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The fuel consumption of a vehicle is shown to be linearly proportional to (1) total vehicle work required to drive the cycle due to mass and acceleration, tire friction, and aerodynamic drag and (2) the powertrain (PT) mechanical losses, which are approximately proportional to the engine displaced volume per unit distance travelled (displacement time gearing). The fuel usage increases linearly with work and displacement over a wide range of applications, and the rate of increase is inversely proportional to the marginal efficiency of the engine. The theoretical basis for these predictions is reviewed. Examples from current applications are discussed, where a single PT is used across several vehicles. A full vehicle cycle simulation model also predicts a linear relationship between fuel consumption, vehicle work, and displacement time gearing and agrees well with the application data.

In this study, tests were performed with modified tires at the right rear location on a solid rear axle sport utility vehicle to compare the vehicle inputs from both: (1) tire tread belt detachments staged by circumferentially cut tires, and (2) a tire tread detachment staged by distressing a tire in a laboratory environment. The forces and moments that transfer through the road wheel were measured at the right and left rear wheel locations using wheel force transducers; displacements were measured between the rear axle and the frame at the shock absorber mounting locations, ride height displacements were measured at the four corners of the vehicle, and accelerations were measured on the rear axle. Onboard vehicle accelerations and velocities were measured as well. The data shows that the tire tread belt detachments prepared by circumferentially cut tires and distressed tires have similar inputs to the vehicle.

In this study, tests were performed with modified tires at the right rear location on a solid axle sport utility vehicle to compare vehicle inputs and responses from both: (1) staged tire tread belt detachments, and (2) stepped diameter (“lumpy”) tires. Lumpy tires consist of equal size sections of tread that are vulcanized at equidistant locations around the outer circumference of the tire casing. Some have used lumpy tires in attempt to model the force and displacement inputs created by a tire tread belt separation. Four configurations were evaluated for the lumpy tires: 1-Lump, 2-Lump (2 lengths), and 3-Lump.

Tires are the only load path between the road and the vehicle's suspension and so play a key role in determining vehicle NVH performance. Tire structure and behavior include many nonlinear phenomena, such as rubber material response to load, tire contact patch conformity with road profile, and bulging of side walls. In addition to structural nonlinearities, the tire's rotational motion introduces nonlinear resonances that are dependent on vehicle speed, and also rotationally induced harmonics. When a tire rolls over a cleat, the rolling resonance at the spindle may vary with the vehicle's speed. Since tire behavior couples several nonlinear parameters, a numerical tire model that can consider physical characteristics such as, rolling resonance dependence on speed and the harmonic resonances, will definitely be helpful for improving vehicle NVH quality. This paper presents a study of a finite element tire model rolling over an impact cleat at different speeds.

Braking has a strong effect on a vehicle's front suspension loads when the vehicle is driven over a pothole. The suspension loads of a vehicle braking while going over a pothole are also affected by vehicle design, vehicle weight and speed. In this study a simplified suspension model is presented, which is then validated by the simulation of a vehicle model. The simplified suspension model provides an efficient approach to evaluate effects of braking on wheel rebound into potholes, which determines the magnitude of impact loads when the tires hit the pothole edge. The vehicle model is used not only to validate the simplified suspension model, but also to provide the information of wheel center loads in addition to the wheel position and velocity. The analysis using the vehicle model agrees with pothole test results. The study reveals how vehicle braking affects the wheel center longitudinal forces during the pothole impact.

Nibble is torsional vibration at the steering wheel of a vehicle. Typically it occurs at a resonant frequency of the steering and suspension system excited by the 1st harmonic tire/wheel force. A nibble target is established to be consistent with customer satisfaction target and then cascaded down to the targets for vehicle nibble sensitivity and tire/wheel inputs. Hence accuracy of the sensitivity and the tire/wheel force is important for a Computer Aided Engineering (CAE) nibble simulation. On-vehicle wheel-end forces are fore/aft and vertical tire/wheel forces acting on a vehicle spindle in an operating condition. This paper presents a methodology to estimate the wheel-end forces. The methodology was applied to investigate the effect of the tire flat-spot on the wheel-end forces. Tires were flat-spotted for one week and two months to simulate customer usage profiles. They were tested to measure the growth of the wheel-end forces.

Vehicle dynamics CAE capabilities has increased in the past few years, specially, for handling and steering attributes. However, secondary ride simulations are still highly depended on the tire model. Such tire model must be capable to simulate high order phenomenon such as impact and harshness transmissibility in three directions. In order to gather tire information sufficient to cope with these phenomena, one needs to perform a series of specific tests, and so be able to build the intended tire model. Still, there could be correlation issues. This whole process takes a lot of time and resources. This article presents a semi-analytical approach, using data gathered via wheel force transducers (WFTs) that are typically used for load cascading and durability purposes. The method main advantage is that since it relies on measured data at the wheel center, it is independent of a tire model, and, as such, it demands less time and resources.

Front road wheel toe dynamics directly affects tire wear and steering wheel vibration, which in turn negatively impacts customer satisfaction. Though static toe can be preset in assembly plants, the front road wheels can vibrate around steering axes or kingpin axes due to tire mass unbalance and nonuniformity. The frequency of the vibration depends on the wheel size and vehicle speed, while the amplitude of the vibration is not only dictated by the tire forces, but also by suspension and steering parameters. This paper presents a study on the sensitivities of the front road wheel toe dynamics to the parameters of a short-long-arm suspension (SLA) and a parallelogram steering system. These parameters includes hard point shift, steering gear compliance, gear friction, control arm bushing rates, friction in control arm ball joints, and compliance in tie rod outboard joints.

The extensive use of rotative machines in the diverse branches of the modern world has made the rising undesirable mechanical and acoustic vibration levels to be a problem of special importance for the machines normal operation as for the communities that are each time more affected by the problem. It makes the study of vibration and acoustic phenomena also to be even more important and the applications of its concepts more sophisticated. Several are the concepts used for decreasing vibration levels, like common dampers, hydraulic dampers, active dampers, natural frequencies changes and others. The choice of use of one or another depends greatly on the engineering possibilities (weight, energy, physical space, other components functional interference, vibration levels, etc.) as well as the cost of implementation of each one.

Road loads tire models are used in the automotive industry in full vehicle simulations to compute the loading from the road into the chassis encountered in proving ground durability events. Such events typically include Belgian Block events, bump events, potholes and others. Correctly capturing tire enveloping forces in such events has historically been challenging - several different approaches exist each with its own limitations. In this paper a model is presented which captures the first order tire dynamics (frequencies lower than 80 Hz) and associated enveloping loading without the need of an effective road profile. The theory behind this tire model is briefly introduced. Importantly, a comprehensive study of the validation of the tire model is given which shows correlation for full vehicle dynamic proving ground events. A Virtual Tire Lab (VTL) pre-processing tool is also presented which is used to compute tire model input parameters from a validated non-linear FEA tire model.

The measured drive-point conductance of a typical passenger car tire was seen to drop steadily for frequencies above 1000 Hz. This behavior is a-typical since SEA theory predicts such conductance should remain relatively flat for high frequencies. It was found that, one has to pay careful attention to errors introduced by the added mass of the measuring transducer and “local” effects due to contact stiffness of the tread rubber. Such effects are investigated and their contributions quantified. Compensation schemes are also developed and implemented. It is shown that, for a 20 grams transducer, the measured and corrected conductances are off by 12 dB. The effects of the local contact stiffness of the rubber at the attachment point are less significant.

The performance of structure-borne road NVH can be cascaded down to three major systems: 1) vehicle body structure, 2) chassis/suspension, 3) tire/wheel. The forces at the body attachment points are controlled by the isolation efficiency of the chassis/suspension system and the excitation at the spindle/knuckle due to the tire/road interaction. The chassis force transmissibility is a metric to quantify the isolation efficiency. This paper presents a new experimental methodology to estimate the chassis force transmissibility from a fully assembled vehicle. For the calculation of the transmissibility, the spindle force/moment estimation and the conventional Noise Path Analysis (NPA) methodologies are utilized. A merit of the methodology provides not only spindle force to body force transmissibility but also spindle moment to body force transmissibility. Hence it enables us to understand the effectiveness of the spindle moments on the body forces.

This paper proposes a method to make diagnostic/prognostic judgment about the health of a tire, in term of its wear, using existing on-board sensor signals. The approach focuses on using an estimate of the effective rolling radius (ERR) for individual tires as one of the main diagnostic/prognostic means and it determines if a tire has significant wear and how long it can be safely driven before tire rotation or tire replacement are required. The ERR is determined from the combination of wheel speed sensor (WSS), Global Positioning sensor (GPS), the other motion sensor signals, together with the radius kinematic model of a rolling tire. The ERR estimation fits the relevant signals to a linear model and utilizes the relationship revealed in the magic formula tire model. The ERR can then be related to multiple sources of uncertainties such as the tire inflation pressure, tire loading changes, and tire wear.

Direct bypass to DC-DC boost converter in traction inverter increases converter's capability and efficiency significantly by providing a lower loss path for power flow between the battery and DC-link terminal. A bypass using diode is an excellent solution to achieve this capability at low cost and system complexity. Bypass diode operates in the linear operating region (DC Q-point) when the battery discharges through the bypass diode to drive the electric motors. Therefore, thermal stress on the DC-link capacitor is shared between the input and DC-link capacitors through the bypass diode. On the other hand, inverters introduce voltage oscillation in the DC-link terminal which results in unwanted energy oscillation through the bypass diode during battery charging. Both of these phenomena have been explained in details.

Power modules play a key role in traction inverters for vehicle electrification applications. The harsh automotive operating environment is a big challenge for power modules. The paper highlights the challenges for power modules usage in electrified vehicles (xEVs), and proposes a design verification procedure for such application in order to ensure the reliable operation under all conditions. First, power modules operate in all climate zones and are exposed to a wide ambient temperature range underhood from -40°C to 105°C. A typical automotive power module should therefore withstand a junction temperature from -40°C to up to 175°C without exceeding its safe operating area (SOA), e.g. avalanche breakdown voltage, maximum current, and thermal limit. Second, an inductive induced high voltage spike could be generated during the power semiconductor fast switching at high voltage and high current conditions.

This paper studies different switching schemes for loss reduction in a traction motor drive. The system under examination is composed of a battery, a 2 level Voltage Source Inverter, and an Interior Permanent Magnet motor. Discontinuous PWM (DPWM) control strategy is widely used in this type of motor drive for the reduction of losses. In some publications, the effect of the DPWM modulation scheme is compared to the reduction of the switching frequency which can also cause a reduction in switching losses of the inverter. Extensive studies have examined the effect of variation of the switching frequency on the motor and inverter losses. However, the effect of applying both switching schemes simultaneously has not been explored. This paper will use a system that is operated at a fixed switching frequency as the baseline. Afterwards, three different switching schemes will be studied and compared to the baseline.

Recently, papers have been published purporting to study the effect of rear axle tramp during tread separation events, and its effect on vehicle handling [1, 2]. Based on analysis and physical testing, one paper [1] has put forth a mathematical model which the authors claim allows vehicle designers to select shock damping values during the development process of a vehicle in order to assure that a vehicle will not experience axle tramp during tread separations. In the course of their work, “lumpy” tires (tires with rubber blocks adhered to the tire's tread) were employed to excite the axle tramp resonance, even though this method has been shown not to duplicate the physical mechanisms behind an actual tread belt separation. This paper evaluates the theories postulated in [1] by first analyzing the equations behind the mathematical model presented. The model is then tested to see if it agrees with observed physical testing.

In repeated physical testing of vehicles at or near their handling limit, tire shoulder wear occurs that is not typical of normal customer use. It has been observed for decades that this type of severe cornering induced tire wear can have a significant effect on the force and moment characteristics of tires. In this study, the severe cornering wear effect was studied by testing vehicles in a highly controlled manner using a robot steering controller. This testing shows how vehicle response to the exact same steering input changes significantly as the number of runs on the same tires accumulates. In fact, vehicles were found to not lift tires from the ground in initial runs then tip-up hard onto outriggers in later runs as the tires are abraded. Additionally, for one vehicle configuration an additional run was made with tires that had accumulated 16,000 km (10,000 miles) of normal customer usage.

Friction reduction in lubricated components through engine oil formulations has been investigated in the present work. Three different DI packages in combination with one friction modifier were blended in SAE 5 W-20 and SAE 0 W-16 viscosity grades. The friction performance of these oils was compared with GF-5 SAE 5 W-20 oil. A motored cranktrain assembly has been used to evaluate these, in which friction mean effective pressure (FMEP) as a function of engine speeds at different lubricant temperatures is measured. Results show that the choice of DI package plays a significant role in friction reduction. Results obtained from the mini-traction machine (MTM2) provide detailed information on traction coefficient in boundary, mixed and elastohydrodynamic (EHD) lubrication regimes. It has been shown that the results from the cranktrain rig are fairly consistent with those found in MTM2 tests for all the lubricants tested.

This paper will discuss the vehicle top-down design approach that includes the non-linearity and sub-system interactions such as tire and road, (left and right) interaction between two or more parts connected by bushings, springs, bolts, stabilizer-bar, etc… The proposed method would allow for the inclusion of realistic boundary conditions and proper load simulation, and it would provide the ability to visualize and evaluate dynamic structural phenomena and complex component interaction. This approach would also facilitate the evaluation of design changes that may affect load propagation and/or load magnitude. All of the advantages of the sub-system analysis method mentioned above would allow for a greater understanding of the sub-system as a whole and help correctly identify the design requirements needed for the individual components that make up such chassis subsystems.