Analytical Dynamic Model Research Articles

Dynamic modelling, validation and handling performance analysis of a skid-steered vehicle

Skid-steering technology has been widely used for wheeled vehicles, because a skid-steered vehicle has great mobility so that it is able to pivot steer a larger internal hull volume. In this paper, an 8 × 8 skid-steered all-terrain vehicle equipped with a double-stream hydromechanical transmission was introduced. In order to discuss the handling performance and to obtain general conclusions, an analytical lateral dynamic model of a skid-steered vehicle was proposed and verified experimentally. Furthermore, the handling performance of the skid-steered vehicle was compared with an Ackermann steered vehicle of the same dimensions. The results show that the skid-steered vehicle has a lower ‘stability factor’ and a totally different motion attitude, that the turn centre of the skid-steered vehicle will move forwards during acceleration at a constant radius and that the transient handling performance of the skid-steered vehicle is better than that of the Ackermann steered vehicle. Furthermore, from an analysis of the lateral slip angles of the tyres during a constant-radius turn, it can be concluded that the tyres of a skid-steered vehicle easily become worn because of the larger lateral slip angles.

Audit of control algorithm quality of drum steam boilers at design stage of automation system

Investigation of complex engineering objects and improving the quality of their management in the classic version come to carry out the decomposition of the object into multiple control loops, which in turn imposes certain limitations in the practical application of research results, and leads to loss of information on the impact of parameters on each other. Therefore, the implementation in practice does not provide a research control facility as a whole. Experimental and analytical complex model of dynamics of drum boiler for all areas of regulation is developed. Algorithm and logical-structural scheme of models allow studying a synthesis of control algorithm of the entire object, to analyze the results on the basis of the transients. The physical implementation of the model assigned to the industrial freely programmable logic controller of module form factor. It is used as a base for the practical implementation of control algorithms. The result is a closed self-contained control system and simulation modeling, which has the ability to interface with external controls on the physical or logical level.

A dynamic model of a passively cooled small modular reactor for controller design purposes

An analytical dynamic model for a passively cooled small modular reactor (SMR) is developed using a state-variable lumped parameter approach. Reactor power is represented by the generation time formulation of the point kinetics equations with a single combined neutron precursor group. The heat transfer process in the core is described via an overall heat transfer coefficient by defining two coolant lumps paired to a single fuel lump. In addition, a thermal–hydraulics model for single-phase natural circulation is incorporated. For the helical-coil steam generator, a moving-boundary model including subcooled, two-phase, and superheated regions is utilized. Finally, the hot leg riser and downcomer regions are expressed by first-order lags. The performance of the overall system described by ordinary differential equations (ODEs) is evaluated by the Simulink dynamic environment and directly using a MATLAB ODE solver recommended for stiff systems. Simulation results based on NuScale SMR design data show that the initial steady-state values for 100% power are within range of the design data and the model can predict the system dynamics due to typical perturbations, e.g., control rod movement and change in feedwater mass flow rate and temperature. The model developed in this work can be utilized as a foundation for designing and testing a suitable control algorithm for reactor thermal power.

Characterization of the dominant structural vibration of hearing aid receivers

The overall aim of this research is to analyze and characterize the mechanical vibration of hearing aid receivers, a key electro-acoustic component of hearing aids. The receiver is a high efficiency miniature sound source which utilizes a balanced armature electromagnetic motor. A standard side effect for most balance armature receivers is structural vibration. This receiver-borne structural vibration can travel through the hearing aid package to the microphones, resulting in undesirable oscillations, just like acoustic feedback. To better understand and control this important source of feedback in hearing aids, a simple dynamic model has been developed to describe the system. The model consists of two rigid bodies connected by a torsional spring and damper. A method was developed to estimate the parameters for the dynamic model using experimental data. The data were collected using translational velocity measurements using a scanning laser vibrometer of a Knowles ED-series receiver on a complaint foundation. The analytical dynamic model was validated with finite element analysis using COMSOL and the multibody dynamics module.

Intelligent Robust Automotive Engine Control

In this research, manage the Internal Combustion (IC) engine modeling and a multi-inputmulti-output artificial intelligence baseline sliding mode methodology scheme is developed with guaranteed stability to simultaneously control fuel ratios to desired levels under various air flow disturbances by regulating the mass flow rates of engine PFI and DI injection systems. Analytical dynamic nonlinear modeling of internal combustion engine is carried out using elegant EulerLagrange method compromising accuracy and complexity. A baseline estimator with varying parameter gain is designed with guaranteed stability to allow implementation of the proposed state feedback sliding mode methodology into a MATLAB simulation environment, where the sliding mode strategy is implemented into a model engine control module (“software”). To estimate the dynamic model of IC engine fuzzy inference engine is applied to baseline sliding mode methodology. The proposed tracking method is designed to optimally track the desired FR by minimizing the error between the trapped in-cylinder mass and the product of the desired FR and fuel mass over a given time interval.

Evaluation of Oceanic and Terrestrial Sources of Moisture for the North American Monsoon Using Numerical Models and Precipitation Stable Isotopes

Abstract This work evaluates the oceanic and terrestrial moisture sources that contribute to North American monsoon (NAM) precipitation over a 30-yr period using the modified analytical dynamic recycling model. This computationally efficient modeling framework reveals previously overlooked moisture source regions such as Central America and the Caribbean Sea in addition to the well-known Gulf of California and Gulf of Mexico source regions. The results show that terrestrial evapotranspiration is as important as oceanic evaporation for NAM precipitation, and terrestrial sources contribute to approximately 40% of monsoonal moisture. There is a northward progression of terrestrial moisture sources, beginning with Central America during the early season and transitioning north into northern Mexico and the NAM region itself during the peak of the monsoon season. The most intense precipitation occurs toward the end of the season and tends to originate in the Gulf of California and the tropical Pacific, associated with tropical cyclones and gulf surges. Heavy stable isotopes of hydrogen and oxygen in precipitation (δD and δ18O) collected for every precipitation event measured in Tucson, Arizona, for the period 1981–2008 complement the numerical results. The analysis shows that precipitation events linked to sources from the Gulf of Mexico and Caribbean Sea are more isotopically enriched than sources from the Gulf of California and tropical Pacific. It is also seen that terrestrial regions that derive their precipitation from the Gulf of Mexico are also more isotopically enriched than moisture sources from the Pacific.

Dynamic installation and monotonic pullout of a torpedo anchor in calcareous silt

Challenges associated with dynamically installed anchors include prediction of the anchor embedment depth, which dictates the anchor's holding capacity. This is particularly true for calcareous sediments, as very little performance data exist for this anchor type in these soils. This paper reports results from a series of model tests undertaken to provide insight into the behaviour of a torpedo anchor during dynamic installation and monotonic pullout in lightly overconsolidated calcareous silt. The tests were carried out in a beam centrifuge, varying the drop height and consequently the impact velocity, and the consolidation period prior to anchor pullout. The mudline load inclination was also varied to encompass various mooring configurations. The centrifuge model test data were used to calibrate: (a) an analytical dynamic embedment model, based on conventional bearing and frictional resistance factors but with strain-rate-dependent undrained shear strength for the soil; and (b) an analytical quasi-static vertical pullout capacity model, accounting for reverse end bearing and frictional resistance. A total energy based expression, appropriate for calcareous silts, was proposed for predicting anchor embedment depth for a given anchor geometry, mass and impact velocity. For assessing anchor vertical holding capacity, a piezocone based direct design approach was also proposed, deriving anchor end bearing and frictional resistance from cone tip resistance and sleeve friction, respectively. Anchor capacity under inclined loading was presented as failure envelopes expressed in terms of dimensionless vertical and horizontal components of anchor net resistance, which agreed well with a finite-element based envelope developed for embedded foundations. The regain of anchor capacity was found to be in good agreement with predictions based on the cavity expansion framework.

Robust Parameter Dependent Receding Horizon H∞ Control of Flexible Air‐Breathing Hypersonic Vehicles with Input Constraints

AbstractThis paper describes the design of a robust parameter dependent receding horizon H∞ controller (PD‐RHHC) for a flexible air‐breathing hypersonic vehicle (ABHSV) model. Because of the complexity and uncertainty of the model of the vehicle dynamics, few control strategies take constraints into account in the computation of the control law. The objective of the current research is to develop a controller design method that can accommodate input saturation. In this paper, starting from the analytical nonlinear dynamic model with aerothermoelastic mode dynamics, a linear parameter varying (LPV) model is obtained by an improved functional substitution method. Tensor product (TP) model transformation technology is then applied to obtain the polytopic representations of the LPV model. Based on the gain‐scheduling method, a novel parameter dependent receding horizon control algorithm by convex optimization solving linear matrix inequalities (LMIs) is presented, which provides stable tracking of the velocity and altitude reference trajectories. The proposed control strategy not only addresses the issue of robustness stability with respect to parametric model uncertainty and aerothermoelastic mode, but also explicitly deals with input constraints and guarantees that the control inputs are within their limits. Finally, the numerical simulation results prove the availability of the proposed method.

CHAOTIC DISINTEGRATION OF THE INNER SOLAR SYSTEM

On timescales that greatly exceed an orbital period, typical planetary orbits evolve in a stochastic yet stable fashion. On even longer timescales, however, planetary orbits can spontaneously transition from bounded to unbound chaotic states. Large-scale instabilities associated with such behavior appear to play a dominant role in shaping the architectures of planetary systems, including our own. Here we show how such transitions are possible, focusing on the specific case of the long-term evolution of Mercury. We develop a simple analytical model for Mercury's dynamics and elucidate the origins of its short term stochastic behavior as well as of its sudden progression to unbounded chaos. Our model allows us to estimate the timescale on which this transition is likely to be triggered, i.e. the dynamical lifetime of the Solar System as we know it. The formulated theory is consistent with the results of numerical simulations and is broadly applicable to extrasolar planetary systems dominated by secular interactions. These results constitute a significant advancement in our understanding of the processes responsible for sculpting of the dynamical structures of generic planetary systems.

Comprehensive Analytical and Experimental Analysis of a Self Excited Induction Generator for Renewable Energy Application

Self excited induction generators have attracted a lot of interest from the researchers in recent past. The main focus in this regard has been on modeling techniques and their verification. Such analyses are invariably restricted exclusively either to dynamic or steady state characteristic evaluation. The objective of this paper is to highlight the operational features of self excited induction generators through detailed experimental results. For analytical verification steady state and dynamic models are implemented through symbolic programming and Simulink modeling approaches respectively. Diverse set of static loads of different power factors as well as dynamic loading is employed to carry out power quality analysis of SEIG on a Fluke 435 II power quality and energy analyzer to conclude the paper. The tests are carried out on an open stator winding, squirrel caged induction motor operated as SEIG

An Experimental Study on Dynamics of a Novel Dual-Belt Continuous Variable Transmission Based on a Newly Developed Test Rig

A novel dual-belt Van Doorne’s continuous variable transmission (DBVCVT) system, which is applicable to heavy-duty vehicles, has been previously proposed by the authors in order to improve the low torque capacity of traditional single-belt CVT. This DBVCVT is a novel design among continuously variable transmissions and is necessary to be prototyped for experimental study, and the analytical dynamic model for this DBVCVT also needs to be experimentally validated. So, this work originally fabricated a prototype of DBVCVT and integrates this prototype to a light-load hardware-in-the-loop test rig by replacing the engine and load equipment with the AC motor and magnetic powder dynamometer. Moreover, with the use of this newly developed test rig, this work implements the experimental study of this DBVCVT for the first time. The comparison of experimental and simulation results validates the previously proposed analytical model for DBVCVT, and some basic characteristics of the DBVCVT in terms of the reliability, speed ratio, and transmission efficiency are also experimentally studied. In all, this developed test rig with the analytical model lays the foundation for further study on this novel DBVCVT.

A New Model of Current Retroflection Applied to the Westward Protrusion of the Agulhas Current

Abstract The dynamics of current retroflection and rings shedding are not yet fully understood. In this paper, the authors develop an analytical model of the Agulhas Current retroflection dynamics using three simple laws: conservation of volume, momentum balance, and Bernoulli’s principle. This study shows that, for a retroflecting current with a small Rossby number, this theoretical model is in good agreement with numerical simulations of a reduced-gravity isopycnal model. Otherwise, the retroflection position becomes unstable and quickly propagates upstream, leaving a chain of eddies in its path. On the basis of these findings, the authors hypothesize that the westward protrusion of the Agulhas retroflection and the local “zonalization” of the Agulhas Current after it passes the Agulhas Bank are stable only for small Rossby numbers. Otherwise, the retroflection shifts toward the eastern slope of the Agulhas Bank, where its position stabilizes due to the slanted configuration of the slope. This study shows that this scenario is in good agreement with several high-resolution numerical models.

An analytical method for reducing combustion instability in homogeneous charge compression ignition engines through cycle-to-cycle control

Late-phasing homogeneous charge compression ignition operating conditions have the potential to expand the useful operating range of homogeneous charge compression ignition in internal combustion engines. However, significant combustion instabilities can occur at late-phasing operating conditions. Combustion phasing and work output variations at these conditions are characterized by a pattern in which the combustion phasing alternates between being earlier than the desired timing and later than the desired timing. This characteristic can be traced to a negative eigenvalue in a simplified, discrete-time analytical model of homogeneous charge compression ignition dynamics. The model forms the basis for the design of a simple controller that is shown to reduce combustion timing variations in simulation. Experimental results illustrate the controller successfully reduces the cyclic variations in combustion by altering the exhaust valve timing, resulting in stable combustion and an expanded operating range.

English

Harmful organisms affect the quality and quantity of food production. In a world of increasing changes in climatic, economic and social conditions, the design of effective measures against these organisms requires more accurate information. Mathematical models provide a scientific and quantitative language to describe the complex relationships that causes pest outbreaks. With the goal of analysing options to deal with this complexity, we discuss different mathematical approaches to modelling. The best model to support plant protection decisions will vary with each situation. Mathematical models range from very simple correlations between events to complex comprehensive systems of differential equations used to represent the dynamics of processes. Large-scale scenarios at the national or continental level can be supported adequately with simple, static and general models. Analytical or descriptive dynamic models are the best options to support pest management in well-defined regions or locations with little variation in external factors. Explanatory dynamic models are needed when great variations in pest behaviour are expected as a result of higher-order interactions with the host and the environment. If necessary, a quantitative analysis can be performed using mathematical modelling. In practice, the feasibility of such a quantitative analysis will depend on the time available for decision-making and data collection concerning the problem. Key words: Mathematical models, plant health, predictive models.

Dynamics of a pneumatic artificial muscle actuation system driving a trailing edge flap

This study presents a time domain dynamic model of an antagonistic pneumatic artificial muscle (PAM) driven trailing edge flap (TEF) system for next generation active helicopter rotors. Active rotor concepts are currently being widely researched in the rotorcraft community as a means to provide a significant leap forward in performance through primary aircraft control, vibration mitigation and noise reduction. Recent work has shown PAMs to be a promising candidate for active rotor actuation due to their combination of high force, large stroke, light weight, and suitable bandwidth. When arranged into biologically inspired agonist/antagonist muscle pairs they can produce bidirectional torques for effectively driving a TEF. However, there are no analytical dynamic models in the literature that can accurately capture the behavior of such systems across the broad range of frequencies required for this demanding application. This work combines mechanical, pneumatic, and aerodynamic component models into a global flap system model developed for the Bell 407 rotor system. This model can accurately predict pressure, force, and flap angle response to pneumatic control valve inputs over a range of operating frequencies from 7 to 35 Hz (1/rev to 5/rev for the Bell 407) and operating pressures from 30 to 90 psi.

Sequential patterns of spikes and scale-invariance in modular networks

It has been reported that there are consistent sequential patterns of spikes after the transitions to the up state during slow wave sleep[1]. The up states may be characterized by critical dynamics[2] for which the avalanche sizes distribution is scale-invariant[3]. In order to understand the mechanism of the sequential patterns, it may thus be necessary to study the fine structure of avalanche transmission between multiple neuronal ensembles at criticality. We have developed an analytical model of avalanche dynamics in modular networks. The univariate distribution of avalanche sizes[4] can be extended to a joint probability distribution Pw({Lu}u∈S) describing the probability that Lu neurons are active in each sub-network u during avalanches that start from the sub-network w with u∈S={1,...,M} and M the number of sub-networks. The mean temporal profile[3] of the avalanches in each sub-network u can then be detailed (see Figure ​Figure11 (A1) and (B1)) and are reminiscent of the temporal patterns observed experimentally. The sequential patterns depend on the average connection strengths between the sub-networks. At criticality, the cumulated temporal profiles can be collapsed using standard rescaling of the axes and yield a single universal scaling function[3] (see Figure ​Figure11 (A2) and (A3)). After rescaling, the mean spiking times in each sub-network are functions of the durations of the avalanches. In Figure ​Figure11 (B3), the intervals between successive mean spiking times - are proportionally shorter for longer avalanches near criticality. Figure 1 (A1) The average number of neurons spiking at the time-step t in the sub-networks u=1, 2, and 3 are shown red, blue, and green, respectively, for avalanches of duration τ=15 starting from the sub-network 1. (B1) ...

Coupling isotachophoresis with affinity chromatography for rapid and selective purification with high column utilization, part 1: theory.

We present a novel technique that couples isotachophoresis (ITP) with affinity chromatography (AC) to achieve rapid, selective purification with high column utilization. ITP simultaneously preconcentrates an analyte and purifies it, based on differences in mobility of sample components, excluding species that may foul or compete with the target at the affinity substrate. ITP preconcentration accelerates the affinity reaction, reducing assay time, improving column utilization, and allowing for capture of targets with higher dissociation constants. Furthermore, ITP-AC separates the target and contaminants into nondiffusing zones, thus achieving high resolution in a short distance and time. We present an analytical model for spatiotemporal dynamics of ITP-AC. We identify and explore the effect of key process parameters, including target distribution width and height, ITP zone velocity, forward and reverse reaction constants, and probe concentration on necessary affinity region length, assay time, and capture efficiency. Our analytical approach shows collapse of these variables to three nondimensional parameters. The analysis yields simple analytical relations for capture length and capture time in relevant ITP-AC regimes, and it demonstrates how ITP greatly reduces assay time and improves column utilization. In the second part of this two-part series, we will present experimental validation of our model and demonstrate ITP-AC separation of the target from 10,000-fold more-abundant contaminants.

Design optimization of an internal combustion engine powered CHP system for residential scale application

We present an analytical dynamic mathematical model and a design optimization of a residential scale combined heat and power system. The mathematical model features a detailed description of the internal combustion engine based on a mean value approach, and simplified sub-models for the throttle valve, the intake and exhaust manifolds, and the external circuit. The validated zero-dimensional dynamic mathematical model of the system is implemented in gPROMS $$^{\textregistered }$$ , and used for simulation and optimization studies. The objective of the design optimization is to estimate the optimum displacement volume of the internal combustion engine that minimizes the operational costs while satisfying the electrical and heating demand of a residential 10-house district. The simulation results show that the mathematical model can accurately predict the behavior of the actual system while the design optimization will later be the basis for advanced control studies.

Temporal and spatial expansion of a multi-dimensional model for electron acceleration in the bubble regime

AbstractAn extended analytical model for particle dynamics in fields of a highly-nonlinear plasma wakefield (the bubble or blow out regime) is derived. A recently proposed piecewise model is generalized to include a time dependent bubble radius and full field solution in the acceleration direction. Incorporation of the cavity dynamics in the model is required to simulate the particle trapping properly. On the other hand, it is shown that the previously reported piecewise model does not reproduce the formation of a mono energetic peak in the particle spectrum. The mono energetic electron beams are recovered only when the full longitudinal field gradient is included in the model.

Dynamic Modeling and Experimental Validating of Large Semi-Rigid Structures

ABSTRACTA new type of large semi-rigid solar array structure with a new structural concept of rigid-flexible combination has developed for space application. Due to the good features of large scale and lightweight, such structure can well satisfy to the large power requirements of spacecraft and thus has drawn increasing attention recently. However, its structural weakness of inherently flexibility makes low frequency vibrations happen much easier. It is highly required to obtain an accurate dynamic model for predicting the dynamic characteristics of this kind of semi-rigid space structure. Because this structure is composed of different components that have quite different stiffness properties respectively, it is very difficult to build up an accurate dynamic model of this complex structure. In this paper, a novel analytical dynamic model is developed for solving this problem. To validate the correctness of the proposed model, experiment studies are conducted. By comparing the simulation results with experimental results, it can be concluded that this dynamic modeling method presented in the paper is credible. The present study is significant for the structural construction and application of this special structure.