The use of electronics into automotive steering systems enables much more sophisticated control to be achieved.
Electric steering is more economical to run, and easier to package and install than conventional hydraulic power steering systems.
Typically, electric and electro-hydraulic power steering systems are also lighter and more compact than conventional hydraulic systems.
Both the electric power steering system and the hydraulic power steering system with a motor-driven pump are now considered as viable alternatives to conventional hydraulic power steering systems because of their energy efficiency and size.
Electrically Powered Hydraulic Steering, or EPHS, replaces the customary drive belts and pulleys with a brushless motor that drives a high efficiency hydraulic power steering pump in a conventional rack and pinion steering system. Pump speed is regulated by an electric controller to vary pump pressure and flow. This provides steering efforts tailored for different driving situations. The pump can be run at low speed or shut off to provide energy savings during straight ahead driving.
An EPHS system is able to deliver an 80 percent improvement in fuel economy when compared to standard hydraulic steering systems.
Electrically assisted steering or EAS, is a power-assist system that eliminates the connection between the engine and steering system. EAS or direct electric power steering takes the technology a step further by completely eliminating hydraulic fluid and the accompanying hardware from the system, becoming a full “electronic power steering system” or EPS.
An EPS Direct electric steering system uses an electric motor attached to the steering rack via a gear mechanism and torque sensor. A microprocessor or electronic control unit, and diagnostic software controls steering dynamics and driver effort. Inputs include vehicle speed and steering, wheel torque, angular position and turning rate.
There are four primary types of electric power assist steering systems:
In these systems “Active control” as it is known provides constant feedback from sensors in the vehicle to the control unit, which calculates sophisticated computer algorithms. This allows the steering system to react to the road, the weather and even the type of driver, and provide assistance to the front or rear road wheels independent of direct driver input.
Active steering produces enhanced steering response, stability & handing improvements to the vehicle without impacting the base steering feel.