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A simple, linear vehicle model is presented which incorporates the most important characteristics of contemporary passenger cars. It is a three mass model with a fixed, inclined roll axis and linear suspension geometric and compliance characteristics. Basic concepts of understeer and oversteer are presented. Static and dynamic requirements are examined, yielding expressions relating the car's design to tire lateral load transfer, total lateral force, and turn radius. Turn kinematics give expressions for the front steer angle and sideslip angle. Suspension geometric and compliance effects describe the rear steer angle, tire inclination angles, and steering wheel angle divided by the overall steering ratio.

Microcomputer technology has added a new dimension to the design of test instrumentation, but the connotations of the name microcomputer have a tendency to build barriers rather than offer solutions to problems. Historically, computers have been treated as systems or identifiable subsystems in instrumentation applications. The implications of complex hardware and mystical programming is often sufficient to direct the user to alternate technologies. In a new light, clear of earlier prejudices, the microcomputer becomes a functional module like other LSI devices. Flexible and economical systems involving logical control, data gathering, and numerical calculations are possible utilizations of these relatively new devices. This paper discusses a facility to assist the designer in development of test instrumentation. Emphasis is placed on use of the microcomputer as an integral part of system design. Test instrument applications are cited.

A real-time process computer network has been developed at the General Motors Research Laboratories. Minicomputers are connected to a large computer in a satellite-host configuration. The minicomputers are dedicated to local experiment activities. The expensive peripherals and the high-level programming capabilities at the host are made available to the minicomputer users.

The General Motors Research Laboratories have equipped two engine test cells with instrument systems containing minicomputers. These systems measure 200 variables and convert them to engineering units for display to the test operator on a high-speed video terminal. The computers also perform calculations such as mass airflow, composite inlet temperature, and equivalent horsepower, which are combinations of several measured variables. Many of the test parameters are corrected to standard conditions of temperature, pressure, and humidity. This paper discusses these systems, mentioning both past experiences and future plans for linking into a host-satellite network.

This paper reports the mass-burning rate in a rotary combustion engine. The mass-burning rate is calculated through an iterative constituent and energy constraints during the combustion process. First approximation is obtained through the firing and motoring-pressure trace as recorded by an image-retaining oscilloscope and recorded subsequently by a polaroid camera. Effect of engine load, engine speed, relative (A/F) on the mass-burning rate and maximum heat release rate were studied. Three different type of fuels were used in the experimental test runs.

Rotary engines, by design, are somewhat more difficult to cool than conventional reciprocating powerplants. This arises in apart from the fact that all four cycles do not take place within the same physical portion of the engine. The basic aim of this research was to study the metal temperatures of many points in the rotary engine with standard and experimental coolants in an attempt to develop a product with superior heat rejection properties in a conventional cooling system. The engine used for the experiment was a two-rotor liquid-cooled Wankel engine obtained from a 1972 Mazda R-100. Both road and chassis dynamometer evaluations were run over a wide range of operating conditions to obtain a comprehensive look at coolant performance. The parameters studied for each coolant were road speed, engine load, coolant concentration, and ambient temperature; the coolants tested were ethylene glycol, water, and the experimental coolants XA-1318L and XA-1318.1L.

In order to predict vehicle brake performance, calculations are made to determine the size of brakes, wheel cylinders, proportioning valves, and metering valves to give the desired results. To achieve this, basic data are required of brake torque output versus brake force input. This requires that a large amount of test data be accumulated from both dynamometer and vehicle tests to obtain the coefficient of friction of disc brake linings and brake factors for drum brakes. All the data available has to be presented in a meaningful form that can be understood with a minimum of study. This report deals with gathering of test data, brake balance calculations, and presentation in a graphical form by means of the IBM 1130 computer and graphing system.

Most motor vehicles operating on our highways today are designed to exhibit high levels of straight-line braking performance without providing sufficient stability during combined braking and steering maneuvers. A basic engineering analysis is presented that allows optimum values of brake balance to be determined for both straight and curved braking. The effects of brake fade on brake balance are discussed. Different wheel antiskid systems are analyzed, and test results are presented for three domestic vehicles. A methodology for determining expected safety benefits of advanced brake systems is reviewed.

Automobile and truck manufacturers have given increasing attention to electronic wheel lock control brake systems during the last few years. These systems prevent continuous wheel lock-up during maximum braking stops, thus aiding the driver in retaining lateral stability and generally improving stopping distances. This presentation discusses a system for preventing continuous rear wheel lock-up of an automobile during maximum braking stops. Included is a description of the control system components, tire and road characteristics, brake and vehicle dynamics, and an analysis leading to the requirements for optimum control.

The overall question of brake actuation, antilock control and other vehicle functions requiring servo assistance will be discussed. Too much effort has been devoted in treating each of these units on an individual basis. This paper describes ways in which this complex subject can be dealt with in a unified manner, to provide a more compact and reliable solution.

Results with a modified dual catalyst system incorporating Gould's Nitrogen Oxide (NOx) reduction catalysts are presented. The key factors controlling durability are examined through laboratory, engine dynamometer, and vehicle tests. Test data is presented showing that control of oxygen input to the NOx catalyst can result in significantly improved durability. Results indicate that by combining oxygen input control with a new low ammonia forming catalyst, stable NOx catalyst performance can be achieved through 25,000 miles of AMA mileage accumulation. Potential failure mode factors are also discussed.

In this paper, some of the design aspects of adaptive brake control systems are studied, especially the interaction of the software with the hardware of the system. Two modes of operation of the brake pressure modulator have been considered; the software changes are effected to modify further the mode of operation of the system. The effect of the rate of rise of wheel cylinder pressure and the effect of rate of decay of pressure on the effectiveness and the maximum wheel slip in the first cycle have been studied. The hardware and the software are so modified as to give satisfactory performance of the wheel and the vehicle for four different forward speeds and for three different road conditions.

Clear identification of motor vehicle controls is necessary for safe operation of a vehicle. Identification of some well-known symbols and some new symbols was investigated by inquiries. Differences in identification between trained and untrained subjects are shown (employees of a vehicle manufacturer versus factory visitors). Influences of sex, age, and professional education are evaluated. The learning effect of identification before and after a purposeful training was investigated by an additional inquiry of factory visitors. The result showed no significant influence of sex, age, professional experience, or ownership of a driver license on the identification after training. This improves the chance of eliminating symbols of insufficient identification.

The purpose of the study was to determine which of three symbols would best represent each of 15 instrument-panel controls. The subjects were required to experience a “pretend” drive in an automobile simulator, the major element of which was a control panel containing the appropriate 15 symbols. For seven of the controls, one symbol was clearly the best of the three. For four of the controls, performance was optimal for all three symbols, while none of the symbols sufficed for the remaining four controls.

A search for methods of switching a proposed three beam headlight system led to the evaluation of 41 possible schemes. Human factors criteria reduced the original 41 to three systems which were tested in a laboratory with a broad range of subjects. Recordings of practice trials, learning trials, and the responses to visual cues projected on a screen were analyzed. The same test procedure was also used to compare three alternative ways of switching conventional two beam headlight systems. Summary data is presented for the six systems tested grouped by test subject age, sex, and driving experience. The most pronounced difference observed was in the subjective preference rating among two beam switching systems. All systems tested resulted in remarkably few learning and practice trials. Small differences were recorded among systems in operational response time.

This paper reports the results of a two-phase study of steering column mounted multifunction controls. A modified Mercedes Benz multifunction control (MFC) unit was installed in a 1972 Chevrolet station wagon. Control functions included were turn signals, washer, wiper, headlight dimmer, and optical horn. Phase 1 of the study investigated response time, error rates, and learning for this particular MFC. Phase 2 investigated subjective preferences, comparing the MFC with conventional controls and comparing alternative functions for inclusion in an “ideal” MFC unit. High error rates were found for first time use; however, subjects quickly learned to operate the unit with performance comparable to a representative panel control. Subjective responses were highly favorable to the concept.

Drivers searched for known symbols on a simulation of a dimly lit (5 1x) instrument panel. The symbols, from 2 mm to 25 mm diameter, were in groups of nine. They were randomly selected from 24 used to identify controls and displays on European Ford vehicles. The probability of recognition was related to size for eight symbols. This gives a rational basis for the size used in vehicles. No reliable difference was found between the performance of black symbols on white backgrounds and white on black. Substantial differences exist between the effectiveness of different symbols. Recommendations for improvements were based on confusions between symbols.

Surveys of rear lighting system malfunctions on passenger cars and light trucks showed that about 4% of vehicles with single compartment rear lamps had an inoperative presence or stop/turn lamp, while less than 1% of vehicles with multiple compartment rear lamps had at least one operating presence lamp compartment working on each side, and about 2.5% had no stop/turn signal lamp compartments operating on one side. Thus, although the frequency of failure of bulbs or circuits was greater in rear lighting systems with multiple compartment than single compartment lamps, the likelihood that at least one presence or signal lamp compartment will be operating on each side of the vehicle is greater in lighting systems with multiple compartment lamps, by 2-3%. The effects of some rear lighting system malfunctions on the ability of drivers to identify signals was evaluated in two experiments using a driving simulator.

General Motors has built an environmental chamber at its Milford Proving Ground to run emission tests at controlled atmospheric conditions. This chamber was designed using constant speed fans and dampers to simulate altitudes between sea level and Denver, which is approximately 5000 ft above sea level. The chamber can also control temperatures within a range of 45-100°F at humidities of 9-100 gr H2O/lb dry air. With this chamber, environmental conditions can be changed to desired levels very quickly to measure the vehicle sensitivity to the change. It is also possible to hold the environment constant and run controlled comparison studies on emission-related components to determine the effect of different distributors, carburetors, etc., relative to emission values. Past test experience has proved that vehicle emissions change with changing environment. However, the degree of change is different from one vehicle to another.

The concepts of “cost-benefit” and “cost-effectiveness” are increasingly cropping up in debate over present and future motor vehicle standards. Often they are introduced to attack, or justify, a particular standard. Just as often, they are misunderstood and misused. Since a motor vehicle safety performance standard has no costs per se, it cannot be evaluated either in cost-benefit or cost-effectiveness terms. It is the particular design alternatives available to manufacturers to achieve the objectives of a standard that have societal costs. The various design alternatives can be evaluated. Cost-effective designs should be chosen to minimize societal costs, and until there is evidence that cost-effective designs have been chosen, cost-benefit studies are premature.