Integral Steering System Explained
In some cases, the vehicles are fitted with controls that switch off the rear steer and option to steer only the rear wheels independent of the front wheels.
A computer is used to control the rear wheels and determines how much and in which direction the rear wheels should move, and whether the rear wheels should turn in the same direction as the front wheels or in the opposite direction. The movement varies up to a couple of inches. At slow speeds, the rear wheels move the opposite direction of the front wheels. This makes for easier parking and maneuvering.
Daimler-Benz had already developed four-wheel drive, four-wheel steering vehicles for the Forest Service in the 1930s. Their rear wheels were designed to turn in the opposite direction to the front wheels so that the vehicle could make sharp turns along narrow mountain roads. However, two of this system's pioneers were Honda’s Prelude line and GM’s Delphi Quadrasteer. Only a few manufacturers then used active four wheel steering in some of their vehicles, such as Infiniti, BMW, Mazda, Nissan and Toyota.
Similarly, the Active Drive chassis with four-wheel steering on the Renault Laguna GT works like this: At speeds of less than 60 km/h, the rear wheels turn in the opposite direction to the front wheels, up to an angle of 3.5°. This brings two advantages: a smaller turning circle, for easy maneuvering; and smaller steering wheel angles thanks
With front wheels and rear wheels turning in opposite directions, the car effectively pivots, which means smaller steering angles are needed for the same turning effect. Whereas it takes a 16° steering wheel angle to produce a 1° turn in the front wheels on New Laguna, it takes just 13.5° with the Active Drive chassis. And this drops to 12° when the rear wheels are turned at the maximum 3.5° angle in the opposite direction to the front wheels.
Finally, the electronic control unit on the 4-Wheel Active Steer system (4WAS) from Infiniti calculates the desired vehicle dynamics from a series of sensors, including vehicle speed and steering angle, and directs the system actuator to change rear geometry by moving both rear suspension lower links.