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Technical Paper

Simple, Closed-Form Expressions Relating Long-Term (Z score) and Short-Term (Defects per Opportunity) Variability

2007-04-16
2007-01-0993
A simple and accurate analytical expression relating the expected process (long term) and sampling (short-term) product variability is developed using a variational mathematical principle. Of the several complex functional forms discovered, simplicity and ease of use are used to select an expression providing the most reliable estimation for and convenient expression of Z score (σ level) as a function of defects per opportunity (DPO) or per million opportunities (DPMO). In the absence of scientific calculators or computers, this expression allows engineers to accurately estimate long term process variability to within 0.01 of its true value without resulting to (laborious) tables or a computer. Also, a high precision approximation is provided for cases when DPO is less than 1% which estimates Z-score to within 0.003 of the actual value (at 6σ).
Technical Paper

A Test-Based Procedure for the Identification of Rack and Pinion Steering System Parameters for Use In CAE Ride-Comfort Simulations

2009-05-19
2009-01-2090
Current CAE modeling and simulation techniques in the time domain allow, by now, very accurate prediction of many ride-comfort performances of the cars. Nevertheless, the prediction of the steering wheel rotation vibration excited by, for instance, wheel unbalance or asymmetric obstacle impact, often runs into the difficulty of modeling the steering line with sufficient accuracy. For a classic rack and pinion, hydraulic assisted steering line, one of the challenges is to model the complex and non linear properties - stiffness, friction and damping - of the rack-rack case system. This paper proposes a rack model, thought for easy implementation in complex multi-body models, and an identification procedure of its parameters, based on measurements, in the operational range of the wheel unbalance excitation. The measurements have been gathered by specific tests on the components and the test set-up is also shown here.
Technical Paper

Steering Grunt Noise Robustness Improvement

2009-05-19
2009-01-2095
Grunt is a structure-born noise caused by resonance of the steering gear torsion bar (T-bar) in an HPAS (Hydraulic Power Assist Steering) system. The goal of this work was to develop techniques to quantify and predict grunt in a RV (rotary valve) steering gear system. First, vehicle testing was used to identify an objective metric for grunt: y = dynamic pressure in the return line. Then, a computer simulation was developed to predict y as a function of two known control factors. The simulation results were correlated to measurements on a test vehicle. Finally, the simulation was expanded to include two additional control factors, and grunt predictions were demonstrated on a different test vehicle.
Technical Paper

Experimental Estimation of On-Vehicle Wheel-End Force and Application to Tire Flat-Spotting Effect

2009-05-19
2009-01-2160
Nibble is torsional vibration at the steering wheel of a vehicle. Typically it occurs at a resonant frequency of the steering and suspension system excited by the 1st harmonic tire/wheel force. A nibble target is established to be consistent with customer satisfaction target and then cascaded down to the targets for vehicle nibble sensitivity and tire/wheel inputs. Hence accuracy of the sensitivity and the tire/wheel force is important for a Computer Aided Engineering (CAE) nibble simulation. On-vehicle wheel-end forces are fore/aft and vertical tire/wheel forces acting on a vehicle spindle in an operating condition. This paper presents a methodology to estimate the wheel-end forces. The methodology was applied to investigate the effect of the tire flat-spot on the wheel-end forces. Tires were flat-spotted for one week and two months to simulate customer usage profiles. They were tested to measure the growth of the wheel-end forces.
Technical Paper

The Handling of Non-Uniform Parts and Peak Hand Forces

2009-06-09
2009-01-2307
Due to the challenges in quantifying hand loads in manufacturing environments it is often assumed that the load is evenly distributed between the hands, even when handling parts with non-uniform mass distribution. This study estimated hand loads for six female subjects, when handling a custom part in 8 different configurations (2 weights, 4 CofM locations). The calculated hand loads varied from 20 to 50% of the weight being handled. The magnitude of asymmetrical hand loading depended on both the part orientation and the location of the CoM. Based on this study the knowledge of part weight, CofM location and hand positioning will allow the users of digital human models to perform more realistic and reliable task analysis assessments as the force distributions will be more representative of the actual loading rather than simply assuming the load is evenly distributed between the hands.
Technical Paper

Mexico City Traffic and Los Angeles City Traffic Testing: An Approach to Test Route Development for Results Homologation

2012-09-17
2012-01-1808
Vehicle testing on public roads is used by the automotive community in different locations to evaluate the noise characteristics of brake systems under typical customer usage conditions. These tests are generally carried out on different locations and show results with questionable compatibility as has been concluded on several investigations over the last years [1]. Global projects on the other hand mandate to have tests that can represent vehicle usage in several types of environments in order to have reliable indicators of performance on different conditions. This paper suggests a method to characterize roads on different sites and modify the route to match a specific target.
Technical Paper

Development of Universal Brake Test Data Exchange Format and Evaluation Standard

2010-10-10
2010-01-1698
Brake system development and testing is spread over vehicle manufacturers, system and component suppliers. Test equipment from different sources, even resulting from different technology generations, different data analysis and report tools - comprising different and sometimes undocumented algorithms - lead to a difficult exchange and analysis of test results and, at the same time, contributes to unwanted test variability. Other studies regarding the test variability brought up that only a unified and unambiguous data format will allow a meaningful and comparative evaluation of these data and only standardization will reveal the actual reasons of test variability. The text at hand illustrates that a substantial part of test variability is caused by a misinterpretation of data and/or by the application of different algorithms.
Journal Article

Modeling and Experimental Investigation of Tire Cavity Noise Generation Mechanisms for a Rolling Tire

2009-05-19
2009-01-2104
Tire cavity noise refers to the excitation of the acoustic mode of a tire cavity. The noise exhibits itself as sharp resonance-like peaks with frequencies typically in the range of 190-250Hz. For a rolling tire, the tire contact with the road moves relative to the tire. Furthermore, the load on the tire breaks the circular symmetry of the tire. Consequently, the peak frequency of the cavity noise shows dependence on the tire load and the vehicle speed. There are no models that simultaneously take these two factors into consideration. In this paper, we propose an analytical model and present experimental verifications of predictions on the noise peak frequency and its dependence on the tire load and vehicle speed. A wireless experimental measurement system is also presented which enables the measurement of tire cavity frequency for both non-rolling and rolling conditions.
Journal Article

Development and Validation of an Analytical Seal Bead Design Model for Automotive Superplastic Forming

2010-04-12
2010-01-0979
With the increasing demand for fuel efficient vehicles, technologies like superplastic forming (SPF) are being developed and implemented to allow for the utilization of lightweight automotive sheet materials. While forming under superplastic conditions leads to increased formability in lightweight alloys, such as aluminum, the slower forming times required by the technology can limit the technology to low to mid production levels. One problem that can increase forming time is the reduction of forming pressure due to pressurizing (forming) gas leaks, during the forming cycle, at the die/sheet/blankholder interface. Traditionally, such leaks have been successfully addressed through the use of a seal bead. However, for advanced die technologies that result in reduced cycle times (such as hot draw mechanical performing, which combine aspects of mechanical preforming of the sheet metal followed by SPF), the use of seal beads can restrict the drawing of sheet material into the forming die.
Technical Paper

Bending Process Optimization of Dual Phase 780 (DP780) Tubes for Body Structural and Chassis Applications

2010-04-12
2010-01-0230
To reach safety, emissions, and cost objectives, manufacturers of automotive body structural and chassis components shape thin gauge, high strength steel tube with a bending, pre-forming and hydroforming process. Challenging grades and bend severity require a careful optimization of the bending procedure. A joint project between Ford and ArcelorMittal Tubular Products investigated suitable bending parameters for severe bends using commercially available thin-walled DP780 and HSLA350 tubes. This paper summarizes the measurement methods found to be capable of capturing small differences in bending formability and details the influence of bender variables such as boost, pressure die, center-line bend radius and bend angle on the wrinkling, thinning and springback of these tubes. As a result of this work, recommendations were made as to effective bender set-ups for these tubes.
Technical Paper

The 1970 Ford Dual Circuit Air Brake System

1970-02-01
700504
The braking system presented in this article represents a new and forward thinking philosophy regarding commercial vehicle air brake systems. A concept that provides responsive service and emergency brake applications with optimum vehicle control, by the same driver action on the brake pedal. The uniqueness of the total system, and each circuit's function thereof, is explained in basic detail. In addition, the engineering, quality control, and assembly techniques to manufacture the vehicle with assurance that design intent is achieved, are discussed.
Technical Paper

The Effect of Friction Modifiers and DI Package on Friction Reduction Potential of Next Generation Engine Oils: Part I Fresh Oils

2018-04-03
2018-01-0933
Friction reduction in lubricated components through engine oil formulations has been investigated in the present work. Three different DI packages in combination with one friction modifier were blended in SAE 5 W-20 and SAE 0 W-16 viscosity grades. The friction performance of these oils was compared with GF-5 SAE 5 W-20 oil. A motored cranktrain assembly has been used to evaluate these, in which friction mean effective pressure (FMEP) as a function of engine speeds at different lubricant temperatures is measured. Results show that the choice of DI package plays a significant role in friction reduction. Results obtained from the mini-traction machine (MTM2) provide detailed information on traction coefficient in boundary, mixed and elastohydrodynamic (EHD) lubrication regimes. It has been shown that the results from the cranktrain rig are fairly consistent with those found in MTM2 tests for all the lubricants tested.
Technical Paper

A Method for Rapid Durability Test Development

2017-03-28
2017-01-0199
Designing a durability test for an automatic transmission that appropriately reflects customer usage during the lifetime of the vehicle is a formidable task; while the transmission and its components must survive severe usage, overdesigning components leads to unnecessary weight, increased fuel consumption and increased emissions. Damage to transmission components is a function of many parameters including customer driving habits and vehicle and transmission characteristics such as weight, powertrain calibration, and gear ratios. Additionally, in some cases durability tests are required to verify only a subset of the total parameter space, for example, verifying only component modifications. Lastly, the ideal durability test is designed to impose the worst case loading conditions for the maximum number of internal components, be as short as practicable to reduce testing time, with minimal variability between tests in order to optimize test equipment and personnel resources.
Technical Paper

Geometrical Optimization of an Automotive Halfshaft

2017-03-28
2017-01-1125
Halfshafts are very important components from vehicle powertrain. They are the element responsible to transmit torque and rotation from transmission to wheels. Its most basic design consists of a solid bar with joints at each extreme. Depending of bar length, the natural frequency of first bending mode might have a modal alignment with engine second order, resulting in undesired noise on vehicle interior. Many design alternatives are available to overpass this particular situation, like adding dampers, use tube shafts or use link-shafts, however, all of them are cost affected. This study proposes an investigation to obtain an optimal profile for a solid shaft, pursuing the lowest possible frequency for the first bending mode by changing its diameter at specific regions. The study is divided in four main stages: initially, a modal analysis of a halfshaft is done at vehicle to determinate its natural frequency when assembled on vehicle.
Technical Paper

Ting Noise Generation in Automotive Applications

2017-03-28
2017-01-1121
Automobile customers are looking for higher performance and quieter comfortable rides. The driveline of a vehicle can be a substantial source of NVH issues. This paper provides an understanding of a driveline noise issue which can affect any variant of driveline architecture (FWD, AWD, RWD and 4X4). This metallic noise is mostly present during the take-off and appropriately termed as ting noise. This noise was not prevalent in the past. For higher fuel economy, OEMs started integrating several components for lighter subsystems. This in effect made the system more sensitive to the excitation. At present the issue is addressed by adding a ting washer in the interface of the wheel hub bearings and the halfshafts. This paper explains the physics behind the excitation and defines the parameters that influence the excitation. The halfshaft and the wheel hub are assembled with a specified hub nut torque.
Technical Paper

Robust Prediction of Lane Departure Based on Driver Physiological Signals

2016-04-05
2016-01-0115
Lane change events can be a source of traffic accidents; drivers can make improper lane changes for many reasons. In this paper we present a comprehensive study of a passive method of predicting lane changes based on three physiological signals: electrocardiogram (ECG), respiration signals, and galvanic skin response (GSR). Specifically, we discuss methods for feature selection, feature reduction, classification, and post processing techniques for reliable lane change prediction. Data were recorded for on-road driving for several drivers. Results show that the average accuracy of a single driver test was approx. 70%. It was greater than the accuracy for each cross-driver test. Also, prediction for younger drivers was better.
Technical Paper

An Indirect Tire Health Monitoring System Using On-board Motion Sensors

2017-03-28
2017-01-1626
This paper proposes a method to make diagnostic/prognostic judgment about the health of a tire, in term of its wear, using existing on-board sensor signals. The approach focuses on using an estimate of the effective rolling radius (ERR) for individual tires as one of the main diagnostic/prognostic means and it determines if a tire has significant wear and how long it can be safely driven before tire rotation or tire replacement are required. The ERR is determined from the combination of wheel speed sensor (WSS), Global Positioning sensor (GPS), the other motion sensor signals, together with the radius kinematic model of a rolling tire. The ERR estimation fits the relevant signals to a linear model and utilizes the relationship revealed in the magic formula tire model. The ERR can then be related to multiple sources of uncertainties such as the tire inflation pressure, tire loading changes, and tire wear.
Technical Paper

Vehicle Deep Data: A Case Study in Robust Scalable Data Collection

2017-03-28
2017-01-1651
Onboard, embedded cellular modems are enabling a range of new connectivity features in vehicles and rich, real-time data set transmissions from a vehicle’s internal network up to a cloud database are of particular interest. However, there is far too much information in a vehicle’s electrical state for every vehicle to upload all of its data in real-time. We are thus concerned with which data is uploaded and how that data is processed, structured, stored, and reported. Existing onboard data processing algorithms (e.g. for DTC detection) are hardcoded into critical vehicle firmware, limited in scope and cannot be reconfigured on the fly. Since many use cases for vehicle data analytics are still unknown, we require a system which is capable of efficiently processing and reporting vehicle deep data in real-time, such that data reporting can be switched on/off during normal vehicle operation, and that processing/reporting can be reconfigured remotely.
Technical Paper

Development of a Thermal Model for a Heated Steering Wheel to Compensate Defective Feedback Variables

2017-03-28
2017-01-1636
Along with the development and marketability of vehicles without an internal combustion engine, electrically heated surfaces within these vehicles are getting more and more important. They tend to have a quicker response while using less energy than a conventional electric heater fan, providing a comfortable temperature feel within the cabin. Due to the big area of heated surface it is important to spread the heating power in a way that different heat conduction effects to underlying materials are considered. In case an accurate sensor feedback of the targeted homogeneous surface temperature cannot be guaranteed, a thermal energy model of the heated system can help to set and maintain a comfortable surface temperature. For a heated steering wheel development project, different models have been created to meet that aim using mechanistic approaches starting with a predominantly first-order dynamics model and ending with a distributed parameter multi-feedback system.
Technical Paper

Complete Seat Load Deflection Testing Methodologies

2017-03-28
2017-01-1391
Load deflection testing is one type of test that can be used to understand the comfort performance of a complete trimmed automotive seat. This type of testing can be conducted on different areas of the seat and is most commonly used on the seatback, the seat cushion and the head restraint. Load deflection data can be correlated to a customer’s perception of the seat, providing valuable insight for the design and development team. There are several variables that influence the results obtained from this type of testing. These can include but are not limited to: seat structure design, suspension system, component properties, seat materials, seat geometry, and test set-up. Set-up of the seat for physical testing plays a critical role in the final results. This paper looks at the relationship of the load deflection data results on front driver vehicle seatbacks in a supported and unsupported test set-up condition.
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