The basic knowledge about power steering's have been illustrated with animations. Why do we need it and how to improve the steering system has change the automobile industry.

1. THE POWER
STEERING SYSTEM
by-
Dr. Vikash Kumar Sharma
Principal, University Polytechnic
GLA University, mathura

2. CONTENTS
• Introduction to power steering.
• Why power steering is needed?
• Hydraulic power steering
• Electric power steering
• Electro Hydro power steering
• Hybrid EPS
• Benefits of EPS
• Characterstics of EPS

3. THINK ABOUT-
• You are driving a car in two cases-
• You will feel exhausted with heavy steering forces.
The power steering system takes the load makes the driving easy by
taking steering forces on it.
1. On heavy traffic market roads 2. On the highway at speed more than 100 km/h.

4. • Future technology trends of commercial
vehicle steering components can be
divided into three types.
• Environment-friendly technologies for
environment-related regulations such as
reducing emissions and improving fuel
efficiency.
• Technology for driving convenience using
electric steering control systems.
• Safety technology to protect drivers,
passengers, nearby vehicles .

5. • In recent technical trend,
improvement in fuel efficiency
and realize autonomous
driving technology, we
designed EHPS and Motor
driven electric control actuator
with the same structure .
• The power used in the EHPS
system is the motor, which
rotates the gear pump to
generate flow and pressure,
and the steering oil is
delivered to the ball nut
gearbox to operate the power
steering system through the
pitman arm.

6. • The advantage of EHPS is that it
does not use the engine drive
torque, so it improves fuel
efficiency by about 1%, and
when the pump is connected in
parallel
• The motor control device is
directly connected to the steering
wheel , and we can design the
actuator system by selecting the
package and the required output
according to the use conditions.
The required steering torque as
a general auxiliary steering was
about 20 Nm, and the C-EPS
type actuator using a worm
reducer

8. • EPS uses an electric motor to assist the driver of a vehicle, unlike traditional systems that act
on hydraulic pressure provided via a pump driven by the vehicle's engine. This pump is
constantly running, whether the steering wheel is being turned or not. That continually places
load on the engine, adversely affecting the vehicle's fuel consumption.
• By moving to an electric motor the load on the engine is reduced to only those occasions
when the steering wheel is being turned one way or the other, therefore producing better fuel
economy.

9. HOW DOES IT WORK?
• An electric motor that is mounted on either the steering column or steering gear
(usually a rack-and-pinion setup these days) applies torque to the steering column,
assisting the driver to turn the steering wheel. Sensors detect the position of the
steering wheel and any input from the driver – hauling on the wheel to change the
vehicle's direction. A control module applies assistive torque via the electric motor. If
the driver is just holding the wheel steady, at the straight-ahead position, the system
doesn't provide any assistance.
• This type of system can now be programmed to support the vehicle's active safety
systems, such as Lane Keep Assist (different manufacturers have different naming
conventions), where a camera or laser recognises the road markings, so that when
the vehicle drifts out of a lane the steering is activated to bring the vehicle back into
the lane.

10. • The electric power steering (EPS) system has been applied to most of the
passenger cars because the EPS is effective in energy saving and can provide the
technical bases of the advanced driver assistance system (ADAS), such as the
Lane Keeping Assist System (LKAS) and the automated driving system.
• Most heavy commercial vehicles, however, still utilize the hydraulic power steering
(HPS) system for which the hydraulic pump is directly connected to the engine
crankshaft by a belt or a gear. This steering system has been proved as effective,
inexpensive, and reliable; nonetheless, its fuel efficiency is ineffective since this.
• The electric motor of the EPS is attached to the conventional HPS system to
generate the additional torque assistance and performs the chassis-control function
for driving convenience and safety.

11. • One of the possible applications is the electro hydraulic power steering (EHPS)
system. Since the hydraulic pump of the EHPS system is independent from the
engine crankshaft, the energy loss that is caused by a pump-rotation load can be
minimized in the case of straight-line driving situations when no assistance is
required. So, theoretically, if the EHPS and EPS systems can be integrated into a
heavy-commercial-vehicle steering system, the enhancements of not only steering
control but also energy efficiency can be achieved in ball-net steering system of
commercial vehicles. The steering system wherein the EPS and EHPS systems are
integrated in the ball-nut steering system that is generally used in heavy commercial
vehicles is called as “Hybrid Electric Power Steering (Hybrid EPS)”

12. SYSTEM DESCRIPTION OF THE HYBRID EPS SYSTEM
• The Hybrid EPS system
in Figure is composed of the EPS
system, a mechanical-steering
system, and the EHPS system
with hydraulic parts such as a
rotary valve, cylinder, and pump.
The EPS system consists of a
surface-mounted permanent
magnet (SPM) motor, torsion bar
and torque sensor, reduction gear,
and an electronic control unit
(ECU) with control logic. The
EHPS system consists of a motor
pump unit (MPU) with external
gear pump, ECU with control logic
and ball-nut gearbox. The EPS
system is attached directly onto
the hydraulic ball-nut gearbox. Schematic diagram of the Hybrid EPS.

13. OPERATION OF HYBRID EPS
• When the driver steers the hand wheel, Torsion Bar 1 is twisted as the driver-input
torque.
• From this torsional angle, the torque angle sensor (TAS) can measure the steering
torque and the angle of the driver input, and the ECU of the EPS system determines
the amount of the assistance torque on the steering column.
• Then, Torsion Bar 2 is also twisted as the summation torque of the driver-input torque
and the assistance torque from the EPS system.
• Subsequently, some orifices of the rotary valve are opened and others are closed so
that the assistance force on the ball-nut cylinder is generated by the differential
pressure between the left and right chambers.
• Since the hydraulic system that has been transferred from the HPS system to the
EHPS system is still in place, the electric motor of the EPS does not need to provide
the full assistance torque. In practice, the assistance torque from the EHPS system is
much higher than that from the EPS system.

14. HOW POWER STEERING WORKS?
• At its most basic, power steering is a system that reduces the effort required of the
driver to turn the steering wheel. Without power assist, the steering of most vehicles
would be extremely heavy, particularly during low-speed maneuvers such as pulling
into a parking spot, turning a 90-degree corner in the city, or maneuvering in a
crowded gas station.

15. HYDRAULIC POWER STEERING
• Hydraulic power steering uses, hydraulic fluid that's pressurized by a pump driven off
the engine, since the pump is running continuously even when the vehicle is driving
straight and there's no assist needed. Plus, the hydraulic fluid needs to be replaced
periodically, and if any of the hydraulic lines springs a leak, it not only makes a mess,
but the power assist is lost. However, it's still possible to steer a car without the power
steering working.

16. ELECTRIC POWER STEERING
• Electric power steering (EPS) is the
norm on today's new cars. EPS uses an
electric motor that draws energy from
the vehicle's electrical system to provide
the steering assistance. This electric
motor can be located either directly on
the steering rack—this arrangement is
more expensive and tends to be used on
the sports- and luxury-car end of the
spectrum—or mounted to the steering
column. Sensors detect the torque, or
effort, that the driver is applying at the
steering wheel, and a computer decides
how much assist needs to be added. In
most systems, the computer changes
the steering effort based on the vehicle's
speed: at parking speeds, the steering is
light and easy to turn, while at highway
speeds, the effort amps up, giving the
driver a feeling of greater stability and
control.

17. EPS BENEFITS
• It improves fuel economy by a few percent, as the electric motor only draws
power when needed; it eliminates the hydraulic fluid maintenance.
• Any driver-assist or convenience feature that involves turning the wheels
without steering input from the driver is enabled by electric power steering.
• Features such as lane-keep assist, automated parking and lane changes,
and the ability to guide the car around obstacles all utilize EPS's ability to
steer itself when necessary.
• Electric power steering is one of the technologies that will enable self-driving
cars.
• What's more, tomorrow's autonomous, self-driving cars will rely on electric
power steering, because it allows the car to be steered by an onboard
computer system when on automatic pilot.

18. ELECTROHYDRAULIC STEERING
• Between the hydraulic and electric types of power steering, there's a hybrid of the two
systems called electrohydraulic. It functions like a hydraulic-assist system, only that the
hydraulic pressure is created by an electric motor, rather than driving the pump off the
engine. This gets rid of the wasted-energy complaint noted earlier but doesn't enable all
of the features possible with electric power steering. Only a few vehicles, including some
heavy-duty pickup trucks, currently use this system.
• If you're interested in a deep dive into the mechanics of how steering assist is created in
either hydraulic or electric power steering systems.

19. STEERING CHARACTERSTICS
• Here at Car and Driver, the three major steering characteristics we evaluate in every
vehicle we test are effort, response, and feedback. Two of those—effort and feedback—
took a turn for the worse in early EPS systems, which didn't replicate the highly evolved,
natural feel-for-the-road imparted by hydraulic systems. This made it hard to sense when a
vehicle's tires were running out grip and starting to slip.
• Although driving enthusiasts like us were, not surprisingly, up in arms about these negative
developments, they actually affected all drivers—and still do. There's a real-world need for
vivid feeling through the steering wheel when a vehicle is approaching its limits—say, when
it's about to skid on a surface that's slick from rain, snow, or ice. A vehicle with more
communicative steering makes for a better-informed, safer, and more confident driver in all
situations. However, the good news is that engineers have spent much time and effort
through the years evolving electric power steering and creating sophisticated algorithms
that faithfully re-create the steering sensations lost after the switch from hydraulic units.
Today, the latest EPS systems—particularly those from Porsche, Mazda, and GM (on
the Chevy Corvette and Camaro, and the Cadillac cars)—now feel intuitive. They let you
know what the front tires are doing just as faithfully as the old hydraulic steering systems
did—which is a very positive development for both cars and their drivers.