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Journal Article

Vehicle Stability Control through Optimized Coordination of Active Rear Steering and Differential Driving/Braking

2018-07-05
Abstract In this article, a hierarchical coordinated control algorithm for integrating active rear steering and driving/braking force distribution (ARS+D/BFD) was presented. The upper-level control was synthesized to generate the required rear steering angle and external yaw moment by using a sliding-mode controller. In the lower-level controller, a control allocation algorithm considering driving/braking actuators and tire forces constraints was designed to assign the desired yaw moment to the four wheels. To this end, an optimization problem including several equality and inequality constraints were defined and solved analytically. Finally, computer simulation results suggest that the proposed hierarchical control scheme was able to help to achieve substantial enhancements in handling performance and stability.
Journal Article

Vehicle Aerodynamic Optimization: On a Combination of Adjoint Method and Efficient Global Optimization Algorithm

2019-04-26
Abstract This article presents a workflow for aerodynamic optimization of vehicles that for the first time combines the adjoint method and the efficient global optimization (EGO) algorithm in order to take advantage of both the gradient-based and gradient-free methods for aerodynamic optimization problems. In the workflow, the adjoint method is first applied to locate the sensitive surface regions of the baseline vehicle with respect to the objective functions and define a proper design space with reasonable design variables. Then the EGO algorithm is applied to search for the optimal site in the design space based on the expected improvement (EI) function. Such workflow has been applied to minimize the aerodynamic drag for a mass-produced electric vehicle. With the help of STAR-CCM+ and its adjoint solver, sensitive surface regions with respect to the aerodynamic drag are first located on the vehicle.
Journal Article

Systematic CFD Parameter Approach to Improve Torque Converter Simulation

2019-04-08
Abstract A systematic parametrization approach was employed to simulate a torque converter operating over a wide range of speed ratios. Results of the simulation yielded torque converter impeller and turbine torques prediction errors below 11% when compared to manufacturer data. Further improvements in the computational fluids dynamic (CFD) model reduced such errors down to 3% for the impeller and 6% for the turbine torque predictions. Convergence was reached well under 300 iterations for the most optimal variable setting, but each speed ratio was let to run for 300 iterations. Solution time for the 300 iterations was 40 minutes per speed ratio. The systematic parametrization provides a very competitive procedure for torque converter simulation with reduced computational error and fast solution time.
Journal Article

Study of the Sliding Door Shaking Problem and Optimization Based on the Application of Euler’s Spiral

2018-10-03
Abstract This study focuses on the sudden shaking phenomenon of a sliding door passing through a corner. This phenomenon requires attention because shaking during movement can lead to a harsh operation feeling and a short service life. An experiment based on a test setup was conducted, and the sudden change in the acceleration of a sliding door panel was measured. Based on multi-body dynamics (MBD) analysis and a rigid-flexible coupled model of the sliding door system, the cause of the sudden shaking was determined to be the discontinuous curvature of the middle rail trajectory. A transition curve was proposed as the solution for the discontinuous curvature, and Euler’s spiral was applied in the redesign of the middle rail trajectory. Verified by simulations, the results exhibit considerable improvement in sliding door movement stability, with large reductions in the maximum center of mass (CM) acceleration and guide roller impact force.
Journal Article

Study of Temperature Distribution and Parametric Optimization during FSW of AA6082 Using Statistical Approaches

2019-02-01
Abstract In this article, Al-Mg-Si-Mn alloy (AA6082) is butt joined by employing friction stir welding (FSW). The mechanical and metallurgical properties of joints are analyzed by conducting tensile and microhardness testing, respectively. To measure the temperature at different locations, eight thermocouples (L-shaped k-type) are placed at equal distance from the centerline. Least square method attempts to calculate the temperature at the centerline of joints. The process parameters are also optimized using Taguchi’s five-level experimental design. The optimum process parameters are determined, employing ultimate tensile strength (UTS) as a response parameter. A statistical test “analysis of variance” is used to check the adequacy of the model. It has been observed that rotational speed and feed rate are the predominant factors for UTS and microhardness.
Journal Article

Structural Optimization of a Pickup Frame Combining Thickness, Shape and Feature Parameters for Lightweighting

2018-08-08
Abstract The methods for improving the torsion stiffness of a pickup chassis frame were discussed, including increasing the part thickness on frame, enlarging the cross section of rails, and adding bulkhead feature inside the rails. Sizing optimization was conducted to get the optimal thickness configuration for frame parts and meet the siffness requirement. The cross section of frame rails were parameterized and shape optimization was conduted to get the optimal rail cross sections for stiffness improvement. Additional bulkheads were added to the frame rails, and sizing optimization conducted to find the most effective bulkheads to add and their optimal gauge. A material efficiency ratio μ is used to evaluate the efficiency of a design change with respect to torsion stiffness. Among those torsion improvement methods, adding bulkhead feature gives the highest material efficiency ratio, but the stiffness improvement range is very limited.
Journal Article

Structural Optimization Techniques to Design Light Weight and Low Radiated Noise Components

2018-07-24
Abstract Structural optimization evolved as a preferred technique across industries to develop lightweight products. One of the widely studied topics in structural optimization is to develop methods that reduce the radiated noise from a structure, where responses like Equivalent Radiated Power (ERP) and natural frequencies used to indirectly address the noise levels. This article compares freeform optimization with topology optimization technique and investigates their effectiveness for reducing radiated noise and weight. To illustrate the same, Finite Element Method (FEM) and Boundary Element Method (BEM) analysis are performed on a sheet metal flat plate (panel) as an example and correlated the same with experimental data. Further, different optimization problem formulations have been explored on those examples and results have been compared.
Journal Article

Robust Design for Steering Mechanism Based on Preference Function

2018-03-01
Abstract In order to improve robustness of vehicle dynamic performance, a steering mechanism model is proposed with alignment parameters of front wheel based on preference function method. In the steering mechanism model controllable variables include the trapezoid connection length, the base angle of steering trapezoid, the kingpin inclination angle, caster, camber and uncontrollable variables include load and initial braking velocity. Optimization objective is some vehicle dynamic performance. In the preference function method the individual performance preference and preference aggregation in designing variable space and performance variable space are analyzed. The individual performance preference includes the controllable variable preference, noise factor preference and optimization objective preference. The aggregation function is developed by aggregating all the individual performance preferences.
Journal Article

Response of Austempering Heat Treatment on Microstructure and Mechanical Property in Different Zones of As-Welded Ductile Iron (DI)

2018-05-08
Abstract Sound ductile iron (DI) welded joints were performed using developed coated electrode and optimized welding parameters including post weld heat treatment (PWHT).Weldments consisting of weld metal, partially melted zone (PMZ), heat affected zone (HAZ) and base metal were austenitized at 900 °C for 2 hour and austempered at 300 °C and 350 °C for three different holding time (1.5 hour, 2 hour and 2.5 hour). In as-weld condition, microstructures of weld metal and PMZ show ledeburitic carbide and alloyed pearlite, but differ with their amount. Whereas microstructure of HAZ shows pearlite with some ledeburitic carbide and base metal shows only ferrite.
Journal Article

Residual Stresses and Plastic Deformation in Self-Pierce Riveting of Dissimilar Aluminum-to-Magnesium Alloys

2018-05-08
Abstract In this work, the complex relationship between deformation history and residual stresses in a magnesium-to-aluminum self-pierce riveted (SPR) joint is elucidated using numerical and experimental approaches. Non-linear finite element (FE) simulations incorporating strain rate and temperature effects were performed to model the deformation in the SPR process. In order to accurately capture the deformation, a stress triaxiality-based damage material model was employed to capture the sheet piercing from the rivet. Strong visual comparison between the physical cross-section of the SPR joint and the simulation was achieved. To aid in understanding of the role of deformation in the riveting process and to validate the modeling approach, several experimental measurements were conducted. To quantify the plastic deformation from the piercing of the rivet, micro hardness mapping was performed on a cross-section of the SPR joint.
Journal Article

Real-Time Optimal Control of Power Management in a Fuel Cell Hybrid Electric Vehicle: A Comparative Analysis

2018-03-08
Abstract Power split in Fuel Cell Hybrid Electric Vehicles (FCHEVs) has been controlled using different strategies ranging from rule-based to optimal control. Dynamic Programming (DP) and Model Predictive Control (MPC) are two common optimal control strategies used in optimization of the power split in FCHEVs with a trade-off between global optimality of the solution and online implementation of the controller. This is due to the fact that DP that offers the global optimal solution requires the pre-known knowledge of the driving condition for the whole drive cycle, which makes the real-time implementation of the strategy more challenging. In this paper, both control strategies are developed and tested on a FC/battery vehicle model, and the results are compared in terms of total energy consumption. In addition, the effects of the MPC prediction horizon length on the controller performance are studied.
Journal Article

Process Regulations and Mechanism of WEDM of Combustor Material

2019-06-07
Abstract This study discusses the experimental investigation on WEDM of combustor material (i.e., nimonic 263). Experimentation has been executed by varying pulse-on time (Ton), pulse-off time (Toff), peak current (Ip), and spark gap voltage (Sv). Material removal rate (MRR), surface roughness (SR), and wire wear rate (WWR) are employed as process performance characteristics. Experiments are designed as per the box-Behnken design technique. Parametric optimization has also been performed using response surface methodology. Besides this, field-emission scanning electron microscope (FE-SEM) and an optical microscope are utilized to characterize WEDMed and worn-out wire surfaces. It is observed that both surfaces contain micro-cracks, craters, spherical droplets, and a lump of debris. Furthermore, the mechanism of recast layer formation has been critically evaluated to apprehend a better understanding of the technique. The key features of the experimental procedure are also highlighted.
Journal Article

Parameter Sensitivity and Process Time Reduction for Friction Element Welding of 6061-T6 Aluminum to 1500 MPa Press-Hardened Steel

2018-12-14
Abstract Conventional fusion joining techniques pervasive in the automotive industry are unable to effectively join aluminum and steel. To solve this problem, a technique termed friction element welding (FEW) has been developed, which is able to join any nonferrous top sheet material to a base steel layer, independent of the base layer strength. FEW works on the same principles as friction welding, as a steel element is pushed and rotated against a nonferrous top sheet to create frictional energy which softens and flows the material around the fastener shaft and under the fastener head, exposing the steel below. The element then contacts the steel and bonds through traditional friction welding. FEW is a four-step process (penetration, cleaning, welding, compression), with two to four parameters (endload, spindle speed, displacement transition, time transition) controlling each step.
Journal Article

PSO-Fuzzy Gain Scheduling of PID Controllers for a Nonlinear Half-Vehicle Suspension System

2018-11-19
Abstract The present article addresses the gain scheduling of proportional-integral-differential (PID) controllers using fuzzy set theory coupled with a metaheuristic optimization technique to control the vehicle nonlinear suspension system. The nonlinearities of the vehicle suspension system are due to the asymmetric piecewise dampers, quadratic tire stiffness, and the cubical spring stiffness. Conventional PID controller suffers from the low performance subject to modeling nonlinearities, while fuzzy logic controller (FLC), as a universal approximator, has the capacity to deal with the nonlinear, stochastic, and complex models. However, finding the optimal Mamdani FLC rules is still a challenging task in addition to a proper architecture of the membership functions (MFs). As a remedy to this drawback, particle swarm optimization (PSO) technique is employed in this article to improve the efficiency of the FLC-based PID controllers.
Journal Article

Optimizing Cooling Fan Power Consumption for Improving Diesel Engine Fuel Efficiency Using CFD Technique

2019-06-11
Abstract Fan cooling system of an air-cooled diesel engine is optimized using 3D CFD numerical simulation approach. The main objective of this article is to increase engine fuel efficiency by reducing fan power consumption. It is achieved by optimizing airflow rates and flow distribution over the engine surfaces to keep the maximum temperature of engine oil and engine surfaces well within the lubrication and material limit, respectively, at the expense of lower fan power. Based on basic fan laws, a bigger fan consumes lesser power for the same airflow rate as compared to a smaller fan, provided both fans have similar efficiency. Flow analysis is also conducted with the engine head and block modeled as solid medium and fan cooling system as fluid domain. Reynolds-averaged Navier-Stokes turbulence (RANS) equations were solved to get the flow field inside the cooling system and on the engine liner fins. The Moving Reference Frame approach was used for simulating the rotation of a fan.
Journal Article

Optimization of WEDM Cutting Parameters on Surface Roughness of 2379 Steel Using Taguchi Method

2018-04-07
Abstract Surface roughness is one of the important aspects in producing quality die. Wire Electrical Discharge Machine (WEDM) is commonly used in tool and die fabrication, since the die material is usually difficult to cut using traditional metal removal processes. Selection of optimal WEDM cutting parameters is crucial to obtain quality die finish. In this study, 2379 steel which equivalent to SKD 11 is selected as the die material. Four main WEDM cutting parameters, namely, pulse duration (A), pulse interval (B), servo voltage (C), ignition pulse current (D), were experimentally evaluated for both main cut and multiple trim cuts using Taguchi Method. Taguchi’s L9 orthogonal array is employed for experimental design and analysis of variance (ANOVA) was used in recognizing levels of significance of WEDM cutting parameters.
Journal Article

Optimization Control for 4WIS Electric Vehicle Based on the Coincidence Degree of Wheel Steering Centers

2018-07-24
Abstract The steering centers of four wheels for passenger car do not coincide, which may result in tire wear and the unharmoniously movement of the vehicle. In this article, an optimization control method for Four Wheel Independent Steering (4WIS) electric vehicle based on the coincidence degree of steering centers is proposed, to improve the driving performance. The nonlinear vehicle model of the four-wheel independent steering vehicle is established, and the formula of the wheel steering center is derived. The coincidence degree of wheel steering centers is defined as the evaluation index, to describe and evaluate the performance of the coordination for wheels’ movement. Meanwhile, the structure design of 4WIS system and the establishment of Direct-Current (DC) steering motor model are carried out, and the Model Predictive Control (MPC) controller for steering actuator is designed.
Journal Article

Optimal Electric Vehicle Design Tool Using Genetic Algorithms

2018-04-18
Abstract The proposed approach present the development of a computer tool that allows, in the first phase, the modeling of the electric vehicle power chain. This phase is based on a library developed under the Matlab-Simulink simulation environment. This library contains all the components of the power chain; it offers the selection of the desired configuration of each component. In the second phase, the tool solves the autonomy optimization problem. This problem is resolved by a program based on genetic algorithms. This program permits to optimize the configuration parameters maximizing the vehicle autonomy of the chosen chain. This tool is based on a graphical interface developed under the Matlab simulation environment.
Journal Article

Numerical and Experimental Investigation of the Optimization of Vehicle Speed and Inter-Vehicle Distance in an Automated Highway Car Platoon to Minimize Fuel Consumption

2018-06-22
Abstract The development of the technology of automated highways promises the opportunity for the vehicles to travel safely at a closer distance concerning each other. As such, vehicles moving in the wake of others experience a reduction in fuel consumption. This article investigates the effect of longitudinal distance between two passenger cars on drag coefficients numerically and experimentally. For the numerical analysis, the fluid flow at car speeds of 70, 90 and 110 km/h were examined. The Artificial Intelligence coding was applied to train an Artificial Neural Network to extend the calculated data. The optimum values for the inter-vehicle distance and the vehicle speed to assure the least drag coefficient are obtained. To support the numerical results an instrument designed and built particularly to accurately measure the fuel consumption was installed on a midsize sedan car and some field tests were carried out.
Journal Article

Numerical Prediction of Various Failure Modes in Spotweld Steel Material

2018-05-11
Abstract Crash simulation is targeted mainly carried out by the collision regulations FMVSS simulation to identify problems in vehicle structures. A modern car structure consist of several thousand weld-type connections, and failure in these connections plays an important role for the crashworthiness of the vehicle. Therefore accurate modeling of these connections is important for the automotive industry in order to improve Vehicle collision characteristics. In pursuit of this key requirement, we introduced a proper methodology for the development detailed weld model to study structural response of the weld when the applied load range is beyond the yield strength. Three-dimensional finite element (FE) models of spot welded joints are developed using the LS-Dyna FE code. In this process the force estimation model of spot welds is explained. The results from this paper shows good agreement between the simulations and the tests.
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