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Electrified Powertrains
Published in Patrick Hossay, Automotive Innovation, 2019
The technologies are not mutually exclusive, of course. A power-split configuration on one axle can be combined with a TTR electric traction drive on the other, as done in the Spyder. The Lexus RX 450 hybrid offers another impressive example. In order to achieve what Lexus calls, dynamic torque control all-wheel drive, the normally front-wheel-drive RX450 is fitted with an additional electric machine at the rear axle. Two motor generators are used at the front axle in a power-split architecture, with the additional traction at the rear coordinated electronically. A voltage boost to the normal battery pack helps ensure extra power is available when the front motor-generator (MG2) and rear motor-generator (MG1) combine with the combustion engine to deliver up to 308 total horsepower.
The effect of the front-to-rear wheel torque distribution on vehicle handling: An experimental assessment
Published in Maksym Spiryagin, Timothy Gordon, Colin Cole, Tim McSweeney, The Dynamics of Vehicles on Roads and Tracks, 2018
F. Bucchi, B. Lenzo, F. Frendo, W. De Nijs, A. Sorniotti
Also in more conventional vehicle layouts, depending on the differential typology and opera-ting condition, the longitudinal tire forces affect the cornering response, as discussed in (Frendo et al. 2006, Frendo et al. 2007). In particular, (Bucchi & Frendo 2016) proposed a detailed yaw moment analysis, assessing the influence of the individual yaw moment contributions, e.g., those related to the lateral tire forces and longitudinal tire forces, on the level of vehicle understeer and oversteer. Interestingly, they found significant differences among the cornering responses of the Front-Wheel-Drive, Rear-Wheel-Drive and All-Wheel-Drive architectures (respectively indicated as FWD, RWD and AWD in the remainder) implemented on the same vehicle plant. In particular, with reference to a skid pad maneuver, the RWD vehicle resulted more understeering than the FWD and AWD configurations, which is the opposite of the common belief (Osborn & Shim 2006). The reduced level of understeer of the FWD configuration is caused by the destabilizing yaw moment of the lateral component (in the vehicle reference system) of the front longitudinal tire forces in traction. These findings were only supported by multibody model simulations, while an experimental proof is missing in the literature, to the knowledge of the authors.
Feedback Properties of Vehicle Controls
Published in Guy H. Walker, Neville A. Stanton, Paul M. Salmon, Vehicle Feedback and Driver Situation Awareness, 2018
Guy H. Walker, Neville A. Stanton, Paul M. Salmon
Haldex-type four-wheel drive systems rely on increasing amounts of electronic control, including an electronically controlled clutch mechanism to divert drive torque to the front or rear of the vehicle. Many current four-wheel drive cars have their drive biased (sometimes quite strongly) to the front, with drive torque only meaningfully applied to the rear wheels under more extreme conditions. This is combined with selective wheel braking to provide a function similar to the more mechanically complex limited-slip differential. All-wheel drive, combined with advanced handling management, offers vehicle designers great scope for resolving some of the compromises inherent in two-wheel drive platforms. A shift to electric power makes the prospect of all-wheel drive even easier to contemplate, with small individual motors providing power to individual wheels, or electric power driving one axle and fossil-fuel power the other.
Multibody dynamics simulation of an all-wheel-drive motorcycle for handling and energy efficiency investigations
Published in Vehicle System Dynamics, 2018
In conditions of low traction and when high performance is required, there has been a trend towards the use of all-wheel-drive (AWD) in vehicles with four or more wheels, as shown in many high performance on-road and off-road vehicles. Not only that designers have been striving for control over exactly how much torque each of the wheels receives and in which situations. This is demonstrated through the use of locking and limited slip differentials and, more recently, electronically controlled differentials in the form of active torque distribution (ATD) [1]. These systems aim to improve tractive force when one or more wheels have low traction, and to improve handling, stability and safety, especially when the vehicle is approaching the limit of adhesion of its tyres. This trend has not been seen in motorcycles, due to the challenge of applying torque to the front wheel because of the steering system.