Government institutions, automotive manufacturers and the research community have mounted pressure on the search for cleaner and more efficient alternatives to pure internal combustion engine powered vehicles. This is as a result of the growing concerns of excess carbon emissions, which have caused an almost irreversible environmental degradation. However, electric vehicles, powered by an internal combustion engine and one electric motor or more, have been globally accepted as promising candidates for short to medium term solutions reference to their noticeable enhanced performance along with lower emissions at competitive costs.
Hybridization of transmission has been a trend where motors have been incorporated into the transmission. In fact, all major types of transmissions, for examples manual transmission, automated manual transmission, and automatic transmission, have hybridized versions. Automated manual transmission has an upside in relation to cost, torque capacity, and overall efficiency. Unfortunately, automated manual transmission is not ideal for passenger vehicles reference to its undesirable drivability. Torque gap and subsequent surging clutch torque normally appear during 3 gear shifts. This duration lasts for about a second, but the severe acceleration change injures drivability severely. It is therefore important to find a method to mitigate this problem.
Hybridized automatic manual transmission has offered alternative methods of filling torque gap by developing independent and semi-independent torque paths from the motor during gearshift. Pre-transmission and post-transmission hybrids are the two ways a motor can be combined with an automatic manual transmission.
Guang Wu and Zuomin Dong from the University of Victoria in Canada proposed a new form of hybrid powertrain system based hybridized automated manual transmission. They implemented the concept of torque-gap-filler, and the proposed hybrid powertrain type had the potential to overcome the issues of torque gap during gearshift. Their research work is published in peer-reviewed journal, Mechanical Systems and Signal Processing.
The proposed hybridized automated manual transmission-based power train was based on the idea of pre- and post-transmission parallel hybrid arrangements. The system integrated an 8-speed parallel shaft gearbox, a motor, and a main clutch into one unit. The gearbox based on manual gearbox had three connection ports, which were connected to the engine through the main clutch, final drive, and motor.
Wu and Dong built an analytical tool, mutli-body model of vehicle fitted with the hybridized automated manual transmission in order to evaluate powertrain dynamics at varying transients and steady modes. In addition, the authors built a Simulink-SimDriveline hybrid vehicle model with new transmission and driveline, based on powertrain system component models obtained from AUTONOME simulation tool. They then built a control strategy in a bid to harmonically coordinate the various powertrain components in order to establish torque-gap-filler function. A vehicle launch simulation test was finally finished under 30% of accelerator pedal position in a move to exhibit details in the course of gearshift.
The simulation results of the study indicated that the proposed hybridized automated manual transmission could eliminate majority of torque gaps that have crippled conventional automated manual transmission. Therefore, the system posted improved performance and drivability. This study demonstrates a new form of transmission featuring high torque capacity, desirable drivability, and high efficiency.
Guang Wu and Zuomin Dong. Design, analysis and modeling of a novel hybrid powertrain system based on hybridized automated manual transmission. Mechanical Systems and Signal Processing, volume 93 (2017), pages 688–705.
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