Model Realistic Clutch Pressure Signals

The most critical addition that you can make to clutch models for greater realism is to change the clutch pressure signals from step functions (0 to 1, or 1 to 0) to signals with a smooth rise and fall. This greater realism results in a more complex model. At any simulation time, it is critical for your model to determine transmission motion by locking exactly the correct number of clutches. If all clutches are unlocked, the transmission is in neutral. Changing the gear settings of a transmission while maintaining this requirement is one of the central problems of transmission design.

Such transmission and vehicle models as CR-CR Four-Speed Transmission and Vehicle with Four-Speed Transmission switch gear settings without placing their transmissions in neutral. Controlling an actual manual transmission requires moving the transmission out of gear and into neutral, picking a new gear setting, and then putting the transmission into the new gear.

In the CRCRFourSpeedTransmissionExample model, with manual transmission control, you can mimic these steps by turning on the Neutral Switch, changing the gear setting, then turning off slipping the Neutral Switch.

In a programmed transmission control model, you can filter clutch pressures with Transfer Fcn blocks, shaping the pressure signals from sharp steps to smooth rises or falls.

Automatic Transmission with a Dual Clutch