3308522 - 3350E vehicle direction control system vdc
General characteristics
The V.D.C. system (Vehicle Dynamic Control System) controls the vehicle during dynamic manoeuvres on the road and intervenes in emergency conditions.In any type of grip conditions this system increases the safety margin for the vehicle in the case of sudden manoeuvres or initial losses of grip (passing through puddles, icy sections, etc.).Whilst the anti-lock braking system (ABS) maintains the stability of the vehicle during rapid deceleration and the traction control systems (ASR or TCS) work during rapid acceleration, the V.D.C. system has been designed to keep the vehicle stable in the case of sudden manoeuvres in order to improve the vehicle's road holding, especially over slippery surfaces.In effect the V.D.C. system reacts to both vehicle oversteer and understeer and is equipped to return it to a stable condition to allow the driver to maintain full control of the vehicle. |
PERFORMANCE
The V.D.C.:
- recognizes the wheels' longitudinal or lateral loss of grip;
- controls all the vehicle's driving conditions, from braking to acceleration to ensure the direction and stability of the geometry;
- assists the driver, even if they are not particularly experienced, to control critical situations within certain limits.
SYSTEM SPECIFICATIONS
Devices adopted
The V.D.C. system is managed by the ABS control unit with the restriction that only vehicles equipped with ABS/ASR can be fitted with this new function.The control unit processes the signals from the following sensors:
- steering angle sensor,
- side acceleration sensor and slewing sensor,
- motorized butterfly,
- wheel rpm sensor,
and uses special algorhythms in the software to obtain the values for dynamic control:
- sliding of the wheels,
- drifting of the axles,
- wheel geometry angles, etc.
In addition to the above mentioned sensors, the minimum interface requirements for the vehicle to fit the system are:
- high speed CAN line,
- power unit with specific brake pump,
- specific ABS unit and/or pre-pressurizing pump,
- instrument panel with special active type warning lights.
OPERATION
Operating principle
The basic idea behind the V.D.C. consists of comparing the nominal parameters (processed by the control unit on the basis of the speed of the 4 wheels, steering angle, slewing speed, lateral acceleration, braking torque and engine torque) with the actual parameters in a given driving situation.In effect, on the basis of the input parameters it is possible to calculate, using a very complex mathematical model, whether the vehicle is taking a bend within the grip limits or whether it is about to skid (oversteer/understeer).Controlling the dynamics of the vehicle in extreme conditions is certainly second nature for a professional driver, but can be complicated for a 'normal' driver who may find themselves in emergency conditions. The V.D.C. system intervenes in such cases, acting to restore driving conditions which are compatible with the current grip conditions.The V.D.C. system uses two sensors, one of which 'reads' the slewing speed, or the rotation around the vertical axis of the vehicle.The sensor sensor, on the other hand, detects lateral acceleration. On the basis of this data, the V.D.C. understands whether the vehicle is about to skid at the front or the back (oversteer/understeer).In order to make it possible to control these critical situations, the system is capable of varying the opning of the electronic butterfly to manage the engine power and decelerate each of the four wheels individually thereby producing a slewing moment which is opposed to the one causing the instability in relation to the normal trajectory.If the vehicle loses grip at the rear, this movement is recovered by deceleration aimed at the outer wheels thereby restoring the necessary side grip to the rear wheels.If the vehicle loses grip at the front, the system implements a reduction in power by shuttering the electronic butterfly and consequently the driving speed, restoring grip to the front.Button/warning light
When the key is turned to the ON position, the VDC warning light in the instrument panel should come on and go off after about 4 seconds.If the warning light does not go out, or remains on whilst driving, this indicates a failure in the system.If the warning light flashes during driving, this means that the VDC system has intervened.
| Usage and failure conditions | System state | ASR warning light on button | VDC warning light in panel | |
|---|---|---|---|---|
| Engine starting (key in ON position) | Warning lights check | On for ~ 3 secondi | On for ~ 4 secondi | |
| Driving in normal conditions | ASR on | ASR enabled VDC enabled | Off | Off |
| ASR off manually | ASR disabled VDC enabled | On | Off | |
| Driving in conditions which could lead to slipping | ASR on | ASR enabled VDC enabled | Off | Flashing |
| ASR off manually | ASR disabled VDC activated | On | Flashing | |
| ASR/VDC system failure | ASR and VDC disabled | Off | On | |