Browse Topic: Rear wheel drive
Generally, in an electric sports utility vehicle with rear mounted powertrain the mass distribution is greater in the rear compared to front. This higher rear to front weight distribution results in oversteer behavior during high-speed cornering deteriorating vehicle handling & risking passenger safety. To compensate this inherent oversteer nature of such vehicles & produce understeer behavior, the steering rack is placed frontwards of the front wheel center for toe-out behavior due to lateral compliance during cornering. This compensation measure results in lower Ackermann percentage resulting in higher turning circle diameter deteriorating vehicle maneuverability. This paper proposes a design to obtain ideal understeer gradient with minimal turning circle diameter through utilization of split link technology with a McPherson Strut based suspension framework & frontwards placed steering rack. This suspension is utilized in our Mahindra Inglo platform. This paper elaborates on how through split links, variable knuckle length arm can be achieved which helps in achieving greater outer to inner wheel steering turn angle rate effectively improving Ackermann percentage & minimizing turning circle diameter. Apart from that the design mentioned herein allows greater manipulation of longitudinal & lateral compliance due to partial decoupling of both by split links. This overall improves longitudinal compliance resulting in better plushness during bumps improving ride without compromising handling characteristics of the vehicle. The suspension design is also optimized for wheel travel of 185mm, higher than benchmarks to provide enough wheel traction as well as comfort on hilly terrains & city roads of India.
Customers are expecting higher level of refinement in electric vehicle. Since the background noise is less in electric vehicle in comparison with ICE, it is challenging for NVH engineers to address even minor noise concerns without cost and mass addition. Higher boom noise is perceived in the test vehicle when driven on the coarse road at a speed of 50 kmph. The test vehicle is rear wheel driven vehicle powered by electric motor. Multi reference Transfer Path Analysis (TPA) is conducted on the vehicle to identify the path through which maximum forces are entering the body. Based on the findings from TPA, solutions like reduction in the dynamic stiffness of the suspension bushes are optimized which resulted in reduction of noise. To reduce the noise further, Operational Deflection Shape (ODS) analysis is conducted on the entire vehicle to identify the deflection shapes of all the suspension components and all the body panels like floor, roof, tailgate, dash panel, quarter panel and doors at the problematic frequency. Based on ODS, the components having higher deflections at the problematic frequency is identified. Modifications are proposed to improve the dynamic stiffness of the structure at the problematic frequency and the contribution of each modification for cabin noise reduction is discussed. Solutions like tuned mass dampers (TMD) on suspension components are explored and the critical parameter which should be considered to get maximum reduction in noise with TMD is also discussed. With all the modifications, the noise levels are reduced by 5 dB (A) at problematic frequency. NVH criteria which should be considered related to suspension system to avoid boom noise concern in electric vehicle is also discussed.
The automotive world has seen an increase in customer demands for vehicles having low noise and vibrations. One of the most important source of noise and vibrations associated with vehicles is the vibration of driveline systems. For commercial vehicles, the refinement of drivelines from NVH point of view is complex due to the cost and efficiency constraints. The typical rear wheel drive configuration of commercial vehicles mostly amplifies the torsional vibrations produced by engine which results into higher noise in the vehicle operating speed range. Theoretically, there are various options available for fine tuning the torsional vibration performance of the vehicle drive train. The mass moments of inertia and stiffness of the drivetrain components play significant role in torsional vibration damping, however, except minor changes to flywheel mass, it is hardly possible to change other components, subject to design limitations. Considering this, clutch disc torque twist characteristics plays an important role in mitigating the NVH concerns. The drive train represents a vibration system with several resonance frequencies which can be calculated using various simulation tools. With the help of simulation tools like 1D or multi body dynamics, optimized solution for the driveline fine tuning can be obtained which can reduce vehicle level noise. In this paper, 1D simulation model is used for the prediction of torsional vibration performance of the vehicle. Theoretical model of drivetrain component engine, clutch, gearbox etc. were built considering mass, inertia and stiffness values. Clutch damper parameters are optimized based on the simulation results and effect is validated by vehicle level noise and torsional vibration measurements.
1 Rear wheel drive vehicles have a long driveline using a propeller shaft with two universal joints. Consequently, in this design usage of universal joints within vehicle driveline is inevitable. However, the angularity of the driveshaft resulting from vertical oscillations of the rear axle causes many torsional and bending fluctuations of the driveline. Unfortunately, most of the previously published research work in this area assume the propeller inclination angle is constant under all operating conditions. As a matter of fact, this assumption is not accurate due to the vehicle body attitudes either in pitch or bounce motions. Where the vehicle vibration due to the suspension flexibility, either passive or active type, exists. Moreover, the relative motion between the body and the wheel make this virtualization is so far from the realty in real ground vehicles In this research work, the hydro-pneumatic limited bandwidth active suspension system with wheelbase preview control is designed to investigate how the active suspension design affects torsional and bending fluctuations of the driveline in comparison with passive suspension. Accordingly, a half car mathematical model with four degrees of freedom ride vibration coupled with the driveline torsional model is constructed and used for these investigations. The results are generated with two control strategies for the limited bandwidth active suspension, the first one emphasizes on ride comfort and the other emphasizes road holding parameters. On the other hand, two road excitations are used to test the model. The results showed that the virtualization of driveline angularity constant is not suitable for ground vehicle simulation and design. The suspension system type has a significant effect on torsional and bending fluctuations of the driveline. For the limited bandwidth, active suspension type with wheelbase preview control proposed in this work a significant improvement is achieved, in comparison with conventional passive suspension system, through reducing the interaction between the vehicle body vertical vibration and driveline torsional vibration.
Recently, electric-powered vehicle such as HV, PHV, EV and FCV has been highly demanded and getting attention due to the increase of environmental-consciousness. Also, environmental regulations are getting more and more strict in many countries and regions. Then, environmental friendly vehicle is needed to be spread more and more than ever. As it is found in “TOYOTA Environmental challenge 2050”, Toyota will rapidly increase the number of new car sales of electric-powered vehicle towards 2050. This paper covers the rear wheel drive Q710 electric drive transaxle for 2nd generation MIRAI FCV. Toyota developed the transaxle for FCV (rear mounted) and for EV (front mounted) simultaneously and achieved coexistence of vehicle mountability and commonization of majority of the parts. This paper describes the hardware feature and the detailed technology which was adopted to Q710. In the 2nd generation MIRAI, the transaxle is mounted under rear floor and contributed to the improvement of drivability by rear wheel drive. In addition, two air-cooled oil cooler are placed in parallel behind transaxle for motor cooling. Based on the adoption of world’s first “differential pressure wind guide oil cooler”, Toyota succeeded in motor cooling by the air-cooled oil cooler which is placed to rear.
As part of an electrified stable primed for the 2019 Los Angeles Auto Show (LAAS), Toyota will display its all-new Mirai fuel-cell electric vehicle (FCEV) and the upcoming plug-in hybrid version of its RAV4 compact SUV. The two 2021 models will further pad the Japanese company's already market-leading six hybrid offerings (12 if the premium Lexus brand is included). On top of previously announced plans for a “major battery electric vehicle (BEV) rollout,” Toyota also announced an extension of its hybrid battery warranties. The second-gen Mirai FCEV - unveiled as a “concept” at a recent media event but appearing in near-production form - will debut as a sleek, rear-wheel-drive (RWD), 4-door, 5-passenger sedan. Toyota says it's targeting a 30% increase in driving range compared to the first-gen Mirai, with the additional range achieved via an improved (and quieter) fuel-cell stack and increased hydrogen storage capacity. The current front-wheel drive (FWD), 4-pasenger Mirai launched in 2015, has an EPA-estimated driving range of 312 miles (502 km) and stores 122.4 L (32 gal) of hydrogen in two tanks.
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.
The increasing pressure on fuel economy has brought car manufacturers to implement solutions that improve vehicle efficiency, such as downsized engines, cylinder deactivation and advanced torque lock-up strategies. However, these solutions have a major drawback in terms of noise and vibration comfort. Downsized engines and lock-up strategies lead to the use of the engine at lower RPMs, and the reduced number of cylinders generates higher torque irregularities. Since the torque generated by the engine is transferred through flexible elements (clutch, torsional damper, gearbox, transmission, tire), these also impact the energy that is transferred to the vehicle body and perceived by the driver. This phenomenon leads to low frequency behavior, for instance booming noise and vibration. This paper presents a combined test and CAE modelling approach (1D/3D) to reverse engineer a vehicle equipped with a CPVA (centrifugal pendulum vibration absorber). The objectives were to fully understand and predict vehicle behavior with respect to the drivetrain torsional oscillations and low frequency booming noise and vibration. For this purpose, the procedure was divided in two phases: testing and modelling. The testing phase was used to get insight into the vehicle behavior, noise sources and noise transfer paths, using operational measurements. Moreover, dedicated component tests were carried out to obtain parameters to be used in the modelling phase, with the CPVA being the most complex and important component. The modelling phase used the test results as input to build a full vehicle model and to validate the booming noise results. The final model was fit for sensitivity studies and was also used to evaluate the performance of the CPVA, which is dedicated to the reduction of lock-up booming noise. Such an approach is a first step which can accelerate the SDPD (system driven product development) into a consolidated MBSE (model based system engineering) framework.
Globally the customers are demanding more powerful yet silent vehicles to enhance their daily commuting and goods transportation needs. The current trend in the design is to enhance the engine power without major change in the physical configurations of the engine systems. Increasing the power and torque of the powertrain will have an undesirable and adverse effect on NVH levels. In this research work, a light weight rear wheel drive vehicle was investigated from torsional vibration perspective. The vehicle is powered by a two cylinder engine with turbo charger. The power and torque of the vehicle was increased approximately two times with the help of turbocharger which resulted in increasing the powertrain torsional vibration. This increased vibration was further amplified through inevitable driveline resonances which causes severe vibration at the passenger seat location and steering. Also, the noise levels are above the comfortable zone. Operational deflection shapes analysis and operational torsional vibration analysis was carried out on the driveline to identify the deflection shape and root cause for severe vibration. A dynamic torsional absorber used in the driveline has reduced torsional vibration to a great extent. The vibration levels are reduced by ∼50%. Also, the outcome of subjective jury conducted is that the noise levels are at completely acceptable level. The design and balancing specifications of torsional damper along the drive shaft is further enhanced to reduce the vibration levels and to sustain the durability criteria considering the real world usage pattern of the vehicle. Alternate methods like enhancing the suspension isolation, body stiffening and translational tuned mass damper are also investigated and their effect is analyzed.
The EcoCAR3 team of California State University, Los Angeles designed a Parallel Post Transmission Plug-in Hybrid Electric Vehicle (PPT PHEV) that will maintain consumer acceptability in the areas of performance, utility and safety with the end-goal of reducing Well-to-Wheel Green House Gas (WTW GHG) emissions and Well-to-Wheel Petroleum Energy Use (WTW PEU). The team utilizes the 2016 Chevrolet Camaro platform with modifications such as 2.4L Ecotec engine, a 134 HP electric motor and a 12.6 KW/h battery pack. The vehicle is estimated to have a fuel economy of 58.7 miles per gallon gasoline equivalent (mpgge). This paper presents the vehicle’s two main operating modes, Electric Vehicle (EV) and Hybrid-Electric Vehicle (HEV) while performing Environmental Protection Agency (EPA) certified drive cycles: 505, HWFET, US06 City and US06 HWY. Also presented, is the optimized propulsion control strategy which lowers WTW GHG and WTW PEU achieved while extending energy storage system life, increasing the mpgge to 59.6 under the new modified control strategy defined as “I.W.U.” (Internal Combustion Engine and Warm Up) mode. The implementation of the new mode allows the full deployment of propulsion, achieving competition and team design targets. In addition, results from running EPA drive cycles with this optimized control strategy, including fault diagnostic section, are presented in this paper. All modeling and simulation data was obtained using Autonomie software from Argonne National Laboratories. This endeavor was made possible with the support from the United States Department of Energy, General Motors, Argonne National Laboratory, Mathworks and other sponsors.
Aisin AW (AW) and Toyota Motor Corporation (TMC) have developed a new RWD 6 speed automatic transmission, AWR6B45(AC60), suitable for SUV’s and LDT’s in the worldwide market, not only for North America but also for other countries including emerging nations. This 6 speed automatic transmission has achieved low cost, equivalent to AW and TMCs’ current 5 speed automatic transmission, while realizing improvement in both fuel economy and driving performance against current in-house 5-speed automatic transmissions, in addition to satisfying both toughness against various usage and light weight/compactness. They are accomplished by using a compact gear train structure, the latest efficiency improvement technologies, and a high-response, compact hydraulic control system. In addition, the compactness of this 6 speed automatic transmission enables it to replace current 4 speed and 5 speed automatic transmissions for various engine applications. This makes it possible to contribute toward Toyota's TNGA (Toyota New Global Architecture) by reducing the number of parts significantly.
This paper describes the capabilities of a new two-motor plug-in hybrid-electric propulsion system developed for rear wheel drive. The PHEV system comprises a 2.0L turbocharged 4-cylinder direct-injected gasoline engine with the new hybrid transmission [1], a new traction power inverter module, a liquid-cooled lithium-ion battery pack, and on-board battery charger and 12V power converter module. The capability and features of the system components are described, and component performance and vehicle data are reported. The resulting propulsion system provides an excellent combination of electric-only driving, acceleration, and fuel economy.
Meeting various customer(s) requirements with the given automotive product portfolio within the stipulated time period is a challenge. Design of product configuration matrix is an intelligent task and it requires information about vehicle performance for different configurations which helps in deciding the level of new development. Most often the situation arises, particularly in the field of NVH, to strike the right balance between engine power and structural parameters of the body. The sensitivity of engine power on the overall NVH behavior is the key information necessary to take major business decisions. In this paper, the effect of change in torsional fluctuation of the engine on the NVH behavior of the rear wheel drive vehicle is experimentally studied. The torsional fluctuation of the driveline is given as an input with the help of an electric motor to the existing test vehicle at its differential end and the current NVH levels are measured. A test rig is built to change the levels of torsional vibration input to the vehicle. The threshold level of torsional fluctuation for the given vehicle structure is obtained by taking into account the target values of tactile vibration and subjective perception. The results are very useful in deciding the acceptable level of change in engine power without carrying any structural change. Also, for a given power, the set of structural changes necessary in the body and suspension linkages to meet the NVH criteria can be studied. The procedure is also extended to an all-wheel drive vehicle with the help of a two wheel drive chassis dynamometer. Obtaining subjective perception of the vehicle NVH even before making the vehicle of target configuration is an inherent advantage of the proposed technique. A good correlation is achieved with the objective results and subjective perception.
In order to introduce Dana's Variglide Continuously Variable Planetary (CVP) technology to the mobility industry, Dana has produced demonstrator transmissions for use in a rear wheel drive C-class car and in a fork lift truck. The intention is to illustrate how the CVP can be combined with conventional transmission technology to produce either a continuously variable transmission with the ratio range comparable to that of the latest step ratio transmissions, or used in a simple IVT configuration for off-highway applications. The co-axial design of the CVP allows it to package well into current drivetrain solutions. The ratio control of the device is fast, precise, and stable and the CVP does not require high power consumption for clamping. Multiple power flow configurations of the CVP are shown to blend well with current conventional transmission technology as well as future hybrid configurations.
There has been a growing need in recent years to further improve vehicle fuel efficiency and reduce CO2 emissions. JATCO began mass production of a transmission for rear-wheel-drive (RWD) hybrid vehicle with Nissan in 2010, which was followed by the development of a front-wheel-drive (FWD) hybrid system (JATCO CVT8 HYBRID) for use on a midsize SUV in the U.S. market. While various types of hybrid systems have been proposed, the FWD system adopts a one-motor two-clutch parallel hybrid topology which is also used on the RWD hybrid. This high-efficiency system incorporates a clutch for decoupling the transmission of power between the engine and the motor. The hybrid system was substantially downsized from that used on the RWD vehicle in order to mount it on the FWD vehicle. This paper describes various seal technologies developed for housing the dry multi-plate clutch inside the motor, which was a key packaging technology for achieving the FWD hybrid system.
Automotive manufacturers are facing unprecedented cost challenges across globe. Market requirement has become very competitive with increased demand for higher performance and value engineering. This is encouraging automotive manufacturers to develop dampers with local suppliers, as there is a huge component cost advantage and also logistic cost savings. However, in emerging markets, supplier capability to develop the component for solving particular NVH problem of OEM is not matured as compared to developed market suppliers. The challenge for auto makers is to develop suppliers who can provide proper performance and durability, while at the same time providing lower cost components. This paper gives an overview of the challenges in the development process to develop a competitive torsional vibration damper for rear wheel drive vehicle to reduce boom noise and vibration. It is also designed to assist local suppliers with the capability to design and develop torsional vibration damper with low cost while meeting vehicle durability and performance requirements. This paper describes: a The methodology developed to tune the torsional vibration damper and optimize the performance for different driving condition; b A new design approach to meet the vehicle durability requirement; c A process to validate different designs for performance and durability requirements; and d A design for six sigma methodology applied in arriving at an optimized and robust solution.
The purpose of this paper is to provide an overview about rowing clunk on RWD MT transmissions for pick-up trucks through means of sound pressure, case acceleration and torsional vibration. Intended to identify the proper synchronizer design features necessary for its prevention. This paper will introduce the rowing clunk phenomena and present the driving maneuvers executed to reproduce the noise. The process of analysis and the phenomena composition based on simulations results, noise measurements and vibration analysis. The objective is to share with Product Engineering community an approach for Rowing Clunk Noise mitigation on Pick-up Trucks.
The paper analyzes the characteristics of driveline torsional vibration of a RWD vehicle and provides the control methods of transmission rattle noise caused by the system torsional resonances. A driveline dynamic model of the RWD vehicle is established by multi-body dynamic method. The natural frequencies and modal shapes are calculated for each gear position and torsional vibration responses are predicted by forced vibration analysis. The system sensitivity and DOE are analyzed based on the parameterized stiffness, inertia and damping. The 2nd and 3rd order modal results show that the transmission shaft possesses the maximum amplitudes and its corresponding modal frequencies vary with different gear position. The sensitivity analysis results show that the system torsional vibration is significantly reduced by reducing clutch stiffness, increasing propeller shaft stiffness, raising half shaft stiffness, increasing the input shaft inertia and increasing the clutch damping. The DOE analysis results show that the clutch stiffness, propeller shaft stiffness, and the inertia of axle pinion shaft and transmission input shaft play an important role in reducing torsional vibration of the transmission gear shafts. A clutch with small stiffness and large torsional angle is tested and the transmission gear rattle noise is greatly reduced. The analysis results show excellent consistency with the test results.
This paper involves the study of implementation of an active electronic differential using torque vectoring in an electric rear wheel drive vehicle. The proposed system works in a closed loop taking feedback in real time from sensors which provides inputs for steering angle, throttle position, angular velocity of wheels, yaw rate, yaw acceleration, longitudinal acceleration and lateral acceleration. The objective of this system is to i) increase the stability and the vehicle response to the driver while turning, and ii) use the traction available on the driven wheels more efficiently. The system involves applying a torque difference between the rear driven tires to create a moment about the centre of mass that causes yaw acceleration and aids in turning the car by increasing yaw rate. The effect of drag forces and the lateral forces on the tires have been included. An optimized desired moment is calculated which is applied via torque difference while turning. A Permanent Magnet DC (PMDC) motor model and a model for the motor controller in torque mode have been developed based on experimental response analysis on a jig setup. A detailed race car model for longitudinal vehicle dynamics is derived from forces acting on the car including the effect of losses due to drag forces, rolling resistance, transmission inefficiency and inertial losses. To validate the proposed system, various throttle profiles and steering inputs are simulated on the vehicle model during a turn. The results are compared to the case when vehicle is turning without using torque differential.
Items per page:
50
1 – 50 of 159