Porsche Dynamic Chassis Control (PDCC)
Porsche Dynamic Chassis Control (PDCC)
The chassis control system Porsche Dynamic Chassis Control (PDCC), which is available on request for all new Cayenne models, can further optimize the already excellent driving dynamics.
PDCC is only available for vehicles with air suspension and PASM. The silver colored chassis control switches on the center console and the logo "PDCC" below the chassis control switches in the interior indicate that a vehicle has PDCC.
PDCC is an active chassis control system. Targeted intervention using active anti-roll bars optimizes the driving characteristics of the vehicle by reducing its tendency to roll.
The actual benefits of the system for customers are apparent in the following areas:
- Reduced lateral inclination (vehicle lean) during cornering.
- Greater agility.
- Improved driving performance.
- Increased driving comfort.
- Better off-road functionality.
Operating Principle
The entire system involves chassis components used to actively stabilize the vehicle. To create a definable force between body and wheel using additional energy in order to improve driving dynamics, driving comfort and safety.
Principle for creating definable forces between body and wheel using active roll stabilization.
During cornering, a rolling torque is build up via the vehicle rolling axis due to the centrifugal force affecting the center of gravity. This force causes the vehicle body to tilt towards the outer wheel during cornering so the vehicle can quickly reach its driving dynamic limits. The use of anti-roll bars is designed to counteract body tilt and the accompanying wheel load difference. The wheel at the outside of the corner is compressed during cornering, while the wheel at the inside of the corner rebounds. This causes the back of the anti-roll bar to turn (twist). The forces occurring in this way in the anti-roll bar bearing points produce a torque that counteracts the body tilt and distributes the load better on both wheels of an axle.
PDCC is an active roll stabilization system, which records the vehicle's lateral inclination during cornering right from the start and reduces this considerably. This is done using active anti-roll bars on the front and rear axle, which ensure stabilization torques on both axles.
This means that the active anti-roll bars build up specific forces to counteract the lateral inclination of the vehicle, depending on the steering lock and lateral acceleration. PDCC reduces the vehicle's lateral inclination by up to 2.5° compared with a vehicle without PDCC. This improves performance due to improved wheel/road contact.
At the same time, PDCC also records uneven road surfaces (bumps) and can compensate for these by evaluating sensor data from the chassis and speed. This significantly improves driving comfort on various types of road surfaces.
The sensor data is evaluated continuously and appropriate control operations are initiated over the vehicle's entire speed range in order to guarantee the horizontal positioning of the vehicle at all times. One sided destabilizing impulses caused by long undulations in the road surface (so-called copying of rolling motion) can be significantly reduced.
PDCC also offers additional driver benefits for off-road driving. Active anti-roll bar control in conjunction with an integrated surface detection system reduces body movements considerably, thereby ensuring significantly improved comfort. The best possible traction on various road surfaces is particularly important for off-road driving. When the driver activates Low Range mode using the rocker switch on the center console, PDCC switches to off-road mode. The swivel motors are enabled in this mode so that the vane controllers in the housing can turn freely and the anti-roll bar halves are decoupled. This results in maximum axle articulation. To prevent instability at higher speeds and during dynamic maneuvers in Low Range mode, the control system is activated again depending on vehicle speed.
Design/Components
PDCC includes a two-piece anti-roll bar with a hydraulic swivel motor, a high pressure oil pump with lines and power distributor, valve blocks for activating the swivel motors and a control unit for each axle.
Anti-roll Bar With Swivel Motor
The core elements of the system are the active anti-roll bars with hydraulic swivel motors, which are integrated on front and rear axle instead of the conventional mechanical anti-roll bars. The hydraulic swivel motor is connected to one half of the anti-roll bar via the swivel motor housing and to the other half of the anti-roll bar via the swivel motor shaft. A vane controller divides the swivel motor into several chambers, which are filled with oil. A torque that affects the anti-roll bar is built up by specifically activating individual chambers and changing the oil pressure. The system has variable control over the oil pressure and oil flow in both rolling directions and can thus counteract lateral inclination forces in order to keep the vehicle horizontal.
Rear-Axle Valve Block
The valve block comprises two pressure sensors (-1- and -2-), a pressure regulating valve (-3-) and the direction valve (-4-). The valve block is installed on the left rear-axle suspension subframe.
Front-Axle Valve Block
The valve block comprises two pressure sensors (-1- and -2-), a failsafe valve (-3-), the direction valve (-4-) and a pressure regulating valve (-5-). The valve block is installed in the right front wheel housing.
Functions
The pressure sensors record the current pressure in the chambers of the swivel motors. Depending on driving dynamics, the direction valves are switched in such a way that pressure is built up or reduced in the chambers in order to create specific forces on the anti-roll bars that will counteract the vehicle's lateral inclination. The pressure regulating valves are activated by the control unit so that the required pressure exists on the swivel motors. The fail-safe valve in the front-axle valve block is de-energized in the event of a fault and reverts to its normal position via spring force. This short circuits the pump hydraulic system and switches the system to a fail-safe mode. For a description, see. "Error message/Fail-safe mode".
Tandem Pump
A tandem pump driven by the drive belt for auxiliary units is responsible for supplying hydraulic pressure. A small fluid reservoir on the pump serves as a pressurized shock absorber. Pressure is controlled on the relevant valve blocks since the pressures in the swivel motors are different. The system is filled with Pentosin CHE 202.
Reservoir
The reservoir (-A-) is located in the left of the engine compartment, next to the power steering reservoir (-B-). A filter, which filters the oil flowing back in, is integrated in the reservoir. An oil dipstick for checking the oil level is fitted on the lid.
Control Unit
The control unit is installed under the rear seat at the right. The input data is evaluated continuously and appropriate control operations are initiated in the valve blocks over the vehicles entire speed range.
Analogue input signals:
- Level sensor, front left/right.
- Level sensor, rear left/right.
- Level sensor, rear right.
- Body acceleration sensor, front left/right.
- Body acceleration sensor, rear right.
- Rear-axle valve block: Pressure sensor 1, pressure sensor 2.
- Front-axle valve block: Pressure sensor 1, pressure sensor 2.
- PDCC button.
Input signals via drive CAN:
- Vehicle speed.
- Lateral acceleration.
- Yawing speed.
- Steering angle.
- Engine speed.
- Nominal engine idle speed.
- Outside temperature.
TECHNICAL MANUAL: Technical Data Increased risk of accidents and material damage if too much Pentosin CHF 202 is filled in or if Pentosin CHF 202 comes into contact with the coolant hoses when filling or topping off.
Output signals:
- Instrument cluster: Text, symbols.
- Rear-axle valve block: Direction valve, pressure regulating valve.
- Front-axle valve block: Direction valve, pressure regulating valve, failsafe valve.
Operation and Display Concept
Porsche Dynamic Chassis Control can be operated using the same chassis control switches Normal, Comfort and Sport that are used for PASM. PASM and PDCC are configured together, depending on which of the three chassis control programmes is selected.
In the Comfort setting, PDCC intervention occurs at reduced control speed so as not to change the character of the high comfort program. Active system intervention in the Sport program, on the other hand, occurs at maximum speed in order to optimize performance.
Enhanced off-road performance is also available automatically as soon as Low Range is activated.
Diagnostics
In addition to on-board diagnosis by the control units and checks on sensors and valves, the pressure that exists in the system is continuously monitored. Depending on the engine speed, the nominal pressure values that are worked out are compared with the current actual pressure values recorded by the four pressure sensors. If a fault is detected, PDCC switches to Fail-safe mode.
Error Message/Fail-Safe Mode
If a fault occurs during PDCC operation, the driver is alerted to this by the message "Chassis system defective" on the on-board computer.
The entire system is switched to fail-safe mode to ensure safe driving. The fail-safe valve in the front-axle valve block is de-energized, which causes the pump hydraulic system to short circuit. The hydraulic oil from the pump flows directly back into the reservoir. At the same time, the connections for the swivel motor are closed so that the pressure in the swivel motor is maintained. The anti-roll bar remains in this position and continues to work in the conventional way.
The hydraulic system on the rear axle is completely depressurized so that the vane controllers in the housing can turn freely and the anti-roll bar halves are decoupled. This increases the vehicle's lateral during cornering. The vehicle responds by understeering slightly, but can be driven at an appropriate speed to the nearest authorized Porsche dealer.