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Technical Paper

Friction Force Measurement at Brake Discs

2011-05-17
2011-01-1576
Experimental researches on brake squeal have been performed since many years in order to get an insight into friction-excited vibrations and squeal triggering mechanisms. There are many different possibilities to analyse brake squeal. The different operating deflection shapes can be detected using e.g. laser vibrometer systems or acceleration sensors. Piezoelectric load cells can be used for the measurement of the normal contact force of the brake pad. The presented test setup measures not only the mean value of the friction force between brake pad and disc at a certain brake pressure, but also the superposed vibration of this force, which only occurs during a squeal event. Therefore the guide pins of the brake caliper are replaced by modified ones. The brake pads are held in position by these pins and the resulting force of the brake torque, hence the friction force, acts on these pins. The shape of the pins is optimized for measuring these forces.
Journal Article

Hot Judder - An Investigation of the Thermo-Elastic and Thermo-Plastic Effects during Braking

2011-05-17
2011-01-1575
Thermo-elastic and thermo-plastic behaviour takes place with a disc brake during heavy braking and it is this aspect of braking that this paper considers. The work is concerned with working towards developing design advice that provides uniform heating of the disc, and equally important, even dissipation of heat from the disc blade. The material presented emanates from a combination of modeling, on-vehicle testing but mainly laboratory observations and subsequent investigations. The experimental work makes use of a purpose built high speed brake dynamometer which incorporates the full vehicle suspension for controlled simulation of the brake and vehicle operating conditions. Advanced instrumentation allows dynamic measurement of brake pressure fluctuations, disc surface temperature and discrete vibration measurements.
Technical Paper

The Development of a Global Brake Insulator Damping Measurement Procedure

2011-05-17
2011-01-1574
The development and validation of a brake pad insulator damping measurement procedure by the SAE Brake NVH Standards Committee was presented at the 2010 SAE Brake Colloquium (Paper 2010-01-1685). In Europe, in 2010, the EKB Working Group identified the need to develop a similar procedure, and started some activities which lead to the release of a standard similar but different than the SAE J3001. The SAE and EKB working groups agreed that having a global standard was of paramount importance, so the 2 groups decided to meet in November of 2010 to flush out the details of the J3001 global procedure. The details of the new test procedure, test setup and recommendation for proper test practices are described in this paper. This description provides an excellent foundation for evaluating the insulator damping properties over a range of temperatures and frequencies.
Technical Paper

Experimental and Analytical Investigation of Countermeasure against Squeal in Floating Type of Car Disc Brake

2011-05-17
2011-01-1579
This paper deals with low-frequency squeal phenomena generated in floating type of car disc brake units. First, the vibration characteristics of low-frequency squeal (about 2 kHz) were investigated. Here, in order to reproduce the squeal, a bench-test apparatus consisting of an actual automotive disc brake unit was utilized, itself comprising a disc, pad, and caliper. With this, the associated frequency characteristics were experimentally determined. It was found that the squeal is caused by coupled out-of-plane vibration modes among the disc and caliper due to Coulomb friction. As an experimental countermeasure, a dynamic absorber was applied to the leading side or the trailing side of the inner caliper. It was found that squeal can be suppressed when the natural frequency of the dynamic absorber is tuned so as to be near the frequency of the squeal, and that squeal can be suppressed even without viscous damping of the dynamic absorber.
Technical Paper

The Influence of Pad Abutment on Brake Noise Generation

2011-05-17
2011-01-1577
The paper overviews the modes of vibration of the principal component parts of a brake and their contribution to system instability during noise generation. It is shown that both in-plane and out-of-plane vibration are present and that both can be related to the vibration of the pad. It is further shown that the pad and its region often provide a solution or “fix” towards noise prevention and it is this area that forms the focus of this investigation. The collective evidence, proposals and associated theory are applied to real brake case studies when it is demonstrated that disc/pad interface “spragging” may be the source of brake noise. Measurements of the position of the dynamic centre of pressure (CoP) support the theoretical predictions that a leading CoP induces brake noise. Design proposals are suggested that may be applied early in the design phase as a means to reduce the propensity of a brake to generate noise.
Journal Article

Aerodynamic Investigation on the Effect of Varying Through-Hub Flow on a Formula One Front Wheel Assembly

2011-04-12
2011-01-1431
For open wheel race cars the front wheel flow and the interaction of its wake with downstream components is of significant importance. Considerable effort goes into the design of front wing end plates, barge boards and underfloor components in order to manage the front wheel flow. In this study a 50% scale Formula One front wheel assembly has been tested in the Durham University 2m₂ open jet wind tunnel to evaluate the effect of through-hub flow on its cooling drag and flow structures. Varying the amount of through-hub flow gave rise to a negative cooling drag trend whereby increasing the flow through the hub resulted in a decrease in drag. This observation has been explained both qualitatively and quantitatively by inlet spillage drag. Lower than optimum airflows through the brake scoop result in undesirable separation at the inside edge and hence, an increase in drag (reversing the cooling drag trend).
Technical Paper

Influence of Surface Modifications on Vehicle Disc Brake Squeal

2009-06-15
2009-01-1977
Squeal from brakes is a problem in the automotive industry and large efforts are made to understand the squeal tendencies. The approach taken is mainly to change the design of the caliper, fine-tune the brake pad material and finally to trim the introducing shims on the backside of the pads. Despite these efforts still no general solutions exist. To advance the situation, a deeper understanding of the actual source of excitation of the sound in the friction interface is needed. However, in the present investigation the surfaces modifications of brake disc and pad have been tested with respect to the understanding properties. The surfaces modifications are slotted pad material and coated disc. All tests have been made in a brake test stand consisting of a complete front wheel corner of a vehicle. The changes have resulted in a significant understand of the generated noise.
Technical Paper

Complex Mode Analysis on Disc Brake Squeal and Design Improvement

2009-05-19
2009-01-2101
Squeal noise in vehicle disc brakes is perceived by comsumers as both annoying and warranty cost. The mechanism is considered a mode coupling phenomenon also referred to as coalescence. In this paper, the system eigenvalues have been computed using a technique based on the • nite element method in order to obtain the dynamical properties of the disc brake assembly. The simulated squeal results were compared with the brake noise test that was in accordance with SAE J2521 standard and showed good correlation for some squeal frequencies which indicated that the research on disc brake squeal using complex mode could predict squeal propensity of the disc brake. Among the methods that have been used to control squeal noise, increasing the system damping has been shown to be very effective. The most commonly used method to increase system damping consists of attaching multi-layer laminates on the back of the brake pads.
Technical Paper

High Frequency Brake Squeal Prediction Index for Disc In-plane Mode

2009-05-19
2009-01-2102
As well as performance and safety, sensibility factor such as brake squeal noise has become an important factor to consider in today’s automotive industry. However, regardless of its importance, reduction of brake squeal noise has remained as one of the biggest challenges that have not yet been solved. Recently, many studies are being conducted to reduce squeal noise with the development of numerical analysis using FEM(Finite Element Method). This paper deals with complex eigenvalue analysis with commercial software program ABAQUS to resolve the squeal noise related to disc in-plane mode which is reported to occur frequently in the squeal noise frequency band 1~20kHz. As the reliability of the FE model is the most critical factor in numerical analysis, the FE model is first correlated with FRF modal test of each brake part and measurement of material property of pad with the anisotropic character through ultrasonic methods.
Journal Article

A Study of Effects of Brake Contact Interfaces on Brake Squeal

2009-05-19
2009-01-2100
Brake squeal is caused by the friction-induced vibration at the rotor/pad interfaces (primary contact interfaces) in a disc brake system. While there have been numerous research work evaluating the influence of primary contact interfaces on brake squeal, few studies can be found on the effect of the secondary contact interfaces, i.e., outer pad/caliper fingers, inner pad/pistons and pad/abutment, which can also significantly affect brake squeal based on our various dynamometer and vehicle tests. It is therefore the objective of this paper to investigate both the primary and the secondary contact interfaces and their influence on brake squeal. Simplified analytical models are created to gain insight into the stability of the brake system under low and high brake pressure; non-linear FEA analysis is employed for parametric study and countermeasure development; dynamometer and vehicle tests are used for verification.
Technical Paper

Braking Systems Creep Groan Noise: Detection and Evaluation

2009-05-19
2009-01-2103
“Creep groan” is a braking systems noise that is observed when a vehicle is starting to move from a stopped condition with brake pressure applied. Motion takes place when brake pressure is reduced while a motive force, such as an idling engine through an automatic transmission, or gravity due to the vehicle being on a slope, is present. The vibration causing the sound is commonly thought to result from friction force variation in stick-slip mode. Detection and evaluation of “creep groan” noise has been a challenge for NVH test groups. First, this sound typically is not purely tonal like the more common brake squeal, although ultimately it may produce a tonal subjective impression. In this work the authors study different methods that may be applied to “creep groan” detection and evaluation.
Technical Paper

A Model for the Mechanical Subsystem of an Air Brake System

2009-12-13
2009-28-0058
Ensuring the safety of passengers is one of the prime challenges for vehicle design engineers. The braking system is the most important safety feature incorporated in a vehicle. Most of the commercial vehicles such as trucks, buses, etc., are equipped with an air brake system. The air brake system is sensitive to maintenance and needs to be monitored regularly to ensure its proper functioning. Current monitoring methods of air brake systems are predominantly manual in nature and can be performed only when the vehicle is stationary. One of the most important parameters that are critical for the proper functioning of an air brake system is the push rod stroke. The push rod stroke is related to the clearance between the brake pad/shoe and the brake drum and hence is indicative of brake wear. The objective of this research work is to study the mechanical subsystem of the air brake system and develop a mathematical model for the same.
Technical Paper

AN OPTIMAL SOLUTION THROUGH LEAN MANUFACTURING USING VALUE STREAM MAPPING TOWARDS EFFICIENT PRODUCTION FOR A WORLD- CLASS AUTOMOBILE BRAKES MANUFACTURING COMPANY

2009-12-13
2009-28-0054
Today, numerous companies have a major opportunity to reduce their costs and customer lead time and cycle time through the application of Lean Manufacturing processes. In recent years, almost every manufacturing industry has been trying to get ‘lean’. Lean thinking represents a set of principles and techniques for the identification and elimination of wastages in manufacturing and administrative processes. Value Stream Mapping (VSM) which is one of the lean manufacturing approaches has emerged as the preferred way to support and implement the lean approach. VSM is a helpful tool to identify the waste and improvement areas. VSM enables a company to see the entire process in both its current and desired future state, and develop the road map that prioritises the projects or tasks to bridge the gap between the current state and the future (lean) state.
Technical Paper

Dynamic Simulation of a Brake Valve in Air Brake System

2009-12-13
2009-28-0030
In the product development cycle, the study on the dynamic behavior of the product helps to freeze the concepts and physical level design rapidly. The lumped parameter approach and bond graph technique makes the dynamic simulation a handy tool for studying the product behavior. In air brake system, the response time for brake application and release is critical for vehicle stopping distance and obtaining appropriate driver feel. In this paper, an attempt has been made to simulate the dynamic response of the brake valve. One of the commercial software which has standard libraries for pneumatic components, employing bond graph technique and lumped system has been used for developing physical-based modeling and to perform the simulation. The model is simulated for the actual test conditions. The simulated results are compared with experimental results.
Technical Paper

A Study of Novel Traction Control Method for Electric Motor Driven Vehicle

2009-01-21
2009-26-0039
Electric-motor-driven vehicles have attractive performance attributes not only for environmental solutions but also for vehicle motion control. An electric motor offers significant advantages such as fast torque response, accurate estimation of torque output and the possibility of distributing motors independently in each wheel. These advantages effectively contribute to advanced motion control. In this study, two feedback controllers were constructed for skid prevention during vehicle acceleration. A model-following controller was used to consider the influence of back electromotive force and a slip ratio controller was used to consider the interaction between traction wheels.
Technical Paper

The Impact of Regenerative Braking on the Powertrain-Delivered Energy Required for Vehicle Propulsion.

2011-04-12
2011-01-0891
Driving schedules prescribed for fuel-economy regulation are composed of two generic modes: (1) accelerations and constant-speed travel, requiring a positive tractive force at a vehicle's driving wheels; (2) decelerations, requiring a negative or braking force at those wheels. In the first mode, a total tractive energy, ETR, is required to overcome a vehicle's tire rolling resistance, aerodynamic drag, and the inertia of its mass. In the second mode, all the kinetic energy that a vehicle's mass acquired in the first mode has to be removed. The inherent rolling resistance and aerodynamic drag remove some of it. The remainder, EBR, has to be removed by a wheel-braking force. In vehicles with conventional braking the wheel-braking force is frictional, and so all of EBR is dissipated. However, if this force is not inherently frictional some of EBR can be captured, stored, and subsequently used to provide part of the ETR required for propulsion.
Journal Article

Accuracy of Event Data Recorder in 2010 Ford Flex During Steady State and Braking Conditions

2011-04-12
2011-01-0812
The accuracy of the Restraint Control Module (RCM) Event Data Recorder (EDR) was tested on a 2010 Ford Flex during both straight line steady state and maximum ABS braking. Six runs were made starting from 48 kph (30 mph), six runs starting from 80 kph (50 mph), and six runs starting from 113 kph (70 mph). Nondeployment events were artificially induced after a period of steady state driving followed by maximum braking for the last 2.5 seconds prior to creating the event, intended to simulate braking just prior to a crash. Following each run data was collected from the RCM EDR using the Bosch Crash Data Retrieval system. A Racelogic VBOX SL3 20 Hz differential GPS speed data recorder also served as a data acquisition system for vehicle CAN bus speed, accelerator position, RPM, and brake tape switch data. Graphs of RCM speed/brake/accel pedal data versus VBOX speed and other data over time are presented.
Technical Paper

Estimation of Pushrod Stroke in an Air Brake System with Parametric Uncertainty

2011-04-12
2011-01-0751
In this paper, we consider the problem of designing an algorithm for estimating the stroke of a pushrod in the presence of uncertainty in the area of the treadle valve. The stroke of pushrod directly relates to the braking force available at the wheels and also affects the response time. The longer the stroke, the volume available for expansion is larger and correspondingly, the response is slower. The stroke depends on the clearance between the brake pad and the drum, which can vary due to variety of factors such as thermal expansion of drum and mechanical wear. Typical safety inspections of air brakes include the measurement of the stroke of the pushrod of each brake chamber. Regulations on trucks such Federal Motor Vehicle Safety Standard (FMVSS) 121 require the inspection to be carried out at 90 psi supply pressure and at full brake application.
Journal Article

Improvement of Heavy Vehicles Ride and Braking Performance via Combined Suspension and Braking Systems Control

2011-04-12
2011-01-0437
Due to the importance of the fast transportation under every circumstance, the transportation process may require a high speed heavy vehicle from time to time, which may turn the transportation process more unsafe. Due to that fact the truck safety during braking and the ride comfort during long distance travelling with high speeds should be improved. Therefore, the aim of this work is to develop a control system which combines the suspension and braking systems. The control system consists of three controllers; the first one for the active suspension system of the truck body and cab, the second one for the ABS and, the third for the integrated control system between the active suspension system and the ABS. The control strategy is also separated into two strategies.
Journal Article

Linear Quadratic Game Theory Approach to Optimal Preview Control of Vehicle Lateral Motion

2011-04-12
2011-01-0963
Vehicle stability is maintained by proper interactions between the driver and vehicle stability control system. While driver describes the desired target path by commanding steering angle and acceleration/deceleration rates, vehicle stability controller tends to stabilize higher dynamics of the vehicle by correcting longitudinal, lateral, and roll accelerations. In this paper, a finite-horizon optimal solution to vehicle stability control is introduced in the presence of driver's dynamical decision making structure. The proposed concept is inspired by Nash strategy for exactly known systems with more than two players, in which driver, commanding steering wheel angle, and vehicle stability controller, applying compensated yaw moment through differential braking strategy, are defined as the dynamic players of the 2-player differential linear quadratic game.
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