bluuebunny/crossref_metadata_2025 huggingface dataset:
Component and Full Scale Tests for Suspension Model Validation
Authors: Mohan Pradeep , Marzougui Dhafer , Kan Cing-Dao , Opiela Kenneth
Published: September 2010

The National Crash Analysis Center (NCAC) at the George Washington University (GWU) has been developing and maintaining a public domain library of LS-DYNA finite element (FE) vehicle models for use in transportation safety research. The recent addition to the FE model library is the 2007 Chevrolet Silverado FE model. This FE model will be extensively used in roadside hardware safety research. The representation of the suspension components and its response in oblique impacts into roadside hardware are critical factors influencing the predictive capability of the FE model. To improve the FE model fidelity and applicability to the roadside hardware impact scenarios it is important to validate and verify the model to multitude of component and full scale tests. This paper provides detailed description of the various component and full scale tests that were performed, specifically, to validate the suspension model of the 2007 Chevrolet Silverado FE model.
Fundamentals of Mass Conservative System Simulation in Fluid Power
Authors: Riedel Christian , Stammen Christian , Murrenhoff H.
Published: September 2010

This article illustrates the development of a dynamic system simulation tool for fluid power on basis of mass flows. The goal is to increase the predictability and efficiency of system simulation tools in fluid power. State of the art simulation tools make use of simplified differential equations. Especially in closed systems or long-term simulations, the volume flow based approach leads to significant variations of simulation results as balancing of flow parameters and its integrations to potentials lead to a violation of the equation of continuity. However, with a mass flow and energy conservative approach we obtain a clear and physically correct model implemented in the simulation tool DSHplus. The new basis of calculation enables further implementation of thermo-hydraulic and multi-phase flow models such as cavitation or particle transport into the concentrated parametric system simulation.
Stiffness and Compliance Control in Dynamical Systems Driven by Muscle-Like Actuators
Authors: Lorussi Federico , Caudai Claudia , De Rossi Danilo , Galatolo Stefano
Published: September 2010

This work reports on the design and the feed forward stiffness control of bioinspired kinematic chains from a static and a dynamic point of view. While position control is clearly referred to common geometrical lagrangian coordinates for the considered system, in order to deal with the stiffness or compliance of the chain, especially in dynamic cases, global and less intuitive variables have to be defined and used. The advantage deriving from a similar control strategy can be important when the chain is part of a complex dynamic system or the computational resources are scarce. By defining and controlling stiffness or compliance for a certain position or trajectory, we can state that, even if the system is not continuously monitored in closed loop, a bounded perturbation cannot produce equilibrium point or trajectory variations greater than a fixed quantity. In a closed loop control strategy, the described methodology can be implemented during the time between two consecutive output sampling and feedback inputs. On the other hand, compliance control permits a kinematic chain to interact with objects without causing damages even if errors in position occur. In this work, the compliance and stiffness concepts, inspired to common reasoning in biological motor control theory, are generalized to a dynamic case and endowed with a mathematical architecture.
Nonlinear Control of NMES: Incorporating Fatigue and Calcium Dynamics
Authors: Sharma N. , Patre P. M. , Gregory C. M. , Dixon W. E.
Published: September 2010

Neuromuscular electrical stimulation (NMES) is a promising technique that has the potential to restore functional tasks in persons with movement disorders. Clinical and commercial NMES products exist for this purpose, but a pervasive problem with current technology is that overstimulation of the muscle (among other factors) leads to muscle fatigue. The objective of the current effort is to develop a NMES controller that incorporates the effects of muscle fatigue through an uncertain function of the calcium dynamics. A neural network-based estimate of the fatigue model mismatch is incorporated in a nonlinear controller through a backstepping based method to control the human quadriceps femoris muscle undergoing non-isometric contractions. The developed controller is proven to yield uniformly ultimately bounded stability for an uncertain nonlinear muscle model in the presence of bounded nonlinear disturbances (e.g., spasticity, delays, changing load dynamics).
Lower Extremity Exoskeleton Reduces Back Forces in Lifting
Authors: Wehner Michael , Rempel David , Kazerooni Homayoon
Published: September 2010

We propose a lower extremity exoskeleton device which adds a passive extensor moment (restoring moment) about the hips during squat lifting, thus reducing forces on the lower back by reducing the required extensor muscle force. Video sequences were recorded of normal speed sagittal squat lifting 44.5 N (10 lb) and 133.5 N (30 lb) packages for marker tracking. Calculations suggested that the device reduces maximum spine compressive forces by approximately 1300 N. Surface electromyography (EMG) was performed on 6 subjects supporting 44.5 N (10 lb) and 133.5 N (30 lb) packages in the static squat posture. With the device, back muscles demonstrated a 54% reduction in muscle activity. This exoskeleton device includes features not available on other devices including highly adjustable moment profile and elimination of high contact stress in the lower extremities by connecting directly with the ground.
A Closed-Loop Strategy of Active Differential Clutch Control
Authors: Ivanovic´ Vladimir , Deur Josˇko , Hancock Matthew , Assadian Francis
Published: September 2010

The paper presents experimentally supported control-oriented analysis of dynamics of an active differential wet clutch actuated by a geared DC motor. A closed-loop clutch control strategy is proposed. The strategy is based on experimentally obtained hysteresis-free clutch applied force vs. motor position curve and related closed-loop motor position control. A controller algorithm is proposed to compensate for the effect of clutch free-play variations due to clutch wear. The proposed control strategy performance is verified on a wet clutch experimental setup.
Individual Muscle Control Using an Exoskeleton Robot for Muscle Function Testing
Authors: Ueda Jun , Hyderabadwala Moiz , Ding Ming , Ogasawara Tsukasa , Krishnamoorthy Vijaya , Shinohara Minoru
Published: September 2010

A functionality test at the level of individual muscles by investigating the activity of a muscle of interest on various tasks may enable muscle-level force grading. This paper proposes a new method for muscle function tests using an exoskeleton robot for obtaining a wider variety of muscle activity data than standard motor tasks, e.g., pushing a handle by his/her hand. A computational algorithm systematically computes control commands to a wearable robot with actuators (an exoskeleton robot, or a power-assisting device) so that a desired muscle activation pattern for target muscle forces is induced. This individual muscle control method enables users (e.g., therapists) to efficiently conduct neuromuscular function tests for target muscles by arbitrarily inducing muscle activation patterns. Simulation results justify the use of an exoskeleton robot for muscle function testing in terms of the variety of muscle activity data.
Optimal Coordination of Mobile Sensor Networks Using Gaussian Processes
Authors: Xu Yunfei , Choi Jongeun
Published: September 2010

In this paper, we introduce a family of spatio-temporal Gaussian processes specified by a class of covariance functions. Nonparametric prediction based on truncated observations is proposed for mobile sensor networks with limited memory and computational power. We show that there is a trade-off between precision and efficiency when prediction based on truncated observations is used. Next, we propose both centralized and distributed navigation strategies for mobile sensor networks to move in order to reduce prediction error variances at positions of interest. Simulation results demonstrate the effectiveness of the proposed schemes.
State Estimator Based Feedback Control for a Metering Poppet Valve System
Authors: Li Chang , Fales Roger
Published: September 2010

In this work, a feedback linearization controller (FLC) is developed for a unique electro hydraulic flow control valve. The valve is a unique design developed at the University of Missouri with two stages: a pilot stage and a main stage which both employ poppet valves rather than more common spool valves. The controller is applied with the aid of the Extended Kalman Filter (EKF). The EKF supplies all the state estimates which are necessary for the installation of the controller in an actual physical system. The simulation results show that the FLC tracks the reference signal accurately and with a fast response. It is also shown that the controller can achieve the tracking task under different operating conditions and has ability to reject system disturbances. From the robustness test, it is shown that an accurate model is necessary for the feedback linearization controller to work.
An Adaptive Weighting Control Strategy to Avoid Magnetic Bearing Contact
Authors: Abulrub Abdul-Hadi G. , Sahinkaya M. Necip , Burrows Clifford R.
Published: September 2010

It was shown in an earlier paper that the authors’ recursive open loop adaptive control strategy can be used as the basis for an adaptive multi-objective control strategy to satisfy design criteria for rotor-bearing systems involving the relative weighting of forces transmitted to the foundation and rotor vibration. This paper describes a complementary-layer adaptive control strategy to limit vibration at critical locations along the rotor, where contact may occur, following changes in operating conditions, e.g. transient disturbances. Experiments are presented to explore the effectiveness of this approach.
Hydraulic Position Control System With Variable Speed Pump
Authors: C¸alıs¸kan Hakan , Balkan Tuna , Platin Bu¨lent E.
Published: September 2010

In this study, a valveless energy saving hydraulic position control servo system controlled by two pumps is investigated. In this system, two variable speed pumps driven by servomotors regulate the flow rate through a differential cylinder according to the needs of the system, thus eliminating the valve losses. The mathematical model of the system is developed in MATLAB Simulink environment. A Kalman filter is applied to reduce the noise in the position feedback signal. In the test set up developed, open loop and closed loop frequency response and step response tests are conducted by using MATLAB Real Time Windows Target (RTWT) module, and test results are compared with the model outputs.
Set-Point Generation Using Kernel-Based Methods for Closed-Loop Combustion Control of a CIDI Engine
Authors: Maringanti Rajaram , Midlam-Mohler Shawn , Fang Ming , Chiara Fabio , Canova Marcello
Published: September 2010

Closed-loop control of diesel combustion is of great interest for improving conventional Diesel engine combustion as well as facilitating new combustion modes such as Homogenous Charge Compression Ignition and other low NOx regimes. Most generalized feedback control systems that can be applied to this problem require a reference or set-point which the control attempts to achieve. Diesel engines are well known for having many degrees of freedom which poses a problem in generating valid set-points for all possible conditions encountered in practice. This problem is compounded by the fact that these set-points are usually determined in steady state operation further limiting the space where set-points can be defined. Kernel-based methods are applied to this problem as a method of generating valid setpoints when operating in regions outside of the space where set-points are defined. This is most useful during transient conditions where conditions such as exhaust gas recycle level, manifold air flow, and fuel mass are far from the steady state values.
Modeling and Diagnostics of Heart Assist Devices
Authors: Wassar Taoufik , Jammoussi Hassene , Borji Rafik , Franchek Matthew A. , Metcalfe Ralph , Benkowski Cedric , Benkowski Robert , Frazier O. Howard , Cohn William E. , Tuzun Egemen , Parnis Steven M.
Published: September 2010

Presented are online adaptive models for ventricular assist devices (VADs). Such devices are used to assist failing hearts or in the case considered here to create a total artificial heart. Adaptive models are developed to estimate cardiac output (CO) and power consumption of the VAD. These parameters are critical to physicians during patient care as well as in diagnosing VAD operation. The online adaptive nature of these models will be used to estimate effective blood viscosity in real-time and to create a mechanism whereby specific VAD diagnostics, important to robust CO delivery, can be identified, isolated and estimated. The experiments conducted were ex-vivo in a mock circulation loop in which the precise nature of the working fluid properties can be controlled and measured.
Air-Fuel Ratio Control of Spark Ignition Engines With TWC Using LPV Techniques
Authors: Zope Rohit A. , Mohammadpour Javad , Grigoriadis Karolos M. , Franchek Matthew
Published: September 2010

Precise control of the air-fuel ratio in a spark ignition (SI) engine is important to minimize emissions. The emission reduction strongly depends on the performance of the air-fuel ratio controller for the SI engine in conjunction with the Three Way Catalytic (TWC) converter. The TWC converter acts as a buffer to any variations occurring in the air-fuel ratio. It stores oxygen during a lean operation and releases the stored oxygen during a rich transient phase. The stored oxygen must be maintained close to the current storage capacity to yield maximum benefits from the TWC converter. Traditionally this is achieved using a simple PI control or a gain-scheduled PI control to address the variability in the operating conditions of the engine. This, however, does not guarantee closed-loop system stability and/or performance. In this work a model-based linear parameter varying (LPV) approach is used to design an H∞ controller. The design goal is to minimize the effect of disturbances on the air-fuel ratio and hence the relative storage level of oxygen in the TWC, over a defined operating range for the SI engine. The design method formulated in terms of Linear Matrix Inequalities (LMIs) leads to a convex optimization problem which can be efficiently solved using existing interior-point optimization algorithms. Simulations performed validate the proposed control design methodology.
Precedent-Free Fault Isolation in a Diesel Engine EGR Valve System
Authors: Cholette Michael E. , Djurdjanovic Dragan
Published: September 2010

In this paper, a framework for isolating unprecedented faults for an EGR valve system is presented. Using normal behavior data generated by a high fidelity engine simulation, the recently introduced Growing Structure Multiple Model System (GSMMS) is used to construct models of normal behavior for an EGR valve system and its various subsystems. Using the GSMMS models as a foundation, anomalous behavior of the entire system is then detected as statistically significant departures of the most recent modeling residuals from the modeling residuals during normal behavior. By reconnecting anomaly detectors to the constituent subsystems, the anomaly can be isolated without the need for prior training using faulty data. Furthermore, faults that were previously encountered (and modeled) are recognized using the same approach as the anomaly detectors.
Tolerant Ethanol Estimation in Flex-Fuel Vehicles During MAF Sensor Drifts
Authors: Ahn Kyung-ho , Stefanopoulou Anna G. , Jankovic Mrdjan
Published: September 2010

Flexible fuel vehicles (FFVs) can operate on a blend of ethanol and gasoline in any volumetric concentration of up to 85% ethanol (93% in Brazil). Existing FFVs rely on ethanol sensor installed in the vehicle fueling system, or on the ethanol-dependent air-to-fuel ratio (AFR) estimated via an exhaust gas oxygen (EGO) or λ sensor. The EGO-based ethanol detection is desirable from cost and maintenance perspectives but has been shown to be prone to large errors during mass air flow sensor drifts [1, 2]. Ethanol content estimation can be realized by a feedback-based fuel correction of the feedforward-based fuel calculation using an exhaust gas oxygen sensor. When the fuel correction is attributed to the difference in stoichiometric air-to-fuel ratio (AFR) between ethanol and gasoline, it can be used for ethanol estimation. When the fuel correction is attributed to a mass air flow (MAF) sensor error, it can be used for sensor drift estimation and correction. Deciding under which condition to blame (and detect) ethanol and when to switch to sensor correction burdens the calibration of FFV engine controllers. Moreover, erroneous decisions can lead to error accumulation in ethanol estimation and in MAF sensor correction. In this paper, we present a cylinder air flow estimation scheme that accounts for MAF sensor drift or bias using an intake manifold absolute pressure (MAP) sensor. The proposed fusion of the MAF, MAP and λ sensor measurements prevents severe mis-estimation of ethanol content in flex fuel vehicles.
Development of an Internet-Distributed Hardware-in-the-Loop Simulation Platform for an Automotive Application
Authors: Ersal Tulga , Brudnak Mark , Salvi Ashwin , Stein Jeffrey L. , Filipi Zoran , Fathy Hosam K.
Published: September 2010

This paper summarizes efforts to integrate, for the first time, two geographically-dispersed hardware-in-the-loop simulation setups over the Internet in an observer-free way. The two setups are the engine-in-the-loop simulation setup at the University of Michigan (UM) in Ann Arbor, MI, USA, and the driver-in-the-loop ride motion simulator at the US Army Tank-Automotive Research, Development and Engineering Center (TARDEC) in Warren, MI, USA. The goal of this integration is to increase the fidelity of experiments and to enable concurrent engineering. First, a model-based simulation of the setup is utilized to analyze the effects of variable delay, an intrinsic characteristic of the Internet, on the integrated system, particularly in terms of stability, robustness, and transparency. Then, experiments with the actual hardware are presented. The conclusion is that the two pieces of hardware can indeed be integrated over the Internet without relying on observers in a stable and subjectively transparent manner, even if the nominal delay is increased by four times.
Nonlinear Interaction Force Analysis of Microcantilevers Utilized in Atomic Force Microscopy
Authors: Eslami Sohrab , Jalili Nader , Passian Ali , Tetard Laurene , Thundat Thomas
Published: September 2010

This paper presents an Euler-Bernoulli microcantilever beam model utilized in non-contact Atomic Force Microscopy (AFM) systems. A distributed-parameters modeling is considered for such system. The motions of the microcantilever are studied in a general Cartesian coordinate with an excitation at the base such that beam end with a tip mass is subject to a general force. This general force comprising of two attractive and repulsive parts with high power terms is taken as the atomic intermolecular one which has a relation with the displacement between the tip mass and the surface such that the total general force will be in the form of an implicit nonlinear equation. It is most desired to observe the effects of the base excitation in high frequencies on the tip van der Waals interaction force. Hence, the general force will produce a peak in the FFT spectrum corresponding to the frequency of the base.
Nonlinear Stability Analysis of Vehicle Lateral Motion With a Hybrid Physical/Dynamic Tire/Road Friction Model
Authors: Yi Jingang , Tseng Eric H.
Published: September 2010

We present a nonlinear analysis of vehicle motion using a hybrid physical/dynamic tire/road friction model. The advantage of the proposed LuGre dynamic tire/road friction model is the simple and attractive structural properties for real-time friction estimation and control. Moreover, the model provides a property of capturing coupling effects between the longitudinal and lateral friction forces. We take advantages of these properties and analyze the vehicle lateral motion stability. We have shown that the existence of longitudinal slip affects the lateral motion stability. The quantitative analysis and relationship are also demonstrated through numerical simulation examples.
Combinatorial Motion Planning for a Dubins Vehicle With Precedence Constraints
Authors: Oberlin Paul , Rathinam Sivakumar , Darbha Swaroop
Published: September 2010

This paper considers a combinatorial motion planning problem of finding a shortest tour for a Dubins’ vehicle that must visit a given set of targets and return to its initial depot while satisfying the motion constraints of the vehicle and the precedence constraints. Precedence constraints restrict the sequence in which a Dubins’ vehicle visits the given set of targets by imposing a partial ordering on the sequence in which the targets must be visited. This problem arises in applications involving fixed wing, Unmanned Aerial Vehicles (UAVs) where the vehicles have fuel and motion constraints. A fixed wing UAV may be modeled as a Dubins’ vehicle that can travel at a constant speed and has an upper bound on its turning rate. This is a difficult problem because it couples the combinatorial problem of optimally visiting a set of targets with the path planning problem of finding the shortest path that satisfies the motion constraints given the sequence in which the targets must be visited. In this paper, the sequence in which the targets must be visited is obtained by solving the combinatorial problem using a split dual algorithm. Using this sequence, the path planning problem is solved using Dynamic Programming. Computational results are given to corroborate the performance of the algorithms.
Identification in Iterative Learning Control: A Model Based, Iteration Varying Learning Filter for Precision Control
Authors: Fine Benjamin T. , Stearns Hoday , Tomizuka Masayoshi
Published: September 2010

Linear Iterative Learning Control (ILC) algorithms have been known to also perform well for nonlinear systems whose dominant system dynamics are linear. In order for the learning filter to take advantage of more system information, we propose here a model based ILC algorithm which uses an iteration varying learning filter. Before the next iteration’s feedforward control is computed, the linearized system model is first estimated using a least squares approximation. We implement this algorithm on a wafer stage prototype whose dominant system dynamics are linear with a weak nonlinear actuator disturbance. Because the nonlinear disturbance is state dependent, the linear dynamics will shift as the ILC algorithm is converging. We show that as the system converges to the desired trajectory the plant parameter also converge.
Cross Coupled Iterative Learning Control of Dissimilar Dynamical Systems
Authors: Barton Kira , Hoelzle David , Alleyne Andrew , Wagoner Johnson Amy
Published: September 2010

Cross Coupled Iterative Learning Control (CCILC) has previously been applied to contour tracking problems with planar robots in which both axes can be characterized as similar systems; having similar dynamics and identical hardware. However, there are many repetitive applications in which dissimilar systems cooperate to pursue a primary performance objective. This paper introduces a novel framework to couple dissimilar systems while applying Iterative Learning Control (ILC), showing the ability to noncausally compensate for a slow system with a fast system. In this framework, performance requirements for a primary objective can more readily be achieved by emphasizing an underutilized fast system instead of straining a less-capable slow system. The controller is applied in simulation and experimentally to a micro-Robotic Deposition (μRD) manufacturing system to coordinate a slow extrusion system axis and a fast positioning system axis to pursue the primary performance objective, dimensional accuracy of a fabricated part. Experimental results show a 30% improvement in fabrication dimensional accuracy with only marginal changes in actuator effort in the slow system, as compared to independently controlled axes.
A Control System for Hill Start Assistance for Commercial Vehicles
Authors: Delvecchio Diego , Savaresi Sergio M. , Spelta Cristiano , Dozio Simone , Mandrioli Leonardo , Cantoni Carlo
Published: September 2010

The topic of this paper is the design and analysis of a control strategy for a hill starting assistance for commercial vehicles equipped with an electric parking brake (EPB). The present hill start assistance system is thought to be installed in a vehicle with manual transmission and it is based on a very simple and low complexity hardware layout. The hill start strategy herein proposed is based on events detection: the detection of the torque transmission from the engine to the wheels and the detection the vehicle movement before the EPB -release. Although all the possible scenarios cannot be tackled, because of the layout constraints and of the presence of the driver in the control loop, the effectiveness of the proposed framework has been experimentally tested.
Anti-Windup LPV Control of Magneto-Rheological Dampers
Authors: Meisami-Azad Mona , Mohammadpour Javad , Grigoriadis Karolos M.
Published: September 2010

In this paper, we develop a linear parameter varying (LPV) model for the structural systems including the Magneto-Rheological (MR) dampers where the LPV parameter is the MR damper velocity. We then propose an LPV anti-windup control design method to prevent the closed-loop system instability and performance degradation due to the MR damper actuator saturation. The proposed control design method accounts for the actuator nonlinearities by representing the status of the saturated actuator as an additional gain-scheduled varying parameter. The resulting controller is scheduled with respect to the system operating parameter and the actuator saturation parameter. Simulation results demonstrate that the anti-windup compensator scheduled based on the MR damper velocity and the saturation parameter is able to keep the voltage within the specified limits and meets the design requirement of rejecting the effect of the external disturbance signals.
Optimality Assessment of Equivalent Consumption Minimization Strategy for PHEV Applications
Authors: Tulpule Pinak , Stockar Stephanie , Marano Vincenzo , Rizzoni Giorgio
Published: September 2010

This paper deals with optimization algorithms for energy management of Plug-in Hybrid Electric Vehicles (PHEVs). In order to maximize fuel economy of a PHEV, the battery should attain its lowest admissible state of charge at the end of the driving cycle by following an optimal State of Charge (SOC) profile. Finding this optimal profile is a challenging optimization problem and requires prior knowledge of the entire driving cycle. There are many different optimization methods that can be applied to the energy management of PHEVs and they are usually classified into two main categories according to the optimality of their solutions. In general, in order to obtain the global optimum, the complete knowledge of future driving conditions is needed. This requirement renders unfeasible the on-line implementation of such strategies. On the other hand, simpler algorithms which are on-board implementable, do not provide the optimal solution. In this paper, a global optimal strategy — Dynamic Programming, is considered as a benchmark for evaluating the performance of an onboard implementable strategy — Equivalent Consumption Minimization Strategy with linearly decreasing reference SOC’. The study is conducted on an energy-based model of a parallel hybrid powertrain developed in Matlab/Simulink environment. The model and each powertrain components are validated based on road tests and laboratory data for a Chevrolet Equinox (hybridized at The Ohio State University Center for Automotive Research). The optimality assessment considers two main metrics, namely fuel economy and deviations from the optimal SOC profile. Simulations are carried out by considering different driving scenarios and battery sizes. Results show that for longer distances and bigger batteries, Equivalent Consumption Minimization Strategy and Dynamic Programming provide similar fuel economy and SOC profiles.
Role of Trip Information Preview in Fuel Economy of Plug-In Hybrid Vehicles
Authors: Zhang Chen , Vahidi Ardalan , Li Xiaopeng , Essenmacher Dean
Published: September 2010

This paper investigates the role of partial or complete knowledge of future driving conditions in fuel economy of Plug-in Hybrid Vehicles (PHEVs). We show that with the knowledge of distance to the next charging station only, substantial reduction in fuel use, up to 18%, is possible by planning a blended utilization of electric motor and the engine throughout the entire trip. To achieve this we formulate a modified Equivalent Consumption Minimization Strategy (ECMS) which takes into account the traveling distance. We show further fuel economy gain, in the order of 1–5%, is possible if the future terrain and velocity are known; we quantify this additional increase in fuel economy for a number of velocity cycles and a hilly terrain profile via deterministic dynamic programming.
Spatial Detection of Areas of Abrupt Change by Robotic Networks
Authors: Gao Hanqiao , Corte´s Jorge
Published: September 2010

This paper studies robotic sensor networks performing spatial detection of areas of rapid change in physical phenomena. We encode the task by means of an objective function, called wombliness, which measures the change of the spatial field along the open polygonal curve defined by the positions of the robotic sensors. This curve can become self-intersecting when evolving along the gradient flow of the wombliness. Borrowing tools from discontinuous dynamics and hybrid systems, we design an algorithm that allows for network re-positioning, splitting, and merging, while guaranteeing the monotonic evolution of the wombliness. We analyze its convergence properties and illustrate our approach in simulations.
Modeling and Validation of a High Speed Rotary PWM On/Off Valve
Authors: Tu Haink C. , Rannow Michael B. , Wang Meng , Li Perry Y. , Chase Thomas R.
Published: September 2010

Efficient high-speed on/off valves are a critical technology for enabling digital control of hydraulic systems via pulse-width-modulation (PWM). High-speed valves, when used in virtually variable displacement pumps (VVDP), increase system bandwidth and reduce output pressure ripple by enabling higher PWM frequencies. Our approach to achieving high speed and large flow area with low actuation power is a unidirectional rotary valve designed specifically for PWM. In comparison to conventional valves, the rotary valve reduces valve actuation power from a cubic dependence on PWM frequency to a square dependence by eliminating motion reversals during transition. This paper presents experimental data that validates the rotary valve concept, valve design equations, and dynamic model of a rotary valve based VVDP. Our unoptimized prototype exhibits 65% efficiency at 50% displacement and 15Hz PWM frequency while the validated model projects that an optimized valve is capable of achieving 85% efficiency at 15Hz and 73% at 75Hz.
Analysis and Control of Halbach Linear Motor for Nanopositioning
Authors: Wang Yigang , Chu Kevin C. , Tsao Tsu-Chin
Published: September 2010

This paper presents control of a Halbach linear motor for nano-precision positioning. Using an FPGA based decoding scheme and sensor signal processing, a 0.23nm root-mean-square (RMS) sensor noise level has been obtained from a 4 micrometer period sinusoidal quadrature encoder. Disturbances to the linear motor are studied at nanometer scale. When the motor is supported by the air bearing without feedback control, the mechanical motion measured by the sensor shows substantial low frequency oscillation around 10Hz. Under a PID digital servo feedback control, the stage can be brought to a regulated state of 11.14nm RMS error at 10kHz sampling rate, otherwise not achieved by lower sampling rate. Although PID servo loop substantially reduces the 10Hz motion, a 60Hz vibration and its harmonics begin to dominate at nanometer level. It is suspected and confirmed by experiments to be due to the coupling of the DC power supply/amplifier and control computer to the AC power source. A robust repetitive control scheme is employed to reject the 60Hz disturbance and its harmonics and bring the regulated state to 1.78nm RMS value.
Limitations of Employing Undirected Information Flow Graphs for the Maintenance of Rigid Vehicular Formations
Authors: Darbha Swaroop , Pagilla Prabhakar R.
Published: September 2010

In this paper, we consider the problem of decentralized control of a collection of homogeneous vehicles trying to maintain a rigid formation. Each vehicle attempts to maintain a specified constant safe distance from its adjacent vehicles in the collection. We consider an identical structure for each decentralized controller so that it is simpler from an implementation viewpoint as it does not depend on collection size or vehicle indices. We call a vehicle B adjacent to vehicle A if the relative position of vehicle B is known to vehicle A either by communication or by sensing. In this paper, we only consider undirected information flow graphs, i.e., graphs where vehicle A is adjacent to vehicle B if and only if vehicle B is adjacent to vehicle A. We consider a point mass model for each vehicle and assume the actuation transfer function, which relates the control input to the force supplied to the vehicle, to be a strictly proper rational transfer function. It is known that spacing errors due to disturbances amplify if the reference vehicle information is not available to Ω(n) vehicles, n being the size of the collection [1]. In this paper, we generalize this result to show the following: If there are two or more vehicles in the collection that are adjacent to Ω(n) vehicles, then there is a critical size N* so that the motion of the collection will be unstable if the size of the collection exceeds N*. Practical issues of fault tolerance indicate that there be at least two vehicles that are adjacent to Ω(n) vehicles in the collection. We also further show that the use of a kinematic vehicle model for analysis of disturbance propagation yields results which may not agree with what is observed in practice and hence are inappropriate.
Indirect Adaptive Robust Control of Uncertain Systems With Unknown Asymmetric Input Deadband Using a Smooth Inverse
Authors: Mohanty Amit , Yao Bin
Published: September 2010

In this paper, we present an indirect adaptive robust controller (IARC) for output tracking of a class of uncertain nonlinear systems with unknown input asymmetric deadband in presence of uncertain nonlinearities and parametric uncertainties. Most of the parameter adaptation algorithms, such as, gradient-type and least squares-type require that the unknown parameters of a system appear in affine with known regressor functions globally. However, deadband nonlinearity can not be represented in those global linear parametric form. Therefore, the existing parameter estimation algorithms for deadband focus on some approximate linear parametric model. Hence, even in absence of any other uncertain nonlinearities and disturbances, these algorithms can never achieve asymptotic tracking. Departing from those approximate deadband estimation, we design an indirect parameter estimation algorithm with online condition monitoring. This parameter estimation algorithm in conjunction with a well-designed robust controller and a deadband inverse function can be used to obtain asymptotic tracking without restoring to discontinuous control law. With this strong result in our repertoire, we proceed to design a smooth deadband inverse (SDI) function to avoid certain problems during implementation, e.g, control input chattering and significant appearance of high-frequency dynamics. The effect of such an approximation on the L2-norm of output tracking error is analytically determined. We also show that while operating away from the deadband, the proposed controller even with an SDI can achieve asymptotic tracking. In presence of disturbances and other uncertain nonlinearities, the proposed IARC controller attains guaranteed transient performance and final tracking accuracy.
Analysis of Hybrid Electric/Thermofluidic Control for Wet Shape Memory Alloy Actuators
Authors: Flemming Leslie , Mascaro Stephen
Published: September 2010

A wet SMA actuator is characterized by an SMA wire embedded within a compliant fluid-filled tube. Heating and cooling of the SMA wire produce a linear contraction and extension of the wire. Thermal energy can be transferred to and from the wire using combinations of resistive heating and free/forced convection using hot and cold fluid. The goal of this paper is to analyze the speed and efficiency of wet SMA actuators using a variety of control strategies involving different combinations of electrical and thermofluidic inputs. A computational fluid dynamic model is used in conjunction with a temperature-strain model to simulate the thermal response of the wire and compute strains, contraction/extension times and efficiency. The simulations produce cycling rates of up to 5 Hz for electrical heating and fluidic cooling, and up to 2 Hz for fluidic heating and cooling. The results demonstrate efficiencies up to 0.5% for electric heating and up to 0.2% for fluidic heating.
Optimal-Control Methods for Design of Two-Degree-Freedom Systems for Nanopositioning
Authors: Lee C. , Salapaka S.
Published: September 2010

This paper presents, reviews, compares, and analyzes optimal-control methods for designing two-degree-of-freedom (2DOF) control laws for nanopositioning. The different methods are motivated by various practical scenarios and difficulty in achieving simultaneously multiple performance objectives of resolution, bandwidth, and robustness by tuning-based or shaping-of-open-loop-plants based designs. In this context, we study fundamental trade-offs between these performance objectives in 2DOF control designs for nanopositioning systems. In particular, in terms of the trade-offs, our analysis shows that the primary role of feedback is providing robustness to the closed-loop device whereas the feedforward component is mainly effective in overcoming fundamental algebraic constraints that limit the feedback-only designs. Experimental results indicate substantial improvements (over 200% in bandwidth) when compared to optimal feedback-only controllers.
Enhanced electron-field emission from nanodiamond ridge-structured emission arrays capped on micropatterned silicon pillars
Authors: Ghosh N. , Kang W. P. , Davidson J. L. , Raina S.
Published: September 2010

In this article, the authors report the fabrication and observation of electron-field emission from nanodiamond ridge structure array capped on micropatterned silicon pillars. The fabrication process began with a deposition of 1.5-μm-thick ridge-structured diamond on a highly conductive n-type silicon substrate using microwave-plasma-enhanced-chemical-vapor deposition followed by patterning and reactive-ion etching techniques to get the device structure, which is an array of 50×50 silicon pillars capped with ridge-structured nanodiamond. Scanning electron microscope image confirms the device structure. The electron-field emission, performed in vertical-diode configuration, demonstrated a low threshold turn-on field of 1.2 V/μm and a high emission current of 150 μA at the anode field of 5.5 V/μm. The emission behavior has been compared with that of planar film of identical nanodiamond morphology. A 6000 times increase in current density is observed and attributed to its better geometrical-enhancement factor.
OWA-BASED NONLINEAR MATHEMATICAL PROGRAMMING APPROACH TO FUZZY MULTI-ATTRIBUTE GROUP DECISION MAKING WITH LINGUISTIC VARIABLES
Authors: LI DENG-FENG
Published: September 2010

The purpose of this paper is to develop a nonlinear programming model and method for solving fuzzy multi-attribute group decision making (FMAGDM) problems with linguistic variables. In this methodology, alternatives are assessed on qualitative attributes using linguistic terms from the designated linguistic term set, which can be expressed with the triangular fuzzy number set designated a priori. Alternatives for decision makers are assessed on the basis of the distances between the ordered weighted averaging (OWA) comprehensive value and the group best alternative which is unknown a priori. The group best alternative is then estimated through solving an auxiliary nonlinear programming model based on the concept that the sum of the distances of alternatives from the group best alternative for the decision makers should be as small as possible. The obtained group best alternative can be expressed using the designated triangular fuzzy numbers, which are corresponding to the designated linguistic terms. A numerical example is examined to demonstrate the difference between the proposed method and the generalized induced OWA operator method.
THE EXISTENCE OF A MAJORITY RULE MAXIMAL SET IN ARBITRARY n-DIMENSIONAL SPATIAL MODELS
Authors: MORDESON JOHN N. , CLARK TERRY D.
Published: September 2010

We examine the effect of indifference on the existence of a majority rule maximal set. In our setting, it is shown in all but a limited number of cases that the maximal set is empty in an n-dimensional spatial model if and only if the Pareto set contains a union of cycles. The elements that constitute the exception are completely characterized.
Recent Advances in Heat Transfer Enhancements: A Review Report
Authors: Siddique M. , Khaled A.-R. A. , Abdulhafiz N. I. , Boukhary A. Y.
Published: September 2010

Different heat transfer enhancers are reviewed. They are (a) fins and microfins, (b) porous media, (c) large particles suspensions, (d) nanofluids, (e) phase-change devices, (f) flexible seals, (g) flexible complex seals, (h) vortex generators, (i) protrusions, and (j) ultra high thermal conductivity composite materials. Most of heat transfer augmentation methods presented in the literature that assists fins and microfins in enhancing heat transfer are reviewed. Among these are using joint-fins, fin roots, fin networks, biconvections, permeable fins, porous fins, capsulated liquid metal fins, and helical microfins. It is found that not much agreement exists between works of the different authors regarding single phase heat transfer augmented with microfins. However, too many works having sufficient agreements have been done in the case of two phase heat transfer augmented with microfins. With respect to nanofluids, there are still many conflicts among the published works about both heat transfer enhancement levels and the corresponding mechanisms of augmentations. The reasons beyond these conflicts are reviewed. In addition, this paper describes flow and heat transfer in porous media as a well-modeled passive enhancement method. It is found that there are very few works which dealt with heat transfer enhancements using systems supported with flexible/flexible-complex seals. Eventually, many recent works related to passive augmentations of heat transfer using vortex generators, protrusions, and ultra high thermal conductivity composite material are reviewed. Finally, theoretical enhancement factors along with many heat transfer correlations are presented in this paper for each enhancer.
Sharp Power Mean Bounds for the Combination of Seiffert and Geometric Means
Authors: Chu Yu-Ming , Qiu Ye-Fang , Wang Miao-Kun
Published: September 2010

We answer the question: forα∈ (0, 1), what are the greatest valuepand the least valueqsuch that the double inequalityMp(a,b) <Pα(a,b)G1−α(a,b)  0 witha≠b. Here,Mp(a,b),P(a,b), andG(a,b) denote the power of orderp, Seiffert, and geometric means of two positive numbersaandb, respectively.
Generalized Superposition Modulation and Iterative Demodulation: A Capacity Investigation
Authors: Schlegel Christian , Burnashev Marat , Truhachev Dmitri
Published: September 2010

Modulation with correlated signal waveforms is considered. Such correlation arises naturally in a number of modern communications systems and channels, for example, in code‐division multiple‐access (CDMA) and multiple‐antenna systems. Data entering the channel in parallel streams either naturally or via inverse multiplexing is transmitted redundantly by adding additional signal waveforms populating the same original time‐frequency space, thus not requiring additional bandwidth or power. The transmitted data is spread over a frame of N signaling intervals by random permutations. The receiver combines symbol likelihood values, calculates estimated signals and iteratively cancels mutual interference. For a random choice of the signal waveforms, it is shown that the capacity of the expanded waveform set is nondecreasing and achieves the capacity of the Gaussian multiple access channel as its upper limit when the number of waveforms becomes large. Furthermore, it is proven that the iterative demodulator proposed here can achieve a fraction of 0.995 or better of the channel capacity irrespective of the number of transmitted data streams. It is also shown that the complexity of this iterative demodulator grows only linearly with the number of data streams.
Effectively Monitoring the Performance of Integrated Process Control Systems under Nonstationary Disturbances
Authors: Kandananond Karin
Published: September 2010

The objective of this paper is to quantify the effect of autocorrelation coefficients, shift magnitude, types of control charts, types of controllers, and types of monitored signals on a control system. Statistical process control (SPC) and automatic process control (APC) were studied under non-stationary stochastic disturbances characterized by the integrated moving average model, ARIMA (0,1,1). A process model was simulated to achieve two responses, mean squared error (MSE) and average run length (ARL). A factorial design experiment was conducted to analyze the simulated results. The results revealed that not only shift magnitude and the level of autocorrelation coefficients, but also the interaction between these two factors, affected the integrated system performance. It was also found that the most appropriate combination of SPC and APC is the utilization of the minimum mean squared error (MMSE) controller with the Shewhart moving range (MR) chart, while monitoring the control signal (X) from the controller. Therefore, integrating SPC and APC can improve process manufacturing, but the performance of the integrated system is significantly affected by process autocorrelation. Therefore, if the performance of the integrated system under non-stationary disturbances is correctly characterized, practitioners will have guidelines for achieving the highest possible performance potential when integrating SPC and APC.