PLANETARY OR EpiCYcLIC TRAINs are commonly used in automatic shifting automotive transmissions as shown in Figure 9-44. At the left is a turbinelike fluid coupling between engine and transmission, called a torque converter. This device allows sufficient slip in the coupling fluid to let the engine idle with the transmission engaged and the vehicle’s wheels stopped. The engine-driven impeller blades, running in oil, transmit torque by pumping oil past a set of stationary stator blades*and against the turbine blades attached to the transmission input shaft. This is one input to the multi-DOF transmission that consists of several stages of epicyclic trains. Automatic transmissions can have any number of ratios. Automotive examples typically have from two to five forward speeds. Truck and bus automatic transmissions may have more.Three epicyclic gearsets can be seen near the center of the four-speed transmission in Figure 9-44. They are controlled by hydraulically operated multidisk clutches and brakes within the transmission that impart zero velocity