Browse Topic: Front wheel drive
Electric vehicles (EV) are much quieter than IC engine powered vehicles due to less mechanical components and absence of combustion. The lower cabin noise in electric vehicles make customers sensitive to even small noise disturbances in vehicle. Road boom noise is one of such major concerns to which the customers are sensitive in electric vehicles. The test vehicle is a front wheel driven compact SUV powered by electric motor. On normal plain road, noise levels are acceptable but when the vehicle has been driven on coarse road, the boom noise is perceived, and the levels are objectionable. Multi reference Transfer Path Analysis (MTPA) is conducted to identify the path through which maximum forces are entering the body. Based on MTPA, modifications are proposed on the suspension bushes and the noise levels were assessed. Operational Deflection Shape (ODS) analysis is conducted on entire vehicle components like suspension links, sub frame, floor, roof, and doors to identify the deflection pattern of the components at frequencies where the noise levels are higher. Based on full vehicle ODS, the critical components with maximum deflection at problematic frequency is identified and modifications are proposed to increase the dynamic stiffness of the components to reduce the noise levels. Effect of increase in stiffness of each critical component on cabin noise has been discussed. Alternative solutions like tuned mass dampers at the anti-nodal point are also explored and the changes required on the parameters of the damper to improve its performance is also discussed. With all modifications, the low frequency booming noise is reduced by ~ 4 dB (A) and the levels are acceptable. Design criteria that should be considered for vehicle components in early phase of development to avoid this concern are elaborated.
This paper focuses on reducing abnormal noise originating from suspension when driving on rough road at the speed of 20 kmph. The test vehicle is a front wheel driven monocoque SUV powered by four cylinder engine. Cabin noise levels are higher between 100 to 800 Hz when driven on rough road at 20 kmph. Vibration levels are measured on front and rear suspension components, front and rear subframe, subframe connections on body to identify the noise source locations. Since the noise levels are dominant only in certain rough patches at very narrow band of time, wavelet analysis is used for identification of frequency at which the problem exist. Based on wavelet analysis, it is identified that the vibration levels are dominant on front lower control arm (LCA). The dynamic stiffness of LCA bushes is reduced by ~ 40% to improve the isolator performance which reduced the noise levels by ~ 9 dB (A) at the problematic frequency band. Modal analysis is conducted on front suspension components to identify the modes and mode shapes and to correlate with underbody noise. Dynamic stiffness of the LCA is increased by ~ 2.5 times which reduced the noise levels by ~ 1.5 dB (A). Noise transfer function and point mobility measurements are conducted at the suspension connection point on body to identify the structurally weak path. Dynamic stiffness at the identified paths is improved by ~ 2 times which further reduced the noise levels to acceptable level. Criteria that should be considered during suspension design to avoid underbody noise are elaborated.
Globally all OEMs are moving towards electric vehicle to reduce emission and fuel cost. Customers expect highest level of refinement and sophistication in electric vehicle. At present, the customers are sensitive to high pitched tonal noise produced by electric powertrain which gives a lot of challenges to NVH engineers to arrive at a cost-effective solution in less span of time. Higher structure borne tonal noise is perceived in electric vehicle at the vehicle speeds of ~ 28 kmph, 45 kmph and 85 kmph. The test vehicle is front wheel drive compact SUV powered by motor in the front. The electric drive unit is connected to cradle and subframe with help of three mounts. Transfer path analysis (TPA) using blocked forces method is carried out to identify the exact forces of the electric drive unit entering the mounts. Powertrain mount is characterized by applying the predicted forces and dynamic stiffness at problematic frequency is measured. By reducing the dynamic stiffness of powertrain mounts, the noise levels are reduced by ~ 5 dB (A). The dynamic stiffness at powertrain mount connection point on cradle and subframe is increased by ~ 2 times which reduced noise by ~ 3 dB (A). With all the modifications, noise levels are considerably reduced by ~ 10 dB (A). NVH criteria which should be considered to avoid the structure borne tonal noise is also elaborated.
As part of the U.S. Environmental Protection Agency’s (EPA’s) continuing assessment of advanced light-duty automotive technologies in support of regulatory and compliance programs, a 2018 Toyota Camry front wheel drive eight-speed automatic transmission was benchmarked. The benchmarking data were used as inputs to EPA’s Advanced Light-duty Powertrain and Hybrid Analysis (ALPHA) vehicle simulation model to estimate GHG emissions from light-duty vehicles. ALPHA requires both detailed engine fuel consumption maps and transmission torque loss maps. EPA’s National Vehicle and Fuels Emissions Laboratory has developed a streamlined, cost-effective in-house method of transmission testing, capable of gathering a dataset sufficient to characterize transmissions within ALPHA. This testing methodology targets the range of transmission operation observed during vehicle testing over EPA’s city and highway drive cycles. With this method, the transmission is tested as a complete system, as opposed to disassembling the transmission components and testing each separately. This paper describes the benchmarking process used to gather transmission data and the test results obtained. A UB80E eight-speed automatic transmission from a 2018 Toyota Camry was installed in an engine dynamometer test cell along with a 4-cylinder 2.5L A25A-FKS engine from the same vehicle. The test dataset collected from the transmission includes gear efficiencies, torque converter slippage and K factors, spin losses, oil temperature and pressure, and CAN bus data. The transmission data collected with this benchmarking method were used as inputs to the ALPHA full vehicle simulation model. ALPHA simulation results were validated using vehicle chassis dynamometer test data from the 2018 Toyota Camry containing this engine and transmission. The ALPHA simulation also allowed the Toyota UB80E transmission to be compared to other benchmarked transmissions.
Maximising the recovered regenerative braking energy during the deceleration can significantly reduce the Electric Vehicle (EV) energy consumption and increase the range. Compared with the Front Wheel Drive (FWD) or Rear Wheel Drive (RWD) EV, an All Wheel Drive (AWD) EV with 2 electric machines (e-machines) has more control degree freedom when developing the regenerative braking control strategy. By implementing the regenerative braking at the front axle, rear axle, or at the front and rear axles simultaneously, the amount of recovered kinetic energy will be affected. Furthermore, the e-machines at the front and rear axle in the AWD EV can have different sizes or be the same. Therefore, the ratio between front and rear e-machine power rating should also be investigated to understand its effect on the amount of recovered energy during deceleration. This paper starts with the analysis of the vehicle braking behaviour compared over different driving cycles, and the comparison of two configurations of regenerative braking system, Category A and B. Then, the AWD EV is modelled, and its regenerative braking controller is developed using Ricardo in-house, proprietary simulation tools. The power rating of front and rear axle e-machines in this model is varied. The regenerative braking controller simulates Category A or B regenerative braking system with various control strategies (such as front axle or rear axle only regenerative braking, and all wheel regenerative braking). Simulation is done to investigate: 1) the difference in recovered energy by implementing the regenerative braking at different axles with Category A or B systems, and 2) how the ratio between the front and rear axle e-machine power rating affects the amount of recovered regenerative braking energy. This in turn affects the overall brake balance distribution and impacts upon vehicle stability. Finally, the simulation result is analysed and discussed.
This paper has the objective to present the study made on a front wheel drive passenger car with “3 Points Pendular Mounts System” to minimize the “Power Hop effect” (powertrain forced oscillation) and reduce the loads on Powertrain Mounts System. In this study, we used the Taguchi Method (Design of Experiments) to optimize the number of tests performed to evaluate the influence of powertrain mounts system design characteristics, as well as axle shafts stiffness, and tire/wheels assemblies size. The data acquisition work was all done in a physical hardware (vehicle) on test track used instrumented parts and load cells. Accelerometers were used in previous tests to get qualitative understanding of the behavior of all interface components (mounts and wheels hubs) during the power hop event. The study results showed the best components combination in order to reduce peak loads over Powertrain System and, as a consequence, reducing the potential of components breakage under extreme conditions. As learning, we got a better understanding of the dynamic behavior of the Powertrain System and its interfaces during power hop event by controlling the main interface components design characteristics of this system.
Introducing all-new front wheel drive hybrid system installed in the 2016 Toyota Prius. This system was completely re-designed to maximize the potential of THS-II (Toyota Hybrid System-II). This system was designed to be able to minimize the mechanical and electrical losses from the previous generation system, improve environmental performance, and also tried to reduce size and weight. We’d like to take this opportunity to introduce the new technology of each component, and hybrid system performance.
Driveshafts are composed of a transmission side joint, wheel side joint, and shaft which connect the two joints. The Rzeppa type constant velocity joint (CVJ) is usually selected as the wheel side joint of a drive shaft for front wheel drive automobiles. Due to recent needs of fuel efficiency and lighter weight for vehicles, it is necessary to reduce the joint size and improve the efficiency of a CVJ. In order to reduce the weight, solving tribology details for long life under high contact pressure is an important issue for developing a CVJ. It is difficult to understand the characteristics of a contact surface, such as relative slip velocity or spin behavior, because the outer race, inner race, cage, and balls, act complicatedly and exchange loads at many points. Meanwhile, after joint endurance tests, ball spalling marks at pole of the ball are sometimes observed. Simulating ball rotational behavior and solving the formation mechanism of such phenomena could contribute to joint durability and joint efficiency improvement. In this paper, ball rotational behavior, is simulated using a multibody dynamics approach including stick slip friction force model that is more accurate than previous. This model enables simulation of ball angular velocity. Through multipoint measuring and graphical analysis, the experiment proves an error of 15% in the simulation result.
In order to illustrate the constant development of the automatic transmission controls area, this paper describes how the garage shift calibration works in vehicles with transverse front wheel drive powertrains. A garage shift (GS) is the turbine speed transient commanded by the shift lever movement from Park to Drive or Reverse, from Neutral to Drive or Reverse, from Drive to Reverse, from Reverse to Drive, or from Drive or Reverse to Neutral [1]. A usual metric to verify the garage shift comfort is the data acquisition of the fore-aft acceleration on the seat track, but also the shift time should be considered, as well as the clutch energy and the repeatability of the shift feeling for different temperatures and engine idle speed levels. This paper demonstrates the transmission calibration strategies to determine a sensitive and a non-sensitive garage shift and its interactions with the engine calibration. Many factors may affect the garage shift calibration, like hardware controls (software and calibration), hydraulic system (fluid and actuators), clutches (design and friction material) step ratios, and non-transmission factors such as idle control and engine torque signal accuracy [2]. The vehicle’s sensitivity to torsional driveline inputs and the powertrain mounts configuration also influence the shift quality perception.
Tactile vibration during vehicle key on/off is one of the critical factors contributing to the customer perceived quality of the vehicle. Minimization of the powertrain transient vibration in operating conditions such as key on/off, tip in/out and engagement/disengagement of engine in hybrid vehicles must be addressed carefully in the vehicle refinement stage. Source of start/stop vibration depends on many factors like engine cranking, engine rpm at which the combustion process starts and rate of engine rpm rise etc. The transfer path consists of elastomeric mounts of powertrain and the part of vehicle structure from mounts to tactile response location. In this paper, the contribution of rigid body motion of powertrain of a front wheel drive vehicle during key on/off is analyzed in both frequency and time domain. The signal is analyzed in frequency domain by using fast fourier transform, short time fourier transform and wavelet analysis. The merits and demerits of each method are illustrated. Wavelet analysis is used to analyze the transient event in frequency domain with small time steps. Also, the operational deflection shape analysis is used to visualize the modal behavior of powertrain at each time step. From the results of wavelet analysis, the contribution of each rigid body mode of the powertrain to the tactile vibration is ascertained by conducting frequency domain transfer path analysis for each time step. Design modifications at the powertrain mount level are suggested to reduce the intensity of tactile vibration presuming that the best is achieved in the parameters related to engine cranking and combustion initiation. Also, time domain transfer path analysis is conducted to estimate the mount forces and path contributions in time domain. The mount forces are estimated using relative displacements and mount stiffness data in time domain. The path contribution in time domain are ascertained by calculating the spectral inverse of product of force spectrums with corresponding vibration transfer function to target locations. The results of path contribution analysis of frequency and time domain methods are compared. The time domain TPA analysis is very useful in understanding the nonlinear behavior of the powertrain mounts. The elastomeric mount design is optimized by considering the vibration comfort and the manufacturability.
This paper details the lightweighting efforts of the Ford Research & Advanced Transmission team as part of the Multi Material Lightweight Vehicle Project. The Multi Material Lightweight Vehicle (MMLV) developed by Magna International and Ford Motor Company is a result of a US Department of Energy project DE-EE0005574. The project demonstrates the lightweighting potential of a five passenger sedan, while maintaining vehicle performance and occupant safety. Prototype vehicles were manufactured and limited full vehicle testing was conducted. The Mach-I vehicle design, comprised of commercially available materials and production processes, achieved a 364kg (23.5%) full vehicle mass reduction, enabling the application of a 1.0-liter three cylinder engine resulting in a significant environmental benefits and fuel consumption reduction. Several Ford 6-speed Front Wheel Drive (FWD) automatic transmission components were considered for lightweighting action with three ultimately being chosen as the best candidates to prototype for the MMLV. The first part is the rear carrier clutch shell & sun gear assembly where the shell was converted from steel to aluminum. The second part is the pump support where the support material was changed from cast iron to cast aluminum and its associated fasteners converted from steel to aluminum. The third part is the cast control body where the body material was changed from cast aluminum to cast magnesium and the associated fasteners converter from steel to aluminum. The associated weight saves were 0.39 kg, 1.84 kg, and 1.3 kg respectively. The specifics of the lightweighting efforts will be presented for each part including the Finite Element Analysis (FEA) results, prototype part fabrication, and all component level test results.
Recent developments in front wheel drive based all-wheel drive (AWD) systems have focused on the disconnection of the secondary driveline to provide a high efficient 2-Wheel Drive (2WD) mode in order to minimize parasitic losses and increase fuel economy when all-wheel drive is not required. This present study compares a base on-demand all-wheel drive system without disconnect features to one with disconnect features in the rear drive module (RDM) and power transfer unit (PTU) to fully disconnect the secondary drive line. In order to further reduce parasitic losses the RDM also utilized an on-demand lubrication system. In conjunction with the active lubrication system, the oil sump level was reduced to assure all clutch housings and their associated plates were above the oil level at all times in order to minimize shear losses. Positive plate separation was also employed to assure ample clearance for free-running clutch plates. Essentially, the tested disconnect system represents the best possible configuration for the reduction in unwanted parasitic losses and their deleterious effects on fuel economy while enhancing the traction and vehicle dynamics performance benefits of independent side to side torque transfer control. Vehicle data shows that the disconnect system increased fuel economy in 2WD mode as compared to the base all-wheel drive system by 3.3% in the FTP75 drive schedule and 2.4% in the Highway Fuel Economy drive cycle. It should also be understood that these fuel economy savings potential represent a 100% 2WD mode duty cycle which is the maximum possible savings. Any AWD mode duty cycle either manual or automatically selected will deteriorate this potential savings under real world driving conditions. The vehicle manufacturer will need to manage this expectation at the consumer level. Fuel economy benefit of a disconnect system is the focus of this paper. Disconnect system response and AWD performance will not be covered.
One primary concern with applying an AWD system to a front wheel drive (FWD) vehicle architecture is the additional weight and drag associated with the AWD drivetrain components, resulting in an increase in fuel consumption compared to FWD-only models. Therefore, Honda recently developed a next-generation integrated AWD unit that reduces weight and drag loss, and increases the SH-AWD cornering performance while maintaining the performance requirements of the previous rear drive unit. These targets were achieved primarily through the application of hydraulically-actuated clutches and an increase in the “speed-increasing ratio”. This paper describes the development, system validation and future technology implications of this recent advancement.
General Motors has introduced a new front wheel drive seven speed dry dual clutch automatic transmission in 2014. The 250 Nm input torque rated gear box was designed and engineered for a global market in both front wheel drive and all-wheel drive configurations. The transmission has integrated start/stop capability enabled by the use of an electric motor driven pump and a pressurized accumulator. The architecture selected was chosen for optimization of packaging, fuel economy, mass, shift pleasability, and NVH. High mileage durability and world class drivability were the cornerstone deliverables during the engineering and design process Fuel efficiency is estimated to be 3% - 10% improvement over a conventional six speed automatic transmission. FWD variant wet mass of 78.1 kg was achieved through the rigorous engineering processes used to optimize the transmission system.
A regenerative braking system coordinated controller was developed for a front wheel drive BEV that also includes an ultra-capacitor storage system. This controller integrates the dual-motor regenerative braking with the hydraulic braking and stability control systems. The vehicle braking mode and the distribution of braking torque were determined according to the vehicle braking requirements, vehicle status and energy storage system (battery plus ultra-capacitor) state, and the stability control torque was provided according to the real-time vehicle stability condition. Simulation results show that, compared with a motor unilateral independence control strategy, the integrated coordinated controller improves the vehicle's stability when the vehicle corners while braking.
One of the key challenges in developing a vehicle for excellent vehicle dynamics is being able to achieve a high level of driving comfort without degrading the steering and handling performance. The part of driving comfort discussed in this paper are tactile vibrations up to f = 100 Hz. This paper describes how Multi-Body Dynamics (MBD) Computer Aided Engineering (CAE) tools are applied to optimize such vibrations in the early phase of the development process. The approach hereby presented combines system level testing with MBD for the study of ride comfort, similar to the way that system level kinematics and compliance testing is combined with MBD to support steering and handling investigations. Laboratory investigations have been executed to fully characterize a reference suspension with respect to frequency and amplitude behavior. The respective MBD models have been subsequently refined and validated versus physical laboratory measurements. Several examples for a front wheel drive passenger car will be given, which show how these models can be used to effectively support chassis development in early design phases. The first example demonstrates the effect of subframe isolation on ride comfort via analyses of the forces transmitted to the vehicle body. The second example demonstrates the sensitivity of bushing stiffness to impact harshness using a full vehicle model. The final example demonstrates how impact harshness can be optimized using different levels of compliance split between the subframe and suspension bushings.
This paper presents the implementation of a vehicle and powertrain model of the parallel hybrid electric vehicle which can be used for several purposes: as a model for estimating fuel consumption, as a model for estimating performance, and as a control model for the hybrid powertrain optimisation. The model is specified as a multi-domain physical model in MATLAB Simscape, which captures the key electrical, mechanical and thermal energy flows in the vehicles. By applying hand crafted boundary conditions, this model can be simulated either in the forwards or backwards direction, and it can easily be simplified as required to address specific control problems. Modelling in the forwards direction, the driver inputs are specified, and the vehicle response is the model output. In the backwards direction, the vehicle velocity as a function of time is the specified input, and the engine torque, and fuel consumption are the model outputs. The model represents a parallel hybrid vehicle, which is being developed in the TC48 project. The project goal is to produce a prototype of a plug-in parallel hybrid system which is integrated into existing front wheel drive powertrains with modest additional engineering, cost, volume, and mass requirements. This paper explains the motivation for the project, and presents examples of the simulations which were used to guide the design. The vehicle simulation models used to evaluate the layout options are described and discussed. Sensitivity analyses are presented which informed the design decisions. A novel use of the Simscape component of MATLAB/Simulink which allows the same model structure to be used for both forwards and backwards simulations is demonstrated. This method has the possibility for more general application, and a toolbox is being developed which assists the generation of mathematical models of this type.
This study is inspired by the calculations and validations required for front wheel drive (FWD)-halfshaft joint selection. To increase design efficiency with decreased response time; a tool is required to validate calculations of strength based on maximum impact torque and endurance life based on corresponding vehicle usage. The tool has been developed to cover both strength and endurance life calculations. It also includes a constant velocity joint (CVJ) size library in order to compare different cases and to be able to see opportunities between different sizes. Validation and correlation has been completed using road load data from actual vehicles and standard load cycle (SLC) rig test results. This study introduces a more efficient methodology that will help the user select a joint that is sized best for strength and cost. After the completion of the study, one can be assured that the joint selected is the proper size-for all kinds of FWD vehicles.
The customer demand for all wheel drive (AWD) vehicles is increasing over the period of time which also requires NVH performance on par with front wheel drive vehicles. AWD vehicles are equipped with power transfer unit, propeller shaft and independent rear differential assembly to achieve their functional requirement. The additional drive train components in AWD vehicles may amplify torsional fluctuations in the drive line. Hence achieving the NVH performance of AWD vehicles on par with FWD vehicles without any major change in the existing design is a major challenge. In this work, an AWD vehicle with severe body vibration and booming noise is studied. The operational measurements are taken throughout the drive train on all sub-systems from engine to the rear part of the body in the problematic operating condition. An operational deflection shape analysis is conducted to visualize the vibration behavior of the drive train. The result of analysis shows that the dynamic torsional fluctuations of the drive shaft and rear drive module (RDM) vibration are the major contributors for the high levels of vibration and noise. Powertrain torsional vibration measurements are also carried out with and without the part of the drive train that belongs to AWD. The reduction in vibration to certain extent is achieved by optimizing the stiffness of RDM mounts. The complete vibration and boom is eliminated by installing a tuned mass damper on RDM. The reduction of 4 dB (A) in interior noise and 5 dB in seat vibration are achieved with the effect of modifications.
This paper describes the interdisciplinary architecture selection study conducted by Embry-Riddle Aeronautical University (ERAU) to determine the Plug-in Hybrid Electric Vehicle (PHEV) architecture for its entry into EcoCAR2: Plugging In To The Future. This study includes a fuel, component, and architecture comparison to determine the most viable strategy to convert the competition vehicle, a 2013 Chevrolet Malibu, into a strong PHEV. Performance, energy, emissions, and consumer acceptability goals were established and summarized in the Vehicle Technical Specifications (VTS). Drive cycle simulations were used to create vehicle and component requirements for achieving the VTS targets. Three candidate architectures were then evaluated and compared for energy consumption, well to wheel (WTW) emissions, WTW petroleum energy usage, performance, packaging, and consumer acceptability. The architectures compared were a front wheel drive Series PHEV, a series-parallel through the road PHEV, and pre-transmission PHEV. Time-based performance simulations were used along with CAD for comparing space claims. A decision matrix summarizes the penalties for all three architectures and provides justification for the final decision. The architecture selection for Embry-Riddle's competition entry is a Series PHEV architecture. The series architecture had the least energy consumption, a favorable engine and interior space claim analysis, and maintained similar drivability and performance during both charge sustaining and charge depleting operation.
We have developed the new SPORT HYBRID SH-AWD system, a hybrid system that provides best in class fuel economy and drivability to exceed customer expectations. The powertrain has a V6 engine and comes with three drive types modes: front wheel drive powered by a 7-speed dual clutch transmission with one built-in motor, rear wheel drive powered by a twin motor unit with two built-in motors, and all-wheel drive powered by a combination of the two. The system can automatically select the most efficient drive method for the driver's needs and the road conditions. The two motors built into the twin motor unit are individually controlled and torque vectoring is used to create a torque difference between the left and right tires, improving the turning performance. The electric drive system was developed with consideration for layout feasibility and quietness. The two motors built into the twin motor unit and the inverter that drives the motors have been newly developed. By installing this system in the 2015 model year RLX, we achieved engine performance equivalent to a car with a V8 engine at 0-60 mph in 5.4sec and fuel economy equivalent to a car with an L4 engine at 30 mpg.
At the GF6 six-speed, front-wheel transmission line at General Motors Powertrain in Toledo, OH, a new front-wheel-drive transmission line for smaller, more fuel-efficient vehicles such as the Chevy Malibu and Chevy Cruze is currently ramping up to its initial goal of 2,200 units per day. A closer look reveals the method used to program this line, implement changeover, stage the workpiece flow, perform all machining and secondary operations, and assemble the finished transmissions.
Vicura is a developer of manual transmissions and dry dual clutch transmissions, as well as powertrain integration in a large number of front wheel drive and all wheel drive applications. The company’s engineers are responsible for a broad range of complex simulation and analysis testing including system, structure, and fluid mechanics. The team performs critical simulation and analysis to ascertain the strength, stiffness, thermal, and dynamic behaviors of all possible transmission assemblies and components (housings, shafts, gears, synchronizers, clutches, etc.).
The automotive industry continues to develop new powertrain technologies aimed at reducing overall vehicle level fuel consumption. The ongoing trends of “downsizing” and “down speeding” have led to the development of turbocharged engines with low displacement and high torque density. In order to meet the launch response requirements with these engines as well as fuel economy needs, transmissions with large ratio spreads will need to be developed. Due to the lack of torque amplification from the torque converter, the next generation of dual clutch transmissions (DCT) will need to have larger launch ratios and ratio spreads than currently available in production today. This paper discusses the development of a new family of DCT (called “xDCT”) for use in front wheel drive vehicles, aimed at meeting some of these challenges. The xDCT family features two innovative concepts, the idea of “gear generation” and “supported shifts”. A combination of these features results in the development of a highly compact and efficient family of DCTs. The paper will begin with a definition of the xDCT concept followed by a layout of the gear sets for 7 and 10 speed versions of this transmission. Simulation results are used to show the powershift capability as well as efficiency of the developed transmission concept. Finally, a 3D design study is utilized to demonstrate key features of the transmission concept that will result in a highly efficient and compact transmission with low mechanical complexity and full powershift capabilities.
As vehicle fuel economy continues to grow in importance, the ability to accurately measure the level of efficiency on all driveline components is required. A standardized test procedure enables manufacturers and suppliers to measure component losses consistently and provides data to make comparisons. In addition, the procedure offers a reliable process to assess enablers for efficiency improvements. Previous published studies have outlined the development of a comprehensive test procedure to measure transfer case speed-dependent parasitic losses at key speed, load, and environmental conditions. This paper will take the same basic approach for the Power Transfer Units (PTUs) used on Front Wheel Drive (FWD) based All Wheel Drive (AWD) vehicles. Factors included in the assessment include single and multi-stage PTUs, fluid levels, break-in process, and temperature effects. The resultant procedure is proposed as a new SAE J-standard (Surface Vehicle Recommended Practice) for release by the AWD Standards Committee. The overview presented in this paper includes definitions for the PTUs used in the study along with an overview of the test setup and instrumentation. This paper will outline some of the key investigations undertaken including the step size and duration, assessment of repeatability, as well as the influences of break-in and oil level. This project was undertaken and financially supported by the Transmission Working Group of the United States Council of Automotive Research (USCAR) for the SAE AWD Standards Committee.
This paper presents a forward-looking simulation (FLS) approach for the front wheel drive (FWD) General Motors Allison Hybrid System II (GM AHS-II). The supervisory control approach is based on a dynamic programming-informed Equivalent Cost Minimization Strategy (ECMS). The controller development uses backward-looking simulations (BLS), which execute quickly by neglecting component transients while assuming exact adherence to a specified drive cycle. Since ECMS sometimes prescribes control strategies with rapid component transients, its efficacy remains unknown until these transients are modeled. This is addressed by porting the ECMS controller to a forward-looking simulation where component transients are modeled in high fidelity. Techniques of implementing the ECMS controller and commanding the various power plants in the GM AHS-II for FLS are discussed. It is shown that FLS-derived component states agree well with states commanded using the BLS-derived robust control strategy, with any difference being accounted for by transient effects. Fuel economy results from FLS decrease, as to be expected, by approximately 3-7% from that of BLS due to the increase in propulsion energy required by component transients. Overall, these two points of good agreement demonstrate the viability of the DP-informed ECMS as an online-implementable supervisory control strategy.
The Wayne State University (WSU) EcoCAR2 student team designed, modeled, Model-In-the-Loop (MIL) tested, Software-In-the-Loop (SIL) simulation tested, and Hardware-In-the-Loop (HIL) simulation tested the team's conversion design for taking a 2013 Chevrolet Malibu and converting it into a Parallel-Through-The-Road (PTTR) plug-in hybrid. The 2013 Malibu is a conventional Front Wheel Drive (FWD) vehicle and the team's conversion design keeps the conventional FWD and adds a Rear Wheel Drive (RWD) powertrain consisting of an electric motor, a single speed reduction gearbox and a differential to drive the rear wheels -where none of these previously existed on the rear wheels. The RWD addition creates the PTTR hybrid powertrain architecture of two driven axles where the mechanical torque path connection between the two powertrains is through the road, rather than a mechanical torque path through gears, chains, or shafts. Finally, a battery pack and an on-board charger are added to complete the plug-in hybrid vehicle powertrain. This paper covers WSU's PTTR plant modeling and simulation, hybrid supervisory controller code development by the team during the first year of the three year competition. The PTTR hybrid powertrain vehicle architecture modeling is discussed in the plant model development section and the results section show the mixed results for SIL testing the physics of plant modeling for following a drive cycle trace and the resulting fuel consumption. The team wrote and MIL tested their hybrid supervisory control software, skipped SIL testing by going straight to HIL testing. The testing is discussed in the powertrain controls integration methods and results sections, with unsatisfactory results achieved during the HIL test demonstration at the final competition of the first year. Safety critical CAN loss detection is discussed as an example of code the team wrote for the hybrid supervisory controller for vehicle operational safety.
Hydrodynamic launch elements, from the Foettinger principle of the torque converter to the first series production HCC wet clutch, are becoming more relied on in the transmission world for their high power density, launch comfort, and vibrational isolation capability. In order to attain the ambitious fuel economy objectives of the future, engine vibrations have to be successfully isolated from the driveline at low engine speed ranges without the use of the hydrodynamic circuit. This is now all the more challenging as new combustion engines are producing higher torsional vibrations as a result of fewer cylinders, higher combustion pressures, cylinder deactivation, and lower critical speeds. This paper will describe the next generation of powertrain vibrational isolation, dampening via powersplit. Additionally, a next generation wet launch element, the Hydrodynamically Cooled Clutch will be discussed. A brief description of the current state of the art dampening technologies will be reviewed, highlighting the limitations of these solutions which pave the way for the new generations. The challenge with front wheel drive or hybrid layouts is to reduce the dimensions of the hydrodynamic and clutch systems, while sustaining high thermal capacity in order to improve vibrational isolation, and ensure protection against judder in a challenging packaging environment.
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