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This paper deals with estimating the lateral stability region of a nonlinear 2 DOF vehicle via Lyapunov Second Method and the non-Lyapunov methods of tangency points and trajectory reversal. The nonlinearity of the model is incorporated in an analytical expression for the lateral tire force. It is shown that the derived analytical expressions for equilibrium points defines the outer limits of the stability region.

The demand for increased performance of heavy earthmoving equipment has spurred the development of computer control for machinery using fluid power systems. Application of standard automatic control components to these systems provides the opportunity to implement advanced control approaches that reduce the operator workload and improve performance. In this work, closed-loop control is applied to the joints of a typical three-link digging device. Because the changing configuration of the device greatly changes the dynamic characteristics, an adaptive control algorithm is introduced to modify the control parameters to maintain consistent performance of the implement.

This paper describes the development of a prototype fluid pumping system for incorporation into a miniaturized flow injection analyzer. The strategy couples the well-established capabilities of reagent-based flow injection analyses (FIA) with our novel concepts for the design of a miniaturized, low-power pumping system, i.e., an electrochemically-driven micropump. The basis of pump actuation relies on the electrochemically-induced surface tension changes at the electrolyte/mercury interface, resulting in a “piston-like” pumping process devoid of mechanically moving parts. We present herein the results from the preliminary performance tests of a miniaturized fluid flow system with the micropump. As described, the flow rates and pumping displacement volumes have been studied as a function of the amplitude and the frequency of the applied voltage waveform.

Today virtually all leading OEMs and suppliers have adopted model-based development using Simulink as part of their processes. Although the issue of revision control and configuration management has been previously addressed, the lack of high-quality diff and merge tools has prevented the adoption of simpler, more robust practices for revision control and configuration management. In 2009, 3-way merge for Simulink models became available for the first time. This timely paper discusses how teams of differing sizes can dramatically improve how they manage their models and collaborate as a team by adopting modern methods enabled by the recent availability of 3-way merge tools for Simulink models.

A particle swarm optimization (PSO) algorithm was implemented with engine testing in order to accelerate the engine development process. The PSO algorithm is a stochastic, population-based evolutionary optimization algorithm. In this study, PSO was used to reduce exhaust emissions while maintaining high fuel efficiency. A merit function was defined to help reduce multiple emissions simultaneously. Engine operations using both single-injection and double-injection strategies were optimized. The present PSO algorithm was found to be very effective in finding the favorable operating conditions for low emissions. The optimization usually took 40-70 experimental runs to find the most favorable operating conditions under the constraints specified in the present testing. High EGR levels, small pilot amount, and late main injection were suggested by the PSO. Multiple emissions were reduced simultaneously without a compromise in the brake specific fuel consumption.

Linear analysis and corresponding vehicle tests have been used since the late 1950's to help understand the directional response of automobiles and commercial vehicles. This work is now well accepted, and linear terms such as understeer gradient and response time are descriptors routinely used to characterize vehicle performance in the linear range. This paper assesses the use of various levels of complexity in linear models. It verifies that, for steady state measures such as understeer gradient, all important effects can be handled quasistatically and a two degree of freedom model is adequate. The paper then illustrates situations in which the roll degree of freedom can be important for transient calculations, and assesses the changes in calculated transient results deriving from the addition to the model of time lags in lateral tire force buildup.

The methyl esters of soybean oil, known as biodiesel, are receiving increasing attention as renewable fuels for diesel engines. Biodiesel has a high cetane number, and offers the potential of emission reduction. The properties of biodiesel vary depending on its composition, and this may affect engine performance and emissions. In this project, biodiesel fuels were prepared from feedstocks with modified compositions including the methyl esters of a low palmitic soybean oil, a partially transesterified soybean oil, a synthetic blend of saturated esters, and a commonly used methyl soyate. These esters were blended with No. 2 diesel fuel in 20% and 50% concentrations. The blended fuels were then tested in a diesel engine to investigate the effect of biodiesel composition on performance, combustion characteristics, and emissions.

The objective of this paper is to present an estimate of the second law thermodynamic efficiencies of the various units comprising an Environmental Control and Life Support Systems(ECLSS). The technique adopted here is based on an evaluation of the ‘lost work’ within each functional unit of the subsystem. Pertinent information for our analysis is obtained from a user interactive integrated model of an ECLSS. The model was developed using a chemical process simulator called ASPEN (Advanced System for Process Enginering). A potential benefit of this analysis is the identification of subsystems with high entropy generation as the most likely candidates for engineering improvements.

An analysis has been conducted on the hydrostatic drive system for driving a soil bin. A comparison of the bin velocity was made between the pure inertia load and inertia plus disturbance. Also, the pressure fluctuations that are predicted are quite sensitive to the leakage values chosen. A low leakage value predicts an oscillatory pressure response. Although no feedback was employed for the velocity output, the load disturbance changed the output velocity very little.

This paper examines the validation process for computer simulations of ground vehicle dynamics. Validation in this context may be defined as the process of gaining confidence that the calculations yield useful insights into the behavior of the simulated vehicle. It is our view that this process requires three separate questions to be addressed: Is the model appropriate for the vehicle and maneuver of interest? Is the simulation based on equations that faithfully replicate the model? Are the input parameters reasonable? This paper addresses each of these questions, mainly from an analytical point of view. The paper then addresses strengths and weaknesses of vehicle testing as part of the validation process.

Using instrumentation designed for the ultrasonic measurement of thickness, a technique has been devised for measuring the isotropic elastic constants of small samples, i. e., samples 1 mm in thickness and a minimum of 5 mm in other dimensions. Young's modulus, the shear modulus and Poisson's ratio are calculated from measurements of density and ultrasonic shear and longitudinal wave velocities. Samples of valve train materials, including chill cast iron, low alloy steel, tool steel, stainless steel, a nickel-base superalloy, and a powder metal alloy were machined from components and analyzed. The magnitude of the measured values of the elastic constants are reasonable when compared with published values. The measurement error on all the constants is estimated to be less than 1%. Moduli determined by this method can be used in finite element analyses to improve designs.

The alkyl esters of plant oils and animal fats are receiving increasing attention as renewable fuels for diesel engines. These esters have come to be known as biodiesel. One objection to the use of the methyl and ethyl esters of soybean oil as a fuel in diesel engines is their high crystallization temperature. One solution to this problem is to use the isopropyl esters of soybean oil which have significantly lower crystallization temperatures. Another method to improve the cold flow properties of esters is to winterize them to sub-ambient temperature. This is accomplished by cooling the esters and filtering out the components that crystallize most readily. Previous work has shown that when methyl, isopropyl and winterized ester blends were compared with No.2 diesel fuel, the isopropyl and winterized methyl esters had at least the same emission reduction potential as the methyl esters, with similar engine performance.

The methyl esters of vegetable oils and animal fats, known as biodiesel, are receiving increasing attention as an alternative fuel for diesel engines. Although the production of biodiesel involves a relatively simple chemical process, there is potential for various contaminants to be present in the fuel. These contaminants include water, free glycerin, bound glycerin, alcohol, free fatty acids, soaps, catalyst, unsaponifiable matter and the products of oxidation. As interest in this fuel grows, quality standards and specifications are being developed. These standards place limits on the amounts of contaminants that may be present in biodiesel. The objective of this project was to develop a database of property data to provide a basis for setting realistic specification values for biodiesel. Small amounts of these various contaminants were added to biodresel and their impact on the properties and performance of the biodiesel was measured.

The differences between courses offered agricultural and mechanical engineers are examined. The topics in the courses are reviewed in some detail. The students start with a review of basic fluid mechanics followed by an introduction to bulk modulus. Governing equations for pumps motors and valves are introduced next. Course emphasis then diverges. The agricultural engineers cover the basics of control theory to cover a deficiency in their undergraduate curriculum. The mechanical engineers embark on more rigorous examination of the simulation of fluid power components. Students in both departments may elect to take a 1 cr. laboratory course. The laboratory exercises are discussed.

The success of agricultural and construction machinery owes a great deal to the effective use of fluid power. Most fluid power systems are configured with a positive displacement fluid pump that is large enough to meet the flow requirements of many work circuits. Different work functions require a variety of fluid flow and pressure values to provide the desired operation. System branches, therefore, must include specialized flow and pressure regulating valves. The development of a mathematical model of a fluid flow control valve follows.

An exploratory concept for a chassis suspension system for improving the operator ride comfort of an agricultural tractor is presented in this paper. The first section of the paper describes the criteria and concepts that have been incorporated into the design of a hybrid leading and trailing arm chassis suspension system. The second section of the paper discusses the evaluation of this suspension system and its parameters by simulating nine (9) different tractor and nine (9) different tractor-plow models, derived from the various combination of suspension configurations and operator cab locations. A generalized mechanical system simulation program is utilized to predict the dynamic linear transfer function behavior of each vehicle model. With frequency domain analysis techniques and the Fast Fourier Transform (FFT) algorithm, the dynamic vehicle response to the ISO 5007 Smooth Track excitation is computed.

European and American suspension systems are described for improving the operator ride comfort on off-road vehicles. Analytical methods are then described to predict the dynamic behavior of a vehicle and human ride response criteria. The approach includes the selection of a terrain input to excite the vehicle model formulated by the generalized mechanical system simulation programs. An example involving an agricultural tractor-plow system is presented to illustrate the techniques.

Linear anaylsis is a frequently used tool to aid in the understanding of directional response. Understeer gradient, characteristic or critical speed, and yaw rate and lateral acceleration response times have been particularly helpful. This paper studies the use of these measures in the context of vehicles with four-wheel steering. The paper shows that, with only a slight change in SAE definitions, the understeer gradient retains its traditional meaning, but the characteristic speed will depend on the steering system if the steady state part of the steering control algorithm is speed sensitive. The paper also discusses testing for the understeer gradient, and the anticipated changes in response time due to four-wheel steering.

This paper presents linear first-order differential equations for a four-wheel steer vehicle which can be solved for yaw rate and sideslip angle as a function of lateral acceleration. These so-called inverse equations are useful for studying the steer angle needed to follow a given path. A root locus analysis of the inverse equations shows that the required frequencies of steer will decrease with increasing ratio of rear steer to front steer. Integration of the equations illustrates the phenomenon in the time domain. The analysis supports speculation that a driver will find it easier to track, closely to a desired path at high speeds with an appropriate ratio of rear to front steer.

The purpose of this paper is to demonstrate a computer program developed for interactive optimization of dynamic systems represented by ordinary differential equations. The program is capable of minimizing a cost function with respect to from one to five design variables. The program is command driven with on line help and has interactive graphics capability for displaying output. Three vehicle dynamics examples are used to demonstrate the capabilities of the program, and in doing so reveal some interesting vehicle handling results.