A number of companies (for example, Delphi, Koyo, Visteon, TRW and BASF) have developed electric power steering systems to replace the traditional hydraulically operated ones. Some models of VW, BMW, and Mazda, as well as other makes, are already using them. The electric systems have several advantages including eliminating the power steering pump, hoses, hydraulic fluid, drive belt and pulley. Fuel economy is improved and is equivalent to that obtained with a manual steering system. What follows is a description of how the Delphi E-Steer system works.
Reference: http://www.epsking.com/attachment/fj...4423989651.pdf
Operation
E-Steer is an all-electric, engine independent power steering system that eliminates the parasitic losses associated with hydraulic systems. It uses sensor input and software algorithms to determine the amount of steering assist required. The controller, responding to inputs from vehicle speed and handwheel sensors sends torque-adjusting commands to the variable speed, electric motor, producing the optimum amount of steering assist based on vehicle conditions. A returnability algorithm is also employed to center the steering wheel. The algorithms are customized to the particular vehicle characteristics. High output current insures high steering load capacity and the brushless, permanent magnet motors employed provide optimum steering characteristics with less wear on the motor and less packaging and mass (25-30% smaller) than brush-type motors.
The electric motor can either be mounted on the steering column or on the rack and pinion steering gear assembly. Column mounting is generally used for compact to mid-size vehicles while rack-mount is more suitable for mid-size cars to full-size trucks.
Consumer Benefits According to Delphi
An on-demand steering assist that saves between .5 to 1-mile/gallon ( ~ a 4% mean improvement) over hydraulic systems. The system is independent of the engine as only the battery is required for E-Steer to function. This engine independence not only improves fuel economy (the lighter mass of electric vs. hydraulic systems is also a factor here) but by reducing parasitic losses, also improves acceleration times. Vehicle safety is enhanced since not only is torque steer reduced during acceleration, but power steering is available even when the engine is off. Assembly plant time is reduced by up to four minutes (fewer components to install), saving on manufacturing costs. The system uses less than .5 amp at idle and 1-2 amps with average use.
Manufacturer Benefits
Besides reducing assembly time, electric power steering also permits easy software tuning of the steering assistance characteristics to suit a variety of cars. For example, a single electric power steering system can be tuned for applications as diverse as a two-seater sports car or a luxury sedan. This can be accomplished through an in-vehicle laptop PC taking a matter of hours as opposed to the months required for the tuning of hydraulic power steering systems.
There is also an opportunity to improve reliability as 53% of all power steering warranty claims are from pump and hose problems. Environmental benefits will also accrue from the decreased requirement for the non-recyclable polymers used in hydraulic hoses as well as lessened need for power steering fluid (worldwide, an estimated 40 million liters of power steering fluid was used in 1995).
Another potential benefit also comes to mind. Since a great deal of engine bay space is made available due to the removal of the pump, drive belt and pulley, simplified mounting of a supercharger and its drive system becomes a real possibility.
Additional Material
An overview of electric power steering systems can be found here:
http://www.just-auto.com/article.aspx?id=92107
Mazda2 (Demio) to receive all-electric power steering in 2008:
http://www.entrepreneur.com/tradejou...171625458.html
Happy Motoring!
Reference: http://www.epsking.com/attachment/fj...4423989651.pdf
Operation
E-Steer is an all-electric, engine independent power steering system that eliminates the parasitic losses associated with hydraulic systems. It uses sensor input and software algorithms to determine the amount of steering assist required. The controller, responding to inputs from vehicle speed and handwheel sensors sends torque-adjusting commands to the variable speed, electric motor, producing the optimum amount of steering assist based on vehicle conditions. A returnability algorithm is also employed to center the steering wheel. The algorithms are customized to the particular vehicle characteristics. High output current insures high steering load capacity and the brushless, permanent magnet motors employed provide optimum steering characteristics with less wear on the motor and less packaging and mass (25-30% smaller) than brush-type motors.
The electric motor can either be mounted on the steering column or on the rack and pinion steering gear assembly. Column mounting is generally used for compact to mid-size vehicles while rack-mount is more suitable for mid-size cars to full-size trucks.
Consumer Benefits According to Delphi
An on-demand steering assist that saves between .5 to 1-mile/gallon ( ~ a 4% mean improvement) over hydraulic systems. The system is independent of the engine as only the battery is required for E-Steer to function. This engine independence not only improves fuel economy (the lighter mass of electric vs. hydraulic systems is also a factor here) but by reducing parasitic losses, also improves acceleration times. Vehicle safety is enhanced since not only is torque steer reduced during acceleration, but power steering is available even when the engine is off. Assembly plant time is reduced by up to four minutes (fewer components to install), saving on manufacturing costs. The system uses less than .5 amp at idle and 1-2 amps with average use.
Manufacturer Benefits
Besides reducing assembly time, electric power steering also permits easy software tuning of the steering assistance characteristics to suit a variety of cars. For example, a single electric power steering system can be tuned for applications as diverse as a two-seater sports car or a luxury sedan. This can be accomplished through an in-vehicle laptop PC taking a matter of hours as opposed to the months required for the tuning of hydraulic power steering systems.
There is also an opportunity to improve reliability as 53% of all power steering warranty claims are from pump and hose problems. Environmental benefits will also accrue from the decreased requirement for the non-recyclable polymers used in hydraulic hoses as well as lessened need for power steering fluid (worldwide, an estimated 40 million liters of power steering fluid was used in 1995).
Another potential benefit also comes to mind. Since a great deal of engine bay space is made available due to the removal of the pump, drive belt and pulley, simplified mounting of a supercharger and its drive system becomes a real possibility.
Additional Material
An overview of electric power steering systems can be found here:
http://www.just-auto.com/article.aspx?id=92107
Mazda2 (Demio) to receive all-electric power steering in 2008:
http://www.entrepreneur.com/tradejou...171625458.html
Happy Motoring!
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