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SAE International Journal of Passenger Cars Mechanical Systems
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Computational-Based Aerodynamic Design for a Formula SAE Vehicle

SAE International Journal of Passenger Cars - Mechanical Systems

McGill Racing Team-Jessica Batty, Thomas Carrel-Billiard, Anna Cybulsky, Lucien Viala
McGill University-Daniel Kelly
  • Journal Article
  • 06-11-01-0003
Published 2018-03-01 by SAE International in United States
The computational analysis and design of an aerodynamics system for a Formula SAE vehicle is presented. The work utilizes a stochastic-approximation optimization (SAO) process coupled with a computational fluid dynamics (CFD) solver. The methodology is presented in a general manner, and is applicable to other complex parametrizable systems. A mix of discrete and continuous variables is established to define the airfoil profile, location, sizing and angle of all wing elements. Objectives are established to maximize downforce, minimize drag and maintain a target vehicle aerodynamic balance. A combination of successive 2D and 3D CFD evaluations have achieved vehicle aerodynamic performance targets at a minimal computational cost.
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Improvement in Gear Shift Comfort by Reduction in Double Bump Force of Passenger Vehicles

SAE International Journal of Passenger Cars - Mechanical Systems

Tata Motors Ltd.-Santosh Deshmane, Onkar Gangvekar, Samson Rajakumar
  • Journal Article
  • 06-11-01-0006
Published 2017-10-08 by SAE International in United States
In today’s competitive automobile market, driver comfort is at utmost importance and the bar is being raised continuously. Gear Shifting is a crucial customer touch point. Any issue or inconvenience caused while shifting gear can result into customer dissatisfaction and will impact the brand image. While there are continual efforts being taken by most of the car manufactures, “Double Bump” in gearshift has remained as a pain area and impact severely on the shift feel. This is more prominent in North-South (N-S) transmissions. In this paper ‘Double Bump’ is a focus area and a mathematical / analytical approach is demonstrated by analyzing ‘impacting parameters’ and establishing their co-relation with double bump. Additionally, the results are also verified with a simulation model.
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Driveline Ratio Selection and Shift Map Optimization for Automatic Transmission Vehicle at Concept Phase through Simulations

SAE International Journal of Passenger Cars - Mechanical Systems

Mahindra & Mahindra, Ltd.-Srinivasan Paulraj, Saravanan Muthiah
  • Journal Article
  • 06-11-01-0005
Published 2017-10-08 by SAE International in United States
Traditionally driveline ratios are selected based on trial and error method of proto vehicle testing. This consumes lot of time and increases overall vehicle development effort. Over last few decades, simulation-based design approach has been extensively used to alleviate this problem. This paper describes torque converter and final drive ratio (FDR) selection at concept phase for new Automatic Transmission (AT) vehicle development. Most of the critical data required for simulating vehicle performance and fuel economy (FE) targets were not available (e.g. shift map, clutch slip map, pedal map, dynamic torque, coast down, etc.) at an initial stage of the project. Hence, the risk for assuming right inputs and properly selecting FDR/Torque converter was particularly high. Therefore, a validated AVL Cruise simulation model based on an existing AT vehicle was used as a base for new AT vehicle development to mitigate the risk due to non-availability of inputs. The simulation model shows 97% correlation with the test results by using base shift map. The shift map was further optimized by using Gear Shifting Program (GSP) and…
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Innovative Approach of Wedge Washer to Avoid Bolt Loosening in Automotive Applications

SAE International Journal of Passenger Cars - Mechanical Systems

VE Commercial Vehicles Ltd.-Suresh Kumar Kandreegula, Rahul Jain, Shivdayal Prasad, Rahul Machiya, Avinash Mandyam
  • Journal Article
  • 06-11-01-0004
Published 2017-10-08 by SAE International in United States
Automotive vehicle includes various systems like engine, transmission, exhaust, air intake, cooling and many more systems. No doubt the performance of individual system depends upon their core design. But for performance, the system needs to be fastened properly. In automotive, most of the joints used fasteners which helps in serviceability of the components. There are more than thousands of fasteners used in the vehicle. At various locations, we found issue of bolt loosening and because of this design intent performance has not met by the system. During product development of ECS (Engine cooling system), various issues reported to loosening the bolt. The pre-mature failure of bolt loosening, increases the interest in young engineers for understanding the behavior of fastener in vehicle running conditions. This paper focuses on the design of wedge shape of washer to avoid bolt loosening. Further, the paper is reinforced with FEA simulation for understanding the behavior of the bolt loosening. The joint in ECS is tested experimentally and FE simulated using simulation tools with various methods under different vibration conditions like…
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Fuzzy Control of Autonomous Intelligent Vehicles for Collision Avoidance Using Integrated Dynamics

SAE International Journal of Passenger Cars - Mechanical Systems

Helwan University-Youssef Sabry, Mahmoud Aly, Walid Oraby, Samir El-demerdash
  • Journal Article
  • 06-11-01-0001
Published 2018-03-01 by SAE International in United States
This study aims to take the first step in bridging the gap between vehicle dynamics systems and autonomous control strategies research. More specifically, a nested method is employed to evaluate the collision avoidance ability of autonomous vehicles in the primary design stage theoretically based on both dynamics and control parameters. An integrated model is derived from a half car mathematical model in the lateral direction, consisting of two degrees of freedom, lateral deviation and yaw angle, with a traction mathematical model in the longitudinal direction, consisting of two degrees of freedom, the longitudinal velocity and rolling velocity of the wheel. The integrated model uses a mathematical power train model to generate the torque on the wheel and connects the two systems via the magic formula tyre model to represent the tyre non-linearity during augmented longitudinal and lateral dynamic attitudes. These mathematical models are represented using MATLAB in the time domain. Fuzzy logic is used for a path-following model to control the vehicle in the longitudinal and lateral directions. The dynamic behaviour is subjectively evaluated using…
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Experimental Investigation of the Near Wall Flow Downstream of a Passenger Car Wheel Arch

SAE International Journal of Passenger Cars - Mechanical Systems

Chalmers University of Technology-Sabine Bonitz, Lars Larsson, Lennart Lofdahl
TU Berlin (Technical University)-Dirk Wieser, Christian Nayeri, Christian Paschereit
  • Journal Article
  • 06-11-01-0002
Published 2018-03-01 by SAE International in United States
The flow around and downstream of the front wheels of passenger cars is highly complex and characterized by flow structure interactions between the external flow, fluid exiting through the wheelhouse, flow from the engine bay and the underbody. In the present paper the near wall flow downstream of the front wheel house is analyzed, combining two traditional methods. A tuft visualization method is used to obtain the limiting streamline pattern and information about the near wall flow direction. Additionally, time resolved surface pressure measurements are used to study the pressure distribution and the standard deviation. The propagation of the occurring flow structures is investigated by cross correlations of the pressure signal and a spectral analysis provides the characteristic frequencies of the investigated flow. It is found that two main flow phenomena can be observed: one originates from flow exiting the upper wheelhouse and a second one resulting from a separation on the lower wheel house edge. The frequency spectrum reveals a dominant Strouhal number of 0.2. As the observed flow structures are attributed to the…
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Contribution of the Mechanical Linkage in Gear Shift Feel of North-South Transmission

SAE International Journal of Passenger Cars - Mechanical Systems

Tata Motors Ltd.-Santosh Deshmane, Vipul Sahu
Tata Technologies, Ltd.-Onkar P. Gurav
  • Journal Article
  • 06-11-01-0008
Published 2017-10-08 by SAE International in United States
Today’s automotive industry is facing cutthroat competition, especially in passenger vehicle business. Manufacturers around the globe are developing innovative and new products keeping focus on end customer; thus customer's opinion and perception about the product has become a factor of prime importance. Customer touch points such as gear shift lever, clutch, brakes, steering etc. are thus gaining more and more importance. Car companies are trying to induce more and more luxuries in these touch points so that they impress customer and create a positive opinion about the product. On the other hand manufacturers are also trying to manage profits. Companies thus need to find the best fit solution for improvising customer touch points with optimized costs. The performance of these touch points is driven by subsystems of mechanical components like mechanical linkage. Quality, functioning and durability of these mechanical component subsystems play a significant role in performance of touch points like gear shift lever. During development of 6-Speed North-South transmission, we came across some facts indicating the relation between the performance of mechanical shifting linkage…
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Statistical Modeling of Plate Clearance Distribution for Wet Clutch Drag Analysis

SAE International Journal of Passenger Cars - Mechanical Systems

Ford Motor Company-Yuji Fujii
University of Michigan-Pengchuan Wang, Nikolaos Katopodes
  • Journal Article
  • 06-11-01-0007
Published 2017-10-08 by SAE International in United States
Wet clutch packs are the key component for gear shifting in the step-ratio automatic transmission system. The clutch plates are coupled or de-coupled to alter gear ratios based on the driver’s actions and vehicle operating conditions. The frictional interfaces between clutch plates are lubricated with automatic transmission fluid (ATF) for both thermal and friction management. In a 10-speed transmission, there may be as many as 6 clutch packs. Under typical driving conditions, 2 to 3 clutch packs are open, shearing ATF and contributing to energy loss. There is an opportunity to improve fuel economy by reducing the associated viscous drag. An important factor that directly affects clutch drag is the clearance between rotating plates. The axial position of clutch plates changes continuously during operation. It is known in practice that not only the total clearance, but also its distribution between the plates affects the viscous drag. However, it is very difficult to measure the actual distribution for every clutch in a running transmission. Because of the limited theoretical understanding of plate movement, a fine tuning…
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