Design, Analysis, Simulation and Development of a Ravigneaux Gear-Train

With increased vehicular traffic density a trend has been observed where customers have started preferring automatic transmission in place of its manual version. This Automatic transmission not only shifts the gear automatically, with the help of sensors and actuators, but they are also tuned for better performance of the vehicle in terms of fuel efficiency and emission. This all comes at the cost of power consumption from the battery, increment in cost, weight and complexity. The main parts of an automatic transmission include Torque Convertor, Sensors, Actuators, Transmission Control Unit (TCU) with the epicyclic gear-train being the heart of it. In terms of use in the automotive, a system of epicyclic gear-train can provide only 2 gear ratios. Ravigneaux gear-train is the modified version of epicyclic gear-train where there are two set of Planet gears and Sun gears or Ring gears thereby capable of giving 4 gear ratios with a single system. This paper discusses the design analysis and optimization of Ravigneaux Gear-train. To compare it with Simpson gear-train, simulation of both the gear-trains are done on MATLAB(Simulink), keeping all other parameters of the vehicle like gear ratios, engine and vehicle parameters etc same and the results are compared. Acceleration for both the vehicles were same as the within 8 sec vehicle crossed the 100 kmph mark. Nature of Engine Power curve is also same for both of them. Finally, a table top model of Ravigneaux gear-train is manufactured and its performance is experimentally observed. The results are compared with percentage change in the velocity ratio and it was found that the results are within 10% of the calculated value.