bluuebunny/crossref_metadata_2025 huggingface dataset:
Quality, phenolic compound and antioxidant activity of wines from Sangyod rice grain, paddy and husk during fermentation
Authors: Klompong Vilailak
Published: November 2018

The objective of this study was to utilize husk, byproduct from milling, and paddy of Sangyod rice that rich in bioactive compound to produce value added product as wine by reducing milling step of paddy. Quality changes, total phenolic content and antioxidant activity of wines from Sangyod rice grain, paddy and husk were monitored throughout the fermentation period. The acceptance of finished products from consumer drinking wine was also investigated. Alcohol content of three types of wine increased as the fermentation time increased. Paddy wine showed the fastest alcohol production following by rice grain and husk wine, respectively (P<0.05). Generally, total soluble solid and pH of wines decreases as the fermentation time increased. Yeast and mold increased throughout the fermentation time. As the fermentation time increased, total phenolic content and antioxidant activity including DPPH radical scavenging activity, ferric reducing antioxidant power (FRAP) and metal chelating activity increased throughout the fermentation period (P<0.05) related to total phenolic content. Total phenolic content in three types of wines increased from 32-53 to 125-178 (mg GAE/ml). Generally, paddy wine possessed the highest total phenolic content and antioxidant activities when compared with rice grain and husk wine (P<0.05). From the sensory evaluation including appearance, odor, taste and overall liking, the scores of rice grain and paddy wines were moderate, while the lowest scores in all attributes was observed in husk wine (P<0.05). Rice grain, paddy and husk wines obtained were amber in color (L*=10.11-16.27, a*=8.07-14.91, b*=10.8-12.18). Thus, the changes of quality, total phenolic contents and antioxidant activity of wine during fermentation were governed by raw material used and fermentation time. Additionally, Sangyod rice grain and paddy could be used as potential raw material for wine production and the wines obtained could be served as potential drinks for health, since containing bioactive compound as antioxidant.
Effect of particle size and co-extractant in Momordica charantia extract yield and diffusion coefficient using supercritical CO2
Authors: Aris Noor Aiysah , Zaini Ahmad Syahmi , Mohd Nasir Hasmida , Idham Zuhaili , Vellasamy Yuvitha , Che Yunus Mohd Azizi
Published: November 2018

Supercritical carbon dioxide (SC-CO2) is a fluid with high diffusivity and low viscosity which can penetrate deep into the solid particle efficiently compared to liquid or gas. SC-CO2 commonly used as a green solvent in the modern extraction of bioactive compound from plants. Sometimes, a co-solvent was added in the system to increase solvent polarity or mix a co-extractant with dried sample to improve solute’s transport properties. Hence, the aim of this study was to determine Momordica charantia extract yield with different mean particle size as well as diffusion coefficient, De in the extraction process with and without co-extractant. Different mean particle sizes used were 0.2, 0.3, 0.5 and 0.7 mm at constant operating condition (20 MPa, 65 oC and 4 mL/min). A ratio 1:3 of pure ethanol was used in the extraction process with co-extractant. Based on the results, mean particle size of 0.3 mm gave the highest extract yield, 3.32% and 1.34% with and without co-extractant respectively. Whereas, the value of De at 0.3 mm mean particle size, with and without co-extractant are 8.820 x 10-12 and 7.920 x 10-12 m2/s respectively. Therefore, 0.3 mm is the best mean particle size to produce highest Momordica charantia extract yield and De value in SC-CO2 extraction with co-extractant.
Effect of putative probiont Enterococcus hirae on the hematological parameters of juvenile African catfish, Clarias gariepinus (Burchell, 1822) during pre- and post-challenge against Aeromonas hydrophila
Authors: Hamid Nur Hidayahanum , Mohd Daud Hassan , Srisapoome Prapansak , Abu Hassim Hasliza , Mohd Yusoff Md Sabri , Kayansamruaj Pattanapon , Hamdan Ruhil Hayati , Mohd Yusoff Siti Fairus , Abu Bakar Siti Nadia
Published: November 2018

Probiotics have been widely known to have the ability to improve the immune system of livestock and aquatic animal. The present study was carried out to evaluate the effect of dietary supplementation of two probiotic isolates of Enterococcus faecium on hematological parameters of juvenile African catfish, Clarias gariepinus during pre- and post-challenge with aquatic pathogen, Aeromonas hydrophila. The probiotics were previously isolated from vegetable wastes (mung bean sprouts, Vigna radiate and cucumber, Cucumis sativus) which have been fermented for 7 days. The experimental fish (270 tails) with an average weight of 5.13 ± 1.03 g were distributed and divided randomly  into  i) control (30 tails), fed with commercial diet ii) E1 (30 tails), fed with  diets  supplemented  with  108 CFU/ml  of  E. faecium isolated from fermented cucumber, iii) E2 (30 tails), fed with 108 CFU/ml  of  E. faecium isolated from fermented mung bean sprouts. The feeding trial was conducted for 50 days. All experimental groups were then challenged with A. hydrophila (1.5 × 106 CFU/mL) via intraperitoneal injection on day 51. Prior to challenge, blood samples were collected from five fish randomly selected from each group on the day 51 (pre-challenge).  After 72 hours of post-challenge, blood samples were again collected from five fish from each groups. The hematological parameters such as total erythrocyte count  (RBC),  total  leucocyte  count  (WBC),  packed cell volume (PCV),  hemoglobin  (Hb), the derived blood indices of mean corpuscular volume (MCV) and corpuscular hemoglobin concentration (MCHC) were examined.  Hematological profiles of pre- and post-challenge infected juvenile catfish were compared with the control groups. The RBC, Hb, WBC, PCV, MCV and MCHC of fish fed with probiotics showed higher significant difference (P<0.05) as compared to control groups during pre- and post-challenge of pathogen. The high level of RBC and WBC during pre- and post-challenge showed the capability of the probiotics to improve the immune response of juvenile African catfish and thus increased the fish disease resistance against A. hydrophila infection. The result suggested that E. faecium could be used effectively as a probiotic in aquaculture.
Blood–brain barrier permeability measured using dynamic contrast‐enhanced magnetic resonance imaging: a validation study
Authors: Varatharaj Aravinthan , Liljeroth Maria , Darekar Angela , Larsson Henrik B.W. , Galea Ian , Cramer Stig P.
Published: November 2018

Key points

The blood–brain barrier (BBB) is an important and dynamic structure which contributes to homeostasis in the central nervous system.

BBB permeability changes occur in health and disease but measurement of BBB permeability in humans is not straightforward.

Dynamic contrast‐enhanced magnetic resonance imaging (DCE‐MRI) can be used to model the movement of gadolinium contrast into the brain, expressed as the influx constant Ki.

Here evidence is provided that Ki as measured by DCE‐MRI behaves as expected for a marker of overall BBB leakage.

These results support the use of DCE‐MRI for in vivo studies of human BBB permeability in health and disease.

Blood–brain barrier (BBB) leakage can be measured using dynamic contrast‐enhanced magnetic resonance imaging (DCE‐MRI) as the influx constant Ki. To validate this method we compared measured Ki with biological expectations, namely (1) higher Ki in healthy individual grey matter (GM) versus white matter (WM), (2) GM/WM cerebral blood volume (CBV) ratio close to the histologically established GM/WM vascular density ratio, (3) higher Ki in visibly enhancing multiple sclerosis (MS) lesions versus MS normal appearing white matter (NAWM), and (4) higher Ki in MS NAWM versus healthy individual NAWM. We recruited 13 healthy individuals and 12 patients with MS and performed whole‐brain 3D DCE‐MRI at 3 T. Ki and CBV were calculated using Patlak modelling for manual regions of interest (ROI) and segmented tissue masks. Ki was higher in control GM versus WM (P = 0.001). CBV was higher in GM versus WM (P = 0.005, mean ratio 1.9). Ki was higher in visibly enhancing MS lesions versus MS NAWM (P = 0.002), and in MS NAWM versus controls (P = 0.014). Bland–Altman analysis showed no significant difference between ROI and segmentation methods (P = 0.638) and an intra‐class correlation coefficient showed moderate single measure consistency (0.610). Ki behaves as expected for a compound marker of permeability and surface area. The GM/WM CBV ratio measured by this technique is in agreement with the literature. This adds evidence to the validity of Ki measured by DCE‐MRI as a marker of overall BBB leakage.
A Framework for the Capture and Analysis of Product Usage Data for Continuous Product Improvement
Authors: Voet Henning , Altenhof Max , Ellerich Max , Schmitt Robert H. , Linke Barbara
Published: November 2018

Product improvement, usually through changes in design and functionality, is relying more and more on the continuous analysis of large amounts of data. Product data can come from many sources with varying effort in obtaining the data, e.g., condition monitoring and maintenance data. Intelligent products, also known as “product embedded information devices” (PEID), are already equipped with sensors and onboard computing capabilities and therefore able to generate valuable data such as the number of user interactions during the use phase. The internet of things (IoT) makes data transfer possible at any time to close the loop for the product lifecycle data and methods like machine learning promote new uses of those data. This paper proposes a methodology to capture the most relevant data on product use and human–product interaction automatically and utilize it as part of data-driven product improvement. Product engineers and designers will gain insights into the use phase and can derive design changes and quality improvements. The methodology guides the user through research on product use dimensions based on the principles of user-centered design (UCD). The findings are applied to define what usage elements, such as specific actions and context, need to be available from the use phase. During systems development, machine learning is suggested to fuse sensor data to efficiently capture the usage elements. After product deployment, use data are retrieved and analyzed to identify the improvement potential. This research is a first step on the long way to self-optimizing products.
Experimental Investigations on the Thermal Performance of a Single Closed Loop Pulsating Heat Pipe Using TiO2 Nanofluid
Authors: Pradeep G. V. , Rama Narasimha K.
Published: November 2018

This paper describes the experimental investigations conducted on a closed loop pulsating heat pipe (CLPHP) for assessing the thermal performance. The pulsating heat pipe has a single closed loop made of copper. The working fluids used are water and titanium dioxide nanofluids with varying concentrations of TiO2 nanoparticles (1.5% and 1%) on weight basis. The TiO2 particles are mixed in water to form a stable suspension using a sonicator. The heat input is varied between 40 W and 100 W in steps of 20 W. All experiments are conducted in the bottom heating mode (evaporator at the top) in the vertical and horizontal orientations. The parameters considered for evaluating the thermal performance are the temperature difference between evaporator and condenser, thermal resistance, heat transfer coefficient, and thermal conductivity. The results of the investigation reveal that the vertical orientation and increase in nanoparticle concentration favors better heat transfer performance of the single closed loop pulsating heat pipe.
Convective Heat Transfer Investigation of a Confined Air Slot-Jet Impingement Cooling on Corrugated Surfaces With Different Wave Shapes
Authors: Ekiciler Recep , Çetinkaya Muhammet Samet Ali , Arslan Kamil
Published: November 2018

In this study, air jet impingement on flat, triangular-corrugated, and sinusoidal-corrugated surfaces was numerically investigated. Bottom surface was subjected to constant surface temperature. Air was the working fluid. The air exited from a rectangular shaped slot and impinged on the bottom surface. The Reynolds number was changed between 125 and 500. The continuity, momentum, and energy equations were solved using the finite volume method. The effect of the shape of bottom surface on heat and flow characteristics was investigated in detail. Average and local Nusselt number were calculated for each case. It was found out that Nusselt number increases by increasing the Reynolds number. The optimum conditions were established to get much more enhancement in terms of performance evaluation criterion (PEC). It was revealed that the shape of the cooling surface (bottom wall) influences the heat transfer substantially.
A Synergistic Combination of Thermal Models for Optimal Temperature Distribution of Discrete Sources Through Metal Foams in a Vertical Channel
Authors: Kotresha Banjara , Gnanasekaran N.
Published: November 2018

This paper discusses about the numerical prediction of forced convection heat transfer through high-porosity metal foams with discrete heat sources in a vertical channel. The physical geometry consists of a discrete heat source assembly placed at the center of the channel along with high thermal conductivity porous metal foams in order to enhance the heat transfer. The novelty of the present work is the use of combination of local thermal equilibrium (LTE) model and local thermal nonequilibrium (LTNE) model for the metal foam region to investigate the temperature distribution of the heat sources and to obtain an optimal heat distribution so as to achieve isothermal condition. Aluminum and copper metal foams of 10 PPI having a thickness of 20 mm are considered for the numerical simulations. The metal foam region is considered as homogeneous porous media and numerically modeled using Darcy Extended Forchheimer model. The proposed methodology is validated using the experimental results available in literature. The results of the present numerical solution indicate that the excess temperature of the bottom heat source reduces by 100 °C with the use of aluminum metal foam. The overall temperature of the vertical channel reduces based on the combination of LTE and LTNE models compared to only LTNE model. The results of excess temperature for both the empty and the metal foam filled vertical channels are presented in this work.
An Analytical and Numerical Estimation of the Effective Thermal Conductivity of Complex Metal Frame Core Structures
Authors: Bai X. , Nakayama A.
Published: November 2018

An analytical and numerical study was conducted for estimation of the effective thermal conductivities of curved metal frame core structures, which can replace metal foams, in views of their advantages over the metal foams for both load bearing and heat dissipation. The trajectory of the frame ligament and its cross-sectional area were allowed to vary arbitrarily in the three-dimensional (3D) space. The analytical formula obtained by extending the formula previously proposed by Bai et al. (2017, “A General Expression for the Stagnant Thermal Conductivity of Stochastic and Periodic Structures,” ASME J. Heat Transfer, 140(5), p. 052001) was examined by comparing it with the numerical results directly obtained from full 3D numerical computations. An air layer partially filled with a collection of coiled circular rods was treated both analytically and numerically. Furthermore, the effect of lattice nodes on the effective thermal conductivity was investigated by introducing an analytical model with the lattice ligaments merging together at one nodal point. The analytical expressions thus derived for the lattice structures with nodes were applied to tetrahedral structure and octet-truss structure to find their effective thermal conductivities, which are found to agree closely with the 3D numerical results. Thus, the present analytical expressions can be used to customize the structure to meet its desired thermal performance.
Real-Time Angular Velocity-Based Misfire Detection Using Artificial Neural Networks
Authors: Zhang Pan , Gao Wenzhi , Song Qixin , Li Yong , Wei Lifeng , Wei Ziqing
Published: November 2018

In this paper, an artificial neural network (ANN) is introduced in order to detect the occurrence of misfire in an internal combustion (IC) engine by analyzing the crankshaft angular velocity. This study presents three reliable misfire detection procedures. In the first two methods, the fault features are extracted using both time domain and frequency domain techniques, and a multilayer perceptron (MLP) serves as the pattern recognition tool for detecting the misfiring cylinder. In the third method, a one-dimensional (1D) convolutional neural network (CNN) that combines feature extraction capability and pattern recognition is adopted for misfire detection. The experimental data are obtained by setting a six in-line diesel engine with different cylinder misfiring to work under representative operating conditions. Finally, all three diagnostic methods achieved satisfactory results, and the 1D CNN achieved the best performance. The current study provides a novel way to detect misfiring in IC engines.
Hybrid Function-Based Moment Method for Luffing Angular Response of Dual Automobile Crane System With Random and Interval Parameters
Authors: Zi Bin , Zhou Bin , Zhu Weidong , Wang Daoming
Published: November 2018

A hybrid uncertain parameter model (HUPM) is introduced to predict the luffing angular response (LAR) field of the dual automobile cranes system (DACS) with random and interval parameters. In the model, all random parameters with specified probabilistic distributions comprise a random vector, while all interval parameters with determined bounds comprise an interval vector. A hybrid uncertain LAR equilibrium equation is established, and a novel approach named as hybrid perturbation compound function-based moment method is proposed based on the HUPM. In the hybrid perturbation compound function-based moment method, the expression of LAR is developed according to the random interval perturbation compound function-based method. More, by using the random interval compound function-based moment method and the monotonic technique, the expectations and variances of the bounds for LAR are calculated. Compared with the hybrid Monte Carlo method (HMCM) and interval perturbation method (IPM), numerical results on different uncertain cases of the DACS demonstrate the feasibility and efficiency of the proposed algorithm. The proposed method is proved to be an effective engineering method to quantify the effects of hybrid uncertain parameters on the LAR of DACS.
The Correcting Approach of Gyroscope-Free Inertial Navigation Based on the Applicable Topological Map
Authors: Dehghani Mehdi , Kharrati Hamed , Seyedarabi Hadi , Baradarannia Mahdi
Published: November 2018

The accumulated error and noise sensitivity are the two common problems of ordinary inertial sensors. An accurate gyroscope is too expensive, which is not normally applicable in low-cost missions of mobile robots. Since the accelerometers are rather cheaper than similar types of gyroscopes, using redundant accelerometers could be considered as an alternative. This mechanism is called gyroscope-free navigation. The article deals with autonomous mobile robot (AMR) navigation based on gyroscope-free method. In this research, the navigation errors of the gyroscope-free method in long-time missions are demonstrated. To compensate the position error, the aid information of low-cost stereo cameras and a topological map of the workspace are employed in the navigation system. After precise sensor calibration, an amendment algorithm is presented to fuse the measurement of gyroscope-free inertial measurement unit (GFIMU) and stereo camera observations. The advantages and comparisons of vision aid navigation and gyroscope-free navigation of mobile robots will be also discussed. The experimental results show the increasing accuracy in vision-aid navigation of mobile robot.
Nonlinear Dynamic Analysis of a Polydyne Cam With Translated Roller Follower Mechanism With Clearance
Authors: Yousuf Louay S. , Drira Anis
Published: November 2018

In this paper, a polydyne cam with translated roller follower over a range of speeds are analyzed. There is a clearance between the follower and the guide. The dynamic simulation is investigated taking into account the impact and the friction. The simulation has been done by using Solidworks program. The effect of follower guides’ clearances on roller follower non-periodicity is considered based on Lyapunov exponent technique. Rosenstein method is used to calculate largest Lyapunov exponent for different angular velocities of the cam. The experimental setup has been implemented by using OPTOTRAK/3020 through a 3-D infrared markers to track follower motion. The power spectrum analysis of Fast Fourier Transform and phase plane contour are examined roller follower non-periodicity.
A Comprehensive Fluid Coupled Lateral Drill String Vibration Model Based on Classical Vibration Theories
Authors: Chodankar Abhijeet D. , Seibi Abdennour
Published: November 2018

The drilling industry has been suffering from huge monetary losses and non-productive time due to wear and fatigue of the drill string components. Vibration mitigation plays a pivotal role in extending the life of drill string components. The development of a comprehensive drill string vibration model will help in classifying the causes of drill string vibrations and helps in planning pro-active measures to suppress it. In the past, researchers have developed models based on factors like drill string length, axial compression load, lateral loads, shear deformation, rotary inertia and fluid damping. The four classical engineering vibration theories will be discussed in detail with the addition of fluid stiffness and fluid damping. This paper develops a drill string vibration model considering the effects of bending, translational inertia, rotary inertia, shear deformation, fluid stiffness and fluid damping. The drill string is considered as a cantilever beam of a circular cross-section immersed in water with equal pressure on both sides. The water is considered to be a spring and dash-pot model in parallel. It adopts a classical solution methodology based on D’Almbert’s principle. The eigen values, normalized mode shape, natural frequencies, orthogonality conditions and dynamic response equations are derived for all the theories. Natural Frequency and Dynamic response of the drill string are used to make informed decisions. Numerical simulation results show the influence of all the factors on vibration damping of the drill string. A critical understanding of the effects of all the above factors individually and in tandem will help in adopting a novel drilling strategy. To conclude, a complete step-by-step methodology for the proposed comprehensive drill string vibration model is put forth to determine the natural frequency and dynamic response of the drill string.
Integrated Steering and Braking Control System for Collision Avoidance by Using Virtual Repulsive Force Field Method
Authors: Yokoyama Atsushi , Raksincharoensak Pongsathorn , Yoshikawa Naoto
Published: November 2018

Advanced Driver Assistance Systems (ADAS) and autonomous driving systems are being enhanced to deal with various types of collision avoidance use-case scenarios. To handle those complicated scenarios, a unified two-dimensional planar motion control methodology assuming virtual repulsive force from obstacles is introduced, which is physically interpretable and comprehensible. The direction and magnitude of virtual repulsive force are determined considering the orientation of obstacle surface planes and the friction limit between tires and road surface respectively. Applying the concept of virtual repulsive force field, the collision avoidance path can be derived from geometrical relationship and the control activation points can be obtained as algebraic solutions.

By using a simple particle mass model, the formulation for path and control activation point is described. The simulation is conducted against not only in the case of a straight roadway but also in the case of a curve roadway. By designing feedforward and feedback controllers based on a two-wheel vehicle dynamics model, the effectiveness of the proposed method is verified and the feasibility of controller implementation for actual vehicle is also investigated.
A Novel Dynamic Model of a Reaction Wheel Assembly for High Accuracy Pointing Space Missions
Authors: Sanfedino Francesco , Alazard Daniel , Pommier-Budinger Valérie , Boquet Fabrice , Falcoz Alexandre
Published: November 2018

This paper proposes a novel dynamic model of a Reaction Wheel Assembly (RWA) based on the Two-Input Two-Output Port framework, already presented by the authors. This method allows the user to study a complex system with a sub-structured approach: each sub-element transfers its dynamic content to the other sub-elements through local attachment points with any set of boundary conditions. An RWA is modelled with this approach and it is then used to study the impact of typical reaction wheel perturbations on a flexible satellite in order to analyze the micro-vibration content for a high accuracy pointing mission. This formulation reveals the impact of any structural design parameter and highlights the need of passive isolators to reduce the micro-vibration issues. The frequency analysis of the transfer between the disturbance sources and the line-of-sight (LOS) jitter highlights the role of the reaction wheel speed on the flexible modes migration and suggests which control strategies can be considered to mitigate the residual micro-vibration content in order to fulfil the mission performances.
On Steady-State Solutions of a Wave Equation by Solving a Delay Differential Equation With an Incremental Harmonic Balance Method
Authors: Wang Xuefeng , Liu Mao , Zhu Weidong
Published: November 2018

For wave propagation in periodic media with strong nonlinearity, steady-state solutions can be obtained by solving a corresponding nonlinear delay differential equation (DDE). Based on the periodicity, the steady-state response of a repeated particle or segment in the media contains the complete information of solutions for the wave equation. Considering the motion of the selected particle or segment as a variable, motions of its adjacent particles or segments can be described by the same variable function with different phases, which are delayed variables. Thus, the governing equation for wave propagation can be converted to a nonlinear DDE with multiple delays. A modified incremental harmonic balance (IHB) method is presented here to solve the nonlinear DDE by introducing a delay matrix operator, where a direct approach is used to efficiently and automatically construct the Jacobian matrix for the nonlinear residual in the IHB method. This method is presented by solving an example of a one-dimensional monatomic chain under a nonlinear Hertzian contact law. Results are well matched with those in previous work, while calculation time and derivation effort are significantly reduced. Also there is no additional derivation required to solve new wave systems with different governing equations.
Algorithms for Localization and Routing of Unmanned Vehicles in GPS-Denied Environments
Authors: Wang Bingyu , Rathinam Sivakumar , Sharma Rajnikant , Sundar Kaarthik
Published: November 2018

A majority of the routing algorithms for unmanned aerial or ground vehicles rely on Global Positioning System (GPS) information for localization. However, disruption of GPS signals, by intention or otherwise, can render these algorithms ineffective. This article provides a way to address this issue by utilizing landmarks to aid localization in GPS-denied environments. Specifically, given a number of vehicles and a set of targets, we formulate a joint routing and landmark placement problem as a combinatorial optimization problem: to compute paths for the vehicles that traverse every target at least once, and to place landmarks to aid the vehicles in localization while each of them traverses its route, such that the sum of the traveling cost and the landmark placement cost is minimized. A mixed-integer linear program is presented, and a set of algorithms and heuristics are proposed for different approaches to address certain issues not covered by the linear program. The performance of each proposed algorithm is evaluated and compared through extensive computational and simulation results.
Genetic Algorithm Approach for UAV Persistent Visitation Problem
Authors: Von Moll Alexander L. , Casbeer David W. , Kalyanam Krishna , Manyam Satyanarayana G.
Published: November 2018

We employ a genetic algorithm approach to solving the persistent visitation problem for UAVs. The objective is to minimize the maximum weighted revisit time over all the sites in a cyclicly repeating walk. In general, the optimal length of the walk is not known, so this method (like the exact methods) assume some fixed length. Exact methods for solving the problem have recently been put forth, however, in the absence of additional heuristics, the exact method scales poorly for problems with more than 10 sites or so. By using a genetic algorithm, performance and computation time can be traded off depending on the application. The main contributions are a novel chromosome encoding scheme and genetic operators for cyclic walks which may visit sites more than once. Examples show that the performance is comparable to exact methods with better scalability.
Monitoring and Control of Workpiece Vibrations Using Proportional Hydraulic Clamping Mechanism
Authors: Yadav Manisha , Mohite Suhas
Published: November 2018

Machining thin-walled components involves continuous decrease in mass and stiffness of the parts being machined, causing increase in vibrations and instability. This leads to undesirable machining errors in dimensional and form tolerances as well as surface finish which adversely affects the quality of machined parts.

To track and quantify the changing dynamic behaviour of Aluminum 6061-T6 workpiece, first, numerical simulations are carried out in ANSYS Workbench 18.2 to extract its modal properties. To validate this, off-line modal hammer tests are carried out on a number of semi-machined fixtured components, representing intermediate stages of machining. The results of the numerical simulations match well with the experimental measurements. With thinning of the walls from 6mm to 4.5mm the natural frequencies and damping ratios are found to drop by a factor of 1.5 and the magnification factor is found to rise by 25% signifying rise in the vibration levels. This obviously would reflect in enhanced vibrations of the workpiece when subjected to dynamic forces during machining. In this paper, this problem is addressed by deploying strain gauge bridge in the feedback and thereby regulating clamping pressure by proportional hydraulic clamping mechanism in an on-line mode. The method is found to compensate the vibration level by 40% and can be integrated in the design of a smart fixtures.
Control Design for the System of Manipulator Handling a Flexible Payload With Input Constraints
Authors: Liu Shuyang , Langari Reza , Li Yuanchun
Published: November 2018

In this paper, we consider the control design for manipulator handling a flexible payload in the presence of input constraints. The dynamics of the system is described by coupled ordinary differential equation and a partial differential equation. Considering actuators saturation, the proposed control law applies a smooth hyperbolic function to handle the effect of the input constraints. The asymptotic stability of the closed-loop system is proved by using semigroup theory and extended LaSalle’s Invariance Principle. Simulation results show that the proposed controller is effective.
A Fault Tolerant Vehicle Stability Control Using Adaptive Control Allocation
Authors: Temiz Ozan , Cakmakci Melih , Yildiz Yildiray
Published: November 2018

This paper presents an integrated fault-tolerant adaptive control allocation strategy for four wheel frive - four wheel steering ground vehicles to increase yaw stability. Conventionally, control of brakes, motors and steering angles are handled separately. In this study, these actuators are controlled simultaneously using an adaptive control allocation strategy. The overall structure consists of two steps: At the first level, virtual control input consisting of the desired traction force, the desired moment correction and the required lateral force correction to maintain driver’s intention are calculated based on the driver’s steering and throttle input and vehicle’s side slip angle. Then, the allocation module determines the traction forces at each wheel, front steering angle correction and rear steering wheel angle, based on the virtual control input. Proposed strategy is validated using a non-linear three degree of freedom reduced two-track vehicle model and results demonstrate that the vehicle can successfully follow the reference motion while protecting yaw stability, even in the cases of device failure and changed road conditions.
Stability Analysis and Controller Design for Fuzzy Parameter Varying Systems Based on Fuzzy Lyapunov Function
Authors: Ban Xiaojun , Zhang Hongyang , Wu Fen
Published: November 2018

The fuzzy parameter varying (FPV) system is a mathematical model proposed to handle nonlinear time-varying dynamical systems encountered in engineering, which has some essential advantages in handling time-varying models. In this article, a new relaxation approach is proposed for the analysis and controller design of the FPV system. Different from the current results on the FPV system, the proposed approach employs the fuzzy Lyapunov function and full block S-procedure to reduce the conservatism in analysis. Furthermore, the relaxation technique proposed in this article can be also used in solving controller synthesis problem effectively. As a result, a design procedure of non-PDC output feedback gain-scheduling controller is provided to ensure asymptotic stability of the closed-loop FPV system. A numerical example is provided to illustrate the proposed method.
Locally Adaptive Online Trajectory Optimization in Unknown Environments With RRTs
Authors: Evans Ethan N. , Meyer Patrick , Seifert Samuel , Mavris Dimitri N. , Theodorou Evangelos A.
Published: November 2018

Rapidly Exploring Random Trees (RRTs) have gained significant attention due to provable properties such as completeness and asymptotic optimality. However, offline methods are only useful when the entire problem landscape is known a priori. Furthermore, many real world applications have problem scopes that are orders of magnitude larger than typical mazes and bug traps that require large numbers of samples to match typical sample densities, resulting in high computational effort for reasonably low-cost trajectories. In this paper we propose an online trajectory optimization algorithm for uncertain large environments using RRTs, which we call Locally Adaptive Rapidly Exploring Random Tree (LARRT). This is achieved through two main contributions. We use an adaptive local sampling region and adaptive sampling scheme which depend on states of the dynamic system and observations of obstacles. We also propose a localized approach to planning and re-planning through fixing the root node to the current vehicle state and adding tree update functions. LARRT is designed to leverage local problem scope to reduce computational complexity and obtain a total lower-cost solution compared to a classical RRT of a similar number of nodes. Using this technique we can ensure that popular variants of RRT will remain online even for prohibitively large planning problems by transforming a large trajectory optimization approach to one that resembles receding horizon optimization. Finally, we demonstrate our approach in simulation and discuss various algorithmic trade-offs of the proposed approach.
Optimal Switching of Voltage Source Inverters Using Approximate Dynamic Programming
Authors: Gogani Khiabani Ataollah , Heydari Ali
Published: November 2018

In this study, approximate dynamic programming is utilized to devise an optimal procedure in order to convert DC voltage to single-phase AC voltage. In order to determine the optimal policy, a function approximator, called critic, is used. The critic, which is defined to be a function of system states and elapsed time, is tuned once offline and then used in feedback control to achieve the desired AC voltage. Simulations show that the proposed controller not only performs successfully with linear and highly nonlinear load, but also has some relative robustness to parameter uncertainty and disturbances.
A Multibody Toolbox for Hybrid Dynamic System Modeling Based on Nonholonomic Symbolic Formalism
Authors: Wang Jiamin , Kamidi Vinay R. , Ben-Tzvi Pinhas
Published: November 2018

This paper proposes a hybrid multibody dynamics formalism with a symbolical multibody toolbox developed in MATLAB Environment. The toolbox can generate the dynamic model of a multibody system with hybrid and nonholonomic dynamic properties. The framework and software structure of the toolbox are briefly demonstrated. The paper discusses the recursive kinematics and modular modeling theories that help improve the modeling performance and offer accessibility into the dynamic elements. The formalism that offers a symbolic solution to nonholonomic and constrained dynamics is explained in detail. The toolbox also provides design tools and auto-compilation of hybrid automata. Two exemplary models and their simulations are presented to verify the feasibility of the formalism and demonstrate the performance of the toolbox.
Multi-Objective Optimal Design of Passive Suspension System With Inerter Damper
Authors: Xu Xiaotian , Sardahi Yousef , Zheng Chenyu
Published: November 2018

This paper presents a many-objective optimal design of a four-degree-of-freedom passive suspension system with an inerter device. In the optimization process, four objectives are considered: passenger’s head acceleration (HA), crest factor (CF), suspension deflection (SD), and tire deflection (TD). The former two objectives are important for the health and comfort of the driver and the latter two quantify the suspension system performance. The spring ks and damping cs constants between the sprung mass and unsprung mass, the inertance coefficient B, and the tire spring constant ky are considered as design parameters. The non-dominated sorting genetic algorithm (NSGA-II) is used to solve this optimization problem. The results show that there are many optimal trade-offs among the design objectives that could be applicable to suspension design in the industry.
Controllability of a Pair of Swimming Microrotors in a Bounded Domain at Low Reynolds Number
Authors: Buzhardt Jake , Fedonyuk Vitaliy , Sudarsanam Senbagaraman , Tallapragada Phanindra
Published: November 2018

We investigate the dynamics of a pair of spinning spheres or microrotors in a fluid at low Reynolds numbers. These microrotors are each approximated by a rotlet, a fundamental singularity of the Stokes equation. Singularities of Stokes flows serve as useful theoretical models for microswimmers and micro-robots. Rotlet models of microswimmers have received less attention since a rotlet cannot generate translation by itself if the only control input is the rate of spin or strength of the rotlet. However a pair of rotlets can interact and execute net motion. In an unbounded domain of fluid, the positions of a pair of rotlets are not fully controllable due to the existence of an invariant. However, in a confined domain, we show that the positions of the pair of spheres are small time locally controllable. We show how control inputs can be constructed based on combinations of Lie brackets to move the rotlets from one point to another in the domain.
Experimental and Numerical Analysis of a Sandwich Beam With Tip Mass
Authors: Joubaneh E. F. , Barry O. R. , Oguamanam D. C. D.
Published: November 2018

This paper presents experimental and numerical analyses of a vibrating sandwich beam with a tip mass. The mathematical formulation is based on higher order sandwich panel theory (HSAPT) and the governing equations of motion and boundary conditions are obtained using Hamilton’s principle. General Differential Quadrature (GDQ) is employed to solve the system governing equations of motion. Experiments are carried out to validate the proposed formulation and the results show very good agreement. Parametric studies are conducted to investigate the influence of key design parameters on the natural frequency and vibration response of the system.
ILC With Time-Varying Delay Estimation: A Case Study on Twin Roll Strip Casting
Authors: Browne Florian , Chiu George , Jain Neera , Rees Brad
Published: November 2018

In this paper we propose an iterative learning control (ILC) algorithm for a class of periodic processes with a variable time-delay that is greater than one iteration in length. We estimate the delay by separating it into two components: an estimate based on the number of iterations contained within a single delay period and an estimate defined as the residual between the actual delay and the iteration-based estimate. This structure enables the derivation of a stability law for an ILC algorithm that is a function of the delay estimation error. The proposed ILC algorithm is then applied to twin roll strip casting and the results are validated using experimental process data. We also demonstrate the sensitivity of the ILC algorithm to estimation error through simulation results.
An Economic Model Predictive Control Approach for Wind Power Smoothing and Tower Load Mitigation
Authors: Alhneaish Mohamed M. , Shaltout Mohamed L. , Metwalli Sayed M.
Published: November 2018

An economic model predictive control framework is presented in this study for an integrated wind turbine and flywheel energy storage system. The control objective is to smooth wind power output and mitigate tower fatigue load. The optimal control problem within the model predictive control framework has been formulated as a convex optimal control problem with linear dynamics and convex constraints that can be solved globally. The performance of the proposed control algorithm is compared to that of a standard wind turbine controller. The effect of the proposed control actions on the fatigue loads acting on the tower and blades is studied. The simulation results, with various wind scenarios, showed the ability of the proposed control algorithm to achieve the aforementioned objectives in terms of smoothing output power and mitigating tower fatigue load at the cost of a minimal reduction of the wind energy harvested.
Planar Motion Control, Coordination and Dynamic Entrainment in Chaplygin Beanies
Authors: Kelly Scott , Abrajan-Guerrero Rodrigo , Grover Jaskaran , Travers Matthew , Choset Howie
Published: November 2018

The Chaplygin beanie is a single-input robotic vehicle for which partial planar motion control can be achieved by exploiting a simple nonholonomic constraint. A previous paper suggested a strategy for such motion control. In the present paper, this strategy is validated experimentally and extended to the context of multi-vehicle coordination. It is then shown that when the plane on which two such vehicles operate is translationally compliant, energy transfer between the two can enable a mechanism whereby one (operating under control) may entrain the other (operating passively), partly coordinating their motion. As an extension to this result, it is further demonstrated that a pair of passive vehicles operating on a translationally compliant platform can eventually attain the same heading when released from their deformed configurations.
Numerical Evaluation of Pressure Drop Across Orifices for Different Gas-Liquid Mixtures
Authors: Khan Zurwa , Tafreshi Reza , Franchek Matthew , Grigoriadis Karolos
Published: November 2018

Modeling two-phase flow across orifices is critical in optimizing orifice design and fluid’s operation in countless architectures and machineries. While flow across different orifice geometries has been extensively studied for air-water flow, simulations and experiments on other two-phase flow combinations are limited. Since every fluid mixture has its own physical properties, such as densities, viscosities and surface tensions, the effect of these properties on the local pressure drops across the orifices may differ. This study aims to investigate the effect of different fluid combinations on the pressure drop across sharp-edged orifices with varying gas mass fractions, orifice thicknesses, and area ratios. A numerical model was developed and validated using experimental data for air-water flow. Then, the model was extended to include various gas-liquid flows including gasoil, argon-diesel and fuel oil. The local pressure drops were then estimated and compared with the existing empirical correlations. The developed model presents a unified approach to measure pressure drop across orifices for different fluid mixtures with different geometries and gas-liquid compositions, unlike existing empirical correlations which are applicable for specific orifice geometries. The results showed that Morris correlation, Simpson correlation, and Chisholm correlation are more appropriate for gasoil, argon-diesel and fuel oil mixtures, respectively. They also yielded that for all fluid combinations, increasing orifice thickness and area ratio led to a decrease in local pressure drop, while increasing gas mass fraction led to an increase in local pressure drop. This revealed that, despite having similar responses to changes in orifice geometries and gas fractions, unlike the assumption made by previous works on air-water flow, no empirical correlation is able to predict pressure drops for all flow mixtures, while the presented numerical model can efficiently determine the local pressure drop for all combinations of flow mixtures, orifice geometries and gas mass fractions.
Stochastic Policies for Online Computation Triggering in Powertrain Control
Authors: Liu Kuan , Wang Yue Yun , Haskara Ibrahim , Chang Chen-Fang , Girard Anouck , Kolmanovsky Ilya
Published: November 2018

With the rapid growth in the amount of computations that need to be performed by modern electronic control units and in the complexity of the algorithms, there is a pressing need to develop approaches to reduce chronometric loading in automotive vehicles. This paper presents a cyberphysical systems framework for the development of stochastic optimal decision policies that trigger the computations online. For a specific case study, we consider online triggering of the computations involved in obtaining a linearized model in a setting when such a linearized model is required by control or estimation algorithms. The objective is to define a policy for triggering the linearization that balances the average model accuracy (or expected closed loop performance) with the average computational cost. The problem is formulated as a stochastic optimal control problem and solved using stochastic dynamic programming (SDP). The approach is described, then illustrated with three examples, a pendulum, a turbocharged diesel engine, and a turbocharged spark ignition engine, that illustrate the trade-off between the computational cost and expected linearized model accuracy.
Prediction of Wheel Slipping Limits for Mobile Robots
Authors: Whitman Alan M. , Clayton Garrett M. , Ashrafiuon Hashem
Published: November 2018

In this paper, we present a method to accurately predict the wheel speed limits at which mobile robots can operate without significant slipping. The method is based on an asymptotic solution of the nonlinear equations of motion. Using this approach, we can predict wheel slipping limits of both the inside and outside wheel when the robot is in a circular motion of any radius. The analytical results are supported by experiments which show that the inside wheel slipping limits for circular motions of various radii occur very close to the predicted values.