Electric Power Assisted Steering
As seen earlier, power steering brought about many other changes in automobiles, includes the way people use them. The leverage of huge steering wheel no longer needed, and with smaller wheel the cockpit could be designed with a more relaxed seating position. The hydraulic boost not only reduced the steering effort, it also allowed the quicker steering ratio. As development continued the size, the price and horse power designs made variable rate power steering possible and electronic controls refined it even further. Today variable rate power steering is a standard feature of almost every car sold in the United States.
A database is used to communicate the vehicle speed and engine speed to the EPAS system and the torque sensor detects the force the driver is using to turn the steering wheel. All this information is passed to the ECU. The ECU uses this information to calculate the additional force required by the EPAS system to achieve the pre programmed steering feel.
The steering power is then transmitted by engine to the steering gear by means of an intermediate gear system. The ratio between manual steering torque and electric power controlled in relation to vehicle speed, offering the relevant assistance at varying speeds. At low speed the system offers maximum power, making the steering easy to operate, and at increased speed, when littleor no assistance is required reduces amount of power supplied.
Download seminar docs :