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A practical methodology is presented for the synthesis of Chassis Systems and their integration into a vehicle design to achieve a specified vehicle dynamic performance. By focusing on the fundamental performance requirements of gain, response time, and stability in midrange handling and the higher level design parameters of front and rear cornering compliance it is possible to find optimum values for these design parameters. The balancing of these higher level design parameters, in the context of overall vehicle performance, determines primary system requirements for the front suspension, rear suspension, tires, and steering system which may in turn be met by a variety of specific hardware designs.

CFD (Computational Fluid Dynamics) has been used to analyze vehicle air flow. In cross wind conditions an asymmetrical flow field around the vehicle is present. Under these circumstances, in addition to the forces present with symmetric air flow (drag and lift forces and pitching moment), side forces and moments (rolling and yawing) occur. Issues related to fuel economy, driveability, sealing effects (caused by suction exerted on the door), structural integrity (sun roof, spoiler), water management (rain deposit), and dirt deposit (shear stress) have been investigated. Due to the software developments and computer hardware improvements, results can be obtained within a reasonable time frame with excellent accuracy (both geometry and analytical solution). The flow velocity, streamlines, pressure field, and component forces can be extracted from the analysis results through visualization to identify potential improvement areas.

A requirement for larger trucks and higher operating speed is indicated. The present report presents wind tunnel data on drag of a Chevrolet truck-trailer combination. Possible means of drag reduction are examined. Although side force and yawing moment data are presented, their effect on directional stability are not, at present analyzed.

Historically, the long development time required to produce a new automobile has meant that the electronics in that vehicle might lag the state-of-the-art by several years. For traditional vehicle electronics, this was certainly an appropriate delay, ensuring through extensive testing and qualification that the quality and reliability of the electronic systems met rigorous standards. However, with the growing consumer-oriented electronics content in today's vehicles, it is becoming more difficult for the automotive manufacturers to meet consumers' expectations with older technology. Couple this with the fast-paced consumer product cycle, typically nine to eighteen and the result is increasing pressure on the vehicle manufacturers from after-market electronics suppliers, who can update their product lines as fast as the component manufacturers can produce new models.

A driving simulator development project at the Systems Engineering and Technical Process Center (SE/TP) is exploring the role of driving simulation in the vehicle design process. The simulator provides two vehicle mockup testing arenas that support a wide field of view, computer-generated image of the road scene which dynamically responds to driver commands as a function of programmable vehicle model parameters. Two unique aspects of the simulator are the fast 65 ms response time and low incidence rate of simulator induced syndrome (about 5%). Preliminary model validation results and data comparing driver performance in a vehicle vs. the simulator indicate accurate handling response dynamics within the on-center handling region (<0.3g lateral acceleration). Applications have included supporting the development of new steering system concepts, as well as evaluating the usability of vehicle controls and displays.

For model year 1994, General Motors has completed the roll out of the 6.5L Diesel Engine, with the introduction of the light duty certified naturally aspirated and turbocharged engines. At the heart of the expanded use of the 6.5L is a new electronic powertrain control system. The objectives for this system were to produce an engine that has less variation, is easier to assemble, low cost and capable of meeting both heavy and light duty future emissions requirements. Control features include Fuel Quantity and Timing, EGR, Wastegate, Glow Plugs, Transmission, Cruise Control and Diagnostics.

This paper describes the performance attributes of the all-new front and rear SLA (short-long arm) suspensions, steering system, and tires of the 1997 Corvette. The process by which these subsystem attributes flowed down from vehicle-level requirements for ride and handling performance is briefly described. Additionally, where applicable, specific subsystem attributes are rationalized back to a corresponding vehicle-level performance requirement. Suspension kinematic and compliance characteristics are described and contrasted to those of the previous generation (1984 to 1996 Model Year) Corvette. Both synthesis/analysis activities as well as mule-level vehicle development work are cited for their roles in mapping out specific subsystem attributes and related vehicle performance.

The more noise and vibration improvements are incorporated into our vehicles, the more customers notice squeaks and rattles (S&R). Customers increasingly perceive S&R as a direct indicator of vehicle build quality and durability. The high profile nature of S&R has the automotive industry striving to develop the understanding and technology of how to improve the S&R performance in the vehicle. Squeaks and itches make up a significant amount of Squeak and Rattle complaints found in today's vehicles. Squeaks and itches are the result of stick slip behavior between two interacting surfaces. Squeak itch behavior is dependent upon a large number of parameters including but not limited to: the material itself, temperature, humidity, normal load, system compliance, part geometry, velocity, surface roughness, wear, contaminants, etc. This paper will describe the analysis of sound data and friction data and the relationship between them.

General Motors has developed a portfolio of advanced propulsion vehicles that has set the standard for optimal fuel economy in full-size utility vehicles. An overview of power electronics used in this portfolio, already available in the market, is presented. These components are key enablers for the strategic products in portfolio. Block diagrams for various configurations are also described to show common power electronics components used in traction and auxiliary systems. Briefly real wheel drive (RWD) and front wheel drive (FWD) vehicle applications are described. Specific analysis and test results are presented from development of Traction Power Inverter used in RWD vehicles. Vehicle-based durability profiles are used in analysis to predict IGBT power modules thermal performance. Using key metrics for volume and mass, benchmarking data is also presented.

The recent development of a new vane-type pump for power steering applications involved paying special attention to the fluid flow dynamics within the pump casing, especially in the flow control or supercharge region, where excess pump fluid flow is diverted to the intake region. Durability testing of initial designs revealed the presence of cavitation damage to the pump casing in the supercharging region. Subsequent Computational Fluid Dynamics (CFD) analyses as well as experimental Flow Visualization studies aided in resolving the cavitation-damage problem. The purpose of this paper is to describe the processes used in the CFD analyses and flow visualization studies. A two-dimensional (2D) convergence study was conducted to determine the CFD meshing requirements across the small orifice at the intersection of the flow-control valve and the supercharge port. An iterative procedure was employed to determine the operating position of the flow-control valve.

The common occurrence of impulsive sounds in automobiles and the recent emphasis on producing vehicles with a “quality sound” has increased the need for a method for measuring the pitch of impulsive sounds. Using Zwicker’s Loudness Patterns as a basis, a data reduction method was developed which summarizes the frequency content of each pattern. The method yields time varying quantities called Percentile Partial Loudness Frequencies from a time series of Loudness Patterns. Several “simple” impulsive sounds, representing a range of pitches, were investigated using this method. Visual inspection of the results has identified trends which seem to rank the impulsive sounds in agreement with subjective pitch rankings of a listening jury. In addition, the method appears to be capable of ranking the early portion of the impulse as a sharp or dull attack. Further investigations are needed to confirm these observations and refine the technique.

SPECIFICATIONS of the new Chevrolet Turbo Thrust V-8 engine described in this paper are: