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Technical Paper

Brake Dynamometer Test Variability - Analysis of Root Causes

Modern project management including brake testing includes the exchange of reliable results from different sources and different locations. The ISO TC22/SWG2-Brake Lining Committee established a task force led by Ford Motor Co. to determine and analyze root causes for variability during dynamometer brake performance testing. The overall goal was to provide guidelines on how to reduce variability and how to improve correlation between dynamometer and vehicle test results. This collaborative accuracy study used the ISO 26867 Friction behavior assessment for automotive brake systems. Future efforts of the ISO task force will address NVH and vehicle-level tests. This paper corresponds to the first two phases of the project regarding performance brake dynamometer testing and presents results, findings and conclusions regarding repeatability (within-lab) and reproducibility (between-labs) from different laboratories and different brake dynamometers.
Technical Paper

New Method to Identify Dynamic Normal Stiffness and Damping of Shims for CAE Modeling

One of the most important means used for suppressing squeal noise in disc brakes is the application of shims on the pad backplates. In many cases this proves a very efficient tool depending on the type of shim applied in the specific cases. Building up knowledge on the effects of shims have been ongoing for several years, and measuring the important parameters characterizing the shims is crucial for understanding how to develop and implement the shims in an optimal way. Several methods are described in literature for measuring the constrained layer damping effect and one method is described for direct measurement of the shear stiffness and shear damping properties. However, up to now no method has been available that can measure and characterize the normal stiffness and damping properties of shims. This is one of the most important properties of shims as it controls the de-coupling effect in the direction of the normal forces.
Technical Paper

Pressure Control Calibration Time Reduction for EHB Systems

An ABS/TC proportional pressure control can be achieved by using some of the control technology applied to an electro-hydraulic brake (EHB) system. This paper describes a new method for reducing the calibration time of an EHB, and this method may be used for potential advanced ABS/TC proportional control systems. A mathematical model is established to analyze the system and by using the model some common physical relationships are identified. Calibration values of a proportional system in certain pressure ranges can be estimated instead of requiring measurement.
Technical Paper

A Mathematical Model for Design and Production Verification Planning

The paper focuses on various important decisions of verification and testing plans of the product during its design and production stages. In most of the product and process development projects, decisions on verification and testing are ad-hoc or based on traditions. Such decisions never guarantee the performance of the product as planned, during its whole life cycle. We propose an analytical approach to provide the concrete base for such crucial decisions of verification planning. Accordingly, a mathematical model is presented. Also, a case study of an automotive Electro-mechanical product is included to illustrate the application of the model.
Technical Paper

Diesel Fuel Injection Control for Optimum Driveability

Performance and refinement are key factors which influence the market acceptance of passenger cars, and consequently in the area of diesel fuel injection control there is increasing pressure for improved driveability. “Driveline shunt” is one important and problematic aspect of driveability, which is also known as “judder”, “chuggle” or “cab-nod”. It has been defined as an objectionable vehicle oscillation which takes place following a rapid throttle input or increase in engine load. This phenomenon is caused by driveline vibrations which can occur as a consequence of variations in engine torque demand. Mathematical modelling and experimentation techniques have been used to establish the behaviour of a fuel injection system, engine and vehicle driveline. Vehicle tests have been conducted in order to relate objective metrics and subjective opinion.
Technical Paper

On Automotive Disc Brake Squeal Part II: Simulation and Analysis

This paper reviews the state of the art of CAE simulation and analysis methods on disc brake squeal. It covers complex modes analysis, transient analysis, parametrical analysis, and operational simulation. The advantages and limitations of each analysis method are discussed. This review can help analysts to choose right methods and decide new lines of method development. For completeness, analytic methods dealing with continuum models are also briefly covered. This review was made from those papers that the authors are familiar with. It is not meant to be all-inclusive even though the best possible effort has been attempted.
Technical Paper

Brake Rattle: Vibration and Noise Testing

The continuous decrease in background noise levels inside vehicles has made other noise sources easily noticeable. Specifically, foundation brake rattle noise is a growing concern to the customer. This brake rattle is primarily due to rigid body impact between brake components. Currently, vehicle and brake manufacturing companies use different testing procedures to evaluate brake rattle that include laboratory vibration shakers, full vehicle shakers (four post), chassis dynamometers and vehicle road testing. These evaluations are subjective in most cases. A method is needed to replicate and quantify vehicle brake rattle in the laboratory to help determine the acceptability of a brake system at a component level. This approach would also help to identify the root cause for brake rattle and evaluate design changes to address that rattle. Some guidelines for better quantifying brake rattle using shakers will be proposed in this paper.
Technical Paper

An Investigation of Metal Pick-Up Generation on Passenger Car Brake Pads in Correlation with Deep Rotor Scoring

This paper reports the progress that has been made to date on a research program that has as its focus to describe the mechanism of metal pick-up generation on passenger car disc brake pads in correlation with deep rotor scoring. In contrast to other existing generation theories, the new investigation considers other aspects of the initial onset of the metal pick-up.
Technical Paper

Design and Development of Single Seat, Four Wheeled All-Terrain Vehicle for Baja Collegiate Design Series

There has been a rapid increase in popularity of multipurpose All-terrain vehicles (ATV) across the globe over the past few years. SAE BAJA event gives student-community an opportunity to delve deeper into the nitty-gritty of designing a single seat, four-wheeled off road vehicle. The design and development methodology presented in this paper is useful in conceptualization of an ATV for SAE BAJA event. The vehicle is divided into various subsystems including chassis, suspension, drive train, steering, and braking system. Further these subsystems are designed and comprehensively analyzed in software like SolidWorks, ANSYS, WINGEO and MS-Excel. The 3-D model of roll cage is designed in SolidWorks and analyzed in ANSYS 9.0 for front, rear and side impact along with front and side roll-over conditions. Special case of wheel bump is also analyzed. Weight, wall thickness and bending strength of tubing used for roll cage are comprehensively studied.
Technical Paper

Brake Squeal Rig and LACT Vehicle Test Correlation Improvements – Focus on Thermal Conditionings

Today's newer friction materials and brake systems are able to operate under extreme conditions that are not normally evaluated with the standard squeal rig procedures. This could cause some discrepancy between the squeal rig test results and the vehicle test results like Los Angeles City Traffic Test (LACT). In some cases the noise behavior of brake systems could change dramatically and take us by surprise with new squeal frequencies being uncovered or get flagged due to high occurrences. This discrepancy could also be a major handicap with respect to developing a noise fix in the lab if the squeal cannot be reproduced. In this paper, we evaluated some case studies where some extreme conditionings especially related to thermal inputs drastically changed the squeal behavior of the brake system.
Technical Paper

Measurement and Analysis of Rotor In-plane Mode Induced Disc Brake Squeal and Beyond

This paper provides measurement and analysis on rotor in-plane mode induced squeal. Methodology is presented to simultaneously acquire both temporal and spatial squeal operational deflection shapes (ODS). Rotor accelerations both in the in-plane and out-of-plane directions were measured during squeal along with rotor's normal ODS using a laser vibrometer. Modal measurement and analysis of the rotor and pad in the in-plane and out-of-plane directions were conducted as installed in system condition. The test results indicating rotor modal coupling in the in-plane are provided, and out-of-plane directions, and conclusions on in-plane mode induced squeal are proposed. In addition, the countermeasure for squeal reduction is discussed.
Technical Paper

Application of Loop Shaping H-infinity Control to Diesel Engine Anti-Oscillation Strategy

The control of fuel delivery to minimize drivetrain oscillations is a major benefit to vehicle refinement and driveability. This paper describes the application of robust H-infinity loop-shaping control to the speed-fuel control loop. A one-degree-of-freedom controller structure (feedback only) is examined and applied to a small passenger car. Using careful implementation, the control algorithm is of low order and efficient requiring only limited microprocessor resources. The robust controller gives excellent performance when operated synchronously to engine rotation, where the dynamics become speed-dependent. Alternatively it can be operated satisfactorily at a fixed sample rate, asynchronous to engine rotation. The design is found to be eminently suitable for production.
Technical Paper

Fluid-Structure Coupled Modeling for HYGE Impact Simulator

The HYGE impact simulator is designed to reproduce the crash pulse of a real world vehicle impact in the laboratory environment. When a crash pulse is given, it usually takes a substantial amount of works and costs to adjust operating parameters to create the desired pulse on the HYGE machine. To save the operational cost, a mathematical model of the impact simulator using Ordinary Differential Equations (ODE's) was established in the early 70's by Milan and Hegel1. This ODE modeling method provides predictions of the crash pulses generated by the HYGE impact simulator. However, during subsequent years of practice, it has been found that in some cases these predictions are inaccurate. It is because the ODE method over-simplifies the physics. To improve the prediction accuracy, more sophisticated model of the physical process must be developed. The Fluid-Structure Coupled (FSC) modeling technique was applied on this dynamics problem of the HYGE impact simulator output prediction.
Technical Paper

LDS- A Back to Basics Approach to Develop Linings for Brake System Integration

It is always a challenging task for the braking industry to maintain consistent friction material behavior during brake system development. Lack of consistency in friction behavior causes significant disruptions in efforts to integrate friction material with the foundation brake system. This is especially true when new friction formulations and/or manufacturing processes are introduced during an application program. Furthermore, every new program has new requirements that introduce new challenges and issues to the brake and friction manufacturers. As issues arise during the Application development, engineers devise countermeasures that often entail new engineering techniques and methods. Sometimes, such countermeasures amount to inventions to cover the inadequacy of lining behavior during brake integration.
Journal Article

Brake Dynamometer Test Variability Part 2- Description of the Influencing Factors

The ISO TC22/SWG2 - Brake Lining Committee established a task force to determine and analyze root causes for variability during dynamometer brake performance testing. SAE paper 2010-01-1697 “Brake Dynamometer Test Variability - Analysis of Root Causes” [1] presents the findings from the phases 1 and 2 of the “Test Variability Project.” The task force was created to address the issue of test variability and to establish possible ways to improve test-to-test and lab-to-lab correlation. This paper presents the findings from phase 3 of this effort-description of factors influencing test variability based on DOE study. This phase concentrated on both qualitative and quantitative description of the factors influencing friction coefficient measurements during dynamometer testing.
Technical Paper

Advancements in Crash Sensing

The crash modes that occur each day on streets and highways have not changed dramatically over the past 50 years. The need to better understand those crash modes and their relation to rapidly emerging, tailorable restraint systems has intensified recently. The algorithms necessary for predicting a deployment event are based on an approach of coupling the occupant kinematics in a crash to the sensing technology that will activate the restraint system. This paper describes methods of computer modeling, occupant sensing and vehicle crash dynamics to define a crash sensing system that reacts to a complex set of input conditions to invoke an effective restraint response.
Journal Article

Mobility and Energy Efficiency Analysis of a Terrain Truck

While much research has focused on improving terrain mobility, energy and fuel efficiency of terrain trucks, only a limited amount of investigation has gone into analysis of power distribution between the driving wheels. Distribution of power among the driving wheels has been shown to have a significant effect on vehicle operating characteristics for a given set of operating conditions and total power supplied to the wheels. Wheel power distribution is largely a function of the design of the driveline power dividing units (PDUs). In this paper, 6×6/6×4 terrain truck models are analyzed with the focus on various combinations of PDUs and suspension systems. While these models were found to have some common features, they demonstrate several different approaches to driveline system design.
Technical Paper

Trade-offs for Vehicle Stability Control Sensor Sets

Customers of new vehicles expect their vehicle to provide reliable operation. One path vehicle manufacturers have chosen to meet this expectation is to offer their customers advanced braking systems. Antilock Brakes (ABS) and Traction Control (TC) are two advanced braking systems that have evolved to a point at which many OEM's offer them as standard equipment. Size, weight, and performance have also improved to the point of near transparent operation in many cases. The current direction of braking system evolution is in making Vehicle Stability Control (VSC) widely available as well. VSC adds the ability to assist the driver in negotiating understeer and oversteer, by adding corrective braking and engine torque to the vehicle as appropriate. A large percentage of VSC system modeling is related to the sensors chosen to provide driver and vehicle dynamic information to the system's electronic control unit (ECU).