Airplane Wing Landing Gear
This model shows a wing landing gear mechanism that can deploy and retract based on the input deploy signal. The mechanism consists of the main column that houses the wheel assembly and the locking mechanism that is used to lock the landing gear in the deployed position.
The mechanism is controlled by two low level controllers (one for deploying and retracting the main column and the other to lock and unlock the main column into position) and a master controller that coordinates them. The low level controllers are both simple PID controllers. The master controller turns on the deploy/retract controller to deploy the landing gear and when the main column is close enough to the deployed position, it disables the deploy/retract controller and uses the locking controller to lock the mechanism into position. The reverse happens during retraction.