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A methodology for dynamic analysis of the Space Station Freedom thermal/ environmental control system is described which uses linear system analysis techniques to determine the ability of the system to accommodate thermal load transients. A nonlinear integrated model of the system as it exists at Stage 6, Man Tended Capability (MTC), is described which encompasses the cabin air cooling system, avionics air cooling system, internal and external thermal control systems. The nonlinear model is linearized at an assumed design operating point, and the linear model is evaluated by comparison with the nonlinear model. Transfer functions are derived to determine the response of the heat rejection system to time-varying thermal loads applied at various points in the heat acquisition system. The frequency response calculated from the transfer functions is used to determine allowable operating envelopes of thermal load magnitude and frequency for each point of application of thermal load.

This paper summarizes the major aspects of linear elastic fracture mechanics (LEFM) as a quantitative design criterion against brittle fracture. It describes the extension of LEFM to subcritical crack growth under fatigue conditions. To apply this design criterion, however, the engineer must accept the notion that his structure or component does contain flaws or cracks. Fatigue design using LEFM thus assumes preexisting flaws or cracks; hence, fatigue life is based on subcritical crack growth followed by final fracture. Subcritical crack growth under both constant amplitude and variable amplitude loading is considered along with peak tensile or compressive overloads.

With the development of modern vehicle chassis control systems, such as Anti-Lock Brake System (ABS), Acceleration Slip Regulation (ASR), Electronic Stability Control (ESC), and Regenerative Braking System (RBS) for EVs, etc., there comes a new requirement for the vehicle brake system that is the precise control of the wheel brake pressure. The Electro-Hydraulic Brake system (EHB), which owns an ability to adjust four wheels’ brake pressure independently, can be a good match with these systems. However, the traditional control logic of EHB is based on the PWM (Pulse-Width Modulation), which has a low control accuracy of linear electromagnetic valves. Therefore, this paper presents a research of the linear electro-magnetic valve characteristic analysis, and proposes a precise pressure control algorithm of the EHB system with a feed forward and a PID control of linear electro-magnetic valves.

A linear impact sled has been set up to develop energy-absorbing bumpers made of urethane foam. The design, development, instrumentation, and use, including advantages and disadvantages, are discussed. The equipment used to impact under high- and low-temperature extremes is also discussed. The sled, while simple, is extremely safe due to numerous built-in interlocks. The equipment can test foam samples, bumpers, or vehicles. Vehicle masses to 5000 lb and velocities to 10 mph are within the machine's capabilities. The methods developed for testing bumpers separate from the vehicle have achieved excellent correlation with testing done on vehicles.

The present research proposes the use of linear model updating along with unrestricted optimization methods, in order to obtain a methodology, which allows the calibration of mathematical models of rotating systems. An experimental set up of a symmetric rotor, on a rigid foundation supported by two hydrodynamic cylindrical bearings and with a central disk of considerable mass, working as an unbalancing excitation force, was used for this purpose. Once the numeric and experimental values are obtained, error vectors are then defined, which serve as minimization parameters, through the variation of the numeric model parameters. The method presented satisfactory results, as it was able to calibrate the mathematical model and then from that, obtain reliable responses for the physical system studied.

This paper is a general discussion of the basic circuit design techniques used in monolithic linear integrated circuits. Basic diode and transistor circuit behavior is defined, and basic general purpose circuits characteristic of monolithic designs are analyzed. These circuits include current sources and mirrors, differential amplifiers, d-c level-shift circuits, Darlington gain blocks, and output stages. The discussions are summarized by an analysis of a simplified CA741-type operational amplifier design.

This paper discusses the design and performance of a miniature, closed cycle, split Stirling, cryogenic cooler that provides 1 watt of cooling at 80 K. The compressor uses two opposed linear motors to drive opposed pistons and the expander uses a pneumatically driven displacer. A single electronics module and compressor has been developed to drive three different expanders that have nominal cold cylinder diameters of 5, 8 and 13 mm.

Simple solenoid plunger type electromagnets are commonly used in devices such as switches, relays, and solenoid valves (to name but a few). In most cases these are on/off applications where the plunger is moved from one extreme position (when turned on) to another (when turned off). In this paper a scheme is presented to enable positioning of a linear actuator based on two simple solenoids, a flat faced electromagnet, and a microprocessor. The paper describes the configuration and performance of such a system which uses pulsed signals from a microprocessor to activate the solenoids and the electromagnet. The plungers connected by a shaft in a push pull arrangement move in an axial direction while an electromagnet orthogonal to the shaft latches it at a desired position. An algorithm to control the input pulses to the solenoids and the electromagnet is developed and experimental results using this control scheme are presented.

Vehicle stability is maintained by proper interactions between the driver and vehicle stability control system. While driver describes the desired target path by commanding steering angle and acceleration/deceleration rates, vehicle stability controller tends to stabilize higher dynamics of the vehicle by correcting longitudinal, lateral, and roll accelerations. In this paper, a finite-horizon optimal solution to vehicle stability control is introduced in the presence of driver's dynamical decision making structure. The proposed concept is inspired by Nash strategy for exactly known systems with more than two players, in which driver, commanding steering wheel angle, and vehicle stability controller, applying compensated yaw moment through differential braking strategy, are defined as the dynamic players of the 2-player differential linear quadratic game.

The engineer frequently encounters experimental data consisting of observations obtained simultaneously on two variables and is interested in studying how these variables are related. This paper describes the statistical technique of linear regression analysis which provides a method for investigating the relationship between two variables. A bivariate example is presented to illustrate the application and interpretation of the technique.

Homogenous Charge Compression Ignition (HCCI) is an alternative to Spark Ignited (SI) combustion, which can provide part-load efficiencies as high as compression ignition engines and energy densities as high as SI engines, without high levels of NOx or Particulate Matter (PM). The principle of operation involves reaching the thermal oxidization barrier of a homogeneous air-fuel mixture. This combustion practice is enabled by diluting then compressing the mixture with the Trapped Residual Gases (TRG) to dilute the initial charge thus keeping combustion temperatures down. Introduction of exhaust gasses in the mixture can be achieved by the use of early exhaust valve closure and late inlet valve opening. The charge is well mixed avoiding particulate emissions, and by using exhaust gasses for load regulation the need for throttled operation is removed allowing the realization of high efficiencies, low pumping losses and a resulting 15 - 20% improvement in fuel economy.

A new rocket engine concept that is presently being evaluated offers significant performance, cost, and configurational advantages. The Linear Rocket Engine System, (LRES) combines the unique performance and operational advantages of the aerospike nozzle with the configuration versatility of low cost modular combustors, which results in a high-performance rocket engine package designed specifically for use in advanced configuration vehicles. This paper describes the design, fabrication, and testing of the LRES concept to evaluate its potential for vehicle integration. The program was conducted under the sponsorship of NASA's Marshall Space Flight Center.

A method for measuring spring rate and damping coefficient is necessary for complete laboratory evaluation of a suspension component. This report outlines a technique by which a linear model is adjusted by an analog computer so that its parameters match those of the test specimen. The accuracy of this linear model is good unless the test specimen parameters are very nonlinear. To determine how structural changes in a suspension unit affect the dynamic action of the unit, measurable suspension parameters must be defined. One set of parameters can be obtained by assuming that, for small angular motion, a single suspension unit can be modelled by a parallel springer-damper combination. This system is completely defined by the two parameters spring rate, K, and damping coefficient, D. This paper outlines a method to measure K and D under laboratory conditions which simulate typical operational environment.

Vehicle model plays an important role during the development process of a new car chassis. There are 2 different ways to set up the vehicle mathematics model, one is set up based on understanding the system mechanism and the other is based on system identification technique. In this paper, the transfer functions of the vehicle at 100 km/h, including yaw rate to the steering angle and lateral acceleration to the steering angle, were identified. And then the transfer functions under other forward speed were derived through studying two degrees of freedom vehicle model equation. At last the identified model at different speed was used to analysis the stability of closed loop system from the classical control theory viewpoint.

The limits associated with the use of linear momentum procedures in impact speed predictions of two-car collisions are well established. A combined linear and rotational momentum procedure is introduced which makes it possible to compute the impact speeds of each vehicle based on the post crash data of only one vehicle, or based on only the angles rotated of each vehicle. The limitations of the combined procedure are discussed. A speed sensitivity analysis is presented which offers a methodology by which reasonably accurate speed predictions can be made. A number of actual computer applications are shown which demonstrates the usefulness and simplicity of the procedure presented.

A linear-shaped module based on Si-Ge alloys has been made for thermoelectric generation. The module is designed for generating electricity by exhaust heat of, e.g., plants, furnaces or automobiles. The module consists of 9 couples of p- and n-type Si-Ge alloy-based thermoelectric semiconductors. Carbon layers are made on both sides of the p- and n-type elements, and then the elements are electrically connected in series using Mo electrodes by blazing method. The size of the module is approximately 3.5 mm in width, 70 mm in length and 9.3 mm in height. Maximum power of the module was 2.0 W at a temperature difference of 509 K between the hot and cold sides of the module. A variation of generating power was measured for 150 modules. Maximum power of every module-block consisting of 10 modules was evaluated at a temperature difference of 400 K. The maximum power of the module-blocks was varied from 6.9 W to 8.7 W.

The loudness of powertrain noise generally increases with increasing rpm. In the case of ‘linear’ powertrain acceleration sound, the loudness versus time relationship is well described by a linear function. Two studies were conducted on powertrain linearity. The first used tests of similarity and preference to determine whether subjects could detect changes in linearity. The second used a subjective test of preference to investigate how subjects' preference varied with differing degrees of linearity. In both studies, stimulus sets were created by artificially introducing a controlled degree of non-linearity into a nominally linear powertrain sound. The results of the first study indicate that linearity is a phenomenon that naive subjects can readily detect, and that it has an effect on overall preference. Furthermore, the second study shows that preference is related to the magnitude and position of nonlinearities in the growth of loudness versus time during an acceleration run.

Successful implementation of temperature control is required in a variety of engineering applications. A method using the I-deas TMG finite volume thermal solver and MATLAB with the Control System Toolbox to characterize the control system performance of a thermal model was described by Saeger [1][2]; this paper describes an alternate approach to this method. The alternate method presented herein uses the TMG thermal solver to create linearized capacitance and conductance matrices of the thermal system. Then, MATLAB uses these matrices to create the frequency response curve using either matrix inversion or eigenvalue solution methods. Once the frequency response is generated, the MATLAB Control System Toolbox can be used to develop the control system.

Nowadays, (engine) downsizing using turbocharging appears as a major way for reducing fuel consumption. With this aim in view, the air actuators (throttle, Turbo WasteGate) control is needed for an efficient engine torque control especially to reduce pumping losses and to increase efficiency. This work proposes Nonlinear Model Predictive Control (NMPC) of the air actuators for turbocharged SI engines where the predictions are achieved by a neural model. The results obtained from a test bench of a Smart MCC engine show the real time applicability of the proposed method based on on-line linearization and the good control performances (good tracking, no overshoot) for various engine speeds.

The cylinder bore honing quality is an essential factor for a good engine performance and durability. A bad surface finish can result in an excessive lubricant oil consumption, high piston ring wear and scuffing occurrence. In this paper the most important characteristics of bore honing for cast iron cylinders and their influence in the combustion engine performance are described and discussed. Despite its importance, the bore honing is commonly undervalued due to various reasons including the difficulty of a practical but sufficient method of quality qualifying. Some honing commonly misunderstood concepts are detailed and SEM photographs of bore surface from both good and bad finish are presented. At the end of this paper it is also presented a recommendation for a practical evaluation method of honing quality.