Talk:Power steering

Abbreviations

These abbreviations are commonly used for power steering systems:

• PAS - Power Assisted Steering
• EPS - Electric Power-assisted Steering
• VAPS - Variable Assist Power Steering

—Preceding unsigned comment added by 212.199.157.54 (talk • contribs) as of 10:13, July 11, 2005 (UTC)

PAS has been split into HPAS and EPAS. EPS is not common. VAPS doesn't mean anything. Do you mean SS PAS? Greglocock (talk) 22:46, 19 April 2020 (UTC)

Hydraulic systems

The article currently states "As the speed of the engine increases, the pressure in the hydraulic fluid also increases, hence a relief valve is incorporated into the system to allow excess pressure to be bled away". This is misleading. It is the flow rate which is automatically increased with rising engine speed. However, because the flow has to pass through the same orifice (known as the "restricting orifice"), the pressure at the pump's outlet increases with engine speed. At a certain engine speed, this pressure causes a flow control valve to open, directing some of the flow back to the pump's inlet. This prevents the steering from operating too quickly. But the key here is flow rate, not pressure. Christidy (talk) 23:00, 26 April 2008 (UTC)

I have now edited the article to reflect this. Christidy (talk) 00:09, 27 April 2008 (UTC)

Electric steering in light vehicles?

I was recently looking up vehicles with the electric steering. So far the heaviest I have found to use it is the Saturn Aura Hybrid. This car weighs 3529 lbs, can it really be considered a "light" vehicle that the article claims electric steering is limited to? I have only seen it installed on I4 engines so far, but if it works on a 3500 pound vehicle, it should be safe to use on cars with V6 engines that generally weigh ~3500 pounds. This covers some light/medium SUV's/Mid size cars, these are definitely not covered under the "light" vehicle category. If anyone else knows of a heavier vehicle using a power steering system, let me know. I believe that the implementation of these devices is not limited to compacts, but will soon cover all mid size cars as well... Another interesting point I believe this section of the article should cover is the fact that Electrical steering systems are almost required in a Hybrid vehicle that operates on its own with the ICE shut off. signed:other person

The 2011 Ford F150 pickup uses EPS, as does the Mustang.--Asher196 (talk) 03:45, 7 September 2011 (UTC)

Just cause there are no heavy vehicles with it doesn't mean it doesn't work. There are other considerations as well and when you have those huge overpowered SUV's with their v6 - v8 engines there really is no point saving a KW here and there. 124.177.184.228 (talk) 13:05, 14 August 2008 (UTC)

The 1 KW comment relates to internal combustion engine vehicles with conventional 12 volt electrical systems. This should probably be stated more explicitly in the article. I am quite sure that the electrical system of a hybrid vehicle is very different from a conventional 12 volt system. Peak output of a 12 volt relies more on the battery than the alternator. 80 amps is a lot of juice. Therefore, it has little to do with the total horsepower of the engine. --Entropy7 (talk) 18:55, 24 August 2008 (UTC)

power steering <howstuffworks>

Power steering is a system which helps to steer the wheels with some source of power other than the drivers’ manual force with which he turns the steering. This feature adds to the comfort while driving as less effort is needed to turn the steering by the driver. Power Steering is especially important for the cars which have engine in front and there is a lot of weight on the front wheels.

For rear engine cars like Tata Nano or light weight cars like Maruti 800, its ok to have no power steering and still drive comfortably because of low weight on the front wheels. But for heavy cars and also as a luxury feature power steering provides lots of ease. Electrically powered steering uses an electric motor to drive either the power steering hydraulic pump or the steering linkage directly. The power steering function is therefore independent of engine speed, resulting in significant energy savings.

Conventional power steering systems use an engine accessory belt to drive the pump, providing pressurized fluid that operates a piston in the power steering gear or actuator to assist the driver. As vehicles have become heavier and switched to front wheel drive, the effort to turn the steering wheel manually has increased - often to the point where major physical exertion is required. To alleviate this, auto makers have developed power steering systems.

Power steering aims to make steering less strenuous for the driver. There are two types of power steering systems:—

1. Hydraulic and
2. Electric/electronic.

There is also a hydraulic-electric hybrid system possible.

HYDRAULIC POWER STEERING Hydraulic power steering uses high pressure fluids for assisting the steering movement. It uses a plunger type arrangement for its working. When the driver turns the steering wheel, it opens up the flow or pressurized fluid in such a way that helps to turns the wheels in the required direction.

ELECTRIC POWER STEERING Electric power steering works with the help of an Electric Motor and a control unit which has some sensors. The motor runs on battery and will use electric power to assist the movement of steering when the driver turns the wheel.

HYDRAULIC STEERING (such as used in heavy vehicles such as centre-pivot machines) Hydraulic power steering uses high pressure fluids for all of the steering movement. It uses a plunger type arrangement for its working. When the driver turns the steering wheel, it opens up the flow or pressurized fluid in such a way that turns the wheels in the required direction. It may have a control system that stops steer movement when a nominal steer movement is reached. 203.51.92.229 (talk) 01:01, 17 December 2009 (UTC)

A "steering sensor" is located on the input shaft where it enters the gearbox housing. The steering sensor is actually two sensors in one: a "torque sensor" that converts steering torque input and its direction into voltage signals, and a "rotation sensor" that converts the rotation speed and direction into voltage signals. An "interface" circuit that shares the same housing converts the signals from the torque sensor and rotation sensor into signals the control electronics can process.

Inputs from the steering sensor are digested by a microprocessor control unit that also monitors input from the vehicle's speed sensor. The sensor inputs are then compared to determine how much power assist is required according to a preprogrammed "force map" in the control unit's memory. The control unit then sends out the appropriate command to the "power unit" which then supplies the electric motor with current. The motor pushes the rack to the right or left depending on which way the voltage flows (reversing the current reverses the direction the motor spins). Increasing the current to the motor increases the amount of power assist.

The system has three operating modes: a "normal" control mode in which left or right power assist is provided in response to input from the steering torque and rotation sensor's inputs; a "return" control mode which is used to assist steering return after completing a turn; and a "damper" control mode that changes with vehicle speed to improve road feel and dampen kickback.

If the steering wheel is turned and held in the full-lock position and steering assist reaches a maximum, the control unit reduces current to the electric motor to prevent an overload situation that might damage the motor. The control unit is also designed to protect the motor against voltage surges from a faulty alternator or charging problem.

The electronic steering control unit is capable of self-diagnosing faults by monitoring the system's inputs and outputs, and the driving current of the electric motor. If a problem occurs, the control unit turns the system off by actuating a fail-safe relay in the power unit. This eliminates all power assist, causing the system to revert back to manual steering. A dash EPS warning light is also illuminated to alert the driver. To diagnose the problem, a technician jumps the terminals on the service check connector and reads out the trouble codes.

Electric power steering (EPS or EPAS) is designed to use an electric motor to reduce effort by providing steering assist to the driver of a vehicle. Sensors detect the motion and torque of the steering column, and a computer module applies assistive torque via an electric motor coupled directly to either the steering gear or steering column. This allows varying amounts of assistance to be applied depending on driving conditions. On Fiat group cars the amount of assistance can be regulated using a button named "CITY" that switches between two different assist curves, while most other EPS systems have variable assist, which allows for more assistance as the speed of a vehicle decreases and less assistance from the system during high-speed situations. In the event of component failure, a mechanical linkage such as a rack and pinion serves as a back-up in a manner similar to that of hydraulic systems. Electric systems have a slight advantage in fuel efficiency because there is no belt-driven hydraulic pump constantly running, whether assistance is required or not, and this is a major reason for their introduction. Another major advantage is the elimination of a belt-driven engine accessory, and several high-pressure hydraulic hoses between the hydraulic pump, mounted on the engine, and the steering gear, mounted on the chassis. This greatly simplifies manufacturing and maintenance. By incorporating electronic stability control electric power steering systems can instantly vary torque assist levels to aid the driver in evasive manoeuvres, Toyota has been doing so since 2002. The peak power output of the electrical system of a vehicle limits the capability of electric steering assist. A 12 volt electrical system, for example, is limited to about 80 amps of current which, in turn, limits the size of the motor to less than 1 kilowatt (12.5 volts times 80 amps equals 1000 watts). This amount of power would be adequate for smaller vehicles. It would probably be considered insufficient for larger vehicles such as trucks and SUVs. There are other types of electrical systems such as the 24-volt electrical system and other variants used for hybrid and electric vehicles. These have greater capacity that enable use of multi kilowatt motors needed for large and mid-size vehicles. Toyota's latest LS 460(4775 lbs) premium luxury car, Highlander and RX 350 midsize SUV's use electric power steering. The first electric power steering system appeared on the Honda NSX in 1990 and then the Honda S2000 in 1999. Today a number of manufactures use electric power steering, Toyota has been working to replace hydraulic systems with electric types on their redesigned cars and car-based platforms.

Reviews in the automotive press often comment that certain steering systems with electric assist do not have a satisfactory amount of "road feel". Road feel refers to the relationship between the force needed to steer the vehicle and the force that the driver exerts on the steering wheel. Road feel gives the driver the subjective perception that they are engaged in steering the vehicle. The amount of road feel is controlled by the computer module that operates the electric power steering system. In theory, the software should be able to adjust the amount of road feel to satisfy drivers. In practice, it has been difficult to reconcile various design constraints while producing a more pronounced road feel. It should be noted that the same argument has been applied to hydraulic power steering as well.

ELECTRO-HYDRAULIC STEERING

In electro-hydraulic steering, one electrically powered steering concept uses a high efficiency pump driven by an electric motor. Pump speed is regulated by an electric controller to vary pump pressure and flow, providing steering efforts tailored for different driving situations. The pump can be run at low speed or shut off to provide energy savings during straight ahead driving (which is most of the time in most world markets).

Electro-hydraulic power steering systems, sometimes abbreviated EHPS, and also sometimes called "hybrid" systems, use the same hydraulic assist technology as standard systems, but the hydraulic pressure is provided by a pump driven by an electric motor instead of being belt-driven by the engine. These systems can be found in some cars by Ford, Volkswagen,Audi, Peugeot, Citroen, SEAT, Skoda, Suzuki, Opel, MINI, Toyota, Honda, and Mazda. Servotronic offers true speed-dependent power steering, in which the amount of servo assist depends on road speed, and thus provides even more comfort for the driver. The amount of power assist is greatest at low speeds, for example when parking the car. The greater assist makes it easier to maneuver the car. At higher speeds, an electronic sensing system gradually reduces the level of power assist. In this way, the driver can control the car even more precisely than with conventional power steering. Servotronic is used by a number ofautomakers,including Audi, BMW, Volkswagen, Volvo and Porsche. Servotronic is a trademark of AM General Corp.

HYDRAULIC POWER STEERING V/S ELECTRIC POWER STEERING Hydraulic power steering is a primitive technology used for decades and has improved a lot with time. Earlier, it did not have any difference in steering response with speed of the car, but the new age of hydraulic power steering are speed sensitive and work better than the older hydraulic power steering. Electric power steering are comparatively new technology with less complicated build and mechanism, takes less space and are more durable. Electric power steering use sensors to sense the car speed and will take care of the different steering response required for different speeds. Some of the main differences are as below: 1. Hydraulic Power Steering System is complicated compared with Electric Power Steering 2. Hydraulic Power Steering System usually weighs more than Electric Power Steering 3. Hydraulic Power Steering uses hydraulic fluids for operation whereas there is no such fluid needed for Electric Power Steering, thus Electric Power Steering needs less maintenance compared to hydraulic power steering. 4. Electric Power Steering gives better response at different speeds as compared to Hydraulic Power Steering 5. Eclectic Power Steering is less prone to problems and faults and are more durable as compared to Hydraulic power steering. 6. Hydraulic power steering extracts power from engine, so it reduces the fuel mileage of the engine. Electric power steering consumes power from battery which is also charged by engine, but it consumes less power compared to Hydraulic power steering. So a car having Electric power steering will give more mileage than one with Hydraulic power steering. Electric Power Steering is better than Hydraulic Power steering. This helps us decide when we look into the features of the car we are going to buy. For instance, comparing Hyundai Santro and Hyundai i10 , Hyundai Santro has Hydraulic Power Steering whereas Hyundai i10 has electric power steering.

HISTORY OF POWER STEERING

The earliest known patent related to power steering was that by Frederick W. Lanchester in the UK,in February 1902. His invention was to "cause the steering mechanism to be actuated by hydraulic power". The next design was filed as recorded by the US Patent Office on August 30, 1932, by Klara Gailis, from Belmont, Massachusetts. There is another inventor credited with the invention of power steering by the name of Charles F. Hammond an American, born in Detroit, who filed similar patents, the first of which was filed as recorded by the Canadian Intellectual Property Office. Chrysler Corporation introduced the first commercially available power steering system on the 1951 Chrysler Imperial under the name Hydraguide. Most new vehicles now have power steering, owing to the trends toward front wheel drive, greater vehicle mass, and wider tires, which all increase the required steering effort. Modern vehicles would be extremely difficult to maneuver at low speeds. —Preceding unsigned comment added by 115.240.177.209 (talk) 17:48, 29 November 2009 (UTC)

DISADVANTAGES OF EPS(Electronic Power Steering) This article section is not fair and balanced to represent the many disadvantages of EPS. The EPS will fail when unrelated systems fail especially electrical ofcourse. This was not the case with older more reliable systems. As an example GM(general motors) has put out a TSB(technical service bulletin)#08-02-32-005, stating that some models have an ignition coil that lacks a ground strap, which in turn causes the alternator to spike and dip in voltage. This ultimately causes the steering to fail, at the worst possible moment when passing or accelerating onto the highway. A failing voltage regulator would also cause the exact same problem. Here is a video for showing the full work up of the problem that I myself diagnosed and fixed. http://www.youtube.com/watch?v=TfKhR2IEYcs&feature=youtube_gdata_player

Actually, it will not cause the steering to fail. It will cause the assist to fail. Steering is still possible.--Asher196 (talk) 03:04, 7 September 2011(UTC)

So you would think. Actually it will also cause the steering to pull the opposite way sometimes, basically because the feedback signal is wrong! Since the feedback is stronger than the average human, it indeed is more than failing, if you want exactly particular about it. Any accident due to this is considered a failure and the mechanical backup doesn't always help in the split second it takes a human to observe it. As I said the opposite steering is the real failure where the steering is completely non responsive!72.71.225.88 (talk)

The scenario you cite should cause the EPS controller to set a fault condition and shut itself down.--Asher196 (talk) 03:41, 7 September 2011 (UTC)

Well it does not always shut itself down. More like 10% of the time it would go opposite. Had I recorded that for you too, would you then believe it? I'm not making the stuff up. Go ahead and look into it yourself since you seem to be misunderstanding the possibility of oppositional steering. You would have people come here and believe that EPS cannot fail and completely ignore user input. Someone could die seriously, or you could get hit yourself as unlikely as it seems. Do the right thing, since it is unlikely a suitable source will admit or fully understand the design failure. Proof can only be obtained by observation and perhaps video of an actual GM tech saying yeah this is an issue.71.168.97.56 (talk) 04:03, 7 September 2011 (UTC)

Notice in the video the check engine light is functional but does not trip after the condition. This car is clear of any diagnostic trouble codes, and never set C0900 or B1325.

I suppose that proves it. The controller was affected or damaged in such a way by the coil/alt interaction(TSB 08-02-32-005) that it allows for a total failure condition in some vehicles, and sometimes will oppose user input to the steering wheel.72.71.225.39 (talk) 20:28, 7 September 2011 (UTC)

This trouble condition causes 18 volts or more, which would make the EPS wattage much higher.

80amps @12.5v = 1000 watts, so then 80amps @18v = 1440 watts. Good luck trying to steer against that rogue assist.71.181.31.142 (talk) 18:20, 11 September 2011 (UTC)

The GM dealer also sited that a worn tierod, wheel bearing, or faulty steering module, torque sensor can also cause the steering to fail. Maintaining this is quite difficult, since there are so many interdependant parts that all need to work flawlessly. The advantage of a non-electric system is that it relies on only the mechanical parts within the system. So we are stating that electonic systems have a distinct disadvantage. Not to mention the pricing of the electronic components and labor. Please present the truth properly so readers of wikipedia are well informed of the truth, even if that truth is unsited by automotive companies that have millions to loose.72.71.225.88 (talk) 23:27, 6 September 2011 (UTC)

Currently the sourced material(17) does not support that EPS is easier to maintain. The article clearly shows the complexity and difficulty of EPS from a design standpoint. The article was written in 2005, at which time failure was not as wide spread. Now we can see in 2011 that it is indeed not easier to maintain or diagnose.71.168.97.56 (talk) 05:35, 7 September 2011 (UTC)

As of 2016 EPAS was fitted to the Ford Ranger (T6), which has a kerb weight of 1900 kg, a GVW of 2900 kg (or more) and 3500 kg towing capacity. It's not just for light vehicles. Greglocock (talk) 21:32, 9 March 2017 (UTC)

See Also links - manufacturers

I find it hard to believe we need a list of manufacturers in the see also section, is this normal? Greglocock (talk) 11:04, 8 August 2015 (UTC)

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