bluuebunny/crossref_metadata_2025 huggingface dataset:
Prediction of Rotordynamic Performance of Smooth Stator-Grooved Rotor Liquid Annular Seals Utilizing Computational Fluid Dynamics
Authors: Mortazavi Farzam , Palazzolo Alan
Published: November 2017

Circumferentially grooved, annular liquid seals typically exhibit good whirl frequency ratios (WFRs) and leakage reduction, yet their low effective damping can lead to instability. The current study investigates the rotordynamic behavior of a 15-step groove-on-rotor annular liquid seal by means of computational fluid dynamics (CFD), in contrast to the previous studies which focused on a groove-on-stator geometry. The seal dimensions and working conditions have been selected based on experiments of Moreland and Childs (2016, “Influence of Pre-Swirl and Eccentricity in Smooth Stator/Grooved Rotor Liquid Annular Seals, Measured Static and Rotordynamic Characteristics,” M.Sc. thesis, Texas A&M University, College Station, TX). The frequency ratios as high as four have been studied. Implementation of pressure-pressure inlet and outlet conditions make the need for loss coefficients at the entrance and exit of the seal redundant. A computationally efficient quasi-steady approach is used to obtain impedance curves as functions of the excitation frequency. The effectiveness of steady-state CFD approach is validated by comparison with the experimental results of Moreland and Childs. Results show good agreement in terms of leakage, preswirl ratio (PSR), and rotordynamic coefficients. It was found that PSR will be about 0.3–0.4 at the entrance of the seal in the case of radial injection, and outlet swirl ratio (OSR) always converges to values near 0.5 for current seal and operational conditions. The negative value of direct stiffness coefficients, large cross-coupled stiffness coefficients, and small direct damping coefficients explains the destabilizing nature of these seals. Finally, the influence of surface roughness on leakage, PSR, OSR, and stiffness coefficients is discussed.
Chip Morphology and Chip Formation Mechanisms During Machining of ECAE-Processed Titanium
Authors: Davis Brian , Dabrow David , Newell Ryan , Miller Andrew , Schueller John K. , Xiao Guoxian , Liang Steven Y. , Hartwig Karl T. , Ruzycki Nancy J. , Sohn Yongho , Huang Yong
Published: November 2017

Severe plastic deformation (SPD) processing such as equal channel angular extrusion (ECAE) has been pioneered to produce ultrafine grained (UFG) metals for improved mechanical and physical properties. However, understanding the machining of SPD-processed metals is still limited. This study aims to investigate the differences in chip morphology when machining ECAE-processed UFG and coarse-grained (CG) titanium (Ti) and understand the chip formation mechanism using metallographic analysis, digital imaging correlation (DIC), and nano-indentation. The chip morphology is classified as aperiodic saw-tooth, continuous, or periodic saw-tooth, and changes with the cutting speed. The chip formation mechanism of the ECAE-processed Ti transitions from cyclic shear localization within the low cutting speed regime (such as 0.1 m/s or higher) to uniform shear localization within the moderately high cutting speed regime (such as from 0.5 to 1.0 m/s) and to cyclic shear localization (1.0 m/s). The shear band spacing increases with the cutting speed and is always lower than that of the CG counterpart. If the shear strain rate distribution contains a shift in the chip flow direction, the chip morphology appears saw-tooth, and cyclic shear localization is the chip formation mechanism. If no such shift occurs, the chip formation is considered continuous, and uniform shear localization is the chip formation mechanism. Hardness measurements show that cyclic shear localization is the chip formation mechanism when localized hardness peaks occur, whereas uniform shear localization is operative when the hardness is relatively constant.
Transient and Stable Chaos in Dipteran Flight Inspired Flapping Motion
Authors: Bose Chandan , Reddy Vikas , Gupta Sayan , Sarkar Sunetra
Published: November 2017

This paper deals with the nonlinear fluid structure interaction (FSI) dynamics of a Dipteran flight motor inspired flapping system in an inviscid fluid. In the present study, the FSI effects are incorporated to an existing forced Duffing oscillator model to gain a clear understanding of the nonlinear dynamical behavior of the system in the presence of aerodynamic loads. The present FSI framework employs a potential flow solver to determine the aerodynamic loads and an explicit fourth-order Runge–Kutta scheme to solve the structural governing equations. A bifurcation analysis has been carried out considering the amplitude of the wing actuation force as the control parameter to investigate different complex states of the system. Interesting dynamical behavior including period doubling, chaotic transients, periodic windows, and finally an intermittent transition to stable chaotic attractor have been observed in the response with an increase in the bifurcation parameter. Similar dynamics is also reflected in the aerodynamic loads as well as in the trailing edge wake patterns.
Multiphoton Polymerization Using Femtosecond Bessel Beam for Layerless Three-Dimensional Printing
Authors: Yu Xiaoming , Zhang Meng , Lei Shuting
Published: November 2017

Photopolymerization enables the printing of three-dimensional (3D) objects through successively solidifying liquid photopolymer on two-dimensional (2D) planes. However, such layer-by-layer process significantly limits printing speed, because a large number of layers need to be processed in sequence. In this paper, we propose a novel 3D printing method based on multiphoton polymerization using femtosecond Bessel beam. This method eliminates the need for layer-by-layer processing, and therefore dramatically increases printing speed for structures with high aspect ratios, such as wires and tubes. By using unmodulated Bessel beam, a stationary laser exposure creates a wire with average diameter of 100 μm and length exceeding 10 mm, resulting in an aspect ratio > 100:1. Scanning this beam on the lateral plane fabricates a hollow tube within a few seconds, more than ten times faster than using the layer-by-layer method. Next, we modulate the Bessel beam with a spatial light modulator (SLM) and generate multiple beam segments along the laser propagation direction. Experimentally observed beam pattern agrees with optics diffraction calculation. This 3D printing method can be further explored for fabricating complex structures and has the potential to dramatically increase 3D printing speed while maintaining high resolution.
Experimental and Novel Analytical Trajectory Optimization of a 7-DOF Baxter Robot: Global Design Sensitivity and Step Size Analyses
Authors: Bagheri Mostafa , Naseradinmousavi Peiman , Morsi Rasha
Published: November 2017

In this paper, we present a novel nonlinear analytical coupled trajectory optimization of a 7-DOF Baxter manipulator validated through experimental work utilizing global optimization tools. The robotic manipulators used in network-based applications of industrial units and even homes, for disabled patients, spend significant lumped amount of energy and therefore, optimal trajectories need to be generated to address efficiency issues. We here examine both heuristic (Genetics) and gradient based (GlobalSearch) algorithms for a novel approach of “S-Shaped” trajectory (unlike conventional polynomials), to avoid being trapped in several possible local minima along with yielding minimal computational cost, enforcing operational time and torque saturation constraints. The global schemes are utilized in minimizing the lumped amount of energy consumed in a nominal path given in the collision-free joint space except an impact between the robot’s end effector and a target object for the nominal operation. Note that such robots are typically operated for thousands of cycles resulting in a considerable cost of operation. Due to the expected computational cost of such global optimization algorithms, step size analysis is carried out to minimize both the computational cost (iteration) and possibly cost function by finding an optimal step size. Global design sensitivity analysis is also performed to examine the effects of changes of optimization variables on the cost function defined.
Double Imaginary Root Degeneracies in Time-Delayed Systems and CTCR Treatment
Authors: Jenkins Ryan R. , Olgac Nejat
Published: November 2017

The dynamics we treat here is a very special and degenerate class of linear time-invariant time-delayed systems (LTI-TDS) with commensurate delays, which exhibit a double imaginary root for a particular value of the delay. The stability behavior of the system within the immediate proximity of this parametric setting which creates the degenerate dynamics is investigated. Several recent investigations also handled this class of systems from the perspective of calculus of variations. We approach the same problem from a different angle, using a recent paradigm called Cluster Treatment of Characteristic Roots (CTCR). We convert one of the parameters in the system into a variable and perturb it around the degenerate point of interest, while simultaneously varying the delay. Clearly, only a particular selection of this arbitrary parameter and the delay enforce the degeneracy. All other adjacent points would be free of the mentioned degeneracy, and therefore can be handled with the CTCR paradigm. Analysis then reveals that the parametrically limiting stability behavior of the dynamics can be extracted by simply using CTCR. The results are shown to be very much aligned with the other investigations on the problem. Simplicity and numerical speed of CTCR may be considered as practical advantages in analyzing such systems. This approach also exhibits the capabilities of CTCR in handling these degenerate cases contrary to the convictions in earlier reports. An example case study is provided to demonstrate these features.
Coordinated Control of Active Steering and Differential Braking Using Extended Command Governor for Rollover Avoidance
Authors: Tian Ran , Bencatel Ricardo , Girard Anouck , Kolmanovsky Ilya
Published: November 2017

This paper develops an Extended Command Governor (ECG) for coordinated control of active steering and differential braking to prevent a vehicle from rolling over when undergoing aggressive maneuvers. The ECG modifies commands to well-designed closed-loop systems when necessary to prevent constraint violations. In this paper, the ECG is applied to a nonlinear vehicle model to maintain the vehicle in a safe state. For rollover avoidance, the ECG is designed to intervene and modify the driver’s input steering and braking commands when it predicts these signals may be unsafe and cause violation of the Load Transfer Ratio constraint. Simulation results show that the ECG can successfully detect and correct the unsafe commands to prevent constraint violation. Moreover, the ECG also behaves less conservatively than a previous design that used active steering control only. Specifically, the ECG described in this work allows the vehicle trajectory to stay closer to the desired trajectory.
A Force Sensing Instrument Assisted Soft Tissue Mobilization Device
Authors: Alotaibi Ahmed M. , Anwar Sohel , Loghmani M. Terry
Published: November 2017

Instrument assisted soft tissue mobilization (IASTM) is a form of massage using rigid manufactured or cast devices. The delivered force, which is a critical parameter in massage during IASTM, has not been measured or standardized for most clinical practices. There is a strong need to characterize the delivered force to a patient. This paper proposes a novel mechatronic design for a specific instrument to apply localized pressure which is a frequently used tool to clinically deliver localize pressure to treat soft tissue. The design is based on 1-D compression load cells, where 4-load cells are used to measure the force components in three-dimensional space. Here the proposed design of the mechatronic IASTM tool is modeled, analyzed, and simulated as a mechanical structure with simplifying assumptions on the elastic behavior of the skin under a certain amount of force conditions. A finite element model of a human arm is simulated to show the relationship between the applied forces, stress and strain on the skin, and force measurements to improve the design. The relation between device’s tip and the modeled arm was assumed to be frictional contact similar to the real IASTM practice.
A Real-Time Pseudo-2D Bi-Domain Model of PEM Fuel Cells for Automotive Applications
Authors: Goshtasbi Alireza , Pence Benjamin L. , Ersal Tulga
Published: November 2017

With the goal of on-line diagnosis for automotive applications in mind, a real-time model of polymer electrolyte membrane (PEM) fuel cell is developed. The model draws from the authors’ previous modeling effort in this area and extends its domain to incorporate transport under the lands. Transport in the catalyst and micro-porous layers, which were previously omitted, are also included in the model. Membrane water transport model is modified accordingly. Moreover, a recently developed homogeneous catalyst layer model is used to describe local oxygen transport resistance in the cathode catalyst layer. Computational efficiency is achieved through spatio-temporal decoupling of the problem, which simplifies the handling of the nonlinear terms. This computational efficiency is demonstrated by a set of simulations that resemble operation under conditions encountered in automotive applications. Moreover, simulation results of the model are in qualitative agreement with earlier computationally intensive modeling studies as well as experimental observations. The current modeling study demonstrates a significant potential for using relatively high-fidelity physics-based models on-line to improve fuel cell performance and durability, which can have a profound impact on its commercialization.
Dynamic Modeling and Control of an Electromechanical Control Actuation System
Authors: Yerlikaya Ümit , Balkan R. Tuna
Published: November 2017

Electromechanical actuators are widely used in miscellaneous applications in engineering such as aircrafts, missiles, etc. due to their momentary overdrive capability, long-term storability, and low quiescent power/low maintenance characteristics. This work focuses on electromechanical control actuation systems (CAS) that are composed of a brushless direct current motor, ball screw, and lever mechanism. In this type of CAS, nonlinearity and asymmetry occur due to the lever mechanism itself, saturation limits, Coulomb friction, backlash, and initial mounting position of lever mechanism. In this study, both nonlinear and linear mathematical models are obtained using governing equations of motion. By using the linear model, it is shown that employing a PI-controller for position and a P-controller for velocity will be sufficient to satisfy performance requirements in the inner-loop control of an electromechanical CAS. The unknown controller parameters and anti-windup coefficient are obtained by the Optimization Tools of MATLAB using nonlinear model. Results obtained from the nonlinear model and real-time unloaded and loaded tests on a prototype developed are compared to verify the nonlinear model.
Using Sensing Coils to Detect and Correct Lateral Misalignments in an Inductive Power-Transfer Wireless Charging System
Authors: Cortes Ivan , Kim Won-jong
Published: November 2017

Inductive power transfer (IPT) remains one of the most common ways to achieve wireless power transfer (WPT), operating on the same electromagnetic principle as electrical transformers but with an air core. IPT has recently been implemented in wireless charging of consumer products such as smartphones and electric vehicles. However, one major challenge with using IPT remains ensuring precise alignment between the transmitting and receiving coils so that maximum power transfer can take place. In this paper, the use of additional sensing coils to detect and correct lateral misalignments in an IPT systems is modeled and tested. The sensing coils exploit magnetic-field symmetry to give a nonlinear measure of misalignment direction and magnitude. Experiments using such sensing coils give a misalignment-sensing resolution of less than 1 mm when applied to a common smartphone wireless charging system. Voltage readings from the sensing coils are used for feedback control of an experimental two-dimensional coil positioner. This system is able to reduce lateral misalignments to less than 2 mm in real time, allowing for efficient power transfer. The results of this experiment give confidence that similar sensing coils can be used to reduce lateral misalignments in scaled IPT systems, such as electric-vehicle wireless chargers.
On Control of Heterogeneous Multiagent Systems With Unknown Leader Dynamics
Authors: Sarsilmaz S. Burak , Yucelen Tansel
Published: November 2017

The contribution of this paper is a distributed control approach for a class of heterogeneous multiagent systems with unknown leader dynamics. Considering fixed and directed communication graph topologies, we establish a global sufficient condition for uniform ultimate boundedness of the output tracking error between the output of each heterogeneous agent and the output of the leader. If, in addition, the output of the leader is constant, we show that uniform ultimate boundedness reduces to asymptotic synchronization. Several illustrative numerical examples are provided to demonstrate the efficacy of the proposed control architecture.
Systematic Feature Selection Process Applied in Short-Term Data-Driven Building Energy Forecasting Models: A Case Study of a Campus Building
Authors: Zhang Liang , Wen Jin , Chen Yimin
Published: November 2017

An accurate building energy forecasting model is a key component for real-time and advanced control of building energy system and building-to-grid integration. With the fast deployment and advancement of building automation systems, data are collected by hundreds and sometimes thousands of sensors every few minutes in buildings, which provide great potential for data-driven building energy forecasting.

To develop building energy forecasting models from a large number of potential inputs, feature selection is a critical procedure to ensure model accuracy and computation efficiency. Though the theory of feature selection is well developed in statistics and machine learning fields, it is not well studied in the application of building energy modeling.

In this paper, a feature selection framework proposed in an earlier study is examined using a real campus building in Philadelphia. This feature selection framework combines domain knowledge and statistical methods and is developed for short-term data-driven building energy forecasting. In this case study, the feasibilities of using this feature selection framework in developing whole building energy forecasting model and chiller energy forecasting model are studied.

Results show that, for both whole building and chiller energy forecasting applications, the model with systematic feature selection process presents better performance (in terms of cross validation error of forecasted output) than other models including that with conventional inputs and that uses only single feature selection technique.
Adaptive Robust Control of a Pump Control Hydraulic System
Authors: Helian Bobo , Chen Zheng , Yao Bin , Yan Yi , Lee Chiang
Published: November 2017

Pump control hydraulic systems have been widely used in industry by the advantages of no throttling loss and overflow loss as well as high power-to-volume ratio. However, the characteristics of high order dynamics, high nonlinearities and disturbances make the accurate position control of those systems very challenging. And to implement the controllers easily, some dynamics such as servo motor loop are usually ignored in most of existing methods, which may lead to the limitation of closed-loop bandwidth and disturbance rejection ability. In this paper, adaptive robust control (ARC) algorithm is utilized in a pump control electro-hydrualic system. The ARC guarantees the stability and high performance in the presence of model uncertainties and nonlinear disturbances. For the high-order of the hydraulic system, a modified three-step backstepping method is constructed which is covering the whole electro-hydraulic system. The servo motor-pump dynamics is taken into considered in the three-step adaptive backstepping controller design. Theoretical control performance based on Lyapunov functions and the simulation results proved that the control strategy this paper proposed achieved high performance in spite of the nonlinearities and uncertainties.
A Driver Model for Predicting Human Steering Performance in Teleoperated Path Following of Unmanned Ground Vehicles
Authors: Mirinejad Hossein , Jayakumar Paramsothy , Ersal Tulga
Published: November 2017

This paper presents a steering model for predicting human performance in teleoperating unmanned ground vehicles (UGVs). The task of path following, including lane keeping and curve negotiation, is considered for a UGV teleoperation system. Human steering performance in teleoperation is notably different than steering performance in on-board driving conditions due to considerable communication delays in remote teleoperation systems and limited information teleoperators receive from the vehicle sensory system. This paper adopts a cognitive model that was originally developed for a typical highway driving scenario when driver is on board and develops a tuning strategy to adjust the model parameters without human data to reflect the effect of various latencies and UGV speeds on driver performance in a teleoperated path following task. It is shown that the proposed model with tuning strategy i) can adequately capture the trend of changes in driver performance for different teleoperated driving scenarios ii) is able to predict an expert human teleoperator’s performance across different speeds and latencies considered. Thus, the tuned model can be an appropriate candidate to be used in place of human drivers for the simulation-based evaluation of UGV mobility in teleoperation systems.
Gait Emulator for Evaluation of a Powered Ankle-Foot Prosthesis
Authors: Ficanha Evandro , Dallali Houman , Rastgaar Mo
Published: November 2017

In this paper we present an enhanced gait emulator and a novel hybrid control system to test powered ankle-foot prostheses with two degrees of freedom in the sagittal and frontal planes. The gait emulator is a nonlinear and non-smooth system that has to follow a precisely timed set of phases to achieve a human-like periodic gait. Despite the complexity and parameter uncertainties of this five degrees of freedom system, our proposed hybrid control system simplifies the walking control by use of state triggered kinematic events. The control system works in closed loop with kinematic event detection to ensure robust and repeatable walking tests as design parameters are varied. The developed gait emulator can be used to test the prosthesis under various loading conditions and walking speeds.
A Data-Driven Approach for UAV Tracking Control
Authors: Vasisht Soumya , Mesbahi Mehran
Published: November 2017

This paper presents a simple data-driven approach to improve ground target tracking by an unmanned aerial vehicle (UAV) for certain classes of target trajectories from learned local linear models. The UAV is assumed to be a small fixed-wing aircraft equipped with a gimbaled camera for visual sensing. We attempt to build a controller from measurement data by building an augmented Linear Quadratic Regulator (LQR) system from an approximated linear operator that indirectly captures the properties of the target system. We evaluate the relative performance improvement gained by this data-driven approach versus the standard target following LQR system and provide bounds for this improved performance. We also consider the effect of sensor noise on the tracking performance resulting from the noisy and erroneous datasets. We demonstrate the performance of this method on a range of numerical data representing different classes of target trajectories.
Engine Calibration Using “Eigenvariables”
Authors: Hu Yiran , Haskara Ibrahim , Chang Chen-Fang , Khodadadi Sadabadi Kaveh , Rezaeian Ayyoub , Midlam-Mohler Shawn
Published: November 2017

To meet the more stringent emissions and fuel economy regulations, engine control system has become significantly more complex than before. As a result of this, engine calibration on the dynamometer now occupies one of the longest time sections in the vehicle development process. One strategy automakers have adopted is to use the same engine in multiple applications to reduce the calibration effort. Even then, vehicle design constraints often require changes to be made to the engine’s external components such as the intake and exhaust manifolds. These changes can create variations in the engine combustion behavior so that the engine must be recalibrated on the dyno, resulting in additional cost and effort. This paper explores the potential of reusing existing engine dyno data for a modified engine in these scenarios through the use of the so-called eigenvariable to describe engine operating conditions. Traditionally, engine dyno data is referenced by engine load and speed along with actuator positions (such as camphaser positions). The proposed approach describes dyno data using eigenvariables or variables that describe the engine in-cylinder condition prior to combustion. Eigenvariables are invariant with respect to external engine hardware. This invariance enables the same dyno data to be applied to a modified engine with the same combustion system design.
Average Reward Dynamic Programming Applied to a Persistent Visitation and Data Delivery Problem
Authors: Kalyanam Krishna , Pachter Meir , Casbeer David
Published: November 2017

We are interested in the persistent surveillance of an area of interest comprised of stations/ data nodes that need to be visited in a cyclic manner. The data collection task is undertaken by a UAV which autonomously executes the mission. In addition to geographically distributed stations, the scenario also includes a central depot, where data collected from the different nodes must be delivered. In this context, the performance criteria, in addition to a desired minimal cycle time, also entails minimizing the delay in delivering the data collected from each node to the depot. Each node has a priority/ weight associated with it that characterizes the relative importance between timely delivery of data from the nodes. We pose the problem as an average/ cycle reward maximization problem; where the UAV gains a reward that is a decreasing function of weighted delay in data delivery from the nodes. Since we aim to maximize the average reward, the solution also favors shorter overall cycle time. In a cycle, each station is visited exactly once; however, we allow the UAV to visit the depot more than once in a cycle. Evidently, this allows for quicker delivery of data from a higher priority node. We apply results from average reward maximization stochastic dynamic programming to our deterministic case and solve the problem using Linear Programming. We also discuss the special case of no penalty on delivery delay, whence the problem collapses to the well known metric Traveling Salesman Problem.
A Data-Driven Exploratory Approach for Level Curve Estimation With Autonomous Underwater Agents
Authors: Lin Hsien-Chung , Solowjow Eugen , Tomizuka Masayoshi , Kreuzer Edwin
Published: November 2017

This contribution presents a method to estimate environmental boundaries with mobile agents. The agents sample a concentration field of interest at their respective positions and infer a level curve of the unknown field. The presented method is based on support vector machines (SVMs), whereby the concentration level of interest serves as the decision boundary. The field itself does not have to be estimated in order to obtain the level curve which makes the method computationally very appealing. A myopic strategy is developed to pick locations that yield most informative concentration measurements. Cooperative operations of multiple agents are demonstrated by dividing the domain in Voronoi tessellations. Numerical studies demonstrate the feasibility of the method on a real data set of the California coastal area. The exploration strategy is benchmarked against random walk which it clearly outperforms.
Frequency Separation Control of Series Sequential Boosting System With Electric Supercharger and Turbocharger
Authors: Xiao Baitao , Buckland Julia H. , Karnik Amey
Published: November 2017

To improve transient torque response of an aggressively downsized turbocharged SI engine a series sequential boosting configuration that utilizes an electrically driven supercharger to assist the main turbocharger compressor is controlled in this paper. A frequency separation controller is designed to decouple the dynamics of the multiple-input-single-output (MISO) system. The controller separates the electric supercharger and turbocharger control actions into different frequency bands that are well suited for the characteristics of each device. The controller can be easily implemented with traditional decentralized single input single output (SISO) control loops.

Significant improvements to the baseline turbocharger only system in transient boost pressure response are observed both in simulation and in vehicle test results. Transitions between the electric supercharger and turbocharger are smooth, without noticeable disturbances, with good coordination between electric supercharger and wastegate control actions.
Multi-Vehicle Platoon Control With Time-Varying Input Delays
Authors: Varada Keely , Yuan Chengzhi , Sodhi Manbir
Published: November 2017

Platooning, or controlled management of vehicle formation, enables multiple vehicles equipped with adaptive cruise control (ACC) systems to drive behind one another with a specified inter-vehicle distance, acting together as one unit. Typically, delays in throttle and brake response, as well as in vehicle computer systems, are unpredictable and time-varying, and can ultimately lead to performance degradation and system destabilization. The platoon control system must thus be designed in a way so as to mitigate the effects delays can impose on system stability. This paper presents a novel robust multi-vehicle platoon control algorithm that compensates for time-varying delays under the integral quadratic constraint (IQC) framework. All vehicle models are assumed to incorporate heterogeneous time-varying actuation/input delays. The simulation results exemplify the controller’s effectiveness in maintaining overall stability and platooning performance in the presence of time-varying input delays.
Backstepping Control of Underactuated Planar Vehicles With Nonholonomic Constraints
Authors: Fetzer Karl Ludwig , Nersesov Sergey , Ashrafiuon Hashem
Published: November 2017

This paper documents the development of a backstepping controller to track a generic underactuated planar vehicle along a trajectory, the implementation of the controller for a surface vessel model in simulation, and its performance validation in experiments. The tracking controller design is made possible by taking the six position / orientation and velocity states and transforming them into four error states. Designing the controller for a generic vehicle means that several different vehicle types can track a trajectory as long as they each satisfy the vehicle’s nonholonomic constraints. The backstepping controller derived herein can be applied to mobile robots, aircraft in the vertical plane, and surface vessels, with the last being implemented in this paper.
Entrepreneurially Minded Learning in a Semester-Long Senior/Graduate Mechatronic Design Project
Authors: Mynderse James A. , Shelton Jeffrey N. , Gerhart Andrew L.
Published: November 2017

This paper describes ongoing progress in facilitating entrepreneurially minded learning through modifications to an existing senior/graduate level mechatronic design course. The semester-long design experience incorporates a prompted real-world problem intended to motivate the design and construction of a fully autonomous robotic vehicle. Introductory lectures and structured laboratory exercises are provided during the first half of the semester, while the remaining half-semester is allocated to team-based robot design and fabrication. Existing problem-based learning activities have been altered to increase student awareness of economic factors, encourage communication of project issues in economic terms, and promote customer engagement. To this end, project assignments were recast as business problems, with an increased emphasis on prototype and operating costs. Additionally, a customer (represented by the instructor) was created to engage with students. Project success has been indirectly assessed by surveying students as to how their actions align with characteristic entrepreneurial behaviors identified by the Kern Entrepreneurial Engineering Network (KEEN).
Entrainment of Ankle-Actuated Walking Model to Periodic Perturbations via Leading Leg Angle Control
Authors: Rigobon Daniel , Ochoa Julieth , Hogan Neville
Published: November 2017

In prior work, a minimal mathematical model of bipedal walking was developed to investigate the experimentally observed entrainment behavior of human locomotion. While that model reproduced several salient properties of human walking, it failed to entrain to periodic perturbations with period longer than preferred walking period. To overcome that limitation, we introduced afferent feedback in the form of leading leg angle control that depended on the energetics of previous steps. The model response to periodic perturbations was again studied in simulation, testing several perturbation periods and initial perturbation phases. This revised model captured important aspects of human locomotion that had been previously observed experimentally: a finite basin of entrainment to both shorter and longer perturbation periods. Regardless of the (random) phases of the step cycle at which perturbations were initiated, all entrained simulations phase-locked with the torque pulses at the end of double stance. However, more than twice as many steps were required to entrain to longer perturbations. The results achieved with this revised walking model emphasize the importance of the oscillatory dynamics of bipedal locomotion and highlight possible applications of gait entrainment as a method for permissive motor guidance in the field of assistive and rehabilitation robotics.
A Personalized Diet and Exercise Recommender System in Minimizing Clinical Risk for Type 1 Diabetes: An In Silico Study
Authors: Xie Jinyu , Wang Qian
Published: November 2017

Risk of having hypoglycemia is one of the biggest barriers preventing Type 1 Diabetes (T1D) patients from performing exercise. In addition, management of diet and exercise levels needs to be personalized for each patient to avoid hypoglycemia and to achieve a good glycemic control. In this paper, we developed a model-based diet and exercise recommender system that could be used to provide an (optimal) personalized intervention on diet and exercise for T1D patients. The recommender system makes prediction of blood glucose at each intervention time based on a patient-specific model of glucose dynamics, and then provides the optimal meal sizes, target heart rates during exercise, pre-exercise carbohydrate and bedtime snack by minimizing a clinical risk function under constraints. Patient-specific models of glucose dynamics were identified for 30 virtual subjects generated from a modified UVa/Padova simulator with an added exercise-glucose subsystem. The performance of the recommender system was then compared to two self-management schemes (the Starter and the Skilled). The latter represents an off-line optimal solution providing a lower bound on the risk index. The average clinical risk under the recommender system was reduced by 49% compared to that under the Starter, and it was comparable to the risk of the Skilled. In addition, the recommender system had less number of post-exercise/nocturnal hypoglycemia events occurred than that under the Starter or the Skilled. Such recommender system can be implemented as an “App” patient advisor to improve T1D patients’ self-management of glucose control.
Fully Pneumatic Semi-Active Vibration Isolator Design and Analysis
Authors: Schaeffer Hans W. , Kelkar Atul G.
Published: November 2017

This paper presents a methodology of designing, modeling, and controlling a fully pneumatic semi-active vibration isolator system. The prototype vibration isolator system consists of an air spring, a variable orifice valve, and an accumulator which has the ability to simultaneously adjust the damping and natural frequency characteristics of the system. This paper presents a comprehensive work of modeling, hardware design, control design, and experimental validation of the proposed semi-active vibration isolation system. A higher fidelity model is obtained by complete characterization of nonlinear relationships between pressure versus volume and effective orifice area versus ride height. The performance of three semi-active controller designs — Linear Quadratic Impulse (LQI), Modified Skyhook, and Relative Displacement — is evaluated and compared experimentally using an OEM Peterbilt cabin suspension unit. The results demonstrate that the properly tuned semi-active suspension provides increased vibration isolation over the traditional passive cabin suspension design.
Adaptive Disturbance Rejection Controller for Pathological Tremor Suppression With Permanent Magnet Linear Motor
Authors: Zamanian Amir Hosein , Richer Edmond
Published: November 2017

This paper presents an adaptive disturbance rejection (ADR) controller developed for the suppression of the pathological tremor in the humans’ wrist. An experimental setup, based on a slotted permanent magnet linear motor (PMLM), was developed to evaluate the ADR’s performance in real-time suppression of the tremor signal recorded from Parkinson’s disease patients. A model-base compensator was utilized to minimize the resistive and cogging forces exhibited by the PMLM. Experimental results showed an average tremor amplitude suppression of 32.61 dB (97.6%) in the first, and 15.23 dB (82.7%) in the second tremor frequency respectively. The average magnitude of the resistance force induced by the system against voluntary motion was 0.36 N. Furthermore, to evaluate the tremor suppression performance of the presented technique the results were compared with two other studies that used pneumatic actuators and magneto-rheological dampers (MRD). The performance of the PMLM was analogous to actively controlled pneumatic actuators and was significantly better than the semi-active controller with MRD.
Estimation and Analysis of Vehicle Lateral Stability Region With Both Front and Rear Wheel Steering
Authors: Huang Yiwen , Chen Yan
Published: November 2017

In this paper, a novel vehicle lateral stability region estimation method considering both front and rear wheel steering is introduced. Vehicle lateral stability regions are estimated by a local linearization method, which guarantees both vehicle local stability and handling stability. The impacts of front and rear wheel steering angles on stability region estimations are formulated and discussed. To quantitatively explain the shifting feature of stability regions under different front/rear steering angles, an explicit analysis about how the equilibrium points and the geometric centers of stability regions change with respect to different steering angles is formulated. The obtained relationship enables the estimation of stability regions in real time for varying front/rear steering angles. The additional rear wheel steering helps to maintain vehicle states stay within estimated stability regions. To show the effectiveness of the proposed real-time stability region estimation method and stability analysis, a Simulink and CarSim® co-simulation is applied to verify that vehicle states are covered within varying stability regions for a single lane change maneuver.
An Inductive, Design-Centric Approach to Control Engineering Education With a Competitive Atmosphere
Authors: Foong Shaohui , Subburaj Karupppasamy , Wood Kristin L.
Published: November 2017

Control engineering is a cornerstone of most undergraduate engineering programs in colleges and universities around the world. The analysis and synthesis of automatic controllers, in particular, the PID controller, is a central focus of these courses and modules. However, due to its highly abstract nature, students usually find the content challenging and difficult to comprehend. This is aggravated by the employment of traditional lecture/recitation deductive teaching formats as means of delivery of the content. Here, an inductive-based week long design activity strategically held in the middle of the semester was conceived to introduce and motivate the notion of feedback control. During the course of the week, students in teams design, analyze and synthesize automatic controllers to enable a standardized differential wheeled robotic platform to traverse a line circuit autonomously. The strategy to achieve this capability is intentionally left to be open-ended, and students have the design freedom to select and position sensors needed to sense the track, as well as implement and troubleshoot the programming required to enable autonomous control. The activity culminates with a pulsating head-to-head single elimination tournament to decide the overall champion.
Control Strategy for an Assistive Exoskeleton for Sit-to-Stand Transition
Authors: Patil Gaurav , Rigoli Lillian M. , Chamnikar Ameya , Miller Amanda , Ralescu Anca , Kiefer Adam W. , Richardson Michael J. , Lorenz Tamara , Kumar Manish
Published: November 2017

Approximately 1.5 million senior citizens live under nursing supervision, and most require assistance with at least one or more Activities of Daily Living (ADL). These include transferring in and out of chairs, beds and toilets, which necessitates the ability to perform sit-to-stand transitions. The sit-to-stand transition is a complex full-body activity that requires the synergistic coordination of the upper and lower limbs and trunk. This paper presents a model-based control approach for an exoskeleton device that can provide assistance at the ankle, knee, and hip joints. Validation of the controller is based on simulations on a four-link model of the human body. The results show that the control strategy is successful for different sit-to-stand transition speeds, and when the user is providing only a part of the required torques or has a single weak joint. The results also demonstrate the effectiveness of the proposed control strategy in the presence of modeling error that provides further support for the robustness of this approach.
Modeling Eddy-Current Damping Force in Magnetic Levitation Systems With Conductors
Authors: Khodabakhsh Mohammad , Ebrahimian Mehran , Epureanu Bogdan
Published: November 2017

An analytical method is used to develop a model to calculate steady-state eddy-current damping effects in two configurations of magnetic levitation (maglev) systems. The eddy-current based force (eddy-current force) is used for high precision positioning of a levitated permanent magnet in maglev systems. In these systems, the motion of the levitated permanent magnet and changes of the coil’s currents, generate eddy current in the conductors. The proposed analytical model is used to calculate both effects. A conductive cylindrical shell around the levitated object is implemented as a new technique to generate eddy currents in maglev systems. The model is also employed to obtain eddy-current damping effects in a system with a conductive plate beneath the levitated object. The analytical models match results from high fidelity finite element analysis (FEA) with acceptable accuracy in a wide range of operations. Advantages of the two configurations are discussed.
Identification and Compensation of Cogging and Friction Forces in Tubular Permanent Magnet Linear Motors
Authors: Zamanian Amir Hosein , Richer Edmond
Published: November 2017

This paper presents the modeling, identification, and compensation of cogging and resistive forces in tubular permanent magnet linear motors (PMLMs). An observer-based model that includes the effects of cogging, backlash, inertia, Coulomb, and viscous frictions, as well as back electromotive force is presented. Least square optimization is carried out to identify the model, and the weakness of fast Fourier transform (FFT) in PMLMs with short translators for precise wavelength determination is discussed. The identified model is used as a directional estimator in a closed-loop controller to compensate the disturbance forces induced by the PMLM to a secondary mechanism. Experimental results show a reduction of the disturbance force energy up to 31.96 dB.
A Robust Feature Extraction for Automatic Fault Diagnosis of Rolling Bearings Using Vibration Signals
Authors: Heydarzadeh Mehrdad , Mohammadi Alireza
Published: November 2017

Bearing faults are one of the main reasons for rotary machine failure. Monitoring bearing vibration signals is an effective method for diagnosing faults and preventing catastrophic failures in rotary mechanisms. The state-of-the-art vibration monitoring algorithms are mainly based on frequency or time-frequency domain analysis of rotary machines that are operating in steady state. However, the steady state assumption is not valid in applications where the loads and speeds are time-varying. Finding a method for capturing the variability in vibration signals, which are caused by varying loads and speeds, is still an open research problem with potentially many applications in emerging areas such as electric vehicles. In this paper, we address the problem of vibration signal monitoring by applying a feature extraction algorithm to rotary machine signals measured by accelerometers. The proposed method, which is based on the wavelet scattering transform, achieves overall high accuracy while being computationally affordable for real-time implementation purposes. In order to verify the effectiveness of the proposed methodology, we apply our technique to a well-known vibration benchmark dataset with variable load. Our algorithm can diagnose various faults with different intensities with an average accuracy of 99% and thus effectively outperforming all prior reported work on this dataset.