Search Results

New developments in road profile measurement systems and in semi-active damper technology promote the application of preview control strategies to vehicle suspension systems. This paper details a new semi-active suspension control approach in which a rule-optimized Fuzzy Logic controller is enhanced through preview capability. The proposed approach utilizes an optimization process for obtaining the optimum membership functions and the optimum rule-base of the preview enhanced Fuzzy Logic controller. The preview enhanced Fuzzy Logic controller uses the feedforward road input information and the feedback vehicle state information as the controller inputs. An eleven degree of freedom full vehicle model, which is validated through laboratory tests performed on a hydraulic four-poster shaker, is used for the controller synthesis.

This paper proposed a novel fault-tolerant control method based on control allocation via dynamic constrained optimization for electric vehicles with XBW systems. The total vehicle control command is first derived based on interpretation on driver's intention as a set of desired vehicle body forces, which is further dynamically distributed to the control command of each actuator among vehicle four corners. A dynamic constrained optimization method is proposed with the cost function set to be a linear combination of multiple control objectives, such that the control allocation problem is transformed into a linear programming formulation. An analytical yet explicit solution is then derived, which not only provides a systematic approach in handling the actuation faults, but also is efficient and real-time feasible for in-vehicle implementation. The simulation results show that the proposed method is valid and effective in maintaining vehicle operation as expected even with faults.

This paper proposes a new method of predicting the sound absorption performance of polymer wool using artificial neural networks (ANN) model. Some important parameters of the proposed model have been adjusted to best fit the non-linear relationship between the input data and output data. What's more, the commonly used multiple non-linear regression model is built to compare with ANN model in this study. Measurements of the sound absorption coefficient of polymer wool based on transfer function method are also performed to determine the sound absorption performance according to GB/T18696. 2-2002 and ISO10534- 2: 1998 (E) standards. It is founded that predictions of the new model are in good agreement with the experiment results.

Durability of a product is related to three major factors, the load, structure and material. The durability performance of an automotive product is, therefore, not only depended on the structure configuration, but also on the road load dynamic characteristics (profiles and frequency spectrum), and the material fatigue properties as well. Due to the dynamic nature of vehicle loads, one of the major technical challenges, to the durability design optimization of automotive products, is how to define a set of representative road loads, for fidelity and efficiency, based on the measured proving ground durability data of huge size. This paper presents a procedure of processing the proving ground road loads, for vehicle durability design and optimization of automotive products, based on the statistical characteristics evaluation and fatigue damage equivalency techniques.

Taguchi method is a technology to prevent quality problems at early stages of product development and product design. Parameter design method is an important part in Taguchi method which selects the best control factor level combination for the optimization of the robustness of product function against noise factors. The air induction system (AIS) provides clean air to the engine for combustion. The noise radiated from the inlet of the AIS can be of significant importance in reducing vehicle interior noise and tuning the interior sound quality. The porous duct has been introduced into the AIS to reduce the snorkel noise. It helps with both the system layout and isolation by reducing transmitted vibration. A CAE simulation procedure has been developed and validated to predict the snorkel noise of the porous ducted AIS. In this paper, Taguchi's parameter design method was utilized to optimize a porous duct design in an AIS to achieve the best snorkel noise performance.

A tire may be one of the most critical and complex components in vehicle dynamics and road loads analyses because it serves as the only interface between the road surface and the vehicle. Extensive research and development activities about vehicle dynamics and tire models have been published in the past decades, but it is still not clear about the applications and parameter identification associated with all of these tire models. In this literature review study, various published tire models used for vehicle dynamics and road loads analyses are compared in terms of their modeling approaches, applications and parameters identification process and methodologies. It is hoped that the summary of this literature review work can help clarify and guide the future research and development direction about tire modeling.

HiSiMo cast irons are frequently used as material for high temperature components in engines as e.g. exhaust manifolds and turbo chargers. These components must withstand severe cyclic mechanical and thermal loads throughout their service life. The combination of thermal transients with mechanical load cycles results in a complex evolution of damage, leading to thermomechanical fatigue (TMF) of the material and, after a certain number of loading cycles, to failure of the component. In this paper (Part I), the low-cycle fatigue (LCF) and TMF properties of HiSiMo are investigated in uniaxial tests and the damage mechanisms are addressed. On the basis of the experimental results a fatigue life model is developed which is based on elastic, plastic and creep fracture mechanics results of short cracks, so that time and temperature dependent effects on damage are taken into account.

Advanced high strength steels (AHSS) offer a good balance of strength, durability, crash energy absorption and formability. Applications of AHSS for lightweight designs of automotive structures are accelerating in recent years to meet the tough new CAFE standard for vehicle fuel economy by 2025. At the same time, the new generation pickup cargo box is to be designed for a dramatic increase in payload. Upgrading the box material from conventional mild steels to AHSS is necessary to meet the conflicting requirements of vehicle light weighting and higher payload. In this paper, typical AHSS grades such as DP590 and DP780 were applied to selected components of the pickup cargo box for weight reduction while meeting the design targets for fatigue, strength and local stiffness.

Weld fatigue evaluation using the mesh-insensitive Battelle structural stress method has been applied to fusion welds, resistance spot welds and non-welded components. The effectiveness of the Battelle structural stress procedure has been demonstrated in a series of earlier publications for welded structures with different joint types, plate thicknesses, and loading modes. In this paper, a weld fatigue evaluation procedure using the Battelle structural stress method is proposed for friction stir welds currently being used in the automotive and aerospace industries. The applicability of the Battelle structural stress procedure is demonstrated by comparing fatigue life predictions for friction stir welded specimens to well-documented test data from the literature. Different specimen types, plate thicknesses and loading ratios were analyzed for several aluminum alloys.

Fatigue test data in finite life region are normally analyzed separately for each stress level because of varying scatters, while another method assuming equal scatters on all levels and thus unifying all data into one model is also welcome for its efficient usage of data. Combining the idea of the two methods, a new method that assumes linear change of scatter according to stress levels is developed in this paper. The algorithm derives from maximum likelihood estimation and general Newton's method. Monte Carlo method is used for theoretical validation and the new method is proved to be correct with the estimations. Finally a set of test data which shows a tendency of trapezoidal data distribution is analyzed and an S-N curve for finite life range is created. The new method has its advantage in certain situations so it's meaningful to add it to the alternatives of fatigue data analysis methods.

HiSiMo cast irons are frequently used as material for high temperature components in engines as e.g. exhaust manifolds and turbo chargers. These components must withstand severe cyclic mechanical and thermal loads throughout their life cycle. The combination of thermal transients with mechanical load cycles results in a complex evolution of damage, leading to thermomechanical fatigue (TMF) of the material and, after a certain number of loading cycles, to failure of the component. In Part I of the paper, a fracture mechanics model for TMF life prediction was developed based on results of uniaxial tests. In this paper (Part II), the model is formulated for three-dimensional stress states, so that it can be applied in a post-processing step of a finite-element analysis. To obtain reliable stresses and (time dependent plastic) strains in the finite-element calculation, a time and temperature dependent plasticity model is applied which takes non-linear kinematic hardening into account.

Light weight alloys are widely used in the automotive industry in order to meet environmental requirements. Cast magnesium alloys are candidate materials due to their high strength to weight ratio, high stiffness and excellent castability. However, some previously reported anomalous cyclic stress-strain behaviours of magnesium alloys have not been fully investigated especially in LCF characterisation. The main objective of this work was to investigate the cyclic loading-unloading behaviour of high pressure die cast (HPDC) AM60B and AE44 magnesium alloys under uniaxial tension or/and compression and its effect on LCF behaviour. It was found that classical linear stress-strain behaviour, for both AM60B and AE44 alloys, applied only to a very small range of stress beyond which significant pseudo-elastic behaviour was discovered. This affected LCF characterisation and subsequent fatigue analysis processes.

Electric motors and generators produce vibrations and noise associated with many physical mechanisms. In this study, we look at the vibrations and noise produced by the transient electromagnetic forces on the stator of a permanent magnet motor. In the first stage, electromagnetic simulation is carried out to calculate the forces per tooth segment of the stator. The harmonic orders of the electromagnetic forces are then calculated using Fourier analysis, and forces are mapped to the mechanical harmonic analysis of the second stage. As a third stage, the vibrations of the structure are used to drive the boundary of acoustic domain to predict the noise. Finally, optimization studies are made over the complete system to improve the motor design and reduce noise. A simulation environment (ANSYS Workbench) is used to integrate a seamless workflow.

A variety of parameters influence the durability of a converter to pipe joint of an automotive exhaust system. Some of the parameters are design variables and some factors are related to manufacturing. The design parameters include the thickness of the components, diameter of the pipe, sleeve length of the cone etc. While the variables like the weld penetration and the fit-up of the joint are related to manufacturing. Traditional durability simulations utilizing computer aided engineering (CAE) methods are conducted using nominal values of the design and manufacturing variables. In reality scatter and randomness in parameters are present due to the tolerance in components and limitations of the manufacturing process. In this paper a CAE based stochastic approach to determine the life distribution for a converter joint of an automotive exhaust system is presented.

Fatigue behavior of aluminum alloys under multiaxial loading was investigated with both cast aluminum A356-T6 and wrought alloy 6063-T6. The dominant multiaxial fatigue crack preferentially nucleates from flaws like porosity and oxide films located near the free surface of the material. In the absence of the flaws, the cracking/debonding of the second phase particles dominates the crack initiation and propagation. The number of cracked/debonded particles increases with the number of cycles, but the damage rate depends on loading paths. Among various loading paths studied, the circle loading path shows the shortest fatigue life due to the development of complex dislocation substructures and severe stress concentration near grain/cell boundaries and second phase particles.

Cooled exhaust gas recirculation (EGR) is widely used in diesel engines to control engine out NOx (oxides of nitrogen) emissions. A portion of the exhaust gases is re-circulated into the intake manifold of the engine after cooling it through a heat exchanger known as an EGR cooler. EGR cooler heat exchangers, however, tend to lose efficiency and have increased pressure drop as deposit forms on the heat exchanger surface due to transport of soot particles and condensing species to the cooler walls. In our previous work surface condensation of water vapor was shown to be successful in removing a significant portion of the accumulated deposit mass from various types of deposit layers typically encountered in EGR coolers. Significant removal of accumulated deposit mass was observed for “dry” soot only deposit layers, while little to no removal was observed for the deposit layers created at low coolant temperatures that consisted of both soot and condensed hydrocarbons (HC).

Future diesel combustion systems may operate with significantly higher levels of boost and EGR than used with present systems. The potential benefits of higher boost and EGR were studied experimentally in a single-cylinder diesel engine with capability to adjust these parameters independently. The objective was to study the intake and exhaust conditions with a more optimum combustion phasing to minimize fuel consumption while maintaining proper constraints on emissions and combustion noise. The engine was tested at four part-load operating points using a Design of Experiments (DOE) approach. Two of the operating points correspond to low-speed and low-load conditions relevant for the New European Driving Cycle (NEDC). The other two points focus on medium load conditions representative of the World-wide harmonized Light-duty Test Procedures (WLTP).

The European Commission (EC) as well as the United States Environmental Protection Agency (EPA) published legislations to regulate or encourage the use of low Global Warming Potential (GWP) refrigerants applied to Mobile Air Conditioning (MAC) systems. Europe mandates a GWP less than 150 of MAC refrigerants for new vehicle types. The thermodynamic refrigerant properties of R-1234yf are slightly different from the properties of R-134a, currently used in MAC systems. Although the basic material data show that R-1234yf is flammable, ignition tests performed for an automotive engine under-hood environment reveal design and packaging influences of its ignition behavior. After extensive collaborative research in 2009, the Society of Automotive Engineers Cooperative Research Team (SAE CRP1234) concluded that R-1234yf is suitable for use in automotive applications. Further ignition risk assessment regarding R-1234yf usage in MAC systems was done by SAE CRP1234-4 in 2013.

Little experimental data have been reported in the crash reconstruction literature regarding high-speed sideswipe collisions. The Insurance Institute for Highway Safety (IIHS) conducted a series of high-speed, small overlap, vehicle-to-barrier and vehicle-to-vehicle crash tests for which the majority resulted in sideswipe collisions. A sideswipe collision is defined in this paper as a crash with non-zero, final relative tangential velocity over the vehicle-to-barrier or vehicle-to-vehicle contact surface; that is, sliding continues throughout the contact duration. Using analysis of video from 50 IIHS small overlap crash tests, each test was modeled using planar impact mechanics to determine which were classified as sideswipes and which were not. The test data were further evaluated to understand the nature of high-speed, small overlap, sideswipe collisions and establish appropriate parameter ranges that can aid in the process of accident reconstruction.

2013 and 2014 Ford Flex vehicles and airbag control modules with event data recorders (EDRs) were tested to determine the accuracy of speed and other data in the steady state condition, to evaluate time reporting delays under dynamic braking conditions, and to evaluate the accuracy of the stability control system data that the module records. This recorder is from the Autoliv RC6 family and this is the first known external research conducted on post 49CFR Part 563 Ford EDRs. The vehicle was instrumented with a VBox and a CAN data logger to compare external GPS based speeds to CAN data using the same synchronized time base. The vehicle was driven in steady state, hard braking, figure 8 and yaw conditions. The Airbag Control Module (ACM) was mounted onto a moving linear sled. The CAN bus data from driving was replayed as the sled created recordable events and the EDR data was compared to the reference instrumentation.