EPAS (Electric Power Assist Steering)

N

n wood

i still think a simple button that you press for full assist then press again for low assist would be a good compromise it keeps things simple and would be cheeper than a fully auto settup, and it would be easy to mount the button on your gearshift also there is already an all singing all dancing setup already on the market for around the £100 mark that has a first class pedigree and would be hard to compeat against unless it could be done a fair bit cheeper
cheers.
 
S

Keith Stafford

Morning Guys, sorry totally forgot to come back on this point,...... we can do the toggle system as Nigel suggests for the EPAS controller, car start at t=0, controller waits 10 secs to initialise EPAS ECU, then goes immediately to high speed (low assist) mode and stays that way until a button press toggles it to low speed (high assist) and stays that way until you press the button again,....

Standard £39 price:-

CORSA RALLY ELECTRIC POWER STEERING CONTROL CONTROLLER UNIT | eBay


If you buy one of these we can deliver in a week or two. Again sorry for the delay, regards Keith
 
S

Keith Stafford

Hey Guys, the quick answer is yes.

The slow answer is, I would need the pulse mapping for the EPAS units in the Alto and Yaris. What I mean by that is this. On the Corsa there are 3 levels of assistance, high assist for low speed (1-15mph), medium assist (15-45mph) and low assist for high speed (45+mph).

when the EPAS unit is in the donor car it gets pulse counts from the engine ECU, these pulse counts are proportional to the car speed, so rather than a speed being given to the EPAS it is simply a pulse rate which varies with speed. My controller basically simulates this pulse count (to the EPAS) and the EPAS varies the assistance accordingly. If you can find out this pulse/MPH (KPH) relationship then let me know, I will code it into the controller. you can usually find this on the forums.

If you can't find this pulse relationship, I could simply take a guess and code in a very slow rate and a very high rate, which would probably work.

one other small point, I was able to source the actual connector used by GM on the corsa EPAS, so this means my controller plugs directly into the corsa EPAS. you may want to source this also for your car's EPAS,... you may have it from the donor vehicle. If not then you can connect (solder) directly to the EPAS.

Hope this helps? K
 
nextstep

Renato

Lifetime Supporter
Darrin, Keith,

When I originally started to look in to EPAS I stumbled across a posting where the guy installed Yaris column and ECU in to a Corolla. The ECU has to be from an non-ABS Yaris. I have a 2007 Yaris ECU. In that case the ECU takes speed signal from a speed sensor rather than from the CAN-BUS.
One of ideas was to make a square wave generator and feed it to the ECU, controlling it with a pot or presets (selector switch). Another idea is to get a speed sensor from Yaris and connect it to the ECU (need to find the p/rev). Never got to any of that, but what I did is check the unit on the bench for current draw and does it actually work. I did the testing by securing the column in to a vise and locking output shaft so it can't move. By turning the steering slightly I saw the unit try to overcome the locked shaft and the amps went up to about 35A. The amperage was proportional to my pressure on the steering wheel. So the unit does what it is supposed to do. I did all this without the speed input. What I did do is momentary input 12VDC to the signal input and that enabled the EPAS. Every time I powered up the system I had to enable it to work. I really don't know to what level of assist it goes to and can't find it anywhere on the internet. Somewhere I read that it has a default low-assist at 0 speed until the car starts moving. For now I'm going to leave it without speed signal and try it out.
BTW, there are few guys that did this with Corollas (no speed signal) and they liked it.

Also, for those who want to try, the manual states the rate is 43Hz at 37MPH (60 KPH). I'll try to post the manual.

Regards,
Renato
 

Attachments

  • Yaris-Repair-Manual-27-Power-Steering.pdf
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S

Keith Stafford

Hi Renato, all I need is the pulse to speed rate, as my product simply outputs a square wave that simulates the speed. the frequency of the square wave is controlled by the button, default state is high pulse rate which simulates high speed (low assistance), push the button to get low pulse rate (high assistance) for a period of 1 minute to allow you to park.

I should also say that there is a chance that the Yaris EPAS has a default state of low assist, so in the absence of any speed pulses, it may default to that, which may be sufficient for the GT40 as it is fairly light at the front, compared to a yaris with its engine sitting over the wheels.

The 43Hz/37MPH figure above is enough to recode the product, we would simply give is a higher rate, say 86Hz (low assist) by default and a lower, say 20Hz (high assist) upon button press. K
 
W

Bill Musarra

Just a note to let all that read this, that I have the original controller that Kieth produced. It took me a year to finally get it tested due to my damage to the rear clip(see rookie mistake). I finished painting the car and took the car for its first outing since the accident. I want you all to know that the system that Kieth and I worked on and he produced, works flawlessly. From the first start up, backup, and drive it works as a smooth transition and is not even noticed. During my drive(some 150 miles of mostly highway travel) the stering was eventless. The car steered quite easily and required very small movements to get a response and was easily controlled. I have a 12" Momo wheel and it gave me no fight at all. Coming into my drive(down hill), I hit the button to transition into high assist. The resulting turn into my lower drive(some 140-160 degrees) was so light I was amazed at the ease of the turn. The effort I needed to make was less than my Volkswagen. My only suggestion is to take this to the next level, and make the system automatic by recognizing speed, and give high assist all the time the speed is below a threshold mph, then switching to low assist for any speeds above that threshold. I don't think a medium assist is really needed. On my return travel I was in some stop and go traffic on the interstate, from the time I entered til I got to the accident some 2 miles ahead of me. There was some lane changing(more than 1) that was handled easily with the low assist, and I never felt I should have changed to the high assist mode. A big difference from a year and a half ago when such a drive resulted in a very painful shoulder that needed to be injected. It was like driving an ordinary car.
Thanks Kieth.

Bill
 
S

Keith Stafford

Hi Bill, I am (very) relieved to hear that,.... I have a couple of Corsa columns that I use for bench testing, but never road tested it! My guess was that the low assist (high speed assist) was sufficient for the GT 40, as it is relatively light at the front.

I do have a circuit for transforming speed pulsed from a Honeywell (hall effect speed) sensor and converting it to the EPAS signal, but still testing it.

Bob, a thousand apologies, I am aware that you asked me for a price, which I responded to, but never heard anything else after that,.... did you PM me, if so I never got it..... I can get them made up if you are still interested? Darrin, do you still want one too? Let me know. Keith
 
K

John

keith the Corsa is sold down here in Aus as the Barina, so would this unit work with a 2004 model, I do have a Suzuki Alto unit but the plug is different, it has two main terminals for power and earth then under that a row of eight tiny spades for the speed tacho sensor etc, I have tracked down a wiring diagram for it if it would help to see if it will work on the Suzi one as well
cheers John
 
K

John

Keith, here is the wiring diagram for the Suzuki EPAS I have
Alto_EPS_1_zps7a2a288c.jpg


cheers John
 
S

Keith Stafford

Thanks John, what I really need to know is the pulse counts the suzi epas needs to give low and high assistance. Do you know this, you may find it on the relevant forums. K
 
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