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Technical Paper

Innovative Graduate Program in Mechatronics Engineering to Meet the Needs of the Automotive Industry

A new inter-disciplinary degree program has been developed at Lawrence Technological University: the Master of Science in Mechatronic Systems Engineering Degree (MS/MSE). It is one of a few MS-programs in mechatronics in the U.S.A. today. This inter-disciplinary program reflects the main areas of ground vehicle mechatronic systems and robotics. This paper presents areas of scientific and technological principles which the Mechanical Engineering, Electrical and Computer Engineering, and Math and Computer Science Departments bring to Mechatronic Systems Engineering and the new degree program. New foundations that make the basis for the program are discussed. One of the biggest challenges was developing foundations for mechanical engineering in mechatronic systems design and teaching them to engineers who have different professional backgrounds. The authors first developed new approaches and principles to designing mechanical subsystems as components of mechatronic systems.
Technical Paper

Fatigue Life Improvement through the “NOVA” Process

The experimental methods focused on utilizing the newly developed NOVA induction heating and hardening manufacturing process as an adapted method to produce high performance engine valve springs. A detailed testing plan was used to evaluate the expected and theorized possibility for fatigue life enhancement. An industry standard statistical analysis method and tools were employed to objectively substantiate the findings. Fatigue cycle testing using NOVA induction-hardened racing valve springs made of ultra-high tensile material were compared to data for springs with traditional heat treatment and those with standard processing. The results were displayed using Wöhler and modified Haigh fatigue life diagrams. The final analysis suggests that NOVA processed springs have a seemingly slight, yet significant benefit in fatigue life of 5 - 7% over springs processed through a competing method.
Journal Article

Analyzing Field Failures of Engine Valve Springs in Presence of Non Metallic Inclusions by Applying Statistical and Fracture Mechanics Models

The reliability of engine valve springs is a very important issue from the point of view of warranty. This paper presents a combined experimental and statistical analysis for predicting the fatigue limit of high tensile engine valve spring material in the presence of non-metallic inclusions. Experimentally, Fatigue tests will be performed on valve springs of high strength material at different stress amplitudes. A model developed by Murakami and Endo, which is based on the fracture mechanics approach, Extreme value statistics (GUMBEL Distribution) and Weibull Distribution will be utilized for predicting the fatigue limit and the maximum inclusion size from field failures. The two approaches, experimental and theoretical, will assist in developing the S-N curve for high tensile valve spring material in the presence of non-metallic inclusions.
Technical Paper

Redesign of a Differential Housing for a Formula Car (FSAE)

A unique differential assembly was needed for the Lawrence Technological University (LTU) SAE Formula race car. Specifically, a differential was required that had torque sensing capabilities, perfect reliability, high strength, light weight, the ability to withstand inertia and shock loading, a small package, no leaks, the ability to support numerous components. In that regard, an existing differential was selected that had the torque sensing capabilities, but had deficiencies that needed to be fixed. Those deficiencies included the following: Differential unit was over 4 kg unmounted, with no housing. This was considered too heavy, when housed properly. Bearing surface was provided on only one end of the carrier. This design provides insufficient bearing surface to support either the differential housing or half-shafts The internal drive splines integral to the case are not optimized for a perpendicular drive/axle arrangement, such as, a chain drive.
Technical Paper

Low Cost Fault Tolerant and Redundant Multiplex Wiring System for Automotive Applications

A low cost fault tolerant and redundant multiplex wiring system specifically designed for automotive applications is described in this paper. Although there are many multiplex wiring systems are being used to simplify the car wiring harness, but very few are low cost, fault tolerant and redundant at the same time. Most of the system address mainly the protocol and software issues and neglected the reliability of the multiplex wiring system. This paper addresses the fault tolerant and redundancy of the system and use hardware based integrated circuit to convert from parallel to serial at the transmitter side and serial to parallel at the receiver side.
Technical Paper

All-Wheel Drive Vehicle Energy Efficiency Evaluation

All-wheel drive (AWD) vehicle performance considerably depends not only on total power amount needed for the vehicle motion in the given road/off-road conditions but also on the total power distribution among the drive wheels. In turn, this distribution is largely determined by the driveline system and its mechanisms installed in power dividing units. They are interwheel, interaxle reduction gears, and transfer cases. The paper presents analytical methods to evaluate the energy and, accordingly, fuel efficiency of vehicles with any arbitrary number of the drive wheels. The methods are based on vehicle power balance equations analysis and give formulas that functionally link the wheel circumferential forces with slip coefficients and other forces acting onto an AWD vehicle. The proposed methods take into consideration operational modes of vehicles that are tractive mode, load transportation, or a combination of both.
Technical Paper

Formula SAE Dual Plenum Induction System Design

A new induction system has been developed, created, and tested for use in the 2001 Formula SAE competition. A 600 Honda CBR F4 four-stroke engine intake is designed using dual plenums, which prevents charging losses due to overlapping intake events at low engine speeds. Dual butterfly valves actuated at high engine speeds enable plenum volume combination for improved high-end performance. The intake restrictor venturi design has also been improved.
Technical Paper

Force Vibrations in Automotive Bevel Gear Differentials

As proven, both friction in the gearing and movement of the contact point of the teeth in mesh along the pressure line generate vibrations of the axial components of the resultant force acting in a couple of mating straight bevel gears. The vibrations of the real forces in gearings cause an increased dynamic pressure on and, accordingly, damage of frictional surfaces of differential parts. The law of summing up the axial components of all the gearings in two and four pinion differentials depends on combinations of numbers of the side gear's and pinion's teeth. A classification of bevel gear differentials into four groups depending on those combinations has been carried out. Differentials of the four groups have different degrees of the axial force vibration. The paper presents a detailed method to evaluate theoretically the axial forces in each of the groups. As shown, differentials from one of the four groups (Group III) have decreased axial force vibrations.
Technical Paper

Throttle Body Design for Optimum Driver Feedback

The airflow through a standard automotive throttle body is not exactly proportional to the displacement of the accelerator pedal. Therefore, another method is needed to open the butterfly valve in order to ensure that airflow through the throttle body is metered equal to pedal displacement. This paper finds that the implementation of a cam-type pulley is necessary to achieve this prescribed goal.
Technical Paper

A Passive Solution to Differential Transient Cooling Issues Using Phase Change Materials

Thermal management systems (TMS) of armored ground vehicle designs are often incapable of sustained heat rejection during high tractive effort conditions and ambient conditions. During these conditions, which mainly consist of high torque low speed operations, gear oil temperatures can rise over the allowable 275°F limit in less than twenty minutes. This work outlines an approach to temporarily store excess heat generated by the differential during high tractive effort situations through the use of a passive Phase Change Material (PCM) retrofit thereby extending the operating time, reducing temperature transients, and limiting overheating. A numerical heat transfer model has been developed based on a conceptual vehicle differential TMS. The model predicts the differential fluid temperature response with and without a PCM retrofit. The developed model captures the physics of the phase change processes to predict the transient heat absorption and rejection processes.
Technical Paper

A Study of the Dynamics of the Rolling Element and its Effect on Outer Race Creep

Bearings are a major component in any rotating system. With continually increasing speeds, bearing failure modes take new unconventional forms that often are not understood. In high speed applications, rolling element forces and gyroscopic moments can be significantly high compared to the applied forces acting on a bearing. Such moments create a “driving” torque causing outer race to creep. In this paper a mathematical model for the dynamics of a rolling element in a high speed bearing is derived. Preload values counterbalancing the torque driving the outer race to rotate can be predicted from this model. An attempt to experimentally measure this torque using a specially designed apparatus with integrated strain gauge torque sensor is also described. Both model and experimental measurements are aimed at understanding, and therefore preventing bearing failures due to outer race (creep) rotations.
Technical Paper

Design of an Aluminum Differential for a Racing Style Car

The 1999 Lawrence Technological University (LTU) drive train consists of a sprocket and chain assembly that delivers the torque, developed by a 600cc Honda F3 engine, to the rear wheels. The torque is transferred through a limited-slip, torque sensing differential unit comprised of a gear set in a student designed housing. The 1999 differential is a second-generation aluminum housing. The idea of using aluminum was first attempted with the 1998 team who successfully completed and used aluminum despite much complexity and a few design flaws. Therefore, in the LTU Formula Team's continuing effort to optimize the design, a new less complex design was conceived to house the gear set. This innovative design reduces the number of housing components from three in 1998, to two in 1999.
Technical Paper

An Adjustable Aluminum Differential

The 2000 Formula SAE Team at Lawrence Technological University (LTU) has designed a chain driven, three-piece aluminum differential unique from past years. This innovative design introduces an adjustable chain mount replacing conventional shackles. Made completely of aluminum, this device moves the entire rear drive train. The gear set remains to be limited slip with a student designed housing. The idea of an aluminum housing with manufactured gear set is a continued project at LTU. After cutting approximately 33% from the weight of the 1999 differential, the 2000 is geared toward a simpler, and smaller design, easier assembly and lighter weight. After reading this brief overview, the idea of this paper is to provide an understanding of the reasoning behind the choices made on the LTU driveline team. FIGURE 1
Technical Paper

Numerical Design of a Low Mass Differential Housing

Lawrence Technological University's 1998 SAE Formula car needed a high performance differential assembly. The performance requirements of a competitive SAE Formula car differential are as follows: Torque sensing capabilities Perfect reliability High strength Low mass Ability to withstand inertia and shock loading Small package Leak proof housing Ability to support numerous components With these requirements in mind an existing differential was selected with the capability for torque sensing. This differential lacked the desired low mass, support, internal drive splines, and proper gearing protection. The differential was re-engineered to remedy the deficiencies. The internal gearing from the selected differential was used in an improved casing. This casing and it's position in the car, reduce the number of side-specific parts required as well as improving the performance. The new design significantly reduces the size and mass of the assembly.
Technical Paper

Dynamic Decoupling of Driveline Dynamics from NVH Driveline Dynamometer: an Industry Sponsored Senior Design Project

The American Axle & Manufacturing Inc. driveline dynamometer provides immense value for experimental validation of product NVH performances. It has been intensively used to evaluate product design robustness in terms of build variations, mileage accumulation, and temperature sensitivity. The current driveline dynamometer input motor system has multiple torsional modes which create strong coupling with test part gear mesh dynamics. Mechanical Engineering seniors at Lawrence Technological University designed, fabricated, and validated a mechanism to decouple the driveline dynamics from the driveline dynamometer dynamics. The student-designed decoupler mechanism is presented with experimental validation of effectiveness in decoupling driveline dynamometer dynamics from the driveline under test.
Technical Paper

Effects of Inlet Curved Spacer Arrancement on Centrifugal Pump Impellers

This paper presents an experimental investigation of flow field instabilities in a centrifugal pump impeller at low flow rates. The measurements of pump hydraulic performance and flow field in the impeller passages were made with a hydraulic test rig. Analysis of Q-ΔP-η data and flow structures in the impeller passages were performed. In the present work, the effect of various flowrates on centrifugal pump impeller performance was analyzed based on pump measured parameters. The impeller’s geometry was modified, with positioning the curved spacer at the impeller suction side. This research investigates the effect of each inlet curved spacer model on pump performance improvement. The hydraulic performance and cavitation performance of the pump have been tested experimentally. The flow field inside a centrifugal pump is known to be fully turbulent, three dimensional and unsteady with recirculation flows and separation at its inlet and exit.
Technical Paper

Subtractive/Additive Rapid Prototyping of a Curve Spacer for Centrifugal Pump Impeller: Design, Manufacturing, and Simulation Analysis

This paper presents methods of rapid prototyping design and manufacturing used in the development of a centrifugal pump impeller with curved spacer (CS). In this research subtractive and additive rapid manufacturing methods were applied to create complex curved spacer profiles for testing as part of geometry optimization process for a high speed and high flow rate centrifugal pump impeller. Seven models for the curved spacer were designed and each model was integrated with the bare impeller separately for simulation analysis. One design was selected for manufacturing with applying subtractive and additive processes. In subtractive manufacturing method, the raw material was removed from a solid shaft by a cutting process under digital control from a computer file. The complexity of the modified impeller spacer profiles required the use of expensive CNC machining with five axis capability.
Technical Paper

Improving Centrifugal Pump Performance under Low Flow Rates by Adding Designed Cylindrical Disks at the Impeller Inlet

Enhancing the performance of centrifugal pumps requires a thorough understanding of the internal flow. Flow simulation inside the pump can help understand the rotatory motion induced by the impellers, as well as the flow instabilities. The flow inside a centrifugal pump is three dimensional, disturbed and accompanied by tributary flow structures. When a centrifugal pump operates under low flow rates, a secondary flow known as recirculation starts to begin. The separation of flow occurs which creates vortices and decreases local pressure which induces cavitation. This phenomenon of recirculation will rise the Net Positive Suction Head Required (NPSHR). This work aims to improve the pump efficiency under low flow rates by adding multiple cylindrical disks at the pump inlet section to suppress the flow recirculation. In this study, a numerical simulation is carried out to investigate the influence on the pump internal flow by adding multi cylindrical disks.
Technical Paper

Optimizing the Rear Fascia Cutline Based On Investigating Deviation Sources of the Body Panel Fit and Finish

A vehicle’s exterior fit and finish, in general, is the first system to attract customers. Automotive exterior engineers were motivated in the past few years to increase their focus on how to optimize the vehicle’s exterior panels split lines quality and how to minimize variation in fit and finish addressing customer and market required quality standards. The design engineering’s focus is to control the deviation from nominal build objective and minimize it. The fitting process follows an optimization model with the exterior panel’s location and orientation factors as independent variables. This research focuses on addressing the source of variation “contributed factors” that will impact the quality of the fit and finish. These critical factors could be resulted from the design process, product process, or an assembly process. An empirical analysis will be used to minimize the fit and finish deviation.