Power Steering: Definition, Types & How Does it Work?

What is Power Steering?

A power steering is a mechanical device equipped on an automobile that helps drivers steer the vehicle by augmenting the steering effort needed to turn the steering wheel, making it easier for the vehicle to turn or maneuver at lower speeds.

Hydraulic or electric actuators add controlled energy to the steering mechanism, so the driver can provide less effort to turn the steered wheels when driving at typical speeds, and reduce considerably the physical effort necessary to turn the wheels when a vehicle is stopped or moving slowly. Power steering can also be engineered to provide some artificial feedback of forces acting on the steered wheels.

Hydraulic power steering systems for cars augment steering effort via an actuator, a hydraulic cylinder that is part of a servo system. These systems have a direct mechanical connection between the steering wheel and the linkage that steers the wheels. This means that power-steering system failure still permits the vehicle to be steered using manual effort alone.

Electric power steering systems use electric motors to provide assistance instead of hydraulic systems. As with hydraulic types, power to the actuator is controlled by the rest of the power steering system.

Other power steering systems have no direct mechanical connection to the steering linkage; they require electrical power. Systems of this kind, with no mechanical connection, are sometimes called “drive by wire” or “steer by wire”, by analogy with aviation’s “fly-by-wire”. In this context, “wire” refers to electrical cables that carry power and data, not thin wire rope mechanical control cables.

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Some construction vehicles have a two-part frame with a rugged hinge in the middle; this hinge allows the front and rear axles to become non-parallel to steer the vehicle. Opposing hydraulic cylinders move the halves of the frame relative to each other to steer.

Power Steering

How Does Power Steering Work?

The power steering system relies on several mechanical parts. Power steering systems function to provide easier maneuverability and a better degree of control over the vehicle, making driving all the more effort-free. It is sometimes referred to as the steering assist system or SAS. Without it, steering would be physically strenuous and challenging to perform.

Power steering systems can either be hydraulic, electric, or a combination of the two. Steering a vehicle involves getting its front wheels to turn synchronously, either to the left or right. This is achieved with the help of different gear systems. The two main steering gear systems are the rack and pinion and the recirculating ball steering gear.

The power steering system uses intermediate electric or hydraulic devices to reduce the effort necessary to steer the front wheels of the vehicle side to side. It multiplies the force applied by the driver through the steering wheel to achieve a smooth and quick directional change of the vehicle. Your car will respond immediately to even the smallest of adjustments you make, and it is easier to stay in your lane when you’re driving in traffic and carrying out complicated parking maneuvers.

How Does Hydraulic Power Steering Work?

Hydraulic power steering uses fluid to intensify the force applied to turn your front wheels. The hydraulic fluid is pressurized by a pump driven off the engine, which provides hydraulic pressure to the steering system. When you turn the steering wheel, hydraulic pressure is applied to your steering gear, which turns your wheels. The whole system relies on the flow of fluid. The harder you turn your wheel, the more fluid flows to the hydraulic cylinder, so the more force is applied to your wheels.

How Does Electric Power Steering Work?

The electric power steering uses an electric motor that draws energy from the vehicle’s electrical system to provide steering assistance. 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. The major benefit of electric power steering over hydraulic power steering is that they can adapt to suit specific driving conditions.

Types of Power Steering

Following are the Types of Power Steering Systems:

  • Hydraulic Power Steering.
  • Electro-Hydraulic Power Steering.
  • Electric Power Steering or Motor-Driven Power Steering.

1. Hydraulic Power Steering

This system uses pressurized power steering fluid, supplied by the power steering pump, to decrease steering effort. An engine-driven accessory drive or serpentine belt turns on the pump and directs high-pressure power steering fluid via the high-pressure hose to the input side of the power steering gear-control valve.

High pressure acting on the control valve assists the driver when turning the front wheels. Power steering fluid is stored in a reservoir. The proper fluid level in the reservoir is maintained when the fluid returns from the steering gear at much lower pressure.

Hydraulic power steering systems continuously pump fluid and are susceptible to engine speed high revolutions per minute equal high-pressure output, lower revolutions per minute equal low-pressure output. To maintain constant pressure, a power steering pump uses a bypass valve to maintain constant pressure no matter what the engine speed.

2. Electro-Hydraulic Power Steering

These systems employ a brushless electric motor to drive the hydraulic power steering pump instead of an engine-driven accessory drive or serpentine belt. This system operates the same and provides the same feel as a conventional hydraulic power steering system.

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.

3. Electric Power Steering or Motor-Driven Power Steering

Electric power steering (EPS) is the norm in today’s new cars. There’s still a solid metal steering shaft running from the steering wheel to the steering rack, which steers the tires, but the rest is high-tech. EPS uses an electric motor that draws energy from the vehicle’s electrical system to provide 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.

No matter what kind of system you have, power steering only acts on the steering gear when the driver turns the wheel.

Advantages of Power Steering

Following are the advantages of power steering:

  • It prevents the wheel from transferring the loading to the steering column.
  • Power steering reduces driver fatigue.
  • It lowers the input torque and continuous steering function.
  • In power steering, the oil output is directly proportional to steer speed.

Disadvantages of Power Steering

Following are the disadvantages of power steering

  • The design of the power steering is complicated.
  • Power steering is costly than the manual steering
  • It has a fluid leakage problem.