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Product sound quality is becoming increasingly critical in recent years. To help improve customer satisfaction and product quality, Delphi Automotive Systems has taken a proactive approach to address sound quality issues. The first step is to identify customers' expectations. This paper describes a sensory approach to develop sound quality criterion for a power product. To identify critical sound quality characteristics, a large number of sound samples were recorded. Jury (focus group) evaluation was conducted to identify the acceptance level and preference of each sample. Then, critical objective measures, and the criterion level of each measure, were identified via correlation analysis with subjective responses. This article presents a practitioner's point of view on how to apply sensory engineering method to engineering practice.

The lateral runout of disc brake corner components can lead to the generation of brake system pulsation. Emphasis on reducing component flatness and lateral runout tolerances are a typical response to address this phenomenon. This paper presents the results of an analytical study that examined the effect that the attachment of the wheel to the brake corner assembly could have on the lateral distortion of the rotor. An analysis procedure was developed to utilize the finite element method and simulate the mechanics of the assembly process. Calculated rotor distortions were compared to laboratory measurements. A statistical approach was utilized, in conjunction with the finite element method, to study a number of wheel and brake corner parameters and identify the characteristics of a robust design.

A front disc brake system is used as an example for an investigation of low frequency squeal. Many different modifications to this disc brake system have been proposed and this paper focuses on a solution that reduces the stiffness of the rotor. This is accomplished by a reduction in the Young's modulus of the rotor material. The complex eigenvalue method is used for a detailed analytical study in order to obtain a better understanding of this solution technique. Modal participation factors are calculated to examine the modal coupling mechanism. Parametric studies are also performed to find out the effects of friction coefficient and rotor stiffness. Results show that shifting rotor resonance frequencies may ecouple the modal interaction and eliminate dynamic instability, which is in agreement with experimental results.

A jury evaluation study has been conducted to determine the hearing threshold of IP gauge stepping motor noise using a transformed up-down procedure. The stepping motor noise was recorded in an anechoic chamber and was used as a signal in the study. To determine the masked threshold, this signal was adjusted to various gain levels and mixed with interior engine noise at selected rpm as masking noise. In this study, the Adaptive Procedure was used, and a software application was developed for this purpose. Twenty subjects, selected based on hearing test results, participated in this jury evaluation. The findings of this study indicated that Adaptive Procedure is an effective approach in determining hearing threshold for automotive applications. A design criterion for acoustical characteristics of the IP gauge DC motor noise has been developed based on the results of this study.

Electric power steering (EPS) is an advanced steering system that uses an electric motor to provide steering assist. Being a new technology it lacks the extensive operational history of conventional steering systems. Also conventional systems cannot be used to command an output independent of the driver input. In contrast EPS, by means of an electric motor, could be used to do so. As a result EPS systems may have additional failure modes, which need to be studied. In this paper we will consider the requirements for successful EPS operation. The steps required to develop diagnostics based on the requirements are also discussed. The results of this paper have been implemented in various EPS-based programs.

Continuous Improvement activities are often based on a list of top concerns, such as highest RPN (Risk Priority Number) on the PFMEA (Process Failure Modes and Effects Analysis), warranty items, or scrap rates. But a company is in business to make a profit for its stockholders. Therefore, money should be considered, rather than just technical engineering tools and RPNs. Current PFMEA methodology (See references 1 and 2) focuses on delivering quality parts to the customer. The financial impact of various potential process problems is not considered directly. A new and extended technique called FMERA (pronounced Fuh-MAIR-uh) can identify and prioritize the process part of potential problems that have the most financial impact on an operation. Alternatives can be evaluated to maximize the financial benefits. FMERA is a method for getting the voice of the stockholder into process decisions.

As compared to home audio, the automobile has a different spatial and spectral distribution of sound. This can cause stereo images to blur or shift due to conflicting localization cues. The impact of interaural time and level differences is discussed, along with frequency-selective pinna and head cues. Review of the literature shows that our poorest localization is for mid frequencies (∼2kHz). Yet in an automobile, low frequencies are severely relocated with a minimum effect on fidelity. It is suggested this is because middle frequencies dominate the perception and localization of sound. Therefore, some high frequency information might also be relocated.

The problem being investigated involves a noise-quality issue on a power steering application, when a sudden change of steering wheel angle generates an unwanted steering system noise or “Squawk.” This phenomenon is mostly observed during parking maneuvers, especially at lock positions and when the hydraulic fluid reaches a critical temperature on the specific application. The objective of the work to solve this noise-quality issue was to first identify the cause and then eliminate the Squawk noise. There were several constraints: No change could be made in the properties or type of hydraulic fluid used due to specification requirements; Steering wheel valve torsion bar characteristic (torque vs. angle) needed to be maintained within specification for ride and handling purposes; and, In addition to the mentioned constraints, a high capability of noise elimination generated by the production tolerances and dispersion has been considered.

The purpose of this report is to quantify the methodology for evaluating and isolating rattle noises in power rack & pinion steering systems. In today's ever changing market of vehicle body & suspension changes, it's very important that the correct process be used to identify the correct noise source. The results of this evaluation procedure will help sort out the difference between hydraulic generated noises and mechanical generated noises. The process used in sorting the hydraulic noise from the mechanical noise is through the use of a “standpipe”, which dampens the hydraulic reaction pulse in the hydraulic steering system. We refer to this hydraulic pulse as “hydraulic rattle”, and is often confused with mechanical rattle during vehicle evaluations. The concept of the standpipe is similar to that used in household plumbing, which reduces the effects of hydraulic hammering in the water pipes.

Brake squeal phenomenon often involves modal coupling between various component modes. In order to reduce or eliminate squeal, it is very important to understand the coupling mechanism so that the key component(s) can be modified accordingly. This paper demonstrates a quantitative method to define system mode shapes using the concept of modal participation factors. This method is implemented on a front disc brake system to identify the modal coupling mechanism associated with its high frequency squeal. Complex eigenvalue analysis is carried out and the squeal frequency is correlated. System mode shapes are then processed with an in-house program to calculate modal participation factors based on a complex MAC (Modal Assurance Criteria) algorithm. The coupling mechanism is identified and possible countermeasures are discussed.

The SuperPlug™ door module is a new Delphi innovation. It is a one-piece composite structure, which integrates several door components into one assembly. This reduces the total part count, simplifies the vehicle level assembly process, and reduces labor cost (see the Appendix). The door slam durability test is an important factor in door module design. As more hardware is integrated into the SuperPlug, this subsystem performance in a door slam test becomes important. Therefore, the correct placement of components and the supporting structure is critical. Currently, the evaluation of door slam durability for the SuperPlug is a process of build then test. This is time consuming and costly due to a long testing lead-time and the expense of tooling a new mold. It was realized that a numerical process for assessing the effect of door slam would be required. This process would compute the dynamic response using finite element analysis (FEA).

Accurately predicting converter assembly deformation and mat pressure is essential in converter packaging design and manufacturing. In stuffing packaging, the annulus between the deformed shell and the catalyst is larger than that between the stuffing cone and the catalyst. As a result, the mat expands and undergoes unloading process. Tests show that the mat exhibits different loading and unloading characteristics. Using such a hysteresis mat pressure vs density curve in finite element analysis, the computed converter deformations closely agree with test data. Conversly, neglecting the mat hysteresis behavior may overestimate the deformation and pressure by a factor of three to four.

This paper is an extension to the work presented in part I [1]. The control objective is still the same - use a logic based control design technique to assign a wheel slip, λ, to each corner of a vehicle, to track overall desired vehicle dynamics. As in part I, a fuzzy logic based controller is the primary control, with additional logic to select the inside/outside classifiers for the wheels. In part I, only the reduction of yaw rate error, e, was considered. It was shown that, although the overall system had satisfactory performance, there was slight deteriorization in the tracking performance when trying to compensate through a significant vehicle sideslip angle, β. In this paper, additional logic is introduced into the control to limit the vehicle sideslip angle, β; thus, allowing for a more robust desired yaw rate, Ωd, tracking control performance. The emergency lane change maneuver is simulated to show the effectiveness of the redesigned control.