High Capacity Active Steering (HICAS)
In 1986, Nissan launched their HICAS system on the rear axle of the R31 Skyline Coupe.
Super HICAS is controlled by a relatively simple open-loop control system. The desired vehicle path dictated by the driver is determined based on signals from the vehicle’s velocity sensors and the steering wheel angle sensor. The appropriate rear-wheel steer angle is then calculated by the system’s ECU. The ECU then actuates a servo valve, which applies pressure to a spring-centered hydraulic cylinder. The stroke of this hydraulic cylinder pivots the rear wheel to the required angle.
Nissan continued to develop the HICAS system into the “Super HICAS” four-wheel steering system, which was featured on the Nissan 300ZX and several Infiniti models between 1989 and 1996.