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Brake pad to rotor adhesion following exposure to corrosive environments, commonly referred to as “stiction”, continues to present braking engineers with challenges in predicting issues in early phases of development and in resolution once the condition has been identified. The goal of this study took on two parts - first to explore trends in field stiction data and how testing methods can be adapted to better replicate the vehicle issue at the component level, and second to explore the impacts of various brake pad physical properties variation on stiction propensity via a controlled design of experiments. Part one will involve comparison of various production hardware configurations on component level stiction tests with different levels of prior braking experience to evaluate conditioning effects on stiction breakaway force.

General Motors recently demonstrated two driveable test vehicles powered by a Homogeneous Charge Compression Ignition (HCCI) engine. HCCI combustion has the potential of a significant fuel economy benefit with reduced after-treatment cost. However, the biggest challenge of realizing HCCI in vehicle applications is controlling the combustion process. Without a direct trigger mechanism for HCCI's flameless combustion, the in-cylinder mixture composition and temperature must be tightly controlled in order to achieve robust HCCI combustion. The control architecture and strategy that was implemented in the demo vehicles is presented in this paper. Both demo vehicles, one with automatic transmission and the other one with manual transmission, are powered by a 2.2-liter HCCI engine that features a central direct-injection system, variable valve lift on both intake and exhaust valves, dual electric camshaft phasers and individual cylinder pressure transducers.

Diesel engines offer better fuel economy compared to their gasoline counterpart, but simultaneous control of NOx and particulates is very challenging. The blended 2-way SCR/DPF is recently emerging as a compact and cost-effective technology to reduce NOx and particulates from diesel exhaust using a single aftertreatment device. By coating SCR catalysts on and inside the walls of the conventional wall-flow filter, the 2-way SCR/DPF eliminates the volume and mass of the conventional SCR device. Compared with the conventional diesel aftertreatment system with a SCR and a DPF, the 2-way SCR/DPF technology offers the potential of significant cost saving and packaging flexibility. In this study, an engine dynamometer test cell was set up to repeatedly load and regenerate the SCR/DPF devices to mimic catalyst aging experienced during periodic high-temperature soot regenerations in the real world.

At the early design stage it is easier to achieve impacts on the brake noise. However most noise analyses are applied later in the development stage when the design space is limited and changes are costly. Early noise analysis is seldom applied due to lack of credible inputs for the finite element modeling, the sensitive nature of the noise, and reservations on the noise event screening of the analysis. A high quality brake finite element model of good components’ and system representation is the necessary basis for credible early noise analysis. That usually requires the inputs from existing production hardware. On the other hand in vehicle braking the frequency contents and propensity of many noise cases are sensitive to minor component design modifications, environmental factors and hardware variations in mass production. Screening the noisy modes and their sensitivity levels helps confirm the major noisy event at the early design stage.

This paper presents the development of a transmission closed loop pressure control system. The objective of this system is to improve transmission pressure control accuracy by employing closed-loop technology. The control system design includes both feed forward and feedback control. The feed forward control algorithm continuously learns solenoid P-I characteristics. The closed loop feedback control has a conventional PID control with multi-level gain selections for each control channel, as well as different operating points. To further improve the system performance, Robust Optimization is carried out to determine the optimal set of control parameters and controller hardware design factors. The optimized design is verified via an L18 experiment on spin dynamometer. The design is also tested on vehicle.

This work discusses the development of SAE procedure J2747, “Hydraulic Pump Airborne Noise Bench Test”. This is a test procedure describing a standard method for measuring radiated sound power levels from hydraulic pumps of the type typically used in automotive power steering systems, though it can be extended for use with other types of pumps. This standard was developed by a committee of industry representatives from OEM's, suppliers and NVH testing firms familiar with NVH measurement requirements for automotive hydraulic pumps. Details of the test standard are discussed. The hardware configuration of the test bench and the configuration of the test article are described. Test conditions, data acquisition and post-processing specifics are also included. Contextual information regarding the reasoning and priorities applied by the development committee is provided to further explain the strengths, limitations and intended usage of the test procedure.

Neck injury assessment is part of the FMVSS208 requirements. Hardware tests are often conducted to validate whether the vehicle safety system meets the requirements. This paper presents a full vehicle finite element model using LS-DYNA, including structural components, restraint system components, and dummies. In the case of a frontal impact at 30deg angle, in the areas of neck compression, neck extension and neck kinematics, it is demonstrated that a good correlation is achieved between the response of a FE dummy in the model and those of ATDs in the physical hardware tests. It is concluded that the math tool may be applied to comprehend test and design variations that may arise throughout a vehicle development lifecycle and to help develop a vehicle restraint system.

In GM R&D Powertrain/Engine Control Group, rapid prototyping controller (RPC) systems with Matlab/Simulink are used extensively to design, simulate and implement advanced engine control algorithms and models. However, those RPC systems use powerful microprocessors with large amounts of RAM contrary to engine control modules (ECM) in production vehicles. Therefore, a thorough analysis on the comparatively much more complicated algorithms and models cannot be performed during the research stage, since there are not enough tools to enable the smooth transition from Matlab/Simulink to the production type processor. The Real-Time Interface (RTI) Blockset for a production like microprocessor would close the transition gap between rapid prototyping controller systems and production type microprocessors by leveraging the power and popularity of Matlab/Simulink in control engineering world and automatic code generation tools.

The optimal selection of vehicle body and powertrain mounts from “mount libraries” is one of the major undertakings to achieve optimal vehicle dynamics and N&V performance through the reuse of existing mount designs. The great challenges of the process are due to the facts that conventional optimization procedures, either through simulation or DOE, can not be used directly because the stiffness rates of the mounts are scattered and bundled. Sorting out the best through hardware tests is generally unrealistic simply due to the huge number of mount combinations. This paper presents a new approach to the optimal mount selection, and demonstrates through applications that it is efficient and reliable. This approach characterizes a mount by its effective stiffness rate and evaluates its deviation from an associated target. Continuous dummy variables are used to determine the selection targets through conventional processes for performance optimization.

Durability of automotive structures is a primary engineering consideration that is evaluated during a vehicle's design and development. In addition, it is a basic expectation of consumers, who demand ever-increasing levels of quality and dependability. Automakers have developed corporate requirements for vehicle system durability which must be met before a products is delivered to the customer. To provide early predictions of vehicle durability, prior to the construction and testing of prototypes, it is necessary to predict the forces generated in the vehicle structure due to road inputs. This paper describes an application of the “virtual proving ground” approach for vehicle durability load prediction for a vehicle on proving ground road surfaces. Correlation of the results of such a series of simulations will be described, and the modeling and simulation requirements to provide accurate simulations will be presented.

4-Post durability test simulations using a nonlinear FEA model have been executed by engineers responsible for structural durability performance and validation. An integrated Body and Chassis, full FEA model has been used. All components of the test load input were screened and only the most damaging events were incorporated in the simulation. These events included the Potholes, Belgian Block Tracks, Chatter Bump Stops, Twist Ditches, and Driveway Ramps. The CAE technology Virtual Proving Ground (eta/VPG®*) was used to model the full system and the 4-Post test fixtures. The nonlinear dynamic FE solver LS-DYNA** was used in this analysis. The fatigue damage of each selected event was calculated separately and then added together according to the test schedule. Due to the lack of stress/strain information from hardware test, only the analyzed fatigue damage results of the baseline model were scaled to correlate with physical test data.

Mechanical Efficiency of toroidal traction drives is the key parameter for transmission engineers worldwide to accept their use in continuously variable transmissions. In this work, the traction drive efficiencies are investigated analytically as well as experimentally as a function of speed, torque, speed ratio and temperature for two different CVU's. In addition, creep at the traction contact is measured and compared with the prediction of the simulation model. In a stand-alone test rig, the drag torque associated with the power-roller thrust bearing is also measured.

This paper describes an axle gear whine noise reduction process that was developed and applied using a combination of experimental and analytical methods. First, an experimental Transfer Path Analysis (TPA) was used to identify major noise paths. Next, modeling and forced response simulation were conducted using the Hybrid FEA-Experimental FRF method known as HYFEX [1]. The HYFEX model consisted of an experimental FRF representation of the frame/body and a finite element (FE) model of the driveline [2] and suspension. The FE driveline model was calibrated using experimental data. The HYFEX model was then used to simulate the axle noise reduction that would be obtained using a modified frame, prior to the availability of a prototype. Hardware testing was used as the final step in the process to confirm the results of the simulation.

The Milford Road Course is a new 2.9 mi (4.6 km), 20 turn, configurable closed course with 135 ft (41 m) of elevation change, constructed at the General Motors Proving Ground in Milford, MI, USA. This facility provides a convenient and safe venue for engineers to evaluate vehicle limit performance over extensive combinations of vertical, lateral and longitudinal acceleration at a wide range of speeds. This paper discusses the vehicle dynamics aspects of the facility design, simulation and construction.

A co-operative program initiated by the Automotive Aluminum Alliance and supported by USAMP continues to pursue the goal of establishing an in-laboratory cosmetic corrosion test for finished aluminum auto body panels that provides a good correlation with in-service performance. The program is organized as a task group within the SAE Automotive Corrosion and Protection (ACAP) Committee. Initially a large reservoir of test materials was established to provide a well-defined and consistent specimen supply for comparing test results. A series of laboratory procedures have been conducted on triplicate samples at separate labs in order to evaluate the reproducibility of the various lab tests. Exposures at OEM test tracks have also been conducted and results of the proving ground tests have been compared to the results in the laboratory tests. Outdoor tests and on-vehicle tests are also in progress. An optical imaging technique is being utilized for evaluation of the corrosion.

This paper describes the development of a generic test cell software designed to overcome many vehicle-component testing difficulties by introducing modern, real-time control and simulation capabilities directly to laboratory test environments. Successfully demonstrated in a transmission test cell system, this software eliminated the need for internal combustion engines (ICE) and test-track vehicles. It incorporated the control of an advanced AC induction motor that electrically simulated the ICE and a DC dynamometer that electrically replicated vehicle loads. Engine behaviors controlled by the software included not only the average crankshaft torque production but also engine inertia and firing pulses, particularly during shifts. Vehicle loads included rolling resistance, aerodynamic drag, grade, and more importantly, vehicle inertia corresponding to sport utility, light truck, or passenger cars.

The Automotive Aluminum Alliance in conjunction with SAE ACAP founded a corrosion task group in 2000 with a goal to establish an in-laboratory cosmetic corrosion test for finished aluminum auto body panels, which provides a good correlation with in-service performance. Development of this test involves a number of key steps that include: (1) Establishing a reservoir of standard test materials to provide a well-defined and consistent frame of reference for comparing test results; (2) Defining a real-world performance for the reference materials through on-vehicle tests conducted in the U.S. and Canada; (3) Evaluating existing laboratory, proving ground, and outdoor tests; (4) Conducting statistically designed experiments to evaluate the effects of cyclic-test variables; (5) Comparing corrosion mechanisms of laboratory and on-vehicle tests; and (6) Conducting a round robin test program to determine the precision of the new test. Several of these key steps have been accomplished.

General Motors Corporation has installed its first production Bag Mini-Diluter Emission Test Site. This site is capable of conducting chassis dynamometer tests in either traditional CFV mode, or BMD mode, and a combination mode in which both technologies sample simultaneously. This paper discusses ambient interferent (Hydrocarbon and humidity) contamination issues which impact data resolution and measurement accuracy as emission standards are lowered. Solutions are recommended which compensate for these effects. This document examines new technologies required for accurate BMD measurements, and presents data obtained from running the site in the dual sampling mode utilizing a four-cylinder PZEV vehicle.

PEM Fuel Cell technology has been advancing rapidly during the last several years as evidenced by various vehicle demonstrations by the major automotive companies. As the development continues to bring hardware to automotive system level solutions, many engineering challenges arise. This paper will deal with two (2) of these areas from an automotive system level perspective: Thermal Management and the Fuel Cell Stack. Both of these sub-system areas are critical to the success of the technology in meeting the requirements of tomorrow's automotive customer.

A program was initiated to improve the emission and fuel economy measurement accuracy and test cell to test cell correlation. Improvements were made to the Constant Volume Sampling System, electric dynamometer, instrument calibration ranges and system checks were initiated to improve the accuracy of the bag emissions, modal emissions, calculated and measured fuel economy. Unique emission and fuel economy problems associated with gasoline and diesel testing were studied and resolutions effected when possible.