Refine Your Search

Topic

Author

Affiliation

Search Results

Technical Paper

Analysis and Development of A Real-Time Control Methodology in Resistance Spot Welding

1991-02-01
910191
The single-parameter, in-process monitor and automatic control systems for the resistance spot welding process have been studied by many investigators. Some of these have already been commercialized and used by sheet metal fabricators. These control systems operate primarily on one of the three process parameters: maximum voltage or voltage drop, dynamic resistance, or thermal expansion between electrodes during nugget formation. Control systems based on voltage or dynamic resistance have been successfully implemented for industrial applications. A great amount of experience on these two control methods has been accumulated through trial-and-error approaches. The expansion-based control system is not commonly utilized due to lack of experience and understanding of the process. Since the expansion displacement between electrodes during welding responds directly to the weld nugget formation, this control parameter provides a better means to produce more precise spot welds.
Technical Paper

Advanced High-Temperature Test Methods for Gasket Materials, 1991

1991-02-01
910204
Equipment and techniques for evaluating the stability, creep, and sealability of gasket facing materials at high temperatures are presented. Mathematical models for predicting long-term failure of elastomer-bonded gaskets from short-term high-temperature tests were used. The value of differential thermal analyses and differential scanning calorimetry in the ranking of facing compositions and alternatives to engine testing to establish confidence in screening gasketing materials are the projects presented.
Technical Paper

Using a Mathematical Flange Distortion Model and Expert System to Optimize Gasket Material Selection

1991-02-01
910202
An expert system called GMX: The Gasket Material Selection Expert was presented at the 1989 SAE Conference(1).* The capabilities of this program have since been increased tremendously by the development of a Mathematical Model which predicts physical flange distortion and gasket compression values for any bolted, gasketed flange configuration. The expert system contains the logic (Rules) and facts (Databases) needed to compare gasket material properties to application-specific requirements and to specify gasket materials that will perform best in the application. The Flange Distortion Model is used by the expert system to calculate certain quantities that are needed to compare materials for the application. This paper describes how material properties and gasket engineering are used to make a material recommendation, and how an expert system and mathematical model have been utilized to make this expertise available to the gasket specifiers.
Technical Paper

Missing Vehicle Algorithm (OLDMISS) Reformulation

1991-02-01
910121
The OLDMISS computer program is used to estimate the ▵V's of vehicles in a collision, when the damage to one of the vehicles is unknown. The program estimates the energy dissipated in the structure of the missing vehicle based on the knowledge of the generic structural characteristics of automobiles, and certain assumptions. OLDMISS has been found to be less accurate for certain impact configurations, especially side impacts. This paper examines the possible sources of errors in the OLDMISS algorithm. This paper also details an alternate algorithm for estimating the energy absorbed by the missing vehicle. This proposed method bypasses the need for estimating the damage profile on the missing vehicle. It also takes into account the presence of induced damage (for side impacts). The new algorithm is validated by reconstructing six vehicle-to-vehicle staged impacts, and twelve RICSAC tests.
Technical Paper

Determination of Collision Configurations from Vehicle Deformation Patterns

1991-02-01
910127
The severity of vehicle crush and occupant injury is explained in terms of the changes in kinetic energy or change in velocity during impact. The work is calculated by mathematical models such as CRASH 3 program on the basis of vehicle damage information collected from the accident scene. In application of CRASH 3, the impact orientation and the direction of the principal force, etc. must be inferred by user, based on measurement and experience. Therefore it is one of the most important tasks to estimate the collision configuration from physical evidence. The individual experience methods in this regard may lead to big misunderstandings and mistaken conclusions in the reconstruction; however, very little has been studied the determination of the collision configuration in the reconstruction.
Technical Paper

Heavy Truck Deceleration Rates as a Function of Brake Adjustment

1991-02-01
910126
When reconstructing a highway accident involving a heavy truck, an accurate deceleration rate is often an elusive piece of the puzzle. This paper presents a method for calculating the deceleration rate of a heavy truck equipped with an air-mechanical brake system. Traditionally a deceleration rate had been more an estimate of the percent of wheel lock-up based on the brake adjustment, and then proportioned to the loading on the axles. Equations for two configurations of brake chamber size and slack adjuster length were written by engineers at the National Highway Traffic Safety Administration's (NHTSA) Vehicle Research and Test Center (VRTC) to describe braking torque as it varies with pushrod stroke. These equations were developed by means of a regression analysis, to fit a curve to dynamometer data produced at the VRTC in East Liberty, Ohio. Once this braking torque is converted to a braking force, it can be compared to the braking force available at the tire/road interface.
Technical Paper

Numerical Simulation of Fully Folded Airbags and Their Interaction with Occupants with Pam-Safe

1991-02-01
910150
With the advent of widespread use of airbags as restraint systems for both driver and passenger, a new challenge has appeared for the design engineer. Numerical models of various degrees of complexity have been developed to model the interaction between airbags and occupants, ranging from simplified models such as the airbags included in rigid body dynamic models, to more sophisticated, fully three-dimensional ones based on Finite Elements (FE). However, some key questions of airbag design such as interaction of the unfolding bag with out-of-position occupants and effects of different airbag folding patterns remained unanswered, and their design still requires extensive test series. In this paper, the approach developed at Engineering Systems International over the past two years to solve the problem of numerical simulation of fully folded bags is presented in the larger context of the PAM-SAFE program for analysis of occupant safety.
Technical Paper

A Mathematical Model Based Method for Diagnosing Failures in Automotive Electronic Systems

1991-02-01
910069
With the increasing use of complex electronics in automobiles, diagnosis of failures (including calibration shift) of components has become a major issue. This paper presents a method which has the capability of diagnosing failures of any component at any level of failure for automotive electronic systems. The method presented here is based upon mathematical models for the system under diagnosis. These models are run onboard the vehicle in a digital computer and implemented with such highly efficient algorithms that real time diagnosis is possible onboard the vehicle. Although the details of the method are specific for failures in each major class of component (e.g. sensor, actuator, controller), this paper demonstrates that any failure which can be represented in the model can be diagnosed uniquely and distinguished from other failures.
Technical Paper

Dynamic Modeling of the Stiller-Smith Mechanism in an Application of a 4-Cylinder Plunger Pump System

1991-02-01
910073
The development of a mathematical model of StillerSmith Mechanism for the application of a 4-cylinder plunger pump system is presented. The magnitude and direction of the internal dynamic load are obtained by solving a set of equations using the overall geometric parameters, prescribed motions, inertia distribution, and applied torques on the system. The simulation presented here yields the history of the internal loads, which are then normalized with respect to the required peak output load on the plungers, through an entire rotary cycle. The approach allows for the development of further design criteria through parametric sensitivity studies.
Technical Paper

Requirements and Performance of Engine Management Systems under Transient Conditions

1991-02-01
910083
Because of the big influence on driveability and exhaust emissions one of the most important challenges of modern fuel injection systems is to ensure a very good constancy of the air/fuel ratio. A precise feedforward control especially for dynamic transitions is necessary because a feedback control of the air/fuel ratio based on an oxygen sensor in the exhaust gas is not able to avoid dynamic deviations. Therefore in this paper a new fuel injection technique is presented which is founded on a simultaneous control of air and fuel in connection with algorithms based on mathematical models of the different physical effects.
Technical Paper

Electronic Sensing of Automobile Crashes for Airbag Deployment

1991-02-01
910276
Although the performance of most of today's airbag crash sensor systems is excellent, it is achieved by using multiple sensors located remotely from the passenger compartment. Those systems which use single sensors in the passenger compartment sometimes fail to actuate when needed or are too slow to provide optimum occupant protection. Installed airbag system cost now suggests that designers should find ways to reduce the number of sensors and the complexity of the system without suffering degradation in performance. An electronic sensor is freed from the constraints of the differential equation of motion of an electromechanical sensor because its algorithm can, in principle, be arbitrary. It can manipulate the acceleration data in new ways, but whatever algorithm is employed must be firmly grounded in some understood physical process to guarantee the ability of the algorithm to perform properly in real world events not recreated on the test track.
Technical Paper

Property Characterization of PC/ABS Blends for Use in Energy Management Applications

1991-02-01
910402
With the implementation of air bags into today's vehicles, the functional requirements of the instrument panel have changed significantly. Screening of different candidate systems is difficult due to the expense and time involved in testing to the FMVSS requirements. Plastic material properties also vary with temperature and strain rate which increases the complexity of the testing required. It is the objective of this paper to investigate the response of PC/ABS blends to this environment. Also, a summary of mathematically modeling plastic materials with commercial software in energy management environments is presented. This paper will discuss the results of testing PC/ABS blends at strain rates and temperatures typical to that of impact conditions and correlation of these tests to different material models used in finite element codes.
Technical Paper

Modeling, Identification, and Torque Control of a Diesel Engine for Transient Test Cycles

1990-02-01
900235
A digital torque controller capable of following the EPA transient test cycle was developed for both a turbocharged diesel engine and a direct current dynamometer. A simplified mathematical model for the throttle-torque system was developed. Off-line parameter identification algorithms were used to find the model parameters. The controller design was carried out using a closed-loop pole assignment technique. Since the model included time delay, a Smith predictor control scheme was used. Feedforward control was added to the Smith predictor for load disturbances caused by speed variations of the engine. Transient engine tests showed that the Smith predictor with feedforward disturbance rejection gave transient cycle performance well within the specifications of the EPA.
Technical Paper

A System Identification Approach to the Modelling of Engine Transients

1990-02-01
900237
Mathematical models of transient engine dynamics have traditionally been produced with analysis from first principles of the physical processes within the engine. However, system identification techniques allow a ‘black box’ model to be derived purely from experimental data. These discrete time models have the advantage of being both straightforward and in a form which is suitable for digital control algorithm design and implementation. This paper describes work which is underway to identify the transient dynamics of a four cylinder 2.0ℓ DOHC multi-point injection engine. The experimental arrangement allows the fuel injection for each power stroke to be individually controlled while data acquisition is synchronised with the engine crankangle. The requirements for the input signal to the engine are discussed and methods used for data analysis are described. Results showing the response of IMEP to perturbations in fuelling are presented.
Technical Paper

Methods of On-Board Misfire Detection

1990-02-01
900232
Misfiring of the engine can cause damage to the catalyst within short time and increase emissions. Under misfiring conditions, unburned fuel and oxygen are pumped into the catalyst, where its combustion heavily increases the temperature. For this reason there is a demand for fast detection of misfiring. Once judged, one can take countermeasures to avoid further temperature rise. Two methods of misfire detection with the prospect of future use in series production are discussed. A first approach uses the trace shape of the λ-sensor signal for evaluation. The second approach uses the speed fluctuations of the engine for detection. Efficient algorithms give the possibility of misfire detection in the full load-speed range with reasonable effort to protect the catalyst. However there will remain some misfire conditions, increasing the emissions above regulation limits, that cannot be detected by those methods.
Technical Paper

In-Cylinder Flow and Combustion Modeling of 1.7L Caterpillar Engines

1990-02-01
900253
This paper details the development of a mathematical model to simulate the incylinder processes in the Caterpillar 1.7L Diesel engine and the results obtained during compression stroke and early part of the combustion stroke. The model includes accurate representation of the geometry of the 1.7L combustion chamber via Body Fitted Coordinates (BFC) which conform to the shape of the piston-dish and cylinder. Also included are the combustion model and evaporation model. This 3-D model predicts average cylinder pressure and temperature variations with degree crank angle which are in good agreement with Caterpillar measurements for this engine.
Technical Paper

Mathematical Modelling of the Semi-Permanent Mould Casting of Aluminium Alloy Cylinder Heads and Engine Blocks

1990-02-01
900657
A study was performed of the sensitivity of computational solidification simulations to variations in several thermophysical properties and indicated that proper incorporation of the latent heat was the most important. Accurate determination of the heat transfer between the casting and the mould or core was also critical. Several applications to automotive castings of the model so developed are presented.
Technical Paper

Application of Self-Tuning Control

1990-02-01
900593
Two kinds of self-tuning control algorithms have been applied using a novel smoke sensor as part of a diesel smoke control system. Firstly, pole assignment self-tuning control was used to achieve the desired engine speed response, with a smoke predictor used to solve the problems caused by the time delay between the fuel input and smoke output; secondly, a Pl self-tuning controller was used to solve the problem caused by the variation of the coefficients in the transfer functions with engine conditions. The experimental results and the problems and the ideas for future work are discussed.
Technical Paper

Model-Based Electronic Diesel Engine and Turbocharger Control

1990-02-01
900595
Design, implementation, and operation of controllers for Diesel engines made great progress in recent years. Nevertheless they could be more efficient if the advanced techniques of modern control theory were applied to them. The efficiency of the most conventional controllers is limited by two major facts: firstly, that they have a fixed structure with constant parameters over the whole operating field of the engine and secondly, that they are designed using a single transfer function of the system that is obtained by linearization at one operating point. Most recent developments using microcomputers allow an easy adjustment of the control strategy to the operating conditions of the engine. Furthermore they allow the control of a multivariable system as is encountered, when the injection and the turbocharger of an engine is controlled simultaneously. This is only possible when a sufficiently large on-line computer capability is available.
Technical Paper

Use of Fuzzy Logic for Engine Idle Speed Control

1990-02-01
900594
A novel approach has been investigated for the application of engine idle speed control. The control method implemented, “Fuzzy Control”, has the advantage of not requiring the knowledge of a mathematical model of the controlled object and is also more robust and flexible than traditional approaches. The experimental results obtained with this method are compared with those obtained with an optimal linear quadratic controller and with those of a conventional PID controller. They indicate that the former has similar capabilities with respect to the optimal approach and better results than the conventional control.
X