Purpose of the System
Purpose of the System
The Dynamic Drive - Active Roll Stabilizer Bar (ARS) is a revolutionary step for chassis technology. ARS goes a long way towards removing the conflict between handling/agility and comfort. ARS has two stabilizer bars that have a positive effect on the body roll and handling, allowing softer springs and dampers to increase comfort.
Dynamic Drive controls two active stabilizer bars on the axles depending on the lateral acceleration.
The two separate stabilizer bars on each axle are mounted in roller bearings and are connected by a hydraulic oscillating motor.
One half of the stabilizer bar is connected to the oscillating motor shaft and the other is connected to the oscillating motor housing.
Active stabilizer bars introduce fewer forces into the body as compared 10 solid stabilizer bars because the separate "halves" will not copy one sided suspension compressions (bounces).
The active stabilizer bars set the stabilizing torque, resulting in:
- Minimizing or completely eliminating body roll while cornering
- Reduction in the "copying effect" of the vehicle
- A high degree of agility and precision throughout the entire speed range
- Produces optimum self steering characteristics
- Improved suspension comfort (when driving straight ahead) because the stabilizer bar halves are independent and do not stiffen the basic suspension during a one-sided compression.
The distribution of the active body torque between the front and rear axle depends on the road speed. The following describes the different body torque distribution
Self Steering Affect
The self steering affect is influenced by the distribution of the stabilizing torque on the axles. The greater the stabilizing torque on an axle, the lower the lateral forces will be that are transmitted on this axle. Two situations are described below with a different distribution of stabilizing torque on the axles:
Identical stabilizing torque on both axles: Handling is "NEUTRAL". The front wheels will apply about the same amount of lateral force to the road as the rear wheels (without drive torque). A vehicle that is tuned to neutral handling provides very agile handling and the steering reacts very quickly. The driver experiences precise handling.
Larger stabilizing torque on the front axle: Handling is "UNDERSTEERING". The front wheels cannot apply the same amount of lateral force to the road as the rear axle wheels. The vehicle tends to go straight requiring an increase in steering to make the vehicle turn.
Dynamic Drive sets the stabilizing torque on the front and rear axle to create a different handling characteristic for low and high speeds.
Road Speed Handling
Low Neutral
High Understeer
Passenger vehicles are designed for slight understeer depending on the speed range. Dynamic Drive is tuned to neutral in the lower speed range, requiring less steering to go around the same corner. This produces optimum handling and agility. In a higher speed range, Dynamic Drive is designed so that a larger active stabilizing torque will occur on the front axle as compared to the rear axle. This means that the vehicle with Dynamic Drive reduces over sensitive steering a higher speeds to enhance handling characteristics.
System Dynamics
When the vehicle changes lanes, corners or changes direction quickly (winding roads), Dynamic Drive reacts very quickly. The system dynamics reaction time is shown in the following steps:
Process Time
Signal detection by sensors,
processing of sensor signals
and valve control. approx. 10 ms
Change of direction, switching
over the torque direction,
direction valve. approx. 30 ms
Pressure build up (force per wheel).
0 to 30 bar (0 to 350 N) approx. 120 ms
0 to 180 bar (0 to 2100 N) approx. 400 ms
Dynamic Drive Bus Structure