Signature Isolation Method (PARSIM) that uses these parameter error estimates for parameter adaptation has been found to have an adaptation precision comparable to that of the Gauss-Newton method for noise-free cases. PARSIM, however, appears to be less sensitive to input conditions, while offering the promise of more effective noise suppression by the capabilities available in the time-scale domain.
Modular Dynamic Model Assembly of Finite Element Models
Authors: Ren Zhen , Radcliffe Clark J.
Published: July 2009

Analytical engineering design is a global activity requiring efficient global distribution of analytical models of dynamic physical systems through computer networks. Finite Element Method (FEM) models are used globally to analyze the response of physical systems assembled from physical components. FEM models from different physical component suppliers often have geometrically incompatible meshes. This geometric incompatibility of mesh node placement typically requires component internal details in the assembly process. The modular model assembly introduced in this paper does not require such component internal details. It assembles incompatible finite element component models fast and with accuracy comparable to traditional reformulation. The proprietary geometry and material component details are not revealed during the assembly. Modular model assembly can be used to assemble distributed component models through the internet in global engineering design. Dynamic examples are provided.
A Robust Approach to Dynamic Feedback Linearization for a Steerable Nips Mechanism
Authors: Ergueta Edgar I. , Seifried Robert , Horowitz Roberto
Published: July 2009

This paper presents two different control strategies for paper position control in printing devices. The first strategy is based on feedback linearization plus dynamic extension (dynamic feed-back linearization). Even though this controller is very simple to design, we show that it is not able to handle actuator multiplicative uncertainties, and therefore it fails when it is implemented on the experimental setup. The second strategy we present uses similar concepts, but it is more robust since feedback linearization is used only to linearize the kinematics of the system and internal loops are used to locally control the actuator’s positions and velocities. Not only do we prove the robustness of the second control strategy, but we also show its successful implementation.
Energy Removal in Dynamical Systems Through an Optimal Sequence of Constraint Application
Authors: Issa Jimmy , Mukherjee Ranjan , Diaz Alejandro R.
Published: July 2009

A sequential application and removal of constraints can remove energy from vibrating systems. In this paper several optimization formulations are suggested, whereby maximum energy removal is achieved by selecting optimal strategies that identify where and when the constraints should be applied. The optimization process is illustrated by means of simple mass-spring and membrane systems and the corresponding problems are solved using a genetic algorithm.
Control Oriented Modeling of a Three Way Catalyst Coupled With Oxygen Sensors
Authors: Midlam-Mohler Shawn , Rajagopalan Sai , Dudek Kenneth P. , Guezennec Yann , Yurkovich Steve
Published: July 2009

Modeling of three-way catalyst behavior in stoichiometric engines is a tovpic with significant depth of research which encompasses complex kinetics based models through highly simplified control-oriented models. For model based control design, one must consider the behavior of the catalyst in conjunction with the feedback oxygen sensors. These sensors have well known influences from exhaust gas species due to interaction with the catalyst which, if ignored, can cause significant difficulties in modeling and control. These effects have often been addressed by calibrating and validating catalyst models under simplified conditions in order to minimize errors. In this work, the root cause of many of these errors is investigated and experimental evidence presented. Additionally, ARMA and Hammerstein models are used to find a model capable of predicting the post-catalyst oxygen sensor response over realistic validation data.
Microcantilever-Based Force Tracking With Applications to High-Resolution Imaging and Nanomanipulation
Authors: Saeidpourazar Reza , Jalili Nader
Published: July 2009

This paper presents the development and implementation of a robust nonlinear control framework for piezoresistive nanomechanical cantilever (NMC)-based force tracking with applications to high-resolution imaging and nanomanipulation. Among varieties of nanoscale force sensing platforms, NMC is an attractive approach to measure and apply forces at this scale when compared with other previously reported configurations utilizing complicated MEMS devices or inconvenient-to-handle nanowires and nanotubes. More specifically, a piezoresistive layer is utilized here to measure nanoscale forces at the NMC’s tip instead of bulky laser-based feedback which is commonly used in Atomic Force Microscopy (AFM). In order to track a predefined force trajectory at the NMC’s tip, there is a need to model the piezoresistive NMC and design appropriate controller to move its base to provide the desired force. In previous publications of the authors, a new distributed-parameters modeling framework has been proposed to precisely predict the force acting on the microcantilever’s tip. In contrast to this approach and in an effort to ease the follow-up controller development, the NMC-based force sensor is modeled here as a lumped-parameters system. However, replacing the NMC with a linear mass-spring-damper trio, creates a variety of uncertainties and unmodeled dynamics that need to be addressed for a precise force sensor’s read-out. Moreover, the very slow response of NMC’s piezoresistive layer to force variations at the NMC’s tip, makes the tracking problem even more challenging. For this, a new controller is proposed to overcome these roadblocks. Using extensive numerical simulations and experimental results it is shown that utilizing the proposed controller instead of the commonly used PID controller can significantly enhance the controller’s stability and performance characteristics, and ultimately the imaging resolution and manipulation accuracy needed at this scale.
On Controllability and Observability of Linearized Liquid Water Distributions Inside a PEM Fuel Cell
Authors: McCain Buz A. , Stefanopoulou Anna G. , Butts Kenneth R.
Published: July 2009

We analyze the controllability and observability (C/O) of first principles-based numeric and reduced semi-analytic PEMFC models, with emphasis on the effects of model reduction on these analyses. The numeric model is a partial differential equation (PDE) based model approximated by difference equations, including both channels and both GDL of a PEMFC. The reduced model uses a semi-analytic solution (SAS) method, which is a combination of analytic and numeric solutions, gaining physical intuition at lower computational cost. The C/O analysis is based on linearizations around multiple operating points of the numeric and the semi-analytic models. The results indicate that stabilizability of the anode water states is possible.
Correlating Nitrogen Accumulation With Temporal Fuel Cell Performance
Authors: Mu¨ller Eric A. , Kolb Florian , Guzzella Lino , McKay Denise A. , Stefanopoulou Anna G.
Published: July 2009

The permeability or crossover characteristics of a typical polymeric perfluorosulfonic acid membrane are used for the temporal and spatial estimation of nitrogen concentration along the anode channels of a fuel cell stack. The predicted nitrogen accumulation is then used to estimate the impact of local fuel starvation on stack voltage through the notion of apparent current density. Despite simplifying assumptions on membrane hydration levels, the calibrated model reasonably predicts the response of a 20-cell stack whenever there is no significant liquid water accumulation in the dead-ended anode. Specifically, the predicted voltage decay and estimated anode outlet gas composition are experimentally validated using stack-averaged voltage and a mass spectrometer. This work shows that the crossover of nitrogen and its accumulation in the anode can cause a considerable stack voltage decay and should be considered under high hydrogen utilization conditions.
Algorithm for Closed Loop System Identification Based on Data Correlation
Authors: Jammoussi H. , Franchek M. A. , Grigoriadis K. , Books M.
Published: July 2009

A closed loop system identification method is developed in which estimation bias from sensor noise and external disturbances is minimized. The method, based on the instrumental variables four step algorithm (IV4), uses three steps. The first step estimates a model using cross covariance calculations between the reference input signal and the control and measured output signals. The second step employs the prefilter identification process from the IV4 process. The third and final step uses the prefilter, the instrumental variables and the reference, control and output signals to estimate the final model. The method is demonstrated on a diesel engine where an open loop model relating fueling to engine speed is sought. The identification example is complicated by the presence of nonmeasurable external torque disturbances due to vehicle accessories.
Modeling and Analysis of the Hydraulic System for Oil Budget in an Automotive Transmission
Authors: Miao Hsu-Chiang , Sun Zongxuan , Fair Jonathan , Lehrmann Joshua , Harbin Samuel
Published: July 2009

Many automotive transmissions, including automatic and hybrid transmissions, employ electro-hydraulics for gear shift, system cooling, and lubrication. Transmission oil budget refers to the process of dynamically distributing pressurized fluid from the pump into the sub-systems of the transmission. The oil budget will ultimately determine the transmission pump size and directly impact vehicle fuel economy. It will further affect the dynamic performance of the transmission. Due to large number of components, complex hydraulic circuits, and dynamic operating conditions, estimating transmission oil budget is extremely complex. To obtain a precise oil budget, we need to not only model each hydraulic component accurately, but also analyze the flow requirement in a dynamic fashion. This paper presents the modeling of the transmission hydraulic system and its application for oil budget analysis.
Estimating Air Flow Rates in a Fuel Cell System Using Electrochemical Impedance
Authors: O’Rourke Judith , Arcak Murat , Ramani Manikandan
Published: July 2009

This paper proposes the use of electrochemical impedance spectroscopy (EIS) to estimate the cathode flow rate in a fuel cell system. Through experimental testing of an eight-cell, hydrogen-fueled polymer electrolyte stack, it shows that the ac impedance measurements are highly sensitive to the air flow rates at varying current densities. The ac impedance magnitude at 0.1Hz allows the distinction of air flow rates (stoichiometry of 1.5–3.0) at current densities as low as 0.1A/cm2. Using experimental data and regression analysis, a simple algebraic equation that estimates the air flow rate using impedance measurements at a frequency of 0.1Hz is developed. The derivation of this equation is based on the operating cell voltage equation that accounts for all the irreversibilities.
Path Following Control of Underactuated Marine Vessels via Dynamic Surface Control Technique
Authors: Oh So-Ryeok , Sun Jing , Li Zhen
Published: July 2009

This paper considers the path following problem of underactuated marine vessels whose control imposes a challenging problem due to its under-actuated nature. The recently developed Dynamic Surface Control (DSC) design method is applied to overcome the problem of explosion of terms associated with the backstepping design procedure. We show that the exponential stability of the resulting closed loop dynamics can be proved using Lyapunov direct method. The feasibility of the proposed Dynamic Surface Controller is evaluated analytically and verified through computer simulations and experiments.
Feedback Frameworks for Active Suspensions With Electrohydraulic Actuator Dynamics
Authors: Tyson Serena , Alleyne Andrew
Published: July 2009

Since the initial conception in the late 1960’s, the field of active suspensions for automotive applications has seen numerous research investigations. While there has been a wealth of information previously published, relatively few of these works have incorporated the dynamics of the actuator in their analysis. Including the electrohydraulic actuator dynamics with the plant model introduces the additional effects of the coupling between the actuator and the vehicle body motion. Controller designs using the linearized actuator dynamics typically use a tracking framework. Electrohydraulic systems are limited in their ability to do force or position tracking control when interacting with an environment possessing dynamics such as the 1/4 car model. This paper introduces a novel framework that includes electrohydraulic actuator dynamics in which the tracking problem is replaced by a properly posed regulation problem. Both force regulation and position regulation frameworks are considered and the relative merits/drawbacks of each presented.
Human Motion Modeling With a Robotics Method: Analysis of a Person Riding a Bus
Authors: Deshpande Ashish D. , Luntz Jonathan E.
Published: July 2009

Deriving models of human body motion is important for prosthetics, rehabilitation and development of humanoids. We present a method that simplifies the derivation of equations of motion of human movements. We illustrate our approach by deriving motion models of a person riding in a moving bus. Our approach simplifies the derivation of dynamics as only open chain dynamics are to be derived. The kinematic constraints are then introduced to represent a complete system model in which the contact forces appear explicitly. We then constrain the contact forces based on the performance requirements to determine the feasibility of motions, which is difficult to determine with the traditional methods. Our model allows for the design and control analysis, specifically, the derivation of the relationship between the change in rider’s posture and the feasibility of motions.
Decentralized Dynamic Control of a Nonholonomic Mobile Manipulator Collective: A Simulation Study
Authors: Su Hao , Krovi Venkat
Published: July 2009

In this paper, we present a decentralized dynamic control algorithm for a robot collective consisting of multiple nonholonomic wheeled mobile manipulators (NH-WMMs) capable of cooperatively transporting a common payload. In this algorithm, the high level controller deals with motion/force control of the payload, at the same time distributes the motion/force task into individual agents by grasp description matrix. In each individual agent, the low level controller decomposes the system dynamics into decoupled task space (end-effector motions/forces) and a dynamically-consistent null-space (internal motions/forces) component. The agent level control algorithm facilitates the prioritized operational task accomplishment with the end-effector impedance-mode controller and secondary null-space control. The scalability and modularity is guaranteed upon the decentralized control architecture. Numerical simulations are performed for a 2-NH-WMM system carrying a payload (with/without uncertainty) to validate this approach.
Mobile Multi-Robot Control in Target Search and Retrieval
Authors: Zhang Guoxian , Garg Devendra P.
Published: July 2009

In this paper, the design of a controller is proposed for a multi-robot target search and retrieval system. Inspired by research in insect foraging and swarm robotics, we developed a transition mechanism for the multi-robot system. Environmental information and task performance obtained by the robot system are used to adjust individual robot’s parameters and guide environment exploration. The proposed control system is applicable in the solution of multi-target problem also where several robots may be needed to cooperate together to retrieve a large target. Simulations show that the task performance improves significantly with the proposed method by sharing information in parameter learning and environment exploration.
Sensor Fault Diagnosis of Electro-Mechanical Brake System
Authors: Hwang Woohyun , Han Kwangjin , Huh Kunsoo , Kim Jongki , Kim Joogon , Kim Dongshin
Published: July 2009

The brake-by-wire units such as EMB (Electro-Mechanical Brake) will be applied to the intelligent vehicles because the brake-by-wire units are lighter in weights and have faster response compared to conventional hydraulic brake units. However, the brake-by-wire units such as EMB should be at least as reliable as the conventional hydraulic brake units. Because there are no mechanical links between the brake pedal and brake-by-wire actuators, FDI (Fault detection and isolation) is essential in implementing EMB units. In this study, a model-based fault diagnosis system is developed for monitoring the brake status utilizing the analytical redundancy method. The performance of the proposed model-based fault diagnosis system is verified in simulations in various faulty cases.
Development of Autonomous Cargo Transport for an Unmanned Aerial Vehicle Using Visual Servoing
Authors: Kuntz Noah R. , Oh Paul Y.
Published: July 2009

This paper presents the design and testing of systems for autonomous tracking, payload pickup, and deployment of cargo via a UAV helicopter. The tracking system uses a visual servoing algorithm and is tested using open loop velocity control of a 3DOF gantry system with a camera mounted via a pan-tilt unit on the end effecter. The pickup system uses vision to control the camera pan tilt unit as well as a second pan tilt unit with a hook mounted on the end of the arm. The ability of the pickup system to hook a target is tested by mounting it on the gantry while recorded helicopter velocities are played back by the gantry. A preliminary semi-autonomous deployment system is field tested, where a manually controlled RC truck is transported by a UAV helicopter under computer control that is manually directed to GPS waypoints using a ground station.
Complementary Sensitivity Design of PID Controllers for Arbitrary-Order Transfer Functions With Time Delay
Authors: Emami Tooran , Watkins John M.
Published: July 2009

A graphical technique for finding all proportional integral derivative (PID) controllers that stabilize a given single-input-single-output (SISO) linear time-invariant (LTI) system of any order system with time delay has been solved. In this paper a method is introduced that finds all PID controllers that also satisfy an H∞ complementary sensitivity constraint. This problem can be solved by finding all PID controllers that simultaneously stabilize the closed-loop characteristic polynomial and satisfy constraints defined by a set of related complex polynomials. A key advantage of this procedure is the fact that it does not require the plant transfer function, only its frequency response.
Strain Sensing With Piezoelectric Zinc Oxide Thin Films for Vibration Suppression in Hard Disk Drives
Authors: Felix Sarah , Kon Stanley , Nie Jianbin , Horowitz Roberto
Published: July 2009

This paper describes the integration of thin film ZnO strain sensors onto hard disk drive suspensions for improved vibration suppression for tracking control. Sensor location was designed using an efficient optimization methodology based on linear quadratic gaussian (LQG) control. Sensors were fabricated directly onto steel wafers that were subsequently made into instrumented suspensions. Prototype instrumented suspensions were installed into commercial hard drives and tested. For the first time, a sensing signal was successfully obtained while the suspension was flying on a disk as in normal drive operation. Preliminary models were identified from experimental transfer functions. Nominal H2 control simulations demonstrated improved vibration suppression as a result of both the better resolution and higher sensing rate provided by the sensors.
Single Feedback Model of Human Goal-Directed Movement
Authors: Kwon Oh-Sang , Shelton Jeffrey N. , Chiu George T.-C.
Published: July 2009

Two prominent models frequently used to explain targeted human movement are the stochastic optimized-submovement model and the minimum variance model. Both successfully explain the speed-accuracy tradeoff known as Fitts’ law, but neither is complete. The former cannot predict movement trajectory between the endpoints, while the latter is not congruent with the multiple movement segments often observed in human motion. In this paper, a new model is proposed in which an aimed movement consists of two submovements and a single feedback instant, with the trajectory of each submovement being individually optimized. Simulations using the proposed model show that the optimal transition between two submovements occurs at an early stage of the movement, and produces a sharp peak in the acceleration profile. This result is consistent with psychophysical data. Also observed in numerical simulation is the bell-shaped positional variance curve that is in agreement with psychophysical data.
Co-Design of a MEMS Actuator and Its Controller Using Frequency Constraints
Authors: Peters Diane L. , Kurabayashi Katsuo , Papalambros Panos Y. , Ulsoy A. Galip
Published: July 2009

A MEMS actuator and its controller are jointly optimized, both sequentially and simultaneously. The sequential problem is formulated to account for controllability by means of a constraint on the actuator’s natural frequency. By varying the frequency constraint, sequential optimization generates a set of designs with significantly increased displacement, compared to the original non-optimized design, and with various settling times. In simultaneous optimization, a non-linearly weighted objective function combines the two objectives, and the relative weights are varied. The tradeoff between the two objectives shows that the use of the frequency constraint serves as an effective surrogate for controllability of the actuator.
Decentralized Feedback Structures of a Vapor Compression Cycle System
Authors: Hencey Brandon , Jain Neera , Li Bin , Alleyne Andrew
Published: July 2009

In vapor compression cycle (VCC) systems, it is desirable to effectively control the thermodynamic cycle. By controlling the thermodynamic states of the refrigerant with an inner-loop, supervisory algorithms can manage critical objectives such as maintaining superheat and maximizing the coefficient of performance, etc. In the HVAC industry, it is generally preferred to tune multiple single-input-single-output (SISO) control inner-loops rather than a single multiple-input-multiple-output (MIMO) control inner-loop. This paper presents a process by which a simplified feedback control structure amenable to a decoupled SISO control loop design may be identified. In particular, the many possible candidate input-output pairs for decentralized control are sorted via a decoupling metric, the relative gain array number. From a reduced set of promising candidate input-output pairs, engineering insight is applied to arrive at the final pairings successfully verified on a refrigeration test stand.
The Existence of M and N Matrices in the Generalized Formulation for MIMO QFT
Authors: Lan Chen-Yang , Jayasuriya Suhada
Published: July 2009

Considered in this paper is the question of for what type of multivariable systems is the generalized formulation effective in conditioning the SISO equivalent plants that are pivotal in MIMO QFT design. It is shown by example that for some plant cases there is no benefit to be gained by using the generalized formulation. However, this does not necessarily suggest that no such M and N matrices exist which give desirable SISO equivalent plants. The Smith-McMillan form is used to derive a result for a general nominal MIMO plant. We show that, for any nominal MIMO plant with no unstable blocking poles there exists a pair of M and N matrices such that the resulting conditioned plant yields stable equivalent SISO plants.
Autonomously Operated Power-Dividing Unit for Driveline Modeling and AWD Vehicle Dynamics Control
Authors: Vantsevich Vladimir V. , Shyrokau Barys N.
Published: July 2009

This article presents a math model of a hypothetical driveline power-dividing unit. The use of this model and generalized vehicle parameters made it possible to synthesize a universal (generalized) model of the vehicle’s driveline system that can be used for modeling virtually all the currently known passive as well as active autonomously operated power-dividing units. The salient feature of the developed computational algorithm consists in its capability to autonomously switch the states of active power-dividing units from one to another, i.e., to control the performance of the power-dividing units. An algorithm for controlling the performance of autonomously operated driveline power-dividing units was also developed. The algorithm allows flexibly controlling the flow of power to the drive wheels and improving the AWD vehicle dynamics. As an illustration the article presents some results of simulating the motion of an AWD middle class SUV with three controlled power-dividing units, control of which provides the specified motion of the vehicle.
Robust Control of Time-Delay Systems With Application to a Supercavitating Vehicle
Authors: Mao Xiaofeng , Wang Qian
Published: July 2009

Traditional underwater vehicles are limited in speed due to dramatic friction drag on the hull. A supercavitating vehicle exploits supercavitation to induce a gaseous cavity that contains most part of the vehicle and separates the vehicle hull from its surrounding water. Thus friction drag is substantially reduced. A supercavitating underwater vehicle can achieve very high speed, but also poses technical challenges in stability, control, and maneuvering due to various characteristics such as instability in open-loop dynamics, nonlinearity, cavity memory effect, etc. Among the existing literature on the control design for supercavitating vehicles, the cavity memory effect is often neglected to simplify system dynamics. In this paper, we take into account the cavity memory effect and model the supercavitating vehicle as a time-delay Quasi-Linear-Parameter-Varying system. Then a robust controller is designed to handle the switched, time-delay dependent behavior of the vehicle. The uncertainties considered in the presented control design include both parameter and planing force modeling uncertainties.
Magnet Levitation and Trajectory Following Motion Control Using a Planar Array of Cylindrical Coils
Authors: Berkelman Peter , Dzadovsky Michael
Published: July 2009

We have formulated and implemented a control system for levitation and motion control of a disk magnet using a planar array of electromagnetic coils and an optical localizer to provide real time position feedback. The significance of this work is that this is the first magnetic levitation system which controls the orientation and position of a levitated body throughout a workspace volume whose dimensions are multiples of those of the levitated body in all directions. Furthermore, the horizontal range of motion can be extended indefinitely by adding more coils to the planar array. The potential applications of this levitation system include any robotic manipulation and positioning tasks such as camera and antenna pointing, materials handling and processing, and haptic interaction. Analysis methods, implementation details, and experimental results are given for our current system with a 37.5 mm diameter and 12.5 mm height magnet and 10 actuator coils, providing an 80×60×30 mm range of motion.
Controller Design for Multi-Body Ground Vehicle Rollover Prevention Using Modified LQR Framework
Authors: Yedavalli Rama K. , Huang Hsun-Hsuan
Published: July 2009

This paper addresses the issue of control design for rollover prevention of a multi-body ground vehicle with army applications. The novelty of the approach lies in expressing the traditional rollover index as a quadratic performance index in Linear-quadratic regulator (LQR) design thereby integrating the roll over index directly and explicitly in the optimization procedure. The control gain obtained based on rollover performance index is more effective for rollover prevention than the gain obtained based on standard LQR design in which there is much ambiguity and labor involved in assigning the weights. The control gain obtained based on the proposed rollover performance index outperforms the standard LQR design, essentially because it introduces a cross coupling term between the state and control variables in the modified performance index. Thus, the proposed rollover prevention technique effectively incorporates the physical nature of the vehicle dynamics in the problem formulation resulting in significantly improved performance.
Estimation of Ethanol Content in Flex-Fuel Vehicles Using an Exhaust Gas Oxygen Sensor: Model, Tuning and Sensitivity
Authors: Ahn Kyung-Ho , Stefanopoulou Anna G. , Jankovic Mrdjan
Published: July 2009

Throughout the history of the automobile there have been periods of intense interest in using ethanol as an alternative fuel to petroleum-based gasoline and diesel derivatives. Currently available flexible fuel vehicles (FFVs) can operate on a blend of gasoline and ethanol in any concentration of up to 85% ethanol. In all these FFVs, the engine management system relies on the estimation of the ethanol content in the fuel blend, which typically depends on the estimated changes in stoichiometry through an Exhaust Gas Oxygen (EGO) sensor. Since the output of the EGO sensor is used for the air-to-fuel ratio (AFR) regulation and the ethanol content estimation, several tuning and sensitivity problems arise. In this paper, we develop a simple phenomenological model of the AFR control process and a simple ethanol estimation law which can be representative of the currently practiced system in FFVs. Tuning difficulties and interactions of the two learning loops are then elucidated using classical control techniques. The sensitivity of the ethanol content estimation with respect to sensor and modeling errors is also demonstrated via simulations. The results point to an urgent need for model-based analysis and design of the AFR controller, the ethanol adaptation law and the fault detection issues in FFVs. Tuning and sensitivity issues are demonstrated via simulations and limitations are also discussed.
Computationally Efficient Optimal Power Management for Plug-In Hybrid Electric Vehicles With Spatial Domain Dynamic Programming
Authors: Gong Qiuming , Li Yaoyu , Peng Zhong-Ren
Published: July 2009

The plug-in hybrid electric vehicles (PHEV), utilizing more battery power, has become a next-generation HEV with great promise of higher fuel economy. Global optimization charge-depletion power management would be desirable. This has so far been hampered due to the a priori nature of the trip information and the almost prohibitive computational cost of global optimization techniques such as dynamic programming (DP). Combined with the Intelligent Transportation Systems (ITS), our previous work developed a two-scale dynamic programming approach as a nearly globally optimized charge-depletion strategy for PHEV power management. Trip model is obtained via GPS, GIS, real-time and historical traffic flow data and advanced traffic flow modeling. The main drawback was the dependency of external server for obtaining the macroscale SOC profile, which makes it difficult to handle the impromptu change of driving decision. In this paper, a computationally efficient strategy is proposed based on road segmentation and lookup table methods. Simulation results have shown its great potential for real-time implementation.
Optimal Control of Web Guides Using a New Fiber Optic Edge Sensor
Authors: Seshadri Aravind , Pagilla Prabhakar R.
Published: July 2009

This paper discusses the development of a linear quadratic optimal control algorithm for web guides, and implementation of the control algorithm using web lateral position feedback from a new, experimental fiber optic sensor. The lateral dynamic model of the web and the measurement characteristics of the fiber optic sensor are conducive for a linear quadratic regulator design. The performance of the optimal control algorithm with web lateral position feedback from the fiber optic edge sensor is evaluated by conducting experiments on a web platform. Experiments were also conducted using the same controller but with an existing industrial infrared sensor for web lateral position measurement. Results from a series of comparative experiments indicate that the optimal control algorithm with feedback from the fiber optic sensor provides accurate lateral position regulation in the presence of disturbances, at various web transport speeds, and with web materials with different mechanical, physical and geometric properties. Based on the analysis of the web lateral dynamic model, recommendations for proper guide operation and selection of appropriate web transport conditions for good guiding performance are also discussed.
TOPL: Tools for Operational Planning of Transportation Networks
Authors: Chow A. , Dadok V. , Dervisoglu G. , Gomes G. , Horowitz R. , Kurzhanskiy A. A. , Kwon J. , Lu X.-Y. , Muralidharan A. , Norman S. , Sa´nchez R. O. , Varaiya P.
Published: July 2009

TOPL is a suite of software tools for specifying freeway operational improvement strategies, such as ramp metering, demand and incident management, and for quickly estimating the benefits of such improvements. TOPL is based on the macroscopic cell transmission model. The paper summarizes the theory of the cell transmission model and describes the procedure to carry out a TOPL application. The procedure is illustrated for the 26-mile long I-210W freeway in California, whose model is calibrated using loop detector measurements of volume and speed. The measurements show that congestion originates in a bottleneck and moves upstream, as predicted by the theory. The simulations show that appropriate ramp metering can dramatically reduce total congestion delay and mainline travel time.
A Framework for Multi-Task Formation Control of Nonholonomic Robotic Systems
Authors: Zhang Junjie , Yi Jingang , Jayasuriya Suhada
Published: July 2009

In practical applications, multi-robot systems may have to simultaneously deal with several tasks: collision-free maneuvers in dynamic environments; tracking certain desired trajectories; forming suitable patterns or geometrical shapes, and/or varying the pattern when necessary. The proposed formation control scheme in this paper addresses these issues. First a dynamic model for a nonholonomic robot prototype is developed. Tracking control is then realized by employing input-output feedback linearization. To achieve typical complex formation missions, a two-layer hierarchical architecture is proposed. At the upper layer, a null-space method is utilized to prioritize the tasks of the robot team and to generate reference trajectories for formation control. In the lower layer, the control scheme for each individual robot guarantees asymptotic tracking of the desired trajectories. Numerical simulations of a realistic case study illustrate the effectiveness of the proposed framework.
LPV Control for Synchronous Disturbance Attenuation in Active Magnetic Bearings
Authors: Balini H. M. N. K. , Ko¨rog˘lu H. , Scherer Carsten W.
Published: July 2009

In this research, we consider the problem of suppressing synchronous vibrations in rotors supported by active magnetic bearings. It is observed that the system dynamics are naturally described by an LPV model and the synchronous disturbances are sinusoids with time-varying frequencies. Given this setting, a notion of almost asymptotic regulation is adopted to synthesize LPV controllers. The rotational speed is viewed as the scheduling parameter. The procedure is applied to a model whose parameters are taken from the literature.
Development of Integrated Chassis Control System for Vehicle Handling Enhancement
Authors: Ghike Chinar , Shim Taehyun
Published: July 2009

Various active chassis control systems have been developed to improve vehicle handling and stability. Brake-based electronic stability programs and advanced driveline technologies can distribute different wheel torque to all four wheels to regulate vehicle motion. Active front and rear steer systems are widely used to control the vehicle yaw rate and side slip responses. In addition, active anti-roll bars can improve vehicle handling by adjusting roll moment distribution. This paper proposes an integrated chassis control scheme that combines these individual systems using nonlinear predictive control theory. An 8 degree-of-freedom vehicle model is used with a Magic Formula tire model for controller development. The performance of proposed controller is compared to individual control system through simulation and shows significant improvement in vehicle handling.
Dynamic Threshold Method Based Aircraft Engine Sensor Fault Diagnosis
Authors: Li Wenfei , Yedavalli Rama K.
Published: July 2009

It is challenging to have a good fault diagnostic scheme that can distinguish between model uncertainties and occurrence of faults, which helps in reducing false alarms and missed detections. In this paper, a dynamic threshold algorithm is developed for aircraft engine sensor fault diagnosis that accommodates parametric uncertainties. Using the robustness analysis of parametric uncertain systems, we generate upper-and-lower bound trajectories for the dynamic threshold. The extent of parametric uncertainties is assumed to be such that the perturbed eigenvalues reside in a set of distinct circular regions. Dedicated observer scheme is used for engine sensor fault diagnosis design. The residuals are errors between estimated state variables from a bank of Kalman filters. With this design approach, the residual crossing the upper-and-lower bounds of the dynamic threshold indicates the occurrence of fault. Application to an aircraft gas turbine engine Component Level Model clearly illustrates the improved performance of the proposed method.