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Technical Paper

Vehicle Controller Area Network Response Time Analysis and Measurement Issues - to Reduce the Gap between Estimation and Measurement

Along with the efforts to cope with the increase of functions which require higher communication bandwidth in vehicle networks using CAN-FD and vehicle Ethernet protocols, we have to deal with the problems of both the increased busload and more stringent response time requirement issues based on the current CAN systems. The widely used CAN busload limit guideline in the early design stage of vehicle network development is primarily intended for further frame extensions. However, when we cannot avoid exceeding the current busload design limit, we need to analyze in more detail the maximum frame response times and message delays, and we need good estimation and measurement techniques. There exist two methods for estimating the response time at the design phase, a mathematical worst-case analysis that provides upper bounds, and a probability based distributed response time simulation.
Technical Paper

Structure-Borne Path Identification of Rumbling Noise in a Passenger Car Based on In-Situ Blocked Force Transfer Path Analysis

It is known that the major source of rumbling noise the combustion force of an engine. The combustion force excites the engine and induces vibrations of the powertrain. These vibrations are then transferred to the body of the vehicle via its structural transfer path. Moreover, the vibrations of the vehicle’s body emit internal vibra-acoustic noise. This noise is often referred to as the rumbling noise due to the structural borne path. If there are structural resonances among the structural paths such as the engine, transmission, mount bracket, suspension, and the vehicle’s body, the rumbling noise could be amplified. To identify the major resonances of the structural transfer path, classical transfer path analysis (CTPA) has been traditionally utilized. The method has a significant limitation in that it is necessary to decouple the substructures to obtain the contact force between individual components and to identify the transfer path of the structure-borne sound.
Technical Paper

A Study on the Methodology for Improving IQS Score for Door Opening/Closing Effort

IQS score (hard to open/close) is a major factor in determining automotive door closing performance. There are several functions that automotive side doors must fulfill: isolation from snow/ rain/ noise/ dust/ high temperature, wind noise, and opening/closing functions. This paper focuses on side door Opening/Closing, which is not only the primary function but also the first operation that all customers experience when car shopping. As the subjective demands of customers have increased and their level of sophistication has grown, the ergonomics of automotive side door functions has become a critical issue for both designer and customer. The side door area does not generally have specifications because door operability totally relies on each customer's senses and there are no parameters to be measured by test/experimental devices. So the IQS score could become the standard for evaluating a door's difficulty of opening and closing.
Technical Paper

Optimization of Body Attachment for Road Noise Performance

It is common knowledge that body attachment stiffness is an important factor of road noise performance. Thus, a high stiffness of body attachments is required, and determining their optimized stiffness and structure is necessary. Therefore, a method for improving body attachment stiffness and validating the relationship between stiffness and road noise through CAE and experimental trials was tested. Furthermore, a guideline for optimizing body structure for road noise performance was suggested.
Technical Paper

A Study on Clamping Force Control in Pulley of CVT for Fuel Efficiency

In CVT, it is essential to optimize Clamping Force in Pulley to improve fuel efficiency. Clamping force in pulley is shaft force to control primary pulley and secondary pulley. It is determined by pulley ratio, input engine torque in CVT and safety factor for protecting belt slip. It is difficult to calculate correct clamping force and detect belt slip. Generally speaking, CVT has a tendency to have excessive Safety factor to prevent belt slip. This excessive safety factor in clamping force leads to lower fuel efficiency. In order to find an optimal clamping force, ‘the minimum clamping force’ which will not induce belt slip should be determined even during decreasing clamping force. Furthermore, clamping force should be maintained near the ‘minimum clamping force’. For this, following logics was developed First, the logic to calculate first safety ratio of belt, Second, the logic to detect belt slip state, Third, the logic to calculate the optimal clamping force.
Technical Paper

Development of a Test Method for BSR Noise and the Full-Vehicle Testing System

Since vehicle NVH reduction technology has improved dramatically, buzz, squeak and rattle (hereafter referred to as “BSR”) noise quantification from interior and exterior of the vehicle becomes an important factor to measure the quality of the vehicle. (The cost rate of BSR noise claims take around 10-15%, moreover BSR noise negatively affects customers to purchase vehicles.) Therefore, a research of BSR evaluation comes to the fore to make a premium car. In this paper, we would like to introduce the development of a vehicle excitation test mode, the full-vehicle BSR test system, and a sound acoustic camera to detect BSR noise. The test profiles were correlated with various road severities such as the domestic field test sites including 5,000km cross-country off road, 19 test tracks for BSR in R&D test center, and quality test tracks in domestic factories. These test modes were classified into 4 levels (Low-Normal-High-Crazy) by judging degrees of GRMS values.
Technical Paper

Wind-Tunnel and On-Road Wind Noise: Comparison and Replication

A KIA Soul was instrumented to measure the relative velocity (magnitude and yaw angle) at the front of the vehicle and in-cabin sound at a location close to the side glass near the A-pillar vortex impingement. Tests were conducted at a proving ground under a range of conditions from low wind conditions (~3 m/s) to moderate (7-8 m/s) wind speeds. For any given set of atmospheric conditions the velocity and sound data at any given position on the proving ground were noted to be very repeatable, indicating that the local wakes dominated the "turbulent" velocity field. Testing was also conducted in an aeroacoustic wind tunnel in smooth flow and with a number of novel turbulence generating methods. The resulting sounds were analyzed to study the modulation at frequencies likely to result in fluctuation strength type noise.
Technical Paper

Extensive Correlation Study of Acoustic Trim Packages in Trimmed Body Modeling of an Automotive Vehicle

In the automotive sector, the structure borne noise generated by the engine and road-tire interactions is a major source of noise inside the passenger cavity. In order to increase the global acoustic comfort, predictive simulation models must be available in the design phase. The acoustic trims have a major impact on the noise level inside the car cavity. Although several publications for this kind of simulations can be found, an extensive correlation study with measurement is needed, in order to validate the modeling approaches. In this article, a detailed correlation study for a complete car is performed. The acoustic trim package of the measured car includes all acoustic trims, such as carpet, headliner, seats and firewall covers. The simulation methodology relies on the influence of the acoustic trim package on the car structure and acoustic cavities. The challenge lies in the definition of an efficient and accurate framework for acoustic trimmed bodies.
Technical Paper

Model-Based Brake Disc Temperature Prediction on High Speed Testing Mode and Circuit

A brake is a mechanical device that inhibits the motion by absorbing energy from a moving system. It is used for slowing or stopping a moving vehicle, wheel, axle, or to prevent its motion, most often accomplished by friction energy. Commonly, most brakes use friction between two surfaces pressed together to convert the kinetic energy of the moving object into heat, though other methods of energy conversion may be employed. If braking is repeated or sustained in high load or high-speed conditions, the motion will be unstable and can lead to a loss of stopping power because the disc capability for braking is not enough. These phenomena are generally defined as brake fading. Brake fade is caused by an overheating brake system. This paper describes the thermal modeling and process to predict the disk temperature under a condition which causes the fade characteristics.
Technical Paper

A Study on Optimization of Brake Cooling System Considering Aerodynamics

As powertrain performance of vehicle improves, brake load is gradually increasing. But it is not easy to increase brake size due to increment of cost and weight despite judder and fade problems are worried in field. Cooling-duct which provides additional forced convection to cool front brake is being considered instead of increasing brake size. However, cooling-duct causes loss of aerodynamic that increases drag coefficient of vehicle. This paper covers the optimization of brake cooling system including cooling-duct, deflector on suspension parts to direct air into front brake and dust cover so that minimize aerodynamic loss and maximize brake cooling performance. The optimal solution had been derived from thermal and aerodynamic simulation with CFD and verified through experimental test with vehicle.