The purpose of this article is to reduce the adverse effects of temperature rise on the electrical connector, reduce the failure risk of electrical connector due to the mismatch of current-carrying capacity selection, and improve the service life of the electrical connector. This article takes a certain type of vehicle electric connector as the research object. An accurate contact pair model of the electrical connector is established by SOLIDWORKS software. The force and thermoelectric coupling simulation analysis of the 3D solid model with reasonable load and boundary conditions was carried out by ABAQUS software. The results show that the insertion force and positive force of the electrical connector terminal are in line with the values specified in the standard. When different currents are applied to terminals connecting wires with different cross-sectional areas, the maximum temperature rise of the terminal is always located at the contact position of the male and female terminals, and this maximum is recorded. Based on the simulation analysis, the relationship curve between current and temperature rise is plotted. Considering the safe use of wire and its maximum current-carrying capacity, the quantitative relationship between ambient temperature and terminal current-carrying capacity is obtained by a method. This method can be used in any automotive electrical connector.
The brake discs are subjected to thermal load due to sliding by the brake pad and fluctuating loads because of the braking load. This combined loading problem requires simulation using coupled thermo-mechanical analysis for design evaluation. This work presents a combined thermal and mechanical finite element analysis and evolutionary optimization-based novel approach for estimating the optimal design parameters of the ventilated brake disc. Five parameters controlling the design: Inboard plate thickness, outboard plate thickness, vane height, effective offset, and center hole radius were considered, and simulation runs were planned. 27 brake disc designs with design parameters as recommended by the Taguchi method (L27) were modeled using SOLIDWORKS, and the FEA simulation runs were carried out using ANSYS thermal & structural analysis tool. The fatigue life results were analyzed using a 3D surface plot for the effect of the design parameters on the response, contour plots for the determination of maximum response, and statistical regression analysis for model interpretation and predictive modeling. Finally, the two most accurate and widely used evolutionary optimization algorithms: genetic algorithm (GA) and particle swarm optimization (PSO) were applied to determine the optimal design parameters for the ventilated brake disc. The brake disc of design parameters predicted by GA and (PSO), gives 12.74% higher fatigue life compared to parametric analysis. These results have shown that the developed approach can be utilized effectively and reliably for solving, design ventilated brake disc problem in the industry.
This article presents the application of the Enhanced Sequence Diagram (ESD) for the analysis of the functionality of a system with shape-changing aspects in the context of its multiple operational modes, considering an active rear spoiler as a case study. The article provides new insights on the ESD support for model-based capture and articulation of functional requirements across multiple operation modes of the same system, with appropriate detail on attributes and metrics, and the alignment of these attributes and metrics in line with the concept of time through scope lines. The article also provides a comprehensive argument and discussion, exemplified based on the case study, for the support that the ESD provides for early systems functional and architecture analysis, within the context of a broader model-based Failure Mode Analysis methodology.
The mechanical efficiency of the current continuously variable transmission (CVT) suffers from high pump loss induced by a high-pressure system. A novel wedge mechanism is designed into the CVT clamp actuation system to generate the majority of clamp force mechanically. Therefore, the hydraulic system can operate at a low-pressure level most of the time, and the pump loss is greatly reduced to improve the CVT's mechanical efficiency. Through dynamic analysis and design optimization, 90% of clamp force is contributed by the wedge mechanism and the rest of the 10% is generated by a conventional hydraulic system. The optimal design is validated through dynamic modeling using Siemens Virtual.Lab software by simulating the wedge clamp force generation, ratio change dynamics, and system response under tip-in conditions. After that, we built prototype components that target 70% of the clamp force contributed by the wedge mechanism and tested them on a transmission dynamometer. The testing results validated the design with reduced hydraulic pressure, the continuous variable unit (CVU) has above 96% peak efficiency and good ratio change capability. It maintains a stable ratio under different vehicle dynamics conditions, such as engine fire torque pulse, pothole, and engine braking. Fuel economy (FE) evaluation is performed under two scenarios with the Federal Test Procedure (FTP) driving cycle. Assuming 70% of pump loss reduction, the composite FE can be improved by 3.4%. More aggressively, assuming 90% of pump loss reduction, the FE improvement can be 4.4%. However, the major challenge of this concept for automotive application is the reverse gear function because the wedge mechanism can only work unidirectionally. A further consideration is needed such as moving the planetary gearset downstream of the CVU so that the wedge does not need to work bidirectionally.
In this article performance of the innovative Crank-Lever Electromagnetic Damper (CLEMD) for an off-road vehicle suspension system is analyzed. To determine the characteristic behavior of the CLEMD, the damping force it provides on the suspension system is varied by changing the values of the damping coefficient in the simulations. Various parameters considered in the analyses include power regenerated, voltage, current, comfort, road-holding, etc. The behavior of all the parameters of the CLEMD is observed for an off-road vehicle by carrying out simulations on country roads since the off-road vehicles are subjected to higher road irregularities and hence provide an opportunity to regenerate a higher amount of power. A two-dimensional (2-D) model of a vehicle developed in SimMechanics is interfaced with a Simulink model of CLEMDs for the analyses. This device allows not only to recover energy while damping the relative motion between the car body and unsuspended masses but also to tune the damping coefficient to alter the response of the vehicle in terms of heave and pitch dynamics. The tuning of CLEMDs was changed to show the trade-of between the power regenerated, comfort, and road-holding. A cost function analysis is carried out to determine the optimum values of the damping coefficient. Also various characteristics including cyclical characteristics of the CLEMD are studied, which are useful for further developments in Electromagnetic Dampers (EMDs).
Gasoline particulate filters (GPFs) are important aftertreatment components that enable gasoline direct injection (GDI) engines to meet European Union (EU) 6 and China 6 particulate number emissions regulations for nonvolatile particles greater than 23 nm in diameter. GPFs are rapidly becoming an integral part of the modern GDI aftertreatment system. The Active Exhaust Tuning (EXTUN) Valve is a butterfly valve placed in the tailpipe of an exhaust system that can befelectronically positioned to control exhaust noise levels (decibels) under various vehicle operating conditions. This device is positioned downstream of the GPF, and variations in the tuning valve position can impact exhaust backpressures, making it difficult to monitor soot/ash accumulation or detect damage/removal of the GPF substrate. The purpose of this work is to present a unique example of subsystem control and diagnostic architecture for an exhaust system combining GPF and EXTUN. In particular, the On-Board Diagnostics (OBD) controls are required to detect a disconnected/plugged downstream hose when combining a differential pressure (dP) sensor and an electronically controlled EXTUN valve in an exhaust system containing a GPF. The regulatory implications related to failing to detect a disconnected/plugged downstream hose are also discussed. Validation data from the control strategy under different operating conditions is reviewed.
This article is motivated by observations of the wind tunnel measurement data acquired during benchmarking and program development for a variety of passenger vehicles over the years. In wind noise development, contribution analysis is a common practice to screen and identify the most significant sources and paths. In order to shed light on the whole picture of the contribution analysis, the work presented in this article falls into two categories. One is the analysis of underlying mechanisms for a better understanding of the phenomena observed in the contribution results. The other is the summarization of wind noise contributions obtained by wind tunnel testing for some representative subsystems, e.g., the contributions based on different reference states, the effect of grilles, underbody, acoustic glass, and auditory masking. A close look at the obtained numbers for each vehicle reveals that all these numbers have their intrinsic characteristics, and the same number may not tell the same story. The components with the same design, cost, and quality behave differently in vehicles with different wind noise levels. This work shows that contributions are generally reference-based and vehicle-dependent, and vary when the reference state is deviated even for the same vehicle. The same subsystem contributes more to a quiet vehicle than a mediocre vehicle, thereby a direct comparison of contributions among different vehicles is unfair and biased against quieter vehicles. As a first approximation, a quantitative estimation is derived to promote a qualitative understanding. It is used to facilitate a fair comparison of contributions, which are based on different reference states from either the same vehicle or different vehicles. It also implies that a vehicle with superior wind noise performance carries with it a much more stringent standard in subsystem design than an average vehicle even though their contribution targets are similar. The understanding of the work presented in this article would further benefit the interpretation of various contribution results, their comparison, and subsystem target setting.
Estimating the power demand of a steering system is one of the main tasks during steering system development in the concept phase of a vehicle development process. Most critical for typical axle kinematics are parking maneuvers with simultaneously high rack forces and velocities. Therefore, the focus of the article is a tire model for standstill, which can be parametrized without measurements, only having tire dimensions and conditions (inflation pressure and wheel load) as input. Combined with a double-track model, a vehicle model is developed, which is able to predict the rack force and is fully applicable during the concept phase. The article demonstrates quantitatively that the tie rod forces, and thereby especially the tire bore torque, cause the largest fraction of the power demand at the rack. For this reason, the prediction of the bore torque is investigated in detail, whereby basic approaches from the literature are analyzed and enhanced. Furthermore, an approach is derived for considering the influence of horizontal forces in the tire contact patch on the bore torque. The development of the tire model is supported by a tire data basis with approximately 900 measured tire configurations. Finally, two test vehicles are used to validate the vehicle model successfully.
It is widely understood that the thermal state of a light-duty vehicle at the beginning of a trip influences the vehicle performance throughout the drive cycle. Cold starts, or initial states with component temperatures near ambient conditions, are strongly correlated with reduced vehicle performance and energy efficiency and with increased emissions. Despite this understanding, there is little literature available that characterizes initial thermal states beyond empirical studies and simplified analyses of dwell times. We introduce a framework that considers vehicle activity patterns, including the previous drive event, duration of the previous dwell event, and relevant ambient conditions occurring during these events. Moreover, the framework allows for technologies to influence the prominence of cold starts and warm starts. An example application of the methodology using a powertrain model approach revealed the significance of all constituent factors: controlling for ambient conditions, the shortest dwell lengths corresponded to an average initial oil temperature of 70 degrees C versus 23 degrees C for the long dwell length simulations, and aggressive conditioning cycles corresponded to an average initial oil temperature of 51 degrees C versus only 35 degrees C for a short conditioning cycle. The coldest ambient conditions evaluated (-30 degrees C to -10 degrees C) produced a weighted initial oil temperature of 19 degrees C versus 57 degrees C for the warmest ambient conditions evaluated (30 degrees C to 50 degrees C). Finally, we introduce weighting factors that account for the real-world frequency of conditioning cycle and dwell length combinations. The procedure outlined may be useful for discovering real-world performance improvements associated with vehicle technologies, a topic of interest to both vehicle manufacturers and regulators.
The transient surface pressure over a full-scale, operational compact automotive vehicle-a Volkswagen Golf 7-exposed to transient crosswinds with relative yaw angles of beta = 22-45 degrees has been characterized. Experiments were performed at the BMW side-wind facility in Aschheim, Germany. Measurements of the incoming flow in front of the car were taken with eleven five-hole dynamic pressure probes, and separately, time-resolved surface pressure measurements at 188 locations were performed. Unsteady characteristics (not able to be identified in quasi-steady modelling) have been identified: the flow in separated regions on the vehicle's leeward side takes longer to develop than at the windward side, and spatially, the vehicle experiences local crosswind as it gradually enters the crosswind. The total effects of these localized unsteady pressure characteristics have also been predicted to affect the vehicle globally, with the evaluation of the transient forces and moments-through pressure integration-exhibiting unsteady characteristics of overshoots, undershoots, and temporal lag; relative to steady crosswind. These results provide new insight into both the characteristics and the causes of the unsteady crosswind response of a real, operational vehicle operating in real-world conditions. This insight can be used in the design of future vehicles to make them less sensitive to unsteady gusts. Further these results can be used to develop and validate numerical and reduced-scale experimental methods that can test and assess new vehicle geometry designs during the early stages of vehicle development.
During certain driving scenarios, low-speed engine vibrations get propagated to the driveline and affect the drivability of a vehicle. To reduce the impact of these vibrations, a locked torque converter lockup clutch (TCC) is allowed to temporarily slip to increase the damping in the driveline. However, the initial slow dynamics of the fluid path of the torque converter cause the vehicle to feel sluggish. In this article, we design a model predictive controller (MPC) that optimally controls the torque request from the actuator (i.e., engine or e-motor) and the lockup clutch capacity for reducing this sluggishness. The study is conducted for a light-duty vehicle and uses an experimentally validated, detailed full-order model (FOM) for developing and validating a computationally efficient, reduced-order driveline model (ROM). The ROM includes the nonlinear dynamics of the torque converter's hydraulic coupling, and the drivetrain response of the ROM is within 2.4% of the FOM's response. The designed controller makes use of an electronic control unit (ECU)-estimated reference turbine torque command, measured actuator, turbine, and wheel speed signals as inputs and provides actuator torque command and TCC capacity command as outputs. We validate the controller's performance using model-in-the-loop (MIL) and processor-in-the-loop (PIL) experiments. The results show the designed controller overcomes the torque lag at the propeller shaft by 83%. We also verify the robustness of the designed controller to various cases of torque converter's transient fluid dynamics and multiple clutch slip initiations. We observe that the controller provides the desired response of the drivetrain with a maximum error of 4.1% in the delivered propeller shaft torque when compared with the locked TCC response.
During vehicle braking, friction forces generated on the vehicle tires and the vehicle resisting aerodynamic forces play a critical role that impact the vehicle's longitudinal braking dynamics such as stopping distance and time. These forces are mainly the tires' braking and rolling resisting forces, vehicle lift, and drag forces. The vehicle aerodynamic forces cannot be neglected due to their impact on the vehicle's longitudinal dynamics, especially at high vehicle speeds. This article investigates the impact of the vehicle's rear spoiler on both vehicle aerodynamic forces and longitudinal dynamic, such as stopping distance and time. A computational fluid dynamics (CFD) model using ANSYS-Fluent (R) is employed to precisely estimate the vehicle's aerodynamic forces in the case of a vehicle without and with a rear spoiler. The two-dimensional (2D) CFD model resolves the airflow all around the vehicle and rear spoiler precisely and allows to compute the drag and lift forces exerted on the vehicle and the rear spoiler. A realistic vehicle braking longitudinal dynamic mathematical model is introduced. The model takes into consideration a realistic random uncertainty that normally exists in the tires' adhesion and rolling coefficients and at the same time takes the vehicle's aerodynamic forces into account. The proposed model is simulated using MATLAB/Simulink (R) with realistic vehicle parameters for the cases of the vehicle without and with the spoiler. The simulation results show the noticeable impact of the vehicle's rear spoiler on both vehicle stopping distance and time, especially at high vehicle speeds. They also prove the validity of the proposed model and highlight the potential benefits of equipping the vehicle with a rear spoiler in braking control system design.
The traditional side mirrors on an automobile could create a substantial part of drag in the total car aerodynamic design consideration. On some concept cars, digital side mirrors (DSM) have been installed with the aim to reduce the total drag; thus the optimization study of DSM configuration becomes an important task. In this study the benchmark DrivAer fastback model is employed for optimization work of DSM via computational fluid dynamics (CFD) software and simulated with a realistic moving ground and rotating wheel conditions. In order to validate the lift and drag coefficients with existing experimental data, the wheel rotation is implemented through three different kinds of rotating methods: Moving Wall (MW), Multiple Reference Frame (MRF), and Sliding Mesh (SM), while the SM method provides the most accurate results. For optimization work, a concept for the DSM configuration is created, and the objective is to achieve the best drag reduction via various installation positions using the surrogate method based on the Kriging model. The results show that, for the best-achieved side mirror location, a positive effect of drag reduction is observed from increasing the intensity of some specific vortices, and its wake region can be weaker than the original configuration.
Non-pneumatic tire has been widely used due to their advantages of no run-flat, no need of air maintenance, low rolling resistance, and improvement of passenger’s comfort due to its better shock absorption. It has variety of application in the military vehicle, earthmovers, lunar rover, stair climbing vehicles etc. Recently UPTIS (Unique Puncture-Proof Tire System) non pneumatic tire has been introduced for passenger vehicles. In this study three different design configuration Tweel, Honeycomb and newly developed UPTIS have been compared. Effect of Polyurethane (PU) material nonlinearity have also been introduced by applying 5 different nonlinear PU material property in the spokes. The combined analysis of the PU material nonlinearity and spoke design configuration on the overall tire stiffness and spoke damage prediction is analysed using 3-Dimensional FEM simulations performed in ANSYS 16.0. It has been observed that Mooney Rivlin 5-parameter model is best to capture all 5 studied PU material’s the nonlinearity. Effect of material nonlinearity on various spoke designs have been studied. The best combination of spoke design and the use of nonlinear material have been suggested in terms of riding comfort, tire stiffness and durability performance.
An effective damper is among the most important components of the suspension system. It ensures the right amount of damping force is acting on the suspension system to provide comfort to the passengers and proper road holding to tires. Unfortunately, the energy absorbed by the dampers from the suspension system gets wasted in the form of heat. In this article, it is proposed to use innovative electromagnetic damper (EMD) with a crank- lever mechanism to recover energy from the suspension system. The goal is to develop a lightweight design of EMD that can recover a high amount of power. For the design, an off-road vehicle is used since in off-road vehicles the amount of power wasted in the suspension system is high. Three different design approaches are used, which include single-stage gearbox type, two-stage gearbox type, and three-stage gearbox type of CLEMD. Out of them, the best design, i.e. three-stage gearbox type of CLEMD is selected because of minimum weight and inertia of the components. This article is focused on the design and analysis of the three-stage gearbox type of CLEMD. On the basis of the output of numerical simulations of vehicle model, specifications for crank- lever electromagnetic damper (CLEMD) are driven and design is carried out. Also, performance analyses of CLEMD are carried out by interfacing model of CLEMD with the model of a vehicle. The advantage of CLEMD is it can act as an actuator to provide active force in an active suspension system.
The ability to efficiently and accurately predict the thermal environment of vehicles is becoming increasingly important. Currently, in the design stage of an automobile, full-vehicle computational fluid dynamics (CFD) simulations are typically used to predict rear fascia temperatures. The plastic fascia can be damaged if excessively high temperatures are encountered, so this prediction is important. As the simulations are expensive, only what is intended to be a worst-case scenario is assessed. This does not allow for the best position of the exhaust to be determined, and it is also possible that the actual worst case is missed during the early design phase, requiring costly latestage design changes. In this article, the dependence of the maximum fascia temperature on geometric (positioning of the exhaust) and nongeometric (vehicle operating condition) parameters is systematically investigated using CFD. A compact sport utility vehicle (C-SUV) is used for the investigation. The key outcomes are ( 1) The location and temperature of the hot spot on the fascia depends on whether there is significant impingement of the exhaust jet(s) or not; (2) the highest fascia temperature will occur at zero or near-zero vehicle speeds with a high engine load; and (3) for each of the four parameters which define the exhaust geometry, the best value is found for keeping the fascia temperature as low as possible. A single simulation of the worst load case can be used to find the absolute maximum temperature of the fascia, and the impact of the exhaust position can be used to guide the design changes if the initial design yields an unacceptably high fascia temperature.
Centrifugal Pendulum Vibration Absorbers (CPVA) are used to reduce the torsional fluctuation of rotating shafts at a certain vibration order. The concept can also be used to reduce the axial or longitudinal vibration of rotating shafts at the desired order. The axial vibration of driveshafts mainly at combustion order, i.e., 2x rpm for four-cylinder engines, is the reason for the generation of a high level of suspension forces and eventually increased levels of noise and vibration inside the passenger compartment of rear-wheel-drive vehicles. The axial vibration of a shaft at multiple orders (1x rpm and 2x rpm) also increases at higher levels of unavoidable parallel or angular misalignment. The vibration at multiple orders needs to be reduced in the vehicle driveline system in rear-wheel-drive vehicles to minimize the noise and vibration and provide enhanced comfort. A single pendulum vibration absorber can attenuate only one vibration order of the rotating shaft, and multiple absorbers are required to reduce the vibration at different orders. The design strategy to reduce the first- and second-order axial vibration, by using circular path pendulum absorbers, is explained in this work. The generated torsional vibration at the second order due to first-order oscillations of the pendulum is counteracted by the design of an additional CPVA. Torsional springs are used at the pivot joints of all pendulum absorbers to counteract the excessive oscillations due to braking and gravitational effects at low speeds. The additional advantage of introducing the springs and their influence on the natural frequencies is analyzed. The second-order equations of motion of the absorbers are solved analytically using the method of multiple timescales with a two-term approximation. The stability characteristics of the solutions are analyzed at the excitation frequencies and different dynamic axial force levels. Analytical results are compared with numerical simulation of a complete set of nonlinear equations. The performance of centrifugal pendulum-type axial vibration absorber (CPAVA) in reducing the predominant second-order longitudinal vibration at differential and passenger compartment is experimentally demonstrated by using CPAVA at the differential flange of a rear-wheel-drive vehicle. The proposed methodology helps in designing the CPAVAs for attenuating the axial vibration at multiple higher orders of rotating shafts.
Thermal comfort and good air distribution are the most important factors to create a good comfortable and healthy environment for passengers in a bus cabin. The investigation is carried out by computational fluid dynamics (CFD) with ANSYS FLUENT 17.2 and the solver is FLUENT. In this article, three studies are investigated, including eight cases, each study investigated has a specific effect on the airflow pattern and thermal comfort inside the bus cabin. The first study investigates the effect of the angle of the adjustable air-conditioning (A/C) outlet of the heating, ventilation, and air conditioning (HVAC) system, through a comparison between four angle cases 0 degrees, 15 degrees, 30 degrees, 45 degrees, and the second study investigates the optimum case conditions from the first study with two variable velocities. The third study investigates the effect of another design where the locations of the A/C outlets of the HVAC system of bus cabin are above every passenger's head without any adjustable angle and the effect of a rectangular-shaped instead of a circular-shaped outlet with the same outlet area and position. A comparison is carried out between all the cases and estimated the optimum design that has good thermal comfort for the passenger.
