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Technical Paper

PIV Analysis Comparing Flow Past NASCAR COT Rear Wing and Spoiler Traveling Forward and Backwards

2011-04-12
2011-01-1432
There have been claims that the rear wing on the NASCAR Car of Tomorrow (COT) race car causes lift in the condition where the car spins during a crash and is traveling backwards down the track at high speed [1,2]. When enough lift is generated, the race car can lose control and even become airborne. At least in part, to address this concern, a new rear spoiler was designed by NASCAR to replace the wing and prevent this dangerous condition. This paper looks at the flow characteristics of both the rear wing and the new spoiler using particle image velocimetry (PIV) to provide qualitative analysis as well as flow visualization. In particular, the interaction of these downforce devices with "roof flaps" (which are designed to prevent lift) is explored. These experiments are done in a continuous flow water tunnel having a cross section of 1.0 m2 using a simplified 10% scale model COT body with either a wing or spoiler attached.
Journal Article

Flexible Real-Time Simulation of Truck and Trailer Configurations

2011-09-13
2011-01-2264
Real-time simulation of truck and trailer combinations can be applied to hardware-in-the-loop (HIL) systems for developing and testing electronic control units (ECUs). The large number of configuration variations in vehicle and axle types requires the simulation model to be adjustable in a wide range. This paper presents a modular multibody approach for the vehicle dynamics simulation of single track configurations and truck-and-trailer combinations. The equations of motion are expressed by a new formula which is a combination of Jourdain's principle and the articulated body algorithm. With the proposed algorithm, a robust model is achieved that is numerically stable even at handling limits. Moreover, the presented approach is suitable for modular modeling and has been successfully implemented as a basis for various system definitions. As a result, only one simulation model is needed for a large variety of track and trailer types.
Technical Paper

Road Noise TPA Simplification for Improving Vehicle Sensitivity to Tire Cavity Resonance Using Helium Gas

2009-05-19
2009-01-2092
Transfer Path Analysis (TPA) is an established tool that can be used to determine path contributions for road noise transmission (e.g. suspension links, sub-frame bushings, etc.) in passenger vehicles. However, due to the large number of paths and the presence of multiple partially-correlated sources in a road noise problem, TPA can be nearly impractical to implement as an experimental diagnostic tool. A simplified approach to Road Noise TPA is desirable to reduce test and analysis times in this era of shortening development cycles. It has been previously established that helium gas can be used to significantly alter the frequency of a tire’s acoustic cavity resonance [1]. Helium is used to “eliminate” excitation sources at the frequencies of tire cavity resonances, thereby reducing the number of paths to consider and simplifying a complex multi-reference TPA down to a single-reference TPA problem.
Journal Article

Modeling and Experimental Investigation of Tire Cavity Noise Generation Mechanisms for a Rolling Tire

2009-05-19
2009-01-2104
Tire cavity noise refers to the excitation of the acoustic mode of a tire cavity. The noise exhibits itself as sharp resonance-like peaks with frequencies typically in the range of 190-250Hz. For a rolling tire, the tire contact with the road moves relative to the tire. Furthermore, the load on the tire breaks the circular symmetry of the tire. Consequently, the peak frequency of the cavity noise shows dependence on the tire load and the vehicle speed. There are no models that simultaneously take these two factors into consideration. In this paper, we propose an analytical model and present experimental verifications of predictions on the noise peak frequency and its dependence on the tire load and vehicle speed. A wireless experimental measurement system is also presented which enables the measurement of tire cavity frequency for both non-rolling and rolling conditions.
Journal Article

Influence of Gyroscopic Effect on Hypoid and Bevel Geared System Dynamics

2009-05-19
2009-01-2070
The noise and vibration response of hypoid or bevel geared rotor system, primarily excited by transmission error (TE), and mesh vector and stiffness variations, can be affected significantly by the coupling between the driveline rotor dynamics and gear vibratory response. This is because of the inherent design comprising of non-parallel rotational axes and time-varying as well as spatial-varying gear mesh characteristics. One of the important factors of the driveline system dynamics is the rotor gyroscopic effect that has not been studied extensively in traditional gear dynamics. To address this gap in the literature, this paper attempts to examine the influence of incorporating gyroscopic terms in the hypoid gear dynamic simulation. A multi-degrees-of-freedom, multi-body dynamic model is used as a generalized representation of a hypoid geared rotor system.
Technical Paper

Modeling and Control of Variable Intake Valve Actuation in IC Engines

2009-11-03
2009-32-0014
This paper studies the dynamic model and associated control methods of a single cylinder four-stroke internal combustion (IC) engine attached with a variable intake-valve actuation mechanism. First, pertinent data of intake and exhaust ports, valve-timing cam, output torque, frictional torque, and crankshaft dynamics obtained from a 125 cc IC engine constitute the dynamic model for further control of the engine performance. Then, calculated data from specific conditions confined by volumetric efficiency and specific fuel consumption generate control commands for intake-valve actuation for various loads governed by a genetic algorithm. For quest of the best fuel economy, MatLab/Simulink programs simulate and evaluate the effective efficacy of the proposed control system under ECE-R40 driving cycle.
Technical Paper

Simulation and Experimental Study of Torque Vectoring on Vehicle Handling and Stability

2009-12-13
2009-28-0062
This paper discusses the effect of torque vectoring differential on improving vehicle handling and stability performance. The torque vectoring concept has been analyzed. The vehicle discussed in this paper is an AWD vehicle with torque vectoring differential in the rear and a torque biasing center differential. First, simulation results with vehicle model in CarSim® and torque vectoring control algorithm in Matlab®/Simulink® is discussed. Then, experimental results for vehicle tested at winter and summer test facility is presented. Both simulation and experimental results demonstrate the effectiveness of torque vectoring differential on vehicle handling & stability.
Technical Paper

Effect of spark assistance on improving cyclic stability of auto-ignition at light load in a small two-stroke engine

2009-11-03
2009-32-0021
Cyclic instability is a common problem in the operation of conventional two-stroke spark-ignition engines. Previous research has shown that auto-ignition (AI) could help solve this problem. However, at light engine loads, even under AI, the cyclic instability may still be significant due to the difficulty in maintaining the minimum temperature required by AI. Despite the benefits brought by AI in fuel consumption and emission reduction, the high level of cycle-to-cycle variation at light load may delay the realization of AI operation in engine products. To solve this problem, spark assistance has been identified as a cost effective and convenient way to improve the stability of AI operation at light load. This paper aims to report our experimental investigation to the effectiveness of spark assistance on cyclic variation of AI at light engine load conditions.
Technical Paper

Modern Tyre Tests Support Vehicle Dynamics Calculations

2009-01-21
2009-26-0069
Nearly all the external accelerating forces acting upon a ground vehicle originate at the tyre/ground interface and are transmitted to the vehicle through its tyres. How much force is applied, how quickly, and with what sensitivity of force to tyre deflection are subjects that can fill one's entire professional career. This paper offers a look at the effect of tyre cornering stiffness upon vehicle handling stability.
Technical Paper

Numerical Investigations on Crosswind Aerodynamics and its Effect on the Stability of a Passenger Car

2009-01-21
2009-26-0059
In crosswind, or while passing another vehicle in still air, the flow around an automobile becomes asymmetric, thus altering the yawing moment, drag and lift. This paper discusses the details of crosswind aerodynamics of a typical sedan. The investigations, limited to numerical analysis, were carried out to predict the drag and lift coefficients, and the yaw moments on the selected car using a commercially available CFD software, FLUENT. The analysis was carried out for three car speeds, six crosswind angles and five crosswind velocities in various combinations. The results have shown that the drag coefficient initially decreases at 15° crosswind angle and then increases as the crosswind angle is increased. Further, the drag coefficient, lift coefficient and the yaw moment increase as the crosswind velocity increases. It is observed that the flow field around the car, especially at the rear, changes substantially with a change in the crosswind angle.
Technical Paper

Testing, Computer Simulation and Analysis of Vehicle Dynamic Performance During Braking of a Small Car with ABS

2009-01-21
2009-26-0010
Road safety is becoming a strategic issue for sustainable development of India. Increasing vehicle population and low road density (India has 2.56 km road/thousand population and 768 km road/thousand km2 of total land.) are aggravating the problem. Introduction of modern safety features in small cars are inevitable to improve the safety scenario. Recently Anti-lock Braking System (ABS) has been started to be introduced in low segment family cars. But still the effect of ABS, fitted on these cars, in reducing the road accident are debatable and in-depth studies are required in this field. A thorough investigation of usefulness of ABS on Indian road condition took place in this paper. An instrumented vehicle has been used to study the braking performance of a small family vehicle with ABS ON and OFF condition on two different types of road surfaces, namely dry and wet. In addition to the vehicle performance the focus has been given to the vehicle stability criteria.
Technical Paper

A Constant Radius Constant Speed Simulation Methodology-Yaw Rate Control

2011-04-12
2011-01-0738
A simulation methodology is developed for the Constant Radius Constant Speed (CRCS) analysis to predict the ISO4138 [1] road test performance. The CRCS analysis can be used to predict the vehicle steady-state handling characteristics such as understeer, rear cornering compliance, and roll gradient, etc. The Yaw-Rate Control methodology is applied to replace the traditional driver-in-the-loop path-following approaches. Comparing to the path-following approaches, the proposed method is simpler to use, more efficient, accurate, and robust.
Technical Paper

Process Automation Wizard for Vehicle Dynamics Applications

2011-04-12
2011-01-0740
The imperative to get to the market faster with new and better products, has determined all automotive OEM to rethink their product development cycle, and, as a result, many hardware based processes were replaced and/or augmented with virtual, software based ones. However, the virtualization itself does not guaranties better and faster products. In the area of vehicle dynamics, we concentrate on improving the multi-body model development process, facilitating comprehensive virtual testing, and verifying the robustness of the design. The authors present a highly flexible and efficient environment that encourages, enforces, and facilitates model sharing, reusing of components, and parallelization of vehicle dynamics simulations, developed on top of an existing commercial off-the-shelf engineering software application.
Technical Paper

Taguchi Method (DOE) Based Performance Optimization of a Three Link Rigid Axle Passenger Car Suspension Using MBD Simulations

2011-04-12
2011-01-0734
This paper describes dimensional synthesis, analysis and performance optimization of a three-link rigid-axle suspension system. This suspension architecture has two longitudinal links and panhard rod as a transverse link. In case of rigid axle with three links, roll stiffness is primarily governed by springs, anti-roll bar, suspension link dimensions and its orientations. Because of suspension architecture, the bushings connecting the longitudinal link to axle will also contribute to the suspension roll stiffness. Typically, this contribution is comparable to the contribution due to the suspension springs. Hence, this paper explores the process of reducing roll stiffness of three-link rigid-axle suspension by identifying and changing high impact parameters. In the multi-step process, the first step is to evaluate the kinematics and compliance performance. This analysis is performed using "ADAMS®" - the multibody dynamics analysis software.
Technical Paper

Influence of Inertial Properties on the Comfort of Road Vehicles

2011-04-12
2011-01-0436
In this paper the comfort sensitivity to the variation of the inertia parameters is studied. For the theoretical approach, two computational models that predict the comfort response of a vehicle are developed and verified. These models are used to study the effect of a change on the inertial properties of the car on its comfort response. The models are developed on a commercial multi-body package and also implementing handwritten equations with a numerical integration algorithm. The influence of the inertial properties on comfort is also experimentally studied. Both approaches use two different road patterns as input generating a roll and pitch excitation. An allowed uncertainty on the inertia properties is proposed, based on the sensitivity to those properties.
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.
Journal Article

FMVSS126 Electronic Stability Control Sine With Dwell Incomplete Vehicle Type 2 Analysis

2011-04-12
2011-01-0956
Incomplete vehicles are partially manufactured by an Original Equipment Manufacturer (OEM) and subsequently sold to and completed by a final-stage manufacturer. Section S8.8, Final-Stage Manufacturers and Alterers, of Federal Motor Vehicle Safety Standard (FMVSS) 126 states “Vehicle that are manufactured in two or more stages or that are altered (within the meaning of 49 CFR 567.7) after having been previously certified in accordance with Part 567 of this chapter, are not subject to the requirements of S8.1 through S8.5. Instead, all vehicles produced by these manufacturers on or after September 1, 2012, must comply with this standard.” The FMVSS 126 compliance of the completed vehicle can be certified in three ways: by the OEM provided no alterations are made to identified components (TYPE 1), conditionally by the OEM provided the final-stage manufacturer follows specific guidelines (TYPE 2), or by the final-stage manufacturer (TYPE 3).
Technical Paper

Overview Introduction of Vehicle Dynamics with Novel Planar Suspension Systems

2011-04-12
2011-01-0957
In a conventional vehicle, the longitudinal shocks caused by the road obstacles cannot be effectively absorbed due to the fact that the longitudinal connections between the chassis and wheels are typically very stiff compared with the vertical strut where the regular spring is mounted. To overcome this limitation, a concept design of a planar suspension system (PSS) is proposed. The rather stiff longitudinal linkages are replaced by a spring-damping strut in a PSS so that the vibration along any direction in the wheel plane can be effectively isolated. For a vehicle with such suspension systems, the wheels can move forth and back with respect to the chassis. The wheelbase and load distribution at the front and rear wheels can change as a consequence of the implementation of the PSS on a vehicle. The planar system can induce changes in the vehicle dynamic behavior. This paper presents the overview introduction of a dynamic study of a vehicle with such suspension systems.
Technical Paper

A Numerical Study for Optimizing Vehicle Dynamics Control Systems in Offset Impacts

2011-04-12
2011-01-0954
In this paper, a novel 3-D dynamic/crash mathematical model is developed and solved numerically to investigate the influence of Vehicle Dynamics Control Systems (VDCS) on vehicle collision mitigation in offset crash scenarios. In this model, the VDCS are co-simulated with a four-wheel vehicle dynamic model and integrated with a nonlinear front-end structure model. In addition, the vehicle body is represented by a lumped mass and four spring/damper units are used to represent the vehicle suspension system. The numerical simulations demonstrate that the vehicle dynamic responses and influence of VDCS on vehicle collisions are captured and analyzed accurately. Furthermore, the mathematical model is shown to be flexible, useful and can be used in optimization studies. The model is validated by comparing the numerical results with other published results and good correlations are achieved.
Technical Paper

Design and Comparative Study of Yaw Rate Control Systems with Various Actuators

2011-04-12
2011-01-0952
The vehicle dynamics control systems are traditionally based upon utilizing wheel brakes as actuators. However, there has been recently strong interest in the automotive industry for introduction of other vehicle dynamics actuators, in order to improve the overall vehicle stability, responsiveness, and agility features. This paper considers various actuators such as active rear and central differentials and active front and rear steering, and proposes design of related yaw rate control systems. Different control subsystems such as reference model, feedback and feedforward control, allocation algorithm, and time-varying controller limit are discussed. The designed control systems are verified and compared by computer simulation for double lane change and slalom maneuvers.
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