System Response In Terms Research Articles

DYNAMIC MATHEMATICAL MODELING AND CONTROL ALGORITHMS DESIGN OF AN INVERTED PENDULUM SYSTEM

The inimitable features of multivariable, instability, non-minimum phase and non-linearity has established an inverted pendulum system as benchmark to investigate and test new emerging control schemes. In this paper, the objectives are to explicitly model the system dynamics of an inverted pendulum and implement different control algorithms that will stabilize the pendulum in the upright vertical position by controlling the input force applied to the cart in the horizontal position. The mathematical model is derived based on the energy property of Lagrange approach and the control algorithms are expanded on the derived mathematical model in MATLAB-SIMULINK environment. Hence, we proposed four different controls algorithms proportional-integral-derivative controller (PID), pole placement feedback controller (PPFC), linear quadratic regulator controller (LQR) and linear quadratic regulator with estimator (LQR+Estimator) for the control of the linearized inverted pendulum system. The study compares the proposed control algorithms in terms of system response and performance.

How do traffic and demand daily changes define urban emergency medical service (uEMS) strategic decisions?: A robust survival model

This paper presents a methodology to locate vehicle base stations using robust optimization to address daily traffic and demand changes, which are due to what we define as city dynamics. The model allows us to better understand how these daily changes affect an urban emergency medical service (uEMS) response system.The methodology incorporates two steps. The first step uses scenario-based optimization and survival function theory to locate vehicle base stations, whereas the second step uses agent-based simulation to assess the solution performance and compare it with less robust and non-survival prone solutions. The proposed models are tested for different situations using real data from the city of Porto.The results of the sensitivity analysis of the model show the relevance of understanding the dynamics of cities and how they impact uEMS response systems. Useful insights regarding the number of stations and the average response time are addressed together with the minimum number of stations required for different maximum response time limits and different survival coefficients.Finally, we conclude on how a robust solution improves response time by accounting for city dynamics, and how a heterogeneous survival based approach benefits victims’ by properly measuring the system response in terms of the victim’ outcomes.

Constrained population extremal optimization-based robust load frequency control of multi-area interconnected power system

This paper proposes a robust proportional-integral (PI) controller with its parameters designed by constrained population extremal optimization for load frequency control problem of multi-area interconnected. During the process of optimization, the robust performance index is used as fitness function, where linear matrix inequalities technique is employed to describe the H∞ constraint, and the taking error performance requirement such as integral time absolute error is incorporated as another constraint. Three different two-area interconnected power systems are used as test systems to demonstrate the effectiveness of the proposed controller by comparing with other PI control methods and one optimized model predictive control. In addition, in order to investigate the performance of proposed controller for the LFC problem of large scale system, a three-area interconnected power system is used as another test system. The comprehensive experimental results fully demonstrate that the proposed control scheme in this paper performs better than other control strategies on the most considered scenarios under the conditions of load disturbance and parameters uncertainties in terms of system response and control performance indices.

New Insights into the Short Pitch Corrugation Enigma Based on 3D-FE Coupled Dynamic Vehicle-Track Modeling of Frictional Rolling Contact

A three-dimensional (3D) finite element (FE) dynamic frictional rolling contact model is presented for the study of short pitch corrugation that considers direct and instantaneous coupling between the contact mechanics and the structural dynamics in a vehicle-track system. In this study, we examine the system responses in terms of vibration modes, contact forces and the resulting wear with smooth rail and corrugated rail with progressively increasing amplitude to infer the conditions for consistent corrugation initiation and growth. Wear is assumed to be the damage mechanism, and short pitch corrugation is modeled using wavelengths from field observations of a Dutch railway. The contribution of this paper is a global perspective of the consistency conditions that govern the evolution of short pitch corrugation. The main insights are as follows: (1) the longitudinal vibration modes are probably dominant for short pitch corrugation initiation; (2) during short pitch corrugation evolution, the interaction and consistency between longitudinal and vertical modes should determine the development of short pitch corrugation, and once a certain severity is reached, vertical modes become dominant; and (3) in the case simulated in this paper, corrugation does not grow probably due to not only the different resulting main frequencies of the vertical and longitudinal contact forces, but also the inconsistency between the frequencies of the vertical and longitudinal vibration modes and the resulting wear. It is inferred that in the continuous process of initiation and growth of the corrugation, there should be a consistency between them, and this could be done by the control of certain track parameters.

Numerical Investigation of the Dynamic Characteristics of a Dual-Throat-Nozzle for Fluidic Thrust-Vectoring

A computational method tailored for the simulation of fluidic thrust-vectoring systems is employed to investigate the dynamic response of a dual-throat nozzle in open- and closed-loop control. Thrust vectoring in fixed, symmetric nozzles is obtained by secondary flow injections that cause local flow separations, asymmetric pressure distributions, and, as a consequence, the vectoring of primary jet flow. The computational technique is based on a well-assessed mathematical model for the compressible unsteady Reynolds-averaged Navier–Stokes equations. A minimal control system governs the unsteady blowing. Nozzle performances and thrust-vector angles have been computed for a wide range of nozzle pressure ratios and secondary flow injection rates. The numerical results are compared with the experimental data available in the open literature. Several computations of the open-loop dynamics of the nozzle under different forcing have been performed to investigate the system response in terms of thrust-vectoring effectiveness and controllability. These computations have been used to extract autoregressive exogenous models of the nozzle dynamics. The effects of including the actuator dynamics are also discussed. Simple strategies of closed-loop control of the nozzle system by proportional–integrative–derivative regulators are investigated numerically. The closed-loop model predictive control of the system, based on the autoregressive exogenous models, is addressed.

Research on the dynamic response of high-contact-ratio spur gears influenced by surface roughness under EHL condition

Employing high-contact-ratio (HCR) gear is an effective method of decreasing the load on a single tooth, as well as reducing vibration and noise. While the spindlier tooth leads to greater relative sliding, having more teeth participate in contact at the same time makes the HCR gear more sensitive to the surface quality. Available literature regarding HCR gear primarily investigates the geometrical optimization, load distribution, or efficiency calculation. Limited work has been conducted on the effect of rough surfaces on the dynamic performance of HCR gear. For this reason, a multi-degree-of-freedom (MDOF) model is presented mathematically to characterize the static transmission error based on fractal theory, investigate the relative sliding friction using an EHL-based friction coefficient formula, and detail the time-varying friction coefficient suitable for HCR gear. Based on numerical results, the surface roughness has little influence on system response in terms of the dynamic transmission error but has a large effect on the motion in off-line-of-action (OLOA) direction and friction force. The impact of shaft-bearing stiffness and damping ratio is also explored with results revealing that a greater shaft-bearing stiffness is beneficial in obtaining a more stable motion in OLOA direction, and a larger damping ratio results in a smaller effective friction force. The theory presented in this report outlines a new method of analyzing the dynamics of HCR gear in respect of introducing surface roughness into MDOF model directly, as well as establishing an indirect relationship between dynamic responses and surface roughness. This method is expected to guide surface roughness design and manufacturing in the future.

Torsional Oscillations in Automotive Transmissions: Experimental Analysis and Modelling

The paper investigates the torsional oscillations of an automotive transmission system by means of an experimental test bench used to validate the proposed lumped parameter model. The rig consists of a Dual Clutch Transmission (DCT) and a Manual Transmission (MT) connected through the respective output shafts, while the excitation is provided by two electric motors, which are controlled in speed or torque. The experimental analysis includes the measurement of the external torques, applied by the two electric motors to the mechanical system, and the measurement of the system response in terms of angular speeds at different positions along the transmission line. The frequency response of the system is estimated from the experimental data and compared with the results of a 5-degree-of-freedom lumped parameter model, which proves to be adequate to describe the dynamic behaviour of the system up to a frequency of 200 Hz. The comparison between simulated results and experimental data shows good agreement, so the model can be used to predict the torsional vibrations of the transmission system in the linear field. Moreover, the effects of the nonlinearities associated with the mean value of the excitations are shown. Finally the influence of the selected gear ratio on the experimental frequency response is discussed.

DEPTH CONTROL OF AN UNDERWATER REMOTELY OPERATED VEHICLE USING NEURAL NETWORK PREDICTIVE CONTROL

This paper investigates the depth control of an unmanned underwater remotely operated vehicle (ROV) using neural network predictive control (NNPC). The NNPC is applied to control the depth of the ROV to improve the performances of system response in terms of overshoot. To assess the viability of the method, the system was simulated using MATLAB/Simulink by neural network predictive control toolbox. In this paper also investigates the number of data samples (1000, 5000 and 10,000) to train neural network. The simulation reveals that the NNPC has the better performance in terms of its response, but the execution time will be increased. The comparison between other controller such as conventional PI controller, Linear Quadratic Regulation (LQR) and fuzzy logic controller also covered in this paper where the main advantage of NNPC is the fastest system response on depth control.

Dynamic behavior of suture-anastomosed arteries and implications to vascular surgery operations.

BackgroundRoutine vascular surgery operations involve stitching of disconnected human arteries with themselves or with artificial grafts (arterial anastomosis). This study aims to extend current knowledge and provide better-substantiated understanding of the mechanics of end-to-end anastomosis through the development of an analytical model governing the dynamic behavior of the anastomotic region of two initially separated arteries.MethodsThe formulation accounts for the arterial axial-circumferential deformation coupling and suture-artery interaction. The proposed model captures the effects of the most important parameters, including the geometric and mechanical properties of artery and sutures, number of sutures, loading characteristics, longitudinal residual stresses, and suture pre-tensioning.ResultsClosed-form expressions are derived for the system response in terms of arterial radial displacement, anastomotic gap, suture tensile force, and embedding stress due to suture-artery contact interaction. Explicit objective functionalities are established to prevent failure at the anastomotic interface.ConclusionsThe mathematical formulation reveals useful interrelations among the problem parameters, thus making the proposed model a valuable tool for the optimal selection of materials and improved functionality of the sutures. By virtue of their generality and directness of application, the findings of this study can ultimately form the basis for the development of vascular anastomosis guidelines pertaining to the prevention of post-surgery implications.

Ecohydrological effects of management on subalpine grasslands: From local to catchment scale

[1] Grassland and pastures are important land uses in subalpine and alpine environments. They are typically subjected to management practices that can change the biophysical structure of the canopy through defoliation and can alter soil hydraulic properties. These modifications have the potential to impact hydrological and energy fluxes as well as the primary productivity of grasslands. We investigate how a series of management practices, such as grass cut, grazing, and the consequent soil compaction due to treading by animals are affecting water resources, flood generation, and grassland productivity in a subalpine region. Results are obtained using a mechanistic ecohydrological model, Tethys-Chloris. The model is first confirmed using energy, water, and carbon fluxes measured at three eddy covariance stations over grasslands in Switzerland and discharge measured in a small experimental catchment. A series of virtual experiments are then designed to elucidate the importance of various management scenarios at the plot and catchment scales. Results show that only severe management actions such as low grass cuts or heavy grazing are able to influence considerably the long-term hydrological behavior. Moderate management practices are typically unable to modify the system response in terms of energy and water fluxes. An important short-term effect is represented by animal-induced soil compaction that can reduce infiltration capacity leading to peak flow considerably higher than in undisturbed conditions. The productivity of vegetation in absence of nutrient limitation is considerably affected by the different management scenarios with tolerable disturbances that lead to higher aboveground net primary production.

Semi-stochastic cell-level computational modeling of the immune system response to bacterial infections and the effects of antibiotics

A mathematical model for the immune system response to bacterial infections is proposed. The formalism is based on modeling the chemokine-determined transmigration of leukocytes from a venule through the venule walls and the subsequent in-tissue migration and engulfment of the pathogens that are responsible for the infection. The model is based on basic principles, such as Poiseuille blood flow through the venule, fundamental solutions of the diffusion-reaction equation for the concentration field of pathogen-released chemokines, linear chemotaxis of the leukocytes, random walk of pathogens, and stochastic processes for the death and division of pathogens. Thereby, a computationally tractable and, as far as we know, original framework has been obtained, which is used to incorporate the interaction of a substantial number of leukocytes and thereby to unravel the significance of biological processes and parameters regarding the immune system response. The developed model provides a neat way for visualization of the biophysical mechanism of the immune system response. The simulations indicate a weak correlation between the immune system response in terms of bacterial clearing time and the leukocyte stiffness, and a significant decrease in the clearing time with increasing in-blood leukocyte density, decreasing pathogen motility, and increasing venule wall transmissivity. Finally, the increase in the pathogen death rate and decrease in pathogen motility induce a decrease in the clearing time of the infection. The adjustment of the latter two quantities mimic the administration of antibiotics.

Performance-based design methodologies for geotechnical earthquake engineering

Performance-based design offers a number of advantages over historically common design approaches. As currently practiced, performance is most commonly evaluated in terms of system response, typically displacement-related, using traditional ground motion intensity measures defined at two or more discrete hazard levels. Such approaches do not necessarily allow all of the potential benefits of performance-based design to be realized. More recently, integral performance-based procedures that account for ground shaking hazards at all hazard levels have been developed. This paper reviews basic concepts of performance and different approaches to the implementation of performance-based design. An load and resistance factor-like methodology is described and illustrated with an example.

A Parametric Study on Performance of Semi-active Suspension System with Variable Damping Coefficient Limit

The research paper involves modeling of semi-active suspension system using quarter car model in Simulink environment. In order to modulate the damping coefficient value, fuzzy logic controller is modeled using Fuzzy Tool Box. Three different damping coefficient limits are selected for analyzing the response of system in terms of ride comfort. Road disturbance profile comprising a combination of two sinusoidal curves is modeled and the three semi-active suspension systems are simulated. Suspension displacement and velocity parameters are selected as the indicators of ride comfort. The results manifest supremacy of the system having damping coefficient limit of 4000N s/m. The optimized system performs well fulfilling the requirements of minimum percentage overshoot and rapid stabilizing time.

Analysis of a Self-Oscillating Bidirectional DC–DC Converter in Battery Energy Storage Applications

This paper combines three different methods for the analysis of a self-oscillating bidirectional dc-dc converter under hysteresis control. First, the describing function method is used to predict the steady-state limit cycle, along with its oscillation amplitude and frequency. Second, the Tsypkin method is applied to provide more precise information on the dynamical behavior of the system. To complete the study, a sliding-mode approach is used to provide more insight into the system response in terms of its parameters. A comparative study among the results obtained from the different approaches in the frequency and time domain is given. Finally, an experimental prototype validates the theoretical and the numerical predictions.

Hybrid Neural-Fuzzy Controller for Motorized Robot Arm

In this study, a design methodology is introduced that blends the neural and fuzzy logic controllers in an intelligent way developing a new intelligent hybrid controller. In this design methodology, the fuzzy logic controller works in parallel with the neural controller and adjusting the output of the neural controller. The performance of our proposed controller is demonstrated on a motorized robot arm with disturbances. The simulation results shows that the new hybrid neural -fuzzy controller provides better system response in terms of transient and steady-state performance when compared to neural or fuzzy logic controller applications. The development and implementation of the proposed controller is done using the MATLAB/Simulink toolbox to illustrate the efficiency of the proposed method.

Power Flow and Sound Radiation of a Submerged Cylindrical Shell with Internal Structural

The vibrational power flow in a submerged infinite cylindrical shell with internal rings and bulkheads are studied analytically. The harmonic motion of the shell and the pressure field in the fluid is described by Flügge shell theory and Helmholtz equation, respectively. The coupling condition on the outer surface of the shell wall is introduced to obtain the vibrational equation of this coupled system. Both four kinds of forces (moments) between rings and shell and between bulkheads and shell are considered. The solution is obtained in series form by expanding the system responses in terms of the space harmonics of the spacing of both ring stiffeners and bulkheads. The vibrational power flow and radiated sound power are obtained and the influences of various complicating effects such as the ring, bulkhead and fluid loading on the results are analyzed. The analytic model is close to engineering practice, which will be valuable to the application on noise and vibration control of submarines and underwater pipes.

Dynamical Characteristic Analysis of a Fluid-Loaded Cylindrical Shell with Structural Discontinuities

By using space-harmonic analysis method, the characteristics of vibrational power flow and sound radiation of an infinite submerged cylindrical shell with internal rings and bulkheads are studied analytically. The harmonic motion of the shell and the pressure field in the fluid are described by Flügge shell equations and Helmholtz equation, respectively. The coupling condition on the outer surface of the shell wall is introduced to obtain the vibrational equation of this coupled system. Both four kinds of forces (moments) between rings and shell and between bulkheads and shell are considered. The solution is obtained in series form by expanding the system responses in terms of the space harmonics of the spacings of both ring stiffeners and bulkheads. The vibrational power flow and radiated sound power are obtained and the influences of various complicating effects such as the ring, bulkhead and fluid loading on the results are analyzed. The analytic model is close to engineering practice, which will give some guidelines for noise reduction of this kind structure.

High dimensional model representation for stochastic finite element analysis

This paper presents a generic high dimensional model representation (HDMR) method for approximating the system response in terms of functions of lower dimensions. The proposed approach, which has been previously applied for problems dealing only with random variables, is extended in this paper for problems in which physical properties exhibit spatial random variation and may be modelled as random fields. The formulation of the extended HDMR is similar to the spectral stochastic finite element method in the sense that both of them utilize Karhunen–Loève expansion to represent the input, and lower-order expansion to represent the output. The method involves lower dimensional HDMR approximation of the system response, response surface generation of HDMR component functions, and Monte Carlo simulation. Each of the low order terms in HDMR is sub-dimensional, but they are not necessarily translating to low degree polynomials. It is an efficient formulation of the system response, if higher-order variable correlations are weak, allowing the physical model to be captured by the first few lower-order terms. Once the approximate form of the system response is defined, the failure probability can be obtained by statistical simulation. The proposed approach decouples the finite element computations and stochastic computations, and consecutively the finite element code can be treated as a black box, as in the case of a commercial software. Numerical examples are used to illustrate the features of the extended HDMR and to compare its performance with full scale simulation.

Tuning fork microgyrometers: Narrow gap vs. wide gap design

We analyse the performances of two different configurations of a tuning fork microgyrometer, the so called ‘wide gap’ design and ‘narrow gap’ design. In the former case the air gap between the vibrating forks and the walls of the surrounding frame is so large that the air flow around each fork is not influenced by the presence of the frame itself. This geometrical configuration results in a very low air damping, and, hence, allows the instrument to operate at atmospheric pressure. In the case of ‘narrow gap’ design the distance between the forks and the frame walls is instead very small. As a consequence, the instrument needs to operate under very low pressure conditions, since, at higher pressures, the presence of a thin layer of air would increase the air damping to very large values, and would not allow the correct operation of the instrument. Although the requirement of low pressure conditions represents a drawback of the narrow gap solution, we show that this instrument configuration, when compared to the wide gap design, allows to achieve a significantly smaller dynamic error and a significantly wider range of linearity. Indeed the thickness of the air gap represents an additional parameter that can be adjusted by the designer to optimise the performances of the instrument. An accurate analytical model of the sensor is presented in the paper, which constitutes a helpful designing tool for this kind of device. In particular we focus the attention on the two tines of the drive mode, which are indeed the structural components that more than others influence the instrument performances. We show that the optimal design of these fundamental elements can be obtained by neglecting the interaction with the remaining part of the sensor structure, and show how to design the instrument to minimise the amplitude error. The influence of air damping, structural damping and geometry on the system response in terms of bandwidth and dynamic error is also investigated.

Emerging school structures and collective dynamics in spawning herring: A simulation study

Schooling fish are known to display various collective behaviours depending on ecological context and life history situation. In Norwegian spring spawning herring (NSS-herring) ( Clupea harengus) different trade-offs during the seasons of feeding, overwintering, migration and spawning are likely to influence school morphology and behaviour. In the field, hydro acoustics are able to record collective patterns, but hardly the mechanisms of how individual decisions and interactions lead to the observed formations. Individual based models (IBMs) on the other hand, are promising simulation tools for investigating how low-level individual behaviour influences large-scale behaviour. We have used this approach with a rule based school model in order to gain understanding of how certain school patterns can emerge during the spawning of NSS-herring. Response to predation and motivation towards spawning are added to the response to nearby fish. Simply by varying population size and synchronisation of spawning motivation we find different system responses in terms of school morphology and dynamics. With high motivational synchronisation, the system is mainly represented by one integrated school, whereas low degree of synchronisation presents a system with frequent split-offs of small schools. An intermediate degree of synchronisation leads to a more complex situation with schools or layers in a dynamic vertical contact and formation of vertical ‘hourglasses’ or cylindrical shaped schools. This suggests that the degree of motivational synchronisation between individuals in a school will determine whether or to what degree a school splits into different components or remains integrated. We also find that with increasing population size there are new system behaviours emerging, not present with lower population size. Larger populations lead to horizontal extension of the pre-spawning components resulting in a double layer system where vertical bridges connecting the two layers are established. The cylindrical bridges are truly emergent properties of the system, formed and maintained by ovulating and spent herring moving across these structures. Similar school formations with vertical connections have been observed acoustically in spawning herring schools.