Automated Manual Transmission 17 System Operation (In the Absence Of Faults): Pressurisation of the Hydraulic Circuit: When the pressure is below the minimum operating threshold, pressurisation of the hydraulic circuit occurs in two different ways: When the driver's door is opened the system automatically pressurises the hydraulic circuit until the pressure value is such to allow, if requested, the subsequent vehicle start-up: therefore, when requested, the system must be ready to open the clutch and engage the neutral without waiting for the hydraulic circuit to be pressurised (WAKE-UP condition). With key on IGNITION ON: the system control unit is supplied (and will remain powered until the key is turned to OFF and the vehicle and engine speed is zero). Automatic Engagement of the Clutch Downhill With the Accelerator Pedal: Released: If the vehicle, with gear engaged, accelerator released and engine started picks up speed because it is going downhill, when a pre-set speed is reached, it automatically closes the clutch to provide the vehicle with engine braking. If the driver presses the accelerator pedal, the torque transmitted is once again controlled directly by the driver. This automatic engagement of the clutch is interrupted if the vehicle moves in the opposite direction to the engaged gear. Vehicle Slowdown In a slowdown situation, for example with gear and accelerator pedal released, the system automatically disengages the clutch to avoid the shutdown of the engine when these come close to the system's idling value. This disengagement takes place at an engine speed that depends on the level of deceleration and driver controls (brake pressed or otherwise). However, the transmission automatically shifts down if a gear higher than 2nd gear is engaged during deceleration. When the vehicle is stationary, 1st gear is automatically engaged. The clutch is opened only if the brake is pressed. When the brake is released, the clutch remains closed and the vehicle runs at idling speed. This function is only enabled for the 1st and 2nd gear. Turning Off the Engine and System: By turning the key to the STOP position the engine is turned off and the system retains any gear engaged. The system deactivates only after the three speeds are zero: engine, gearbox input, gearbox output and after having saved the functional and diagnosis data on the stable memory of the control unit (EEprom). It switches off after a maximum of around 10 seconds with the vehicle stationary and the engine switched off. Functional Interaction Logics with Other Systems: The system interacts with other systems according to the logics shown below. Interaction with Engine Management: When driving the two systems do not interact, because the system does not perform any work, therefore only information and signal exchange persists. During a gear change, the system must be "master" with respect to engine management, i.e. the gearbox control system must ask the engine (through the CAN network) what the engine torque should be (decrease while the clutch is open and increase when the gear change is complete and the clutch is
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