Active Suspension systems, that is the ones in which desired suspension characteristics as per requirement are achieved during running by means of computer controlled actuators. Such systems are usually introduced in premium cars from where they come to the mainstream models. Some of such technologies are :-



1. Using air springs to vary ride height according to requirements example on Land Rover Range Rover and LR4, Audi Q7, Mercedes-Benz ML550 and Jeep Grand Cherokee. Audi's air suspension varies its height by 95 mm between the lifted and lowered modes. Besides, a driver selectable dynamic driving mode drops the ride height by 15 mm lowering the centre of gravity and improving handling. For high speed driving on expressway, Q7 is lowered automatically from its static height by 34.8 mm, which lowers its drag coefficient from 0.37 to 0.35. Jeep Grand Cherokee's Quadra Life air suspension can vary the vehicle's height by 104 mm from an Offroad mode which lifts it 66 run higher than the normal, to a park mode which lets it down by 38 mm to fit in garage. It even lowers 15 mm automatically at highways speeds to reduce drag coefficient.

2. Rear air springs to compensate for loads as on Lexus LX 570.

3. Adjustable shock absorber damping on Grand Cherokee.

4. Active anti roll bars on Mercedes and Jeep.

5. A system of linked shock absorbers as on the Infinity QX56, which dispenses with anti roll bar and permits or softer spring rate. Tenneco Inc, USA's Kinetic H2 active hydraulic shock absorber technology hydraulically connects the compression side of a shocker on one side of the vehicle with the ribound side of the shocker on the other side and vice versa. Besides, each shocker is plumbed to the opposite function in the shocker diagonal from it on the vehicle. Thus the shockers are connected in both roll and pitch. Due to this when an unweighted shocker extends, it sends extra pressure to the shocker opposite it, which provides roll stiffness on turns and resistance to squat and dive when accelerating and braking. In addition, since the wheels and now not tied together by a conventional anti roll bar, they can maintain contact with the ground, which improves both the ride as well as the traction.