bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrically-Assisted Forming of Magnesium AZ31: Effect of Current Magnitude and Deformation Rate on Forgeability
Authors: Jones Joshua J. , Mears Laine , Roth John T.
Published: May 2012

Currently, the automotive and aircraft industries are considering increasing the use of magnesium within their products due to its favorable strength-to-weight characteristics. However, the implementation of this material is limited as a result of its formability. Partially addressing this issue, previous research has shown that electrically-assisted forming (EAF) improves the tensile formability of magnesium sheet metal. While these results are highly beneficial toward fabricating the skin of the vehicle, a technique for allowing the use of magnesium alloys in the production of the structural/mechanical components is also desirable. Given the influence that EAF has already exhibited on tensile deformation, the research herein focuses on incorporating this technique within compressive operations. The potential benefit of using EAF on compressive processes has been demonstrated in related research where other materials, such as titanium and aluminum, have shown improved compressive behavior. Therefore, this research endeavors to amalgamate these findings to Mg AZ31B-O, which is traditionally hard to forge. As such, to demonstrate the effects of EAF on this alloy, two series of tests were performed. First, the sensitivity of the alloy to the EAF process was determined by varying the current density and platen speed during an upsetting process (flat dies). Then, the ability to utilize impression (shaped) dies was examined. Through this study, it was shown for the first time that the EAF process increases the forgeability of this magnesium alloy through improvements such as decreased machine force requirements and increased achievable deformation. Additionally, the ability to form the desired final specimen geometry was achieved. Furthermore, this work also showed that this alloy is sensitive to any deformation rate changes when utilizing the EAF process. Last, a threshold current density was noted for this material where significant forgeability improvements could be realized once exceeded.
Femtosecond Laser-Induced Simultaneous Surface Texturing and Crystallization of a-Si:H Thin Film: Absorption and Crystallinity
Authors: Wang Hongliang , Kongsuwan Panjawat , Satoh Gen , Lawrence Yao Y.
Published: May 2012

Hydrogenated amorphous silicon (a-Si:H) thin films have been considered for use in solar cell applications because of their significantly reduced cost. Their overall efficiency and stability, however, are less than that of their bulk crystalline counterparts. Limited work has been performed on solving the efficiency and stability issues of a-Si:H simultaneously. In this study, both surface texturing and crystallization on a-Si:H thin film are achieved through one-step femtosecond laser processing. The nanoscale conical and pillar-shaped spikes formed on the surface of a-Si:H films by femtosecond laser irradiation in both air and water are presented and enhanced light absorption is observed due to light trapping based on surface geometry changes, while the formation of a mixture of hydrogenated nanocrystalline silicon (nc-Si:H) and a-Si:H after crystallization suggests that the overall material stability can potentially be increased. The relationship among crystallinity, fluence, and scan speed is also discussed. Furthermore, a comparison of absorptance spectra for various surface morphologies is developed. Finally, the absorptance measurement across the solar spectrum shows that the combination of surface texturing and crystallization induced by femtosecond laser processing is very promising for a-Si:H thin film solar cell applications.
Effect of Severe Plastic Deformation in Machining Elucidated via Rate-Strain-Microstructure Mappings
Authors: Shekhar S. , Abolghasem S. , Basu S. , Cai J. , Shankar M. R.
Published: May 2012

Machining induces severe plastic deformation (SPD) in the chip and on the surface to stimulate dramatic microstructural transformations which can often result in a manufactured component with a fine-grained surface. The aim of this paper is to study the one-to-one mappings between the thermomechanics of deformation during chip formation and an array of resulting microstructural characteristics in terms of central deformation parameters–strain, strain-rate, temperature, and the corresponding Zener–Hollomon (ZH) parameter. Here, we propose a generalizable rate-strain-microstructure (RSM) framework for relating the deformation parameters to the resulting deformed grain size and interface characteristics. We utilize Oxley’s model to calculate the strain and strain-rate for a given orthogonal machining condition which was also validated using digital imaging correlation-based deformation field characterization. Complementary infrared thermography in combination with a modified-Oxley’s analysis was utilized to characterize the temperature in the deformation zone where the SPD at high strain-rates is imposed. These characterizations were utilized to delineate a suitable RSM phase-space composed of the strain as one axis and the ZH parameter as the other. Distinctive one-to-one mappings of various microstructures corresponding to an array of grain sizes and grain boundary distributions onto unique subspaces of this RSM space are shown. Building on the realization that the microstructure on machined surfaces is closely related to the chip microstructure derived from the primary deformation zone, this elucidation is expected to offer a reliable approach for controlling surface microstructures from orthogonal machining.
Enhanced Laser Shock by an Active Liquid Confinement—Hydrogen Peroxide
Authors: Liao Yiliang , Yang Yingling , Cheng Gary J.
Published: May 2012

This letter investigates a unique process to generate enhanced laser shock by applying an active liquid confinement—hydrogen peroxide (H2O2). The mechanism of fast chemical etching-assisted laser ablation is proposed. As a result, comparing with utilizing water as confinement, the efficiency of laser shock peening (LSP) of aluminum alloy 6061 with an active liquid confinement is improved by 150%, and the ablation rate of pulse laser ablation (PLA) of zinc is enhanced by 300%. This method breaks the major limitation of underwater pulsed laser processing caused by the breakdown plasma, with additional mechanisms to generate higher ablation rate and shock pressure under the same laser intensities.
Novel Form-Finding of Tensegrity Structures Using Ant Colony Systems
Authors: Chen Yao , Feng Jian , Wu Yongfen
Published: May 2012

Tensegrity structures have remarkable configurations and are drawing the attention of architects and engineers. They possess inextensional mechanisms and self-stress states at a static equilibrium configuration under no external loads. For geometry with its nodes fixed, different connectivity patterns of the compression bars and tension cables might bring some novel tensegrity structures. Thus, form-finding is the key to designing novel tensegrity structures. Here, we develop a discrete optimization model for the form-finding and convert it into a modified traveling salesman problem (TSP). The ant colony system (ACS) is used to search for feasible solutions, where all the predetermined nodes are taken as different cities in the network. An objective function that considers the stability and the relative stiffness is developed to obtain the optimized configurations of tensegrity structures. Examples based on some regular geometries (including a hexagon and two polyhedra) and two nonregular geometries are carried out using the proposed technique. Many different configurations of the pin-jointed assemblies are transformed into interesting tensegrity structures. To verify the proposed method, some physical models are constructed and compared to the tensegrity structures obtained from the form-finding process. We conclude that this novel algorithm can be applicable to the form-finding of both regular and nonregular tensegrity structures.
The Theoretical Bandwidth Frequency of a Three-Way Hydromechanical Valve
Authors: Manring Noah D. , Zhang Shusen
Published: May 2012

In this paper, the dynamic characteristics of the three-way hydromechanical valve are studied using numerical and analytical techniques. The full nonlinear model for this valve is derived by taking into consideration the capacitance of the downstream load chamber and the fluid momentum effects acting on the valve. Using non-dimensional analysis it is shown that the higher order dynamics of the valve itself are negligible compared to other forces acting on the valve, and that the transient flow-forces are also of negligible size. Using this information, a reduced order model is developed for studying the bandwidth frequency in closed form and for employing perturbation techniques to identify the relative impact of various design changes for the valve. In conclusion it is shown that the most significant design change that can be made for increasing the bandwidth frequency of the valve is to reduce the load capacitance by either shrinking the load-chamber volume or increasing the fluid bulk modulus. The impact of other design perturbations is also discussed including the effect of increasing the overall valve size, the supply pressure to the valve, and the mechanical spring rate.
Trip Specific Worthiness of Replacement of Individual Cells for Battery Pack in Electric Vehicles
Authors: Ugle Rohit , Li Yaoyu
Published: May 2012

Ever increasing acceptance of electric vehicles relies on better operation and control of large battery packs. The individual cells in the large battery packs cannot have identical characteristics and may degrade differently due to its manufacturing variability and other factors. It is beneficial to evaluate the performance gain by replacing certain battery modules/cells during actual driving. We have a two-fold objective for this research. First, we are developing an on-line battery module degradation diagnostic scheme using the intrinsic signals of a battery pack equalization circuit. Therefore, a battery “health map” can be constructed and updated in real time. Secondly, based on the derived battery health map, the performance of the battery pack will be evaluated for customer specified trip so as to evaluate the “worthiness of replacing” certain modules/cells.
Stability of a Consensus Protocol for Second Order Agents With Multiple Time Delays
Authors: Cepeda-Gomez Rudy , Olgac Nejat
Published: May 2012

In this study we consider the consensus problem for a group of second order agents interacting under a fixed, undirected communication topology. Communication lines are affected by two rationally independent delays. The first delay is assumed to be in the position information channels whereas the second one is in the velocity information exchange. The delays are assumed to be uniform throughout the entire network. We first reduce the complexity of the problem, by performing a state transformation that allows the decomposition of the characteristic equation of the system into a set of second order factors. The stability of the resulting subsystems is analyzed exactly and exhaustively in the domain of the time delays using the Cluster Treatment of Characteristic Roots (CTCR) paradigm. CTCR is a recent method which declares the stability features of the system for any composition of the time delays. Example cases are provided to verify the analytical conclusions.
Design and Analysis of a Localization Method Using a Laser Sensor for Indoor Wheeled Mobile Robots
Authors: Govindarajan Madhu Soodhanan , Wang Junmin , Post Bill , Fox Andrew
Published: May 2012

A new approach to localize an indoor wheeled mobile robot (WMR) using a low-cost laser sensor is proposed. An onboard laser sensor moving inside a guide way is used to recognize the unique pattern of a target, by virtue of which the vehicle is localized globally. A kinematic model is developed, which determines the vehicle orientation and location with respect to the center of the target object. Here, the design parameters of the target and guide way lengths are analyzed in terms of their influence on the localization accuracy in the presence of noise in measurements. The kinematic model and the design parameter analysis are validated by the simulation results.
Estimation of Time-Delays Using the Characteristic Roots of Delay Differential Equations
Authors: Yi Sun , Yu Sangseok
Published: May 2012

In this short paper, the preliminary result of a new method for estimation of time-delays of time-delay systems is presented. The presented method makes use of the Lambert W function, and is for scalar first-order delay differential equations (DDEs). Possible extension to general systems of DDEs and application to physical systems are also discussed.
Optimal Constrained Balancing Control of a Standing Biped
Authors: Sun Yuming , Wu Qiong
Published: May 2012

Balancing control is important for biped locomotion. In spite of large efforts, it is extremely difficult to design balancing control strategies for a standing biped satisfying the following three requirements simultaneously: maintaining postural stability, improving energy efficiency and guaranteeing satisfaction of the constraints between the biped feet and the ground. In this paper, a proportional-derivative (PD) controller developed from the genetic algorithm (GA) satisfying all three requirements is proposed for a standing biped, which is simplified as a two-link inverted pendulum with one additional rigid foot-link. The simulation results show that with the proposed controller the biped can be maintained at the upright position with the minimal energy consumption, and the constraints between the foot-link and the ground are satisfied during quiet standing. By using the concept of Lyapunov exponents (LEs), the stability analysis of the controlled biped is provided. Morever, structural stability of the biped subject to the different control gains is also investigated, and parts of the stability regions in the parametric space of control gains are identified. The paper contributes to the biped balancing control, which is significant to the development of biped robots.
A Comparison Between Model-Based and Data-Driven Design of an Active Stability Control System for Two-Wheeled Vehicles
Authors: De Filippi Pierpaolo , Formentin Simone , Savaresi Sergio M.
Published: May 2012

The design of an active stability control system for two-wheeled vehicles is a fully open problem and it constitutes a challenging task due to the complexity of two-wheeled vehicles dynamics and the strong interaction between the vehicle and the driver. This paper describes and compares two different methods, a model-based and a data-driven approach, to tune a Multi-Input-Multi-Output controller which allows to enhance the safety while guaranteeing a good driving feeling. The two strategies are tested on a multibody motorcycle simulator on challenging maneuvers such as kick-back and strong braking while cornering at high speed.
H
2-H∞ Control of Discrete Time Nonlinear Systems Using the SDRE Approach
Authors: Wang Xin , Yaz Edwin E. , Schneider Susan C. , Yaz Yvonne I.
Published: May 2012

A novel H2–H∞ State Dependent Riccati Equation control approach is presented for providing a generalized control framework to discrete time nonlinear system. By solving a generalized Riccati Equation at each time step, the nonlinear state feedback control solution is found to satisfy mixed performance criteria guaranteeing quadratic optimality with inherent stability property in combination with H∞ type of disturbance attenuation. Two numerical techniques to compute the solution of the resulting Riccati equation are presented: The first one is based on finding the steady state solution of the difference equation at every step and the second one is based on finding the minimum solution of a linear matrix inequality. The effectiveness of the proposed techniques is demonstrated by simulations involving the control of an inverted pendulum on a cart, a benchmark mechanical system.
VSC Approach Angle Based Boundary Layer Thickness: A New Variation Law and Its Stability Proof
Authors: Carneiro J. Falca˜o , de Almeida F. Gomes
Published: May 2012

A major drawback on the use of sliding mode controllers is their inherent intense control activity. A usual strategy to cope with this problem is to use a boundary layer around the switching surface. The boundary layer thickness choice is based on a compromise between smoothness in the control action and tracking error. Since this compromise may be difficult to achieve, several boundary layer thickness variation laws (BLTVL) have been proposed in literature. In a recent study [1] an interesting BLTVL was proposed, based on the approach angle of the state to the switching surface. Although innovative, that study does not provide a proof of the stability of the controller. Furthermore, the BLTVL definition varies according to the system order and sliding surface definition. This paper extends the work done in [1] by presenting a new BLTVL based on a generalised definition of the approach angle that can be applied to systems of any order using any sliding surface. Furthermore, an innovative stability proof of a variable structure controller (VSC) using the new BLTVL is provided. Experimental results obtained in a servopneumatic system validate the usefulness of this approach.
Trade-Off Between Fuel Economy and Battery Life for Hybrid Electric Vehicles
Authors: Ebbesen Soren , Guzzella Lino
Published: May 2012

In this paper, we adopted a simple yet useful capacity fade model of a Li-ion battery for a hybrid electric vehicle application. Its simple structure permitted us to embed it in the formulation of the optimal energy management control problem, which we solved using dynamic programming. In this way, we were able to study the trade-off between globally optimal fuel economy and battery life. This trade-off was quantified in terms of total cost of fuel and battery projected to the entire vehicle life. Furthermore, a sensitivity analysis was performed to investigate the influence of time-varying fuel and battery prices on total cost of ownership.
Model Complexity Requirements in Design of Half Car Active Suspension Controllers
Authors: Wakeham Keith J. , Rideout D. Geoff
Published: May 2012

This paper investigates the appropriate level of model complexity when designing optimal vehicle active suspension controllers using the Linear Quadratic Regulator (LQR) method. The LQR method requires the formulation of a performance index with weighting factors to penalize the three competing objectives in suspension design: suspension travel (rattle space), sprung mass acceleration (ride quality) and tire deflection (road-holding). The optimal control gains are determined from the solution of a matrix Riccati equation with dimension equal to the number of state variables in the model. A quarter car model with four states thus poses a far less onerous formulation problem than a half or full car model with eight or more states. However, half and full car models are often assumed to be more accurate than quarter car models, and necessary for capturing and controlling degrees of freedom such as pitch and roll motion which are not directly available from a quarter car. The vertical acceleration, pitch acceleration and roadholding of a pitch plane vehicle are controlled in this paper using both quarter and half car-based controllers. First, optimal gains are calculated for each of the front and rear actuators assuming that the front and rear of the vehicle can be separately modeled as quarter cars with four states each. Then, half car-based optimal gains, based on feedback of eight states for the entire vehicle, are computed. Using quarter car-based controllers at the front and rear of a half car gives superior performance in reducing sprung mass inertial acceleration, and can effectively control pitch motion even when interactions between front and rear suspensions are not decoupled. Minimizing vertical motion of the front and rear ends indirectly regulates pitch motion. Improvements resulting from the additional complexity of the half car-based controller are seen only when the weighting factor for pitch suppression is very high in the performance index.
Adaptive Cancelation of Matched Unknown Sinusoidal Disturbances for LTI Systems by State Derivative Feedback
Authors: Bas¸tu¨rk Halil I˙. , Krstic Miroslav
Published: May 2012

Solutions already exist for the problem of canceling sinusoidal disturbances by measurement of state or an output for linear and nonlinear systems. In this paper, we design an adaptive controller to cancel matched sinusoidal disturbances forcing a linear time-invariant system by using only measurement of state-derivatives. Our design is based on three steps; 1) parametrization of the sinusoidal disturbance as the output of a known feedback system with an unknown output vector, 2) design of an adaptive disturbance observer and, 3) design of an adaptive controller. We prove that the equilibrium of the closed-loop adaptive system is globally uniformly asymptotically stable and locally exponentially stable. The effectiveness of the controller is illustrated with a simulation example of a second order system.
Design and Control of a Compact Light-Weight Planar Positioner Moving Over a Concentrated-Field Magnet Matrix
Authors: Nguyen Vu Huy , Kim Won-jong
Published: May 2012

In this paper, a single-moving-part planar positioner with 6 coils is designed and implemented. A concentrated-field permanent-magnet matrix is employed as the stationary part. The moving platen has a compact size (185.4 mm × 157.9 mm), light mass (0.64 kg) and low center of mass. The moving platen carries three planar-motor armatures with two phases per motor. Force calculation is based on the Lorentz force law and conducted by volume integration. In order to deal with the nonlinearity due to trigonometric terms in the force-current relation, modified PID (proportional-integral-derivative) and lead-and-PI controllers are designed with computed currents to close the control loop and obtain the desired performances. Experimental results verify the commutation law and the force calculation. The new design with only 6 coils allows for simplification of the control algorithm and reduced power consumption of the positioner. The maximum travel ranges in x, y, and the rotation about the vertical axis are 15.24 cm, 20.32 cm, and 12.03°, respectively. The positioning resolution in x and y is 8 μm with the root-mean-square (rms) position noise of 6 μm. The positioning resolution in rotations about the vertical axis is 100 μrad.
An E/H Control Design for a Hydraulic Variable Displacement Axial Piston Motor
Authors: Du Hongliu
Published: May 2012

A simple and novel speed control scheme for variable displacement motors has been developed under the consideration of some system uncertainties. Theoretical analysis and experimental test results have shown that the proposed control strategy is capable of driving the swashplate to track its desired trajectory with robust stability and satisfactory performance. An adaptive learning algorithm enables the controls to automatically adjust for uncertainties in the control bias current. Compared with its hydro-mechanical counterpart, the provided E/H control results in a hydraulic variable displacement motor with lower cost and better performance.
An Intelligent Nonlinear System Identification Method With Robust State Estimation
Authors: Kolodziej Jason R.
Published: May 2012

An approach is presented for nonlinear system identification by combining a proven state estimation technique, Minimum Model Error (MME) estimation, with a feed-forward neural network. The MME/NN hybrid algorithm first determines from measurement data a smooth state estimate of the system as well as identifying a correction to the assumed system model. Next, the state estimates are then used as training data for the neural network’s representation of the unmodeled system dynamics. The performance is then shown to be an improvement over a stand alone black-box neural network.
Energy Efficient Variable Pressure Valve-Controlled Hydraulic Actuation
Authors: Scopesi Marco , Plummer Andrew , Du Can
Published: May 2012

The subject of this paper is a VPVC (variable pressure valve-controlled) hydraulic actuation system, which is a hydraulic plant with variable supply pressure. The concept is similar to a load sensing system but it is implemented using an electronic controller, instead of a hydraulic one, and the flow is provided using a servo pump, instead of a variable displacement pump. The intention is to maintain a high dynamic response but substantially improve efficiency compared to a conventional system with fixed supply pressure. FPVC (fixed pressure valve-controlled) systems are unable to completely modulate the input energy due to the constant supply pressure. However, since the ability to control the energy flow is usually needed, a proportional valve for each actuator is used to dissipate the extra input energy. This leads to a simple but inefficient way to control, for example, the velocity of a piston. The idea of a VPVC system is that, instead of dissipating energy by throttling flow, it is better to generate less fluid power in the first place: this is achieved by adjusting the speed of the servo pump as well as the spool positions. In this paper, a controller for a VPVC system is presented along with numerical simulations showing a comparison with a fixed pressure system. Up to 70% energy saving is predicted.
Physics Based Control Oriented Modeling of Exhaust Gas Enthalpy for Engines Utilizing Variable Valve Actuation
Authors: Koeberlein Ed , Kocher Lyle , Van Alstine Dan , Stricker Karla , Shaver Greg
Published: May 2012

Accurate calculation of the conditions (i.e., temperature, pressure, and enthalpy) of internal combustion engine cylinder exhaust is critical to the modeling of, and control design development for, gas exchange in modern and future diesel engine systems. In this paper, a physically-based model for cylinder exhaust temperature, pressure, and enthalpy for engines equipped with variable valve actuation is outlined and extensively validated against experimental data from 193 operating points. The model takes the known conditions when the intake valves close and steps through a polytropic compression process, constant pressure combustion process beginning at top-dead center, and a polytropic expansion process to achieve the desired results when the exhaust valves open. To incorporate the flexibility of modulating the intake valve opening and closing, the effective compression ratio is used to establish the conditions when the intake valves close. Experimental model validation, via a unique multi-cylinder diesel engine utilizing fully flexible intake valve actuation, shows that the model captures the influences of all of the model inputs: engine speed, charge flow, total fueling quantity, intake manifold pressure, and effective compression ratio.
MPPT and Integrated Diagnostics for Multi-String PV System With Multi-Input ESC
Authors: Lei Peng , Li Yaoyu , Seem John E.
Published: May 2012

Multi-string configuration is commonly seen in practical photovoltaic (PV) applications, to secure the Maximum Power Point (MPP) for each string, individual string is equipped with its own DC-DC converter for voltage regulation. This study presents an integrated framework that achieves dual purposes simultaneously: maximum power point tracking (MPPT) control and detection of the change in internal resistance. An multi-channel extremum seeking control (ESC) strategy is developed to maximize the power output of multi-string PV system by regulating the voltage input to the DC-DC converter, overall MPPT can be obtained by delivering the power from strings to the DC bus. Simulation results show that the ESC can achieve multi-string overall MPPT with periodic dither signals such as sinusoidal and square wave signals. As change in internal resistance is coupled with many degradation factors for the PV cell, e.g. increase in the series resistance and decrease in the shunt resistance, the capability of integrated detection of internal resistance can be used as a diagnostic probe for PV online diagnostics. Square Wave ESC dither signal is a useful tool to detect the change of internal resistance as the rise time or settling time on a square wave rising edge is more amplified with internal change of a PV system. Therefore, the voltage output transient under square-wave dithering can be changed remarkably with degradation induced change of internal resistance. Simulation results have also confirmed such correlation. The ESC with square wave dithering can thus provides the dual benefits of MPPT and internal resistance change simultaneously.
Numerical Simulation of Electromechanical Dynamics in Paced Cardiac Tissue
Authors: Xia Henian , Zhao Xiaopeng , Wong Kwai
Published: May 2012

We study electromechanical dynamics in paced cardiac tissue using numerical simulations of a mathematical model that accounts for excitation-contraction coupling as well as mechanoelectrical feedback. A previously developed finite element based parallel platform is adopted. Extensive numerical simulations are carried out on a 2d tissue and a 3d tissue to investigate the influences of various parameters on the stability of propagating cardiac waves, including conduction velocity, pathological scars, contraction, and stretch activated channels.
Dynamic Model of Dual Clutch Lever-Based Electromechanical Actuator
Authors: Ivanovic´ Vladimir , Deur Josˇko , Milutinovic´ Milan , Tseng H. Eric
Published: May 2012

The paper presents a dynamic model of a dual clutch lever-based electromechanical actuator. Bond graph modeling technique is used to describe the clutch actuator dynamics. The model is parameterized and thoroughly validated based on the experimental data collected by using a test rig. The model validation results are used for the purpose of analysis of the actuator behavior under typical operating modes.
Design and Implementation of an Ionic-Polymer-Metal-Composite Aquatic Biomimetic Robot
Authors: Chang Yi-chu , Kim Won-jong
Published: May 2012

Smart materials have been used in various applications. In this paper, a walking robot with six two-degree-of-freedom (2-DOF) legs made of ionic polymer metal composite (IPMC) is designed and implemented. Each leg can work as both a supporter and a driver, closely mimicking a real insect. To support and drive the robot, thicker (around 1 mm in thickness) IPMC strips were fabricated and used, and a 0.2-rad/s square wave is given as an input signal. The IPMC strips exhibit better performance in response to the square wave (8 mm) than sawtooth (4 mm) and sinusoidal (6 mm) waves in deflection. By applying this input signal in sequence, all the IPMC strips bend and walk in the form of six legs. In addition, thin magnet wires were used to supply power to each strip to prevent from confining the motion of our robot. Six lower legs are divided into two groups that work in the opposite directions to move the robot forward by turns. Upper legs are also divided into two groups to lift up their lower legs from making the robot to move back to the same place. The sizes of the IPMC strips and our robot (102 mm × 80 mm × 43 mm) were decided to exhibit better performance (0.5 mm/s) according to our tests.
Terrain-Aided Localization Using Feature-Based Particle Filtering
Authors: Kadetotad Sneha , Vemulapalli Pramod K. , Brennan Sean N. , Lagoa Constantino
Published: May 2012

The localization of vehicles on roadways without the use of a GPS has been of great interest in recent years and a number of solutions have been proposed for the same. The localization of vehicles has traditionally been divided by their solution approaches into two different categories: global localization which uses feature-vector matching, and local tracking which has been dealt by using techniques like Particle Filtering or Kalman Filtering. This paper proposes a unifying approach that combines the feature-based robustness of global search with the local tracking capabilities of a particle filter. Using feature vectors produced from pitch measurements from Interstate I-80 and US Route 220 in Pennsylvania, this work demonstrates wide area localization of a vehicle with the computational efficiency of local tracking.
Three-Dimensional Large Deformation of a Compliant Beam Designed for a Flexonic Mobile Node
Authors: Guo Jiajie , Xie Yang , Lee Kok-Meng
Published: May 2012

This paper presents design and analysis of a flexonic mobile node (FMN) for structural health monitoring. Unlike rigid configurations with a fixed distance between the front and rear axles, this FMN features various deformable configurations in three-dimensional (3D) space by incorporating a compliant beam (connecting the front and rear axles with a controlled pin joint). Hence, this FMN has more flexibility to negotiate corners and attach sensors on ferromagnetic structures. These functions are facilitated by the guidance of an embedded vision controlled system. Controlling a continuous compliant beam is a challenging task in terms of nonlinear deformation with infinite degrees of kinematic redundancy. Detailed discussion focuses on a theoretical beam model for simulating its 3D deformed shape. Results include the relations between input/output displacements and rotation angle for control implementation in sensor attachment and corner negotiation. Experiment is provided for model validation by comparing with the analysis for sensor attachment.
Mobile Exoskeleton for Spinal Cord Injury: Development and Testing
Authors: Strausser Katherine A. , Swift Timothy A. , Zoss Adam B. , Kazerooni H. , Bennett Bradford C.
Published: May 2012

For those who have lost the ability to walk due to paralysis or other injuries, eLEGS, a mobile robotic exoskeleton, offers the chance to walk again. The device is a mobile exoskeleton with actuated sagittal plane hip and knee joints which supports the user and moves their legs through a natural gait. The device uses a multi-leveled controller that consists of a state machine to determine the user’s intended motion, a trajectory generator to establish desired joint behavior, and a low level controller to calculate individual joint controller output. The system can be controlled by a physical therapist or can be controlled by the user. Subject testing results are presented from a seven subject pilot study including patients with complete and incomplete injuries. The testing resulted in six of the seven subjects walking unassisted using forearm crutches after a single two hour testing session.
Control Design Amenable Model of Needle Position for a Direct Acting Piezoelectric Fuel Injector
Authors: Ruikar Neha S. , Satkoski Chris A. , Shaver Greg
Published: May 2012

Piezo electric injectors provide a means to lower emissions, noise and fuel consumption in advanced IC engines, by providing the capability to allow for tightly spaced injections and rate shaping. With a focus on generating a control design amenable model capturing the injector needle dynamics, the effort described here includes a model simplification and reduction strategy of an experimentally validated, physics-based 13 state model of a direct acting piezo electric injector. The resulting reduced order model for needle dynamics is validated for both single and multi pulse conditions.
A Neighboring Optimal Controller for Disturbance Rejection During Vehicle Evasive Maneuvers
Authors: Soudbakhsh Damoon , Eskandarian Azim , Chichka David
Published: May 2012

This paper presents design of a neighboring optimal controller for vehicle evasive maneuvers. The developed controller is tested in presence of varying and constant side force disturbances. A model of wind side force is presented and the controller is tested. On simulated vehicle maneuver cases, the controller shows good disturbance rejection capabilities. The controller is able to perform the maneuver even in presence of 30 m/s (67 mph) wind gust with less than 1cm of error. Also, testing the controller with different bank angles shows that even with 10% bank angle the vehicle performs the maneuver with only 5 cm of error.
Quantized Particle Swarm Optimization: An Improved Algorithm Based on Group Effect and Its Convergence Analysis
Authors: Liu Zhenyi , Deshpande Sagar , Hui Qing
Published: May 2012

In this article a new simple-structure variation of Particle Swarm Optimization (PSO) algorithm is proposed. Since the standard PSO has a very good performance, the new variation retains many properties of standard PSO such as stochasticity and some other properties similar to those in Evolutionary Algorithms. However, unlike the standard PSO algorithm, in the new algorithm the particles can not only communicate with each other via the objective function but, via a new variable named “quantizer”, and hence, the new algorithm is labeled as the Quantized Particle Swarm Optimization algorithm. In addition, extensive simulations are given to show the advantages of the new algorithm over the standard PSO. Finally, the convergence analysis for deterministic version of the new algorithm is also presented.
Dubins Vehicle Tracking of a Target With Unpredictable Trajectory
Authors: Anderson Ross , Milutinovic´ Dejan
Published: May 2012

Motivated by a fixed-speed, fixed-altitude Unmanned Aerial Vehicle (UAV), we seek to control the turning rate of a planar Dubins vehicle that tracks an unpredictable target at a nominal standoff distance. To account for all realizations of the uncertain target kinematics, we model the target motion as a planar random walk. A Bellman equation and an approximating Markov chain that is consistent with the stochastic kinematics is used to compute an optimal control policy that minimizes the expected value of a cost function based on the nominal distance. Our results illustrate that the control can further be applied to a class of continuous, smooth trajectories with no need for further computation.
On the Stability of Swarm Consensus Under Noisy Control
Authors: Rogers Bruce , Fricke Gregory K. , Garg Devendra P.
Published: May 2012

Representation of a swarm of independent robotic agents under graph-theoretic constructs allows for more formal analysis of convergence properties. We consider the local and global convergence behavior of an N-member swarm of agents in a modified consensus problem wherein the connectivity of agents is governed by probabilistic functions. The addition of a random walk control ensures ε-stability of the swarm consensus. Simulation results are given to show the rate of convergence to consensus and planned experiments are described.
Long-Range Temporal Correlations, Multifractality, and the Causal Relation Between Neural Inputs and Movements
Authors: Gao Jianbo , Zheng Yi , Hu Jing
Published: May 2012

Understanding the causal relation between neural inputs and movements is very important for the success of brain machine interfaces (BMIs). In this study, we perform systematic statistical and information theoretical analysis of neuronal firings of 104 neurons, and employ three different types of fractal and multifractal techniques (including Fano factor analysis, multifractal detrended fluctuation analysis (MF-DFA), and wavelet multifractal analysis) to examine whether neuronal firings related to movements may have long-range temporal correlations. We find that MF-DFA and wavelet multifractal analysis (but not Fano factor analysis) clearly indicate that when neuronal firings are not well correlated with movement trajectory, they do not have or only have weak temporal correlations. When neuronal firings are well correlated with movements, they are characterized by very strong temporal correlations, up to a time scale comparable to the average time between two successive reaching tasks. This suggests that neurons well correlated with hand trajectory experienced a “re-setting” effect at the start of each reaching task. We further discuss the significance of the coalition of those important neurons in executing cortical control of prostheses.
Fast Monitoring of Epileptic Seizures Based on Recurrence Time Analysis of EEGs
Authors: Gao Jianbo , Hu Jing
Published: May 2012

Epilepsy is one of the most common disorders of the brain. Currently, studies of epileptic seizures often involve tedious and time-consuming visual inspection of multi-channel long EEG data by medical experts. To better monitor seizures and make medications more effective, we propose a recurrence time based approach to characterize brain electrical activity. Unlike many other nonlinear methods, the proposed approach does not require that the EEG data be chaotic and/or stationary. It only contains a few parameters that are largely signal-independent, and hence, is very easy to use. The method detects epileptic seizures with accuracy close to 100% (when subclinical seizures are not counted) and false alarm rate per hour close to 0. Most critically, the method is very fast: with an ordinary PC (CPU speed less than 2 GHz), computation of the recurrence time from one channel EEG data of duration one hour with sampling frequency of 200 Hz takes about 1 minute CPU time. Therefore, with an ordinary PC, the method is able to process all 28 channels of 1-hour EEG data in about half an hour, and thus faster than the data being continuously collected. The method can also effectively monitor propagation of seizures in the brain. Therefore, it has the potential to be an excellent candidate for real-time monitoring of epileptic seizures in a clinical setting.
Mobile Robot Navigation in Hilly Terrain Using Reinforcement Learning Techniques
Authors: Tennety Srinivas , Kumar Manish
Published: May 2012

Mobile robot navigation in unknown, unstructured environments such as hilly terrains is often complex due to uncertainties associated with classification of terrain features as traversable or non-traversable and identification of paths between start and goal that pose minimum danger to the robot during navigation. Humans possess an uncanny ability to identify paths under the presence of uncertainties and determine whether a terrain feature is safe to traverse or not. Therefore, it is beneficial if such human knowledge is taken advantage of when available. This paper discusses the use of reinforcement learning techniques for navigation in hilly type terrains with and without the human assistance. When a prior knowledge such as low resolution aerial view about the terrain is available, a human expert can suggest paths that are relatively safe to traverse. A value matrix is developed using those expert paths that could be used by the robot to steer from any start position in the terrain to the goal position. Matlab based simulations have been carried out and the results have been presented for robot navigation in a terrain in the presence of multiple expert suggested paths.
Modeling and Feedback Control of Inspired Oxygen for Premature Infants
Authors: Keim Timothy , Amjad Ramak , Fales Roger
Published: May 2012

Premature infants are commonly treated for respiratory problems due to their underdeveloped lungs. Due to Respiratory Distress Syndrome, the infant requires mechanical ventilation or increased inspired oxygen. If the blood oxygen saturation is kept a too high of a level, the infant is at risk for retinopathy of prematurity. A safe level for the infant’s blood oxygen saturation is between 85–92%. An automatic control system would aid nurses in care of premature infants. Since each infant is different, the control system must be robust enough to achieve adequate control of the percentage of oxygen in inspired air administered to the patient. Clinical data is acquired from patient bedside monitors. A parameter estimating extended Kalman filter assuming a first order model is applied to the data to calculate a range of system gains and time constants. An error model is then created using the resulting ranges of parameters. Performance specifications are defined and a μ-synthesis controller is developed to automatically control the oxygen percentage of inspired air. The control system is analyzed using H∞ methods to determine whether robust stability and robust performance are achieved in the presence of system uncertainty described by the error model.
Simulation and Experimental Analysis of a Portable Powered Ankle-Foot Orthosis Control
Authors: Li Yifan , Shorter K. Alex , Hsiao-Wecksler Elizabeth T. , Bretl Timothy
Published: May 2012

A portable powered ankle-foot orthosis (PPAFO) was previously developed using off-the-shelf pneumatic components to explore new opportunities for fluid power in human assist devices. The untethered pneumatically powered ankle-foot orthosis provides both motion control and torque assistance at the ankle via a binary, event-based control scheme that uses solenoid valves. While stable, the binary actuation of the solenoid valves that results from this approach limits the overall performance of the system. This paper addresses the limitations of the current system using a modeling approach for both hardware and control design. Hardware and control configurations were first evaluated using simulations of the modeled PPAFO and shank-foot system during a simplified functional gait task: assistive propulsive torque during stance. These simulations demonstrated that the introduction of a proportional valve and new control architecture resulted in PPAFO performance improvements during the task. These results were then confirmed experimentally with the PPAFO attached to a physical model of a shank and foot.
Friction Fault Detection of an Electrohydrostatic Actuator
Authors: Gadsden S. A. , Song Y. , McCullough K. R. , Habibi S. R.
Published: May 2012

This article discusses the application of a novel model-based fault detection method. The method is based on the interacting multiple model (IMM) strategy, which makes use of a finite number of known operating modes. A filter is used in conjunction with the IMM in order to estimate the states and parameters of the system. The smooth variable structure filter (SVSF) is a relatively new estimation strategy, and is based on sliding mode concepts which introduces an inherent amount of robustness and stability. The combined SVSF-IMM strategy is applied on an electrohydrostatic actuator (EHA), which is a device used in the aerospace industry. Two different operating modes were created, based on varying degrees of friction acting on the EHA cylinder. The results of the friction fault detection were compared with the popular Kalman filter (KF) based IMM strategy.
Estimating Dynamics On-the-Fly Using Monocular Video
Authors: Agarwal Priyanshu , Kumar Suren , Corso Jason J. , Krovi Venkat
Published: May 2012

We present an optimization framework to help estimate on-the-fly both the motion and physical parameters of an articulated multibody system using uncalibrated monocular image sequences. The algorithm takes video images of a physical system as input and estimates the motion together with the physical system parameters, given only the underlying articulated model topology. A valid initial pose of the system is found using a sequential optimization framework and used to bootstrap the successive pose estimation as well as estimation of physical system parameters (kinematic/geometric lengths as well as mass, inertia, damping coefficients). We also address the issue of robustly estimating a dynamically-equivalent system using partial state information (solely from noisy visual observations) and without explicit inertial parameter information. This framework results in a robust dynamically-equivalent system with good predictive capabilities when tested on a double pendulum system.