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Electric power steering for my 8N

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JF in MI
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PostPosted: Tue Jan 14, 2020 6:26 am    Post subject: Re: Electric power steering for my 8N Reply to specific post Reply with quote

TOH; it is what it is. You have to stop think about this so hard. You might prematurely wear out your brain. Look what happened to me ;)
 
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TheOldHokie
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PostPosted: Tue Jan 14, 2020 6:58 am    Post subject: Re: Electric power steering for my 8N Reply to specific post Reply with quote

CVPost-JF in MI wrote:
(quoted from post at 10:26:20 01/14/20) TOH; it is what it is. You have to stop think about this so hard. You might prematurely wear out your brain. Look what happened to me ;)


Cant see a lot wrong with your faculties. The big danger is what happens to a brain when you dont exercise it hard.

I am curious about your broaching operation. That cutoff shaft does not strike me as a very effective broaching tool - all one diameter with a sharpened leading edge? I would not expect that to cut full depth in one pass.

TOH
 
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Ultradog MN
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PostPosted: Tue Jan 14, 2020 7:51 am    Post subject: Re: Electric power steering for my 8N Reply to specific post Reply with quote

JF,
Am thinking about this while I'm working here and have a question that I don't remember being addressed in these EPS threads.
How many turns from lock to lock does it take to steer an 8N from full left to full right?
And how many does it take to do the same with the eps unit? If the number of turns is not the same what did you do to correct things so it doesn't either understeer or over steer your wheels. Is the unit adjustable that way?
If they were close to the same you could maybe live with it. If not a guy might adjust things somewhat by shortening or lengthening the steering arms but that would be another piece of the puzzle that he'd want to figure out.
 
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TheOldHokie
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PostPosted: Tue Jan 14, 2020 7:59 am    Post subject: Re: Electric power steering for my 8N Reply to specific post Reply with quote

CVPost-Ultradog MN wrote:
(quoted from post at 11:51:41 01/14/20) JF,
Am thinking about this while I'm working here and have a question that I don't remember being addressed in these EPS threads.
How many turns from lock to lock does it take to steer an 8N from full left to full right?
And how many does it take to do the same with the eps unit? If the number of turns is not the same what did you do to correct things so it doesn't either understeer or over steer your wheels. Is the unit adjustable that way?
If they were close to the same you could maybe live with it. If not a guy might adjust things somewhat by shortening or lengthening the steering arms but that would be another piece of the puzzle that he'd want to figure out.


The EPS assist is a simple right angle worm drive applied to the solid steering wheel shaft. No change in ratio.

TOH
 
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JF in MI
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PostPosted: Tue Jan 14, 2020 8:50 am    Post subject: Re: Electric power steering for my 8N Reply to specific post Reply with quote

As TOH says it is a worm gear drive setup. If no steering box was connected to the output shaft you could keep turning the steering wheel infinitely. The mechanism that controls it is an electronic version of a hydraulic spool valve like those used in old fashion (I hate having to refer to it like that) integral power steering box. The input shaft has a sensor on it and is attached to a small torsion bar. The other end of the torsion bar is attached to the output shaft which also has a sensor on it. When you turn the steering wheel the resistance of the tires causes the torsion bar to deflect and thus the two sensors are now out of alignment. The control module (computer) reads this misalignment and applies whatever power and direction is necessary to bring the sensors back in alignment. The beauty is here; you can buy third party electronics that, with the turn of an adjustment knob, tells the computer that the difference in the sensors is greater or less than it actually is giving more or less power assist. In a car this task is usually taken by a vehicle speed sensor applying more power while parking and less at highway speeds.
As a side note I noticed that while parked on dry concrete it takes about 15 momentary amps to steer. Once rolling at speed it takes less than 4 and zero when going straight.
 
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Ultradog MN
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PostPosted: Tue Jan 14, 2020 8:57 am    Post subject: Re: Electric power steering for my 8N Reply to specific post Reply with quote

Thank you.
 
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TheOldHokie
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PostPosted: Tue Jan 14, 2020 9:41 am    Post subject: Re: Electric power steering for my 8N Reply to specific post Reply with quote

CVPost-JF in MI wrote:
(quoted from post at 12:50:58 01/14/20) As TOH says it is a worm gear drive setup. If no steering box was connected to the output shaft you could keep turning the steering wheel infinitely. The mechanism that controls it is an electronic version of a hydraulic spool valve like those used in old fashion (I hate having to refer to it like that) integral power steering box. The input shaft has a sensor on it and is attached to a small torsion bar. The other end of the torsion bar is attached to the output shaft which also has a sensor on it. When you turn the steering wheel the resistance of the tires causes the torsion bar to deflect and thus the two sensors are now out of alignment. The control module (computer) reads this misalignment and applies whatever power and direction is necessary to bring the sensors back in alignment. The beauty is here; you can buy third party electronics that, with the turn of an adjustment knob, tells the computer that the difference in the sensors is greater or less than it actually is giving more or less power assist. In a car this task is usually taken by a vehicle speed sensor applying more power while parking and less at highway speeds.
As a side note I noticed that while parked on dry concrete it takes about 15 momentary amps to steer. Once rolling at speed it takes less than 4 and zero when going straight.


That may confuse some people so let me clarify a bit. The steering shaft is a solid connection to the steering box and the torque sensors are in parallel. In the event the EPS unit loses power the steering operates exactly as it did without it. The worm drive free wheels and you are back to factory manual steering.

I would be interested in a simple easy to obtain metric for obtaining the level of assist you are getting. Parked on concrete with wheels straight ahead put a torque wrench on the steering wheel nut and measure the torque needed to turn the wheel 90 degrees to the right. Repeat with EPS unplugged. Move tractor to grass and repeat as above to see how intelligent that aftermarket controller is.

TOH
 
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JF in MI
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PostPosted: Tue Jan 14, 2020 10:13 am    Post subject: Re: Electric power steering for my 8N Reply to specific post Reply with quote

OK TOH, your wish is my command (sort of). I put a torque wrench on the bolt holding the steering wheel on and was up to 175 inch pounds with the power off on dry concrete. The
wheels weren't turning yet but the bolt kept tightening down and I was afraid of stripping it so I went no further. I'm only guessing that the wheels may have started turning in
the 200s somewhere. With the power on it takes 20 inch pounds to turn the wheels on concrete. Can't do a grass test because we don't have any, just snow at the moment.
 
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JF in MI
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PostPosted: Tue Jan 14, 2020 10:19 am    Post subject: Re: Electric power steering for my 8N Reply to specific post Reply with quote

Oh, and BTW. The controller is factory Toyota and is one of the type that goes into "failsafe" mode (after about 6 seconds) and does not require any 3rd party electronics.

The "broaching" tool does NOT make a perfect cut with one pass which is the way I wanted it because it leaves kind of an interference fit which was exactly what I was looking for.
 
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TheOldHokie
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PostPosted: Tue Jan 14, 2020 10:22 am    Post subject: Re: Electric power steering for my 8N Reply to specific post Reply with quote

CVPost-JF in MI wrote:
(quoted from post at 14:13:45 01/14/20) OK TOH, your wish is my command (sort of). I put a torque wrench on the bolt holding the steering wheel on and was up to 175 inch pounds with the power off on dry concrete. The
wheels weren't turning yet but the bolt kept tightening down and I was afraid of stripping it so I went no further. I'm only guessing that the wheels may have started turning in
the 200s somewhere. With the power on it takes 20 inch pounds to turn the wheels on concrete. Can't do a grass test because we don't have any, just snow at the moment.


Dang you are quick - I think you like doing this stuff ;-) That result is interesting in and of itself. With no EPS 15 lb-ft isn't moving the wheels but with EPS they move at just about 1. Where do you have the boost set on the controller?

TOH
 
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JF in MI
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PostPosted: Tue Jan 14, 2020 12:09 pm    Post subject: Re: Electric power steering for my 8N Reply to specific post Reply with quote

Actually I got curious to see if I still owned one of those "Bend-O-beam" torque wrenches and that's what got me going. Once again; I do not have any 3rd (required) party
electronics added to the module to change the setting. That's why I bought this type of unit (I would have preferred a smaller one but couldn't be sure they have 'fail safe'
mode) because the factory compatible controller (compatible with that type of torque sensor) falls into a default power setting shortly after being turned on when is sees no
speed sensor. There is no adjustment. Some different model unit/controllers have no default setting and if it doesn't sense a vehicle speed sensor will not work at all unless
you spend another $50 on 3rd party electronics (Ebay) which is used to "fool" the computer into thinking it sees a speed sensor set at a certain "speed" and applies power
accordingly. Only then can you adjust the power output by making the controller "think" the vehicle is at whatever speed you dial in (slow speed for more power, fast speed for
less).
 
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TheOldHokie
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PostPosted: Tue Jan 14, 2020 1:10 pm    Post subject: Re: Electric power steering for my 8N Reply to specific post Reply with quote

CVPost-JF in MI wrote:
(quoted from post at 16:09:34 01/14/20) Actually I got curious to see if I still owned one of those "Bend-O-beam" torque wrenches and that's what got me going. Once again; I do not have any 3rd (required) party
electronics added to the module to change the setting. That's why I bought this type of unit (I would have preferred a smaller one but couldn't be sure they have 'fail safe'
mode) because the factory compatible controller (compatible with that type of torque sensor) falls into a default power setting shortly after being turned on when is sees no
speed sensor. There is no adjustment. Some different model unit/controllers have no default setting and if it doesn't sense a vehicle speed sensor will not work at all unless
you spend another $50 on 3rd party electronics (Ebay) which is used to "fool" the computer into thinking it sees a speed sensor set at a certain "speed" and applies power
accordingly. Only then can you adjust the power output by making the controller "think" the vehicle is at whatever speed you dial in (slow speed for more power, fast speed for
less).

AFAIK this vintage of system all use a torsion bar for the steering shaft and the torque sensor is mounted on rings around it so you have mechanical fail safe in the event of any electronic failure.

I was also under the impression the IC used in the motor controller also performed rudimentary control of assist level based on the steering wheel shaft torque sensors. Increases in shaft twist automagically generates more assist at the IC level. That basic adaptuve control is fine tuned for road speed, steering wheel angular velocity, and similar variables by the vehicle or steering specific ECU. Do I have that division of logic wrong?

TOH
 
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JF in MI
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PostPosted: Tue Jan 14, 2020 2:30 pm    Post subject: Re: Electric power steering for my 8N Reply to specific post Reply with quote

No, you have this correct. The difference in the torque sensors determines the amount of power supplied. The harder you turn the steering wheel the more power is applied. I
think the confusion comes in about the speed sensor so I'll try to explain. The way the torque sensor works is that the driver "feels" pretty much the same resistance on the
steering wheel no matter how much resistance is working against the tires. As the vehicle speeds up the caster, however slight, wants to keep the car tracking straight down the
road and "feeling" stable. People complained (I'm assuming) that at faster speeds the steering would become too sensitive so what the computer does is drop the power response so
the "feel" (effort put in) is greater. The object being, I assume, is that lightly resting your hand on the wheel at 70 MPH won't cause you the inadvertently steer off the road.
 
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Lance-W
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PostPosted: Tue Jan 14, 2020 3:59 pm    Post subject: Re: Electric power steering for my 8N Reply to specific post Reply with quote

:) I have a couple of questions.

Will you share the part numbers you used? Especially the EPS unit?

After mounting it sticks forward into the toolbox area or the battery area? (There's not a good angle of that in the pictures)

Did you think about having it stick out towards the rear (the shifter might be in the way but I think your knees would be far enough away?) or towards the side? I understand you tried to hide it under the hood but just wondered what else you considered?

Thanks,
Lance
 
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TheOldHokie
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PostPosted: Tue Jan 14, 2020 4:38 pm    Post subject: Re: Electric power steering for my 8N Reply to specific post Reply with quote

CVPost-JF in MI wrote:
(quoted from post at 18:30:16 01/14/20) No, you have this correct. The difference in the torque sensors determines the amount of power supplied. The harder you turn the steering wheel the more power is applied. I
think the confusion comes in about the speed sensor so I'll try to explain. The way the torque sensor works is that the driver "feels" pretty much the same resistance on the
steering wheel no matter how much resistance is working against the tires. As the vehicle speeds up the caster, however slight, wants to keep the car tracking straight down the
road and "feeling" stable. People complained (I'm assuming) that at faster speeds the steering would become too sensitive so what the computer does is drop the power response so
the "feel" (effort put in) is greater. The object being, I assume, is that lightly resting your hand on the wheel at 70 MPH won't cause you the inadvertently steer off the road.


If you think about it the torque sensor can simulate road feel all by itself. I think that was it's original purpose and that is why I wanted you to test grass vs concrete. The motor controller logic "should" be able to maintain a constant steering effort over varying ground conditions with no need for any additional sensor data. It's just a shaft torsion value that can be maintained directly using a simple IC. No computer needed. I'd still like to see that test when weather permits. I bet you could figure out a way other than the bolt to attach that torque wrench to the wheel if you gave it a little thought.

I believe that simple feedback model quickly evolved into something else. Modern cars have lots of data, a network bus with lots of bandwidth, and ECUs with plenty of processing power. So the engineers started to create a conputational model that used data like road speed, stability control sensors, wheel slip, wheel angle, etc to try and make the steering motor smarter than the driver. In other words I am not sure the "speed sensor" line is used solely for that purpose in today's cars. I suspect it has evolved into a general purpose biasing signal to the IC in the motor controller. It is likely managed by the ECU and is the computationally derived result of a model that incorporates many operational factors and more sensors than just road speed. But I could also be full of it ;-)

TOH
 
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