Transmission

This model shows a model of a car with a transmission. A transmission is generally used when an engine has a relatively narrow band over which the maximum power of the engine is available. In order to obtain high torque over a wider range of speeds, the engine is connected to a set of gears with different size ratios (the transmission). The efficiency function used for this model can be seen in this model.
A car with a transmission is a classic example of a hybrid system, since the continuous dynamics of the car depend on the current discrete state of the transmission. An automatic transmission can be viewed as a feedback control system which takes the current continuous and discrete states of the system, in addition to the throttle input from a driver, and generates a signal which is the current gear selection. Designing a "good" transmission that balances driver comfort (minimum jerkiness) with performance (maximum applied torque) over all parameters (engine speed, vehicle speed, and throttle) while incorporating practical details (implementation limitations, material wear) is a challenging problem. The block diagram for the model was constructed using the Ptolemy II schematic editor called Vergil.