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Technical Paper

Automated highway driving motion decision based on optimal control theory

2020-04-14
2020-01-0130
According to driving scenarios, intelligent vehicle is mainly applied on urban driving, highway driving and close zone driving, etc. As one of the most valuable developments, automated highway driving has great progress. This paper focuses on automated highway driving decision, and considering decision efficiency and feasibility, a hierarchical motion planning algorithm based on dynamic programming was proposed, and simultaneously, road coordinate transformation methods were developed to deal with complex road conditions. At first, all transportation user states are transformed into straight road coordinate to simplify modeling and planning, then a set of candidate paths with Bezier form was developed and with the help of obstacles motion prediction, the feasible target paths with collision-free were remains, and via comparing vehicle performance for feasible path, the optimal driving trajectory was generated.
Technical Paper

Adaptive sampling in the design space exploration of the automotive front end cooling flow

2020-04-14
2020-01-0149
Adaptive sampling in the design space exploration of the automotive front end cooling flow (Author)Venkata Krishna Mohan Chagarlamudi, FCA NA - mohan.chagarlamudi@fcagroup.com, (Co-Author) Arturo Guzman FCA NA - arturo.guzman@fcagroup.com, (Co-Author) Mark Doroudian FCA NA - mark.doroudian@fcagroup.com, (Co-Author) Dr. Malik KAYUPOV Dassault Systemes Simulia Corp - malik.kayupov@3ds.com One of the key inputs 1-D transient simulation takes is a detailed front end cooling flow map. These maps that are generated using a full vehicle 3D CFD model require expensive computational resources and time. This paper describes how an adaptive sampling of the design space allowed the reduction of computational efforts while keeping desired accuracy of the analysis. The idea of the method was to find a pattern of DOE sampling points for 3D CFD simulations that would allow a creation of an approximation model accurate enough to predict output parameter values in the entire design space of interest.
Technical Paper

Investigate partial cabin air re-circulation strategy to improve HVAC system's heating performance using 1D simulation

2020-04-14
2020-01-0159
In cold weather conditions, cabin heating performance is critical for retaining the thermal comfort. Heat is absorbed from the engine by circulating coolant through the engine water jacket and same will be rejected by the heater core. A variable speed blower is used to transfer heat from the heater core to the passenger compartment through floor ducts. The time taken to achieve comfortable cabin temperature determines the performance and capacity of heating ventilating and air conditioning (HVAC) system. In current automotive field, the engine options are provided to customers to meet their needs on the same vehicle platforms. Hence few engine variants cannot warm the cabin up to customer satisfaction. To improve the existing warm up performance of system, Positive thermal coefficient heater (PTC), electric coolant PTC heater, auxiliary pump etc. can be used which increases the overall cost of the vehicle. During warm-up, HVAC system operates in 100% fresh mode.
Technical Paper

Robust piston thermal analysis using a novel fast averaging technique

2020-04-14
2020-01-0166
The advancement of computational resources has enabled the increased utilization of predictive numerical analysis in the design and optimization of automotive components. One such component is the piston of a high-power IC engine which is cooled by oil jet. This study describes a simplified methodology to study the impinging oil jet aimed at cooling the piston. In this method, the piston is held stationary and the relative velocity between the piston and the jet is imposed at the exit of the oil squirter. This modeling approach reduces the simulation time significantly compared to the case where piston motion is simulated. The numerical approach uses a de-coupled simulation strategy to determine temperature distribution on the piston. The impinging oil jet is simulated using the volume of fluid method.
Technical Paper

Energy, Fuels, and Cost Analyses for the M1A2 Tank: A Weight Reduction Case Study

2020-04-14
2020-01-0173
Reducing the weight of the Abrams M1A2 tank has been studied by lightweighting three separate components: hull, suspension, and track, resulting in 5.1, 1.3, and 0.6 percent tank mass reductions, respectively. The impact of replacing an existing with a lightweight component on tank performance are evaluated in terms of three metrics: primary energy demand (PED), cost, and tank operational fuel consumption (FC). The life cycle phases included are: preproduction, material production, part fabrication, and tank operation. The metrics for each of the tank lightweight components are expressed as ratios: for example, the sum of PED for the four life cycle phases of the lightweight tank / the PED for the operational phase only of the base case (unmodified) tank. For Army defined duty cycles, a FC/mass elasticity of 0.55 was employed for estimating changes in tank FC upon mass reductions.
Technical Paper

A Study on Bolted Joint Finite Element Modeling for Vehicle Level Durability Analysis

2020-04-14
2020-01-0178
Bolted joints are widely used connections in automotive vehicle structures. However, it has been a challenge to accurately predict static and fatigue behavior of the sheet metal adjacent to the bearing area of bolted joints when linear analysis approach is used. This paper describes an experiment study on static and fatigue behavior of sheet metal adjacent to bearing area of bolted joints which are typically found on vehicles. These joints cover different bolt sizes (M6 to M14), and nut types (hex nut, hex flange nut, round nut, welded nut etc.). Different sheet metal material grades were selected which were, mild steel, high strength steel, dual phase steel and aluminum. The joints were subjected to coach-peel loading condition, because fastened joints have lowest strengths under this condition. 25 different joint combinations were included in this experimental study. For both static and fatigue tests, three samples were tested for each joint type and loading condition combination.
Technical Paper

Frame structure durability development methodology for various design phases

2020-04-14
2020-01-0196
It is a challenging task to find an optimal design concept for a truck frame structure given the complexity of loading conditions, vehicle configurations, packaging and other requirements. In addition, there is a great emphasis on light weight frame design to meet stringent emission standards. This paper provides a framework for fast and efficient development of a frame structure through various design phases, keeping durability in perspective while utilizing various weight reduction techniques. In this approach frame weight and stiffness are optimized to meet strength and durability performance requirements. Fast evaluation of different frame configurations during the concept phase (I) was made possible by using DFSS (Design For Six Sigma) based system synthesis techniques. This resulted in a very efficient frame ladder concept selection process.
Technical Paper

A Crack Detection Method for Self-Piercing Riveting Button Images through Machine Learning

2020-04-14
2020-01-0221
Self-piercing riveting (SPR) is a key joining technique for lightweight materials, and it has been widely used in the automobile manufacturing. Manual visual crack inspection of SPR joints could be time-consuming and might rely on high-level training for engineers to distinguish features subjectively. This paper presents a machine learning based crack detection method for SPR button images. Firstly, sub-images were cropped from the button images and preprocessed into three categories (cracks, edges, others) as training samples. Then, Artificial Neural Network (ANN) was chosen as the classification algorithm for sub-images. During the training of ANN, three pattern descriptors were proposed as feature extractors of sub-images respectively, and compared with validation samples. Lastly, a search algorithm was developed to extend the application of the learned model from sub-images to the original button images.
Technical Paper

Parameter Sensitivity Study of Self-piercing Rivet Insertion Process using Finite Element and Machine Learning Method

2020-04-14
2020-01-0219
Self-piercing rivets (SPR) are efficient and economical joining methods for lightweight automotive body structure manufacturing. Finite element method (FEM) is a potential effective way to assess joining process while some uncertain parameters can be employed in the simulation based on the prior knowledge, which could lead to significant mismatches between CAE predictions and physical tests. Thus, a sensitivity study on critical CAE parameters is important to guide the high-fidelity modeling of SPR insertion Process. In this paper, a 2-D symmetrical CAE model is constructed to simulate the insertion process of the SPR using LS-DYNA/explicit. Then, several surrogate models are trained using machine learning methods to build the linkage between selected inputs (e.g. material properties, interfacial frictions, clamping force) and outputs (cross-section dimensions).
Technical Paper

Real-Time Embedded Models for Simulation and Control of Clean and Fuel-Efficient Heavy-Duty Diesel Engines

2020-04-14
2020-01-0257
The ever increasing demand for fuel economy and stringent emission norms drives researchers to continuously innovate and improve engine modes to implement adaptive algorithms, where the engine states are continuously monitored and the control variables are manipulated to operate the engine at the most efficient regime. This paper presents a virtual engine developed by modeling a modern diesel engine and aftertreatment which can be used in real-time on a control unit to predict critical diesel engine variables such as fuel consumption and feed gas conditions including emissions, flow and temperature. A physics-based approach is followed in order to capture vital transient airpath and emission dynamics encountered during real driving condition. A minimal realization of the airpath model is coupled with a cycle averaged NOx emissions predictor to estimate transient feed gas NOx during steady state and transient conditions.
Technical Paper

A Comprehensive Approach to Evaluate Emission Reliability for Full Useful Life

2020-04-14
2020-01-0375
As legislations around the globe tighten vehicle emission regulations, it has become more and more difficult for vehicles to meet the regulatory requirements on emissions. If emission failures occur while vehicles are in use, the manufacturer may face recalls or penalties which will result in heavy financial losses to the manufacturer. In order to prevent emission failures in real usage, manufacturers should evaluate the emission reliability of all vehicle programs to ensure that 1) all vehicles will comply with regulatory emission requirements throughout the full useful life and no emission failures will occur in in-use verification testing, and 2) to identify any risks in emission reliability so that necessary remedy actions can be taken before production launch. This paper introduces a comprehensive approach to evaluate emission reliability. By this approach, a certain number of test vehicles from each vehicle family are selected to represent all vehicle configurations.
Technical Paper

Optimization Design and Analysis of Automobile Powertrain Mount System

2020-04-14
2020-01-0407
Automotive powertrain mounting system (PMS) plays a key role in the vibration isolation and the comfort improvement in vehicle. So far, most of powertrain is modeled as a rigid body in 6 Degrees of Freedom (DOF) in research. Few comprehensive and overall optimization are considered which addresses the excitation of the powertrain, the vibration and noise inside the body and the transmission path of vibration together. In this paper, a 13-DOF model including automotive powertrain mounting system and the full vehicle is developed in order to achieve comprehensive and overall optimization for PMS. The minimum of vertical vibration at seat track and the noise at driver ear on the right side, the maximum of system's vibration isolation rate and the energy decoupling rate, the reasonable allocation of system natural frequencies are considered as the optimization targets. Genetic algorithm is used to solve the multi-objective optimization problem.
Technical Paper

A dynamic trajectory planning for automatic vehicles based on improved discrete optimization method

2020-04-14
2020-01-0120
The dynamic trajectory planning problem for automatic vehicles in complex traffic scenarios is investigated in this paper. A hierarchical motion planning framework is developed to complete the complex planning task. An improved dangerous potential field in the curvilinear coordinate system is constructed to describe the collision risk of automatic vehicles accurately instead of the discrete Gaussian convolution algorithm. At the same time, the driving comfort is also considered in order to generate an optimal, smooth, collision-free and feasible path in dynamics. The optimal path can be mapped into the Cartesian coordinate system simply and conveniently. Furthermore, a velocity profile considering practical vehicle dynamics is also presented to improve the safety and the comfort in driving. The effectiveness of the proposed dynamic trajectory planning is verified by numerical simulation for several typical traffic scenarios.
Technical Paper

A Method Using FEA for the Evaluation of Tooling and Process Requirements to Meet Dimensional Objectives

2020-04-14
2020-01-0497
Dimensional Engineering concentrates effort in the early design phases to meet the dimensional build objectives in automotive production. Design optimization tools include tolerance stack up, datum optimization, datum coordination, dimensional control plans, and measurement plans. These tools are typically based on the assumption that parts are rigid and tooling dimensions are perfect. These assumptions are not necessarily true in automotive assemblies of compliant sheet metal parts on high volume assembly lines. To address this issue, FEA has been increasingly used to predict the behavior of imperfect and deformable parts in non-nominal tooling. This paper demonstrates an application of this approach. The complete analysis is divided into three phases. The first phase is a nominal design gravity analysis to validate the nominal design and tooling. In the second phase, the worst case scenarios are considered based on the previous programs to see their effects on assembly.
Technical Paper

Sensitivity Analysis of Coastdown Test Cycle Averaged Drag Coefficient for Several Functions of Drag Coefficient vs. Speed

2020-04-14
2020-01-0663
Aerodynamic testing for predicting fuel economy effects is typically done at EPA nominal ambient conditions, with nominal ‘2 Pass’ vehicle attitude. Essentially, the EPA standard coastdown is simulated in the wind tunnel. This predictive model is typically used well in advance of production manufactured vehicles, when prototype models are used for wind tunnel testing. However, in reality the actual loading of the vehicle due to manufacturing tolerances, changes in ride height with test loading, and the change in drag coefficient CD with speed, results in some variation in the vehicle CD during a coast down test. By testing the prototype vehicle on track with ride height sensors and at several ride height variations in the wind tunnel, a mathematical model can be used to predict the coast down speed effects on aerodynamic drag.
Technical Paper

Numerical investigations on the characterization of interactions between the tire-wake-vortices and 5-belt RRS turn table

2020-04-14
2020-01-0683
Approximately ninety percent of automotive wind tunnels in the world have incorporated or been built with a rolling road systems (RRS). However, very little research has been published in the literature on the interaction of the RRS and the vehicle. The goal of this paper is to characterize the flow structures and unsteady motion of the isolated wheel wake and its interaction with a 5-belt rolling road system (RRS) using numerical simulations. This paper is divided into three parts. In the first part, a Computational Fluid Dynamics (CFD) study is carried out on the Mears (2004) wheel using IDDES model where the CFD process to be used later is validated against the experimental data. In the second part, a simulation is carried out for a 5-belt RRS system and the validation is carried out using the von Karman formula for the boundary layer development over the belts.
Technical Paper

Robust assessment of automotive door structure by considering manufacturing variations

2020-04-14
2020-01-0910
The automotive door structure experiences various static and dynamic loading conditions going through an opening and closing operation. A typical swing door is attached to the body with two hinges and a check strap. These mechanisms carry the loads while the door is opened. Similarly, when closing the door, the latch/ striker mechanism along with the seal around the periphery of the door react all loads. Typically, computer aided engineering (CAE) simulations are performed considering a nominal manufacturing (or build) tolerance condition. This results in one loading scenario but it is found that build variations in the various mechanisms mentioned above can result in different loading scenarios which should be evaluated. This paper discusses various tolerances that should be accounted for in the CAE simulations to generate a robust door assembly.
Technical Paper

DAMPED TAILGATE SYSTEM DROP DYNAMICS and EVALUATION of STRUT FORCE for DURABILITY

2020-04-14
2020-01-0908
Abstract :- This paper describes a simplified CAE simulation method for the calculation of peak strut force in a damped tailgate system. Tailgate systems in the past included a torsion rod for lift assist, but did not include damping in the opening/drop direction. Newer tailgate systems include a strut to provide damping during drop and possibly lift assist. These tailgates may also be designed to experience a free fall for a few degrees after being unlatched and before the strut engages. When the latch is released, the tailgate accelerates as it falls freely and then encounters a rapidly increasing damping force as the strut engages. The deceleration of the gate depends upon the damping force, yet the damping force depends upon the deceleration of the tailgate, making a precise calculation of the damping force difficult.
Technical Paper

The Application of Simplified Loadpath Models (SLMs) to Improve Body Structure Knowledge and Efficiency

2020-04-14
2020-01-0912
Simplified Loadpath Models (SLMs) of the advanced body in white (BIW) design concept provide a highly flexible and rapid platform to explore body structure loadpath alternatives and performance:weight optimization. The SLM modelling process combines higher order Beam and Bush finite elements with coarsened Shell-meshed panels to represent the body structure. FCA US LLC has understood and validated the SLM build process for a BIW, and correlated key structural performance metrics to higher order, detailed Finite Element (FE) models. While the benefits of loadpath optimization through Beam element parameter variation is well-documented and applied extensively for these types of models, this paper covers another valuable benefit of the SLMs; to provide a better understanding of the sensitivities and influence of joint stiffnesses on key body structure attributes to promote more intelligent and efficient body structure joint designs.
Technical Paper

A Design and Optimization Method for Pedestrian Lower Extremity Injury Analysis with the aPLI Model

2020-04-14
2020-01-0929
As pedestrian protection tests and evaluations have been officially incorporated into new C-NCAP, more stringent requirements have been placed on pedestrian protection performance. In this study, in order to reduce the injury of the vehicle front end structure to the pedestrian's lower extremity during the collision, the advanced pedestrian legform impactor (aPLI) model was used in conjunction with the finite element vehicle model for collision simulation based on the new C-NCAP legform test evaluation regulation. This study selected the key components which have significant influences on the pedestrian's leg protection performance based on the CAE half-vehicle model, including front bumper, front-cover plate, upper impact pillar, impact beam and lower support plate, to form a simplified model and conducted parametric modeling based on it.
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