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Electric Power Steering Types and Vehicle Suitability

by Emilia Latvala

Changes are happening with power steering systems as electric systems are fast replacing hydraulic systems in newer car models due to a variety of reasons. Foremost, they have eliminated the bulk of the hydraulic systems that translated to more fuel consumption. Electric systems calculate specific steering assist requirements using vehicle torque, tire speed and other considerations, quickly translating this information into the right amount of assist. Electric power steering systems do not require much maintenance and are very durable. Hydraulic systems, on the other hand, require maintenance for better functionality. The fluids have to be changed, hydraulic pumps monitored and delivery pipes are always prone to leaking. The energy required to power electric systems comes from the battery while that required to power hydraulic systems comes from the engine. This also helps in the reduction of fuel use by cars using electric power steering systems. 

There are different types of electric power steering systems available. The principle operating mechanism in these different types remains the same: an electric motor commanded by a processor provides steering assist. The position of various components, however, differs. These differences result in varying outputs.

Column type electric power steering

For vehicles with smaller engine room space, the power assist unit is placed in the cabin. This position is suitable for light, compact and medium cars. The result of this positioning is slightly less calmness during steering power assist. The power steering effectively conducts steering assist and only uses power when steering assistance is required.

Pinion type electric power steering

This type of power steering is suitable for vehicles with more engine room. The power assist unit is situated on the pinion shaft. The position of this unit translates into more calm power assist in comparison to the column type power steering. There is single pinion type as well as dual pinion type electric power steering system. The dual-pinion type features an assist function that is separated from the steering wheel shaft. This results in more output from the power steering and more strength in design. They are usually easier to install as well.

Rack direct drive type electric power steering

In these systems, the assist function directly assists the rack shaft. Cars with this type of power steering experience very low friction during steering assist. The position also translates to the ideal steering feel much preferred by many drivers. A final type of electric power steering also common in several car models features both electric and hydraulic components. It is pretty much a hydraulic system with an electronic brain centre and, thus, energy saving but still susceptible to the various disadvantages of hydraulic power steering systems.