A rack and pinion system was used to drive a car in the correct direction in earlier times, before there was any kind of driving aid. Then came hydraulically assisted steering, which was introduced by Chrysler in 1951 and quickly took over the automotive industry.
This type of technology makes use of a hydraulic pump that is driven by an engine belt. The hydraulic fluid, which is pressurized through the action of the belt, moves a power ram. Depending on the steering input, a control valve determines how much hydraulic pressure is required to move the wheels in either direction. The hydraulics increase the force being given to the steering rack, which lowers the amount of effort required to turn the vehicle.
Hydraulic systems certainly have drawbacks, despite the fact that they are still widely used and nearly faultless. The use of hydraulic assistance is viewed as a parasitic loss because the pump is technically powered by the engine. This implies that a tiny amount of engine power is lost to power the pump, lowering the powertrain’s overall efficiency. These days, drivers of performance automobiles must be able to choose from a variety of settings, and the majority of those modes incorporate steering-wheel adjustments. Since the hydraulic fluid being pumped through the system will have a fixed viscosity (how freely a fluid flows), some other type of limitation must be applied because this is not practical for hydraulics.
The decision to switch from hydraulics to electric motors was made by engineers in the last ten years, which wasn’t unexpected given the trend towards fully electric vehicles. In order to bring power steering into the twenty-first century, the motors are typically mounted either at the base of the steering column or directly on the steering rack. Electronic sensors detect the degree of steering lock being used and increase the steering input force proportionally. The motor is rotated by electrical charge, and when the energy is transferred, a lateral force is created to facilitate movement along the steering rack.
Steering feel is the fundamental criticism of electronic systems. Hydraulics are favored by purists because the amount of feedback that can be passed through the steering rack and back to the steering wheel makes them tactile due to the presence of a viscous fluid. Therefore, many road testers complained about a lack of input when electric steering systems first came into use. It is reasonable to assume that relatively little reaction force will pass back through an electric motor since electricity is essentially a non-tactile material.
However, as EPAS (electric power assisted steering) systems have been developed and improved, producers like Porsche have been able to produce electronic systems that almost exactly equal the feel of a hydraulic system and go on to outperform the mechanical approach in many areas. By switching the feedback loop’s direction within the electronics, Porsche has achieved this. While most manufacturers use a system that calculates the steering assistance force from a torque sensor from the wheels, Porsche uses yaw sensors, steering angle, and other values from the stability control to increase and decrease assistance accordingly and at a much more frequent rate. This means that the EPAS system now incorporates a sense of “feel,” and aside from drivers of wholly unassisted vehicles, there are no significant distinctions between modern EPAS systems and an HPAS system.
Other benefits of EPAS include packaging, convenience, and efficiency. Due to the absence of parasitic engine waste, Chevrolet has witnessed a 2.5% boost in fuel efficiency after switching to electronic steering. Electronic steering is undoubtedly here to stay given the tremendous push toward automation and the fact that radar-guided parking also functions in conjunction with an EPAS system.
The Porsche 911 is a fantastic case study for the benefits of an EPAS system in terms of packing. Before going electronic, a lengthy hydraulic piping path from the rear-mounted engine to the front wheels had to be designed into the automobile. Porsche decided to use a full EPAS system on the 991 series of vehicles so that the motors could be placed at the front of the vehicle without the need for extensive pipework. This helped the 911’s weight distribution, which is crucial for a rear-engined vehicle.
In performance automobiles from the past ten years, EPAS systems allow modifications to be made to the weight and speed of the steering input by merely altering the amount of charge generated by the electronic motor, which in turn alters the degree of steering assistance. To modify the amount of steering input necessary to maneuver the car in an HPAS system, these adjustments may need to be made physically, such as by changing the rack or fluid pressure.
Modern EPAS systems are becoming increasingly difficult to distinguish from sophisticated HPAS systems, and the advantages of electronics far outweigh those of more conventional hydraulic arrangements. Despite the fact that some businesses create hybrid systems that use an electric motor to drive a hydraulic ram system, the great majority of producers are currently pushing toward purely electric assisted steering. You shouldn’t anticipate any hydraulic pump troubles on your future maintenance expenses.
In This Article...
What is the mechanism of an electric power steering?
The power steering system is supported by a number of mechanical components. Driving is made even more effortless by power steering systems’ ability to offer improved vehicle control and smoother maneuverability. The SAS, or the steering assist system, is another name for it. Without it, steering would be difficult and physically demanding. Systems for power steering might be hydraulic, electric, or a hybrid of the two. Getting a vehicle’s front wheels to turn simultaneously, either left or right, is the process of steering. It is accomplished with the use of various gearing schemes. The rack and pinion and the recirculating ball steering gear are the two primary steering gear systems.
The power steering system uses intermediary hydraulic or electric devices to lessen the effort needed to turn the vehicle’s front wheels in either direction. It increases the force the driver applies through the steering wheel to enable a seamless and rapid change in the vehicle’s direction. When you drive in traffic or do challenging parking maneuvers, your car will react quickly to even the tiniest adjustments you make, making it simpler to stay in your lane.
How Does Hydraulic Power Steering Work?
Fluid is used in hydraulic power steering to increase the force needed to turn your front wheels. A pump powered by the engine pressurizes the hydraulic fluid to supply hydraulic pressure to the steering system. Hydraulic pressure is delivered to your steering gear as you crank the steering wheel, turning your wheels. The fluid flow underlies the entire system. More fluid flows to the hydraulic cylinder as you turn your wheel more forcefully, which is sent to your wheels.
How Does Electric Power Steering Work?
An electric motor powered by the car’s electrical system is used by the electric power steering to help with steering. A computer determines the amount of assistance that has to be added after sensors measure the torque or effort the driver is exerting at the steering wheel. The ability of electric power steering to adjust to certain driving circumstances is its main advantage over hydraulic power steering.
With a car examination from an auto repair shop, problems like a power steering leak can be avoided. It’s one of the greatest methods to guarantee that the remainder of your vehicle’s essential parts, like the power steering system, can operate at their peak efficiency. If turning seems more difficult than usual, your power steering may be malfunctioning. Your steering should be responsive and easy to use. Make an appointment or drive your car to a nearby auto repair shop for power steering maintenance.
What causes failure of electric power steering?
When evaluating and fixing today’s EPS systems, the three primary types of electronic system failures you’re likely to run into are motor, electronic board, and torque sensor problems. The sorts of failures connected to each of these service categories are listed below in brief. The electronic column drive system with a mounted electric motor and manual rack & pinion is responsible for these failure modes.
Motor
The mounted electric motor may malfunction in today’s computerized power steering systems. The failure modes are particularly likely to be caused by the motor becoming overheated. EPS failure will also probably result from water, dirt, or other contaminants getting into the system environment. Additionally, carbon contamination may cause steering failure in brush style systems exclusively. Brush type generally has a higher failure rate than brushless.
Electronic Board and Circuitry
The electronic board and circuits are yet another area of worry. The EPS board is a hub of communication between sensors and circuits in the system and handles electrical signals moving through it. Heat and power cycling over time are two specific failure modes to watch out for (mosfets, relays, capacitors, resistors). When these are close to the engine and exhaust components, they become more problematic. EPS breakdowns can also be brought on by water, dirt, or other impurities getting within the system. However, microprocessor failure is uncommon, thus during diagnosis and repair, they shouldn’t be the primary focus.
Torque Sensor
Finally, the torque sensor is a component that has frequent failures. The most frequent failure on a column assist system is a torque sensor failure, and contacting style torque sensors fail significantly more frequently than non-contacting ones. The metallic contact points on sensors have a tendency to corrode over time.
Does fluid exist for electrical power steering?
The three power steering systems all carry out the same crucial task, but they do so in three different ways. An electric system employs an electric motor and sensors, an electro-hydraulic system uses an electric motor to pressurize fluid, and a hydraulic system uses high pressure fluid that is physically pushed. The ultimate result is always the same: The steering wheel is simple to turn. Fully electric power steering systems are more dependable than hydraulic systems, use less fuel, and require less maintenance.
Hydraulic Power Steering
To reduce steering effort, this system uses pressurized power steering fluid, which is supplied by the power steering pump. High-pressure power steering fluid is delivered to the input side of the power steering gear-control valve via the high-pressure hose by the pump, which is activated by an engine-driven accessory drive or serpentine belt.
When moving the front wheels, the driver is helped by high pressure acting on the control valve. A reservoir is used to store the power steering fluid. When the fluid returns from the steering gear at a significantly reduced pressure, the reservoir’s proper fluid level is maintained. Systems with hydraulic power steering constantly pump fluid and are vulnerable to engine speed Low revolutions per minute provide low pressure, while high revolutions per minute produce high pressure. A power steering pump employs a bypass valve to maintain consistent pressure so that it is independent of engine speed.
Electro-Hydraulic Power Steering
Instead of using a serpentine belt or an accessory drive powered by the engine, these systems use a brushless electric motor to drive the hydraulic power steering pump. The functionality and feel of this system are identical to those of a traditional hydraulic power steering system.
Electric Power Steering or Motor-Driven Power Steering
Hydraulics and pressurized fluid are not used in this system. A brushless bi-directional permanent magnet motor attached to the steering gear or steering column rotates the front wheels whenever the driver turns the steering wheel. To help the steering gear turn in the right direction, sensors track which way the steering wheel is turned.
Power steering only affects the steering gear when the driver moves the wheel, regardless of the type of system you have.
What drawbacks exist with electric power steering?
In today’s autos, electric power steering systems have almost entirely replaced traditional hydraulic ones.
Technology is quickly consigning hydraulic systems to the past, from common vehicles like the Suzuki Swift to the iconic sports car, the Porsche 911.
But why is it important for future automobiles, and what do automakers see in electric power steering systems?
What is it and how does it work?
The majority of electric power steering systems use an electric motor mounted to the side of the steering rack that drives a ball-screw mechanism that engages a spiral cut in the exterior of the steering rack, as opposed to hydraulic power steering systems, which use pressurized fluid divided between two chambers in the steering gear’s cavity to provide steering assistance.
When to activate and offer steering assistance is determined by a computer under the supervision of a torque sensor attached to the steering shaft.
The pros
Most of the time, electric power steering is easier to operate than traditional hydraulic systems, requiring less effort to spin the wheel.
This advantageous characteristic will typically become apparent at low speeds, such as during parking maneuvers.
However, in order to accomplish the same outcome, variable-assist systems were added to some vehicles with hydraulic power steering.
In terms of physical weight, electric systems are better since the weight over the front axle is reduced by their more simpler configurations.
This is so that the hydraulic fluid in the steering gear can be moved by hydraulic systems, which employ a pump that is driven by a belt. This adds to the engine’s workload, which is much less with electric installations.
When it comes to performance vehicles, electric power steering offers greater steering adjustment options. For instance, using a Sport mode to make the steering seem heavier and a Comfort mode to make the steering feel lighter around town are both options.
The cons
The diminished steering feel is the biggest drawback of using an electronic system, and it is mostly a problem for driving purists.
Less road feedback is conveyed to the driver through the steering wheel when the mechanical link to the steering rack is muffled, yet some manufacturers have nevertheless developed technologies that impart artificial feedback.
When the system has been improperly calibrated, electric power steering can also be less predictable than hydraulic power steering, which can make some electric installations feel less linear than hydraulic systems.
Why does it matter?
Electric power steering may not have the same steering sensation as conventional power steering, but automakers like it because it can save weight and fuel consumption.
However, these systems are required to improve the autonomous technology being incorporated into today’s automobiles.
Electric power steering is essential for all driving functions, from radar-guided parking to the semi-autonomous driving modes currently on display in early models of some high-end cars. This is because the computer in the car needs to be able to operate the steering itself in order to carry out these operations.
Future uses include directing the vehicle just before a collision to make sure the protective cell provides the greatest amount of protection, in addition to steering the vehicle automatically into a parking place.
More significantly, it enables automakers to completely do away with the steering wheel in a world when fully autonomous vehicles are on the road.