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Detect ABS engagement


turbogrill
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Hi,

 

Anyone have any good way of detecting if the ABS is engaged? I want to blink a light if that happens and also log it to our race capture.

The pulse in the pedal is not super strong, you feel it in the pits but during exciting racing moments you might not notce it.

 

So far I have:

 

1. Measure brake pressure (very nice but a little invovled)

2. Measure current draw to the dedicated "ABS Selonid fuse"

3. Log wheelspseed over the CAN and write a script to detect an issue (the race capture can do this)

 

A have a couple of analog inputs left for my race capture so adding sensors is easy.

 

Any other ways of doing it?

 

The NC Miata also has something called "ICE Mode". The ABS module will reduce the brakes thinking you are on a slippery surface. I think this only happens with bad breaking habits and unbalanced front/rear grip or brake power. I think this happened once when we had more aggressive front pads, tire pressures all screwed up and the driver (me) misused the brakes. Essentially I almost crashed into another Miata ( @ETR).

 

 

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1 minute ago, Slugworks Paul said:

Brake pressure is really the best way... and I don't think it's that involved though last I checked a sensor that can handle that high a pressure isn't cheap.

Is your ABS module on the CAN bus? Might be another way if you can snoop the message.

 

It is CAN, and some one has reversed engineered the Wheel speed sensor message.

 

But it doesn't seem to be a known "ABS engaged" CAN message.

 

The sensors are $71 each from Digikey and would require some kind of T-Fitting into the wilwood caliper. Curious if I can use on of the unused blead screws, the sensor would then hang from the bottom.

 

 

 

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3 minutes ago, turbogrill said:

 

It is CAN, and some one has reversed engineered the Wheel speed sensor message.

 

But it doesn't seem to be a known "ABS engaged" CAN message.

 

The sensors are $71 each from Digikey and would require some kind of T-Fitting into the wilwood caliper. Curious if I can use on of the unused blead screws, the sensor would then hang from the bottom.

 

 

 

 

I would not recommend attaching a sensor to the caliper. I would tee into the hard line from the ABS module to the caliper.

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38 minutes ago, Slugworks Paul said:

 

I would not recommend attaching a sensor to the caliper. I would tee into the hard line from the ABS module to the caliper.

 

That sounds safer

 

7 minutes ago, Team Infiniti said:

Idiot light tied to ABS pump motor

 

the ABS pump is inside the module. But I think there is a special fuse for the motor. I don't want to run anything in series to the motor. Maybe there is a small voltage drop when the pump works. 

Wonder how many AMPs it might be.

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12 minutes ago, turbogrill said:

 

That sounds safer

 

 

the ABS pump is inside the module. But I think there is a special fuse for the motor. I don't want to run anything in series to the motor. Maybe there is a small voltage drop when the pump works. 

Wonder how many AMPs it might be.

Honestly, if you capture brake pressure there's additional analysis you can do on brake performance and driving strategies between drivers, etc. by gathering brake pressure. It's a very common parameter to gather by data acquisition systems.

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What about screwing a T-fitting directly into the NPT port of the Wilwood caliper (where the brake hose goes).

 

the sensor would be remote on the control arm with a line to the T-fitting?

 

I want the pluming to be safe.

 

image.png.55d870478a135f093e24857a65cf3709.png

 

 

13 minutes ago, Huggy said:

Best to put the sensor between the master and the ABS pump so you capture driver input, not computer-pump-module output pressure.

 

 

 

good idea!

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1 minute ago, turbogrill said:

What about screwing a T-fitting directly into the NPT port of the Wilwood caliper (where the brake hose goes).

 

the sensor would be remote on the control arm with a line to the T-fitting?

 

I want the pluming to be safe.

 

image.png.55d870478a135f093e24857a65cf3709.png

 

 

 

 

NO!

 

Thats adding additional failure points to a safety critical system in a vulnerable positon.

 

Unsprung, vibrating, subject to debris damage.  Now you have two vulnerable hydraulic lines in that space.  It doesn't gain you anything to put the sensor at the caliper.

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37 minutes ago, Huggy said:

Best to put the sensor between the master and the ABS pump so you capture driver input, not computer-pump-module output pressure.

 

 


Then he can't capture what he's after. Although maybe you could still detect pressure spikes there from pulsing the brakes. 

I'd care about what is actually getting to the wheels.

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14 minutes ago, Slugworks Paul said:

I'd care about what is actually getting to the wheels.

 Agree but graphing pressure spikes should be still visible on the master side, not the way I would do it. 

Sometime ago there was discussion about finding cheap high pressure sensors and it was agreed they were available from the junkyard on certain Bmw and other cars.

 

 Monitoring amps on the ABS fuse would definitely show something,  but not really sure how good the data would  be,  all this would say would be how often a driver is using the nanny,   I personally use it with no guilt.  

Like mentioned above, mapping brake pressure would give much more, including watching for ripples if that is the sole intended reason for monitoring.

Edited by Team Infiniti
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4 minutes ago, Team Infiniti said:

 Agree but graphing pressure spikes should be still visible on the master side, not the way I would do it. 

Sometime ago there was discussion about finding cheap high pressure sensors and it was agreed they were available from the junkyard on certain Bmw and other cars.

 

 Monitoring amps on the ABS fuse would definitely show something,  but not really sure how good the data would  be,  all this would say would be how often a driver is using the nanny,   I personally use it with no guilt.  

Like mentioned above, mapping brake pressure would give much more, including watching for ripples if that is the sole intended reason for monitoring.


Yeah I'm not really sure the goal, just trying to answer the question. I would be curious how much we use our ABS.

I failed a diff carrier bearing in my eclipse trans which I think was partially caused by excessive use of ABS and shock loading the diff.

Edited by Slugworks Paul
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37 minutes ago, Slugworks Paul said:

I failed a diff carrier bearing in my eclipse trans which I think was partially caused by excessive use of ABS and shock loading the diff

Wow, never heard that before, from a logic stand point I don't see the carrier bearings taking the brunt from ABS. Was it a one time fail or repeat?

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3 minutes ago, Team Infiniti said:

Wow, never heard that before, from a logic stand point I don't see the carrier bearings taking the brunt from ABS. Was it a one time fail or repeat?


One time (so far). locking up the carrier can generate thrust and radial loads on the bearings for sure, but the diff might have not been shimmed optimally as well.

Edited by Slugworks Paul
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Am I missing how this wiring works? You probably said why this wouldn't work, but is that circuit energized when the pump is not engaged? Hopefully it is not... just wire an LED into the pump +12v (or ground depending on what is switched to activate it) if it is not?

 

 

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20 minutes ago, CBraden said:

Am I missing how this wiring works? You probably said why this wouldn't work, but is that circuit energized when the pump is not engaged? Hopefully it is not... just wire an LED into the pump +12v (or ground depending on what is switched to activate it) if it is not?

 

 

 

Everything is integrated, the pump is internal to the module. I would have to open the ABS module.

 

Measure current probably work, but I would really like to use a non-invasive sensor instead of a shunt resistor (might burn up and requries chopping up the harness).

 

Another option might be to put a simple pizeo element at the pump housing, I would assume the ABS module would vibrate like crazy when the ABS engages.

 

This is what it looks like:

 

image.png.be252948a093ed55903a0359b2b5d3ed.png

 

 

I wish I had a datalog showing wheelspeed vs GPS speed (don't log wheelspeed as of now). I would imagine the de-acceleration on the wheel speed to be jerky vs constant on the GPS speed.

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53 minutes ago, turbogrill said:

 

Everything is integrated, the pump is internal to the module. I would have to open the ABS module.

 

Measure current probably work, but I would really like to use a non-invasive sensor instead of a shunt resistor (might burn up and requries chopping up the harness).

 

Another option might be to put a simple pizeo element at the pump housing, I would assume the ABS module would vibrate like crazy when the ABS engages.

 

This is what it looks like:

 

image.png.be252948a093ed55903a0359b2b5d3ed.png

 

 

I wish I had a datalog showing wheelspeed vs GPS speed (don't log wheelspeed as of now). I would imagine the de-acceleration on the wheel speed to be jerky vs constant on the GPS speed.

GPS updates at only 10hz, and isn't super accurate either (+/- feet iirc), so the GPS speed will also be very jerky, but maybe not as jerky as a wheel speed sensor when wheel is "ABSing". Try plotting GPS speed from a raw data output and then use that data to calculate instantaneous acceleration... you will see what I mean. In order to get any 'smooth' acceleration data from that kind of output I have had to do significant "smoothing".

Edited by enginerd
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1 minute ago, enginerd said:

GPS speed updates at only 10hz, and isn't super accurate either (+/- feet iirc), so the GPS speed will also be very jerky. Try plotting GPS speed from a raw data output and then use that data to calculate instantaneous acceleration... you will see what I mean. In order to get any 'smooth' acceleration data from that kind of output I have had to do significant "smoothing".

 

Hmm...This just become very complicated :)

 

 

 

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Seems that even if the pump is integrated into the system, they would have a separate power for the pump that gets switched via a relay.  The power requirements for the pump are leaps and bounds more than the control of it.  Can you put an amp-meter on that circuit?

 

 

Other method would be to unplug the unit and drive without it.  I talked to a guy who watched the data set up on an a Grand Am team.  He commented that most drivers would drive the car w/o no assist first, learn the car, then try it with ABS, but in the end most drove without out and were no slower.

 

The "ice mode" scares the crap out of me having seen a few cars go off as a result of lock up.  Often where you get some wheel hop due to a bump.   Not to mention the fact that the ABS wants to keep the wheels turning, so when you spin you will slow down, then it catches while you're aimed back into the oncoming traffic.  It defeats the ability to go "two feet in".

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9 hours ago, MMiskoe said:

Seems that even if the pump is integrated into the system, they would have a separate power for the pump that gets switched via a relay.  The power requirements for the pump are leaps and bounds more than the control of it.  Can you put an amp-meter on that circuit?

 

 

Other method would be to unplug the unit and drive without it.  I talked to a guy who watched the data set up on an a Grand Am team.  He commented that most drivers would drive the car w/o no assist first, learn the car, then try it with ABS, but in the end most drove without out and were no slower.

 

The "ice mode" scares the crap out of me having seen a few cars go off as a result of lock up.  Often where you get some wheel hop due to a bump.   Not to mention the fact that the ABS wants to keep the wheels turning, so when you spin you will slow down, then it catches while you're aimed back into the oncoming traffic.  It defeats the ability to go "two feet in".

 

Yes I can put an amp meter around it, the pump has a separate fuse as you say. Should be easy, but seems like most clamp ammeters are AC?

 

The ABS module also controls brake bias, not sure if this is mechanical or electrical.

Either way I will try.

 

The Canada model came with out ABS, seems like it easy to replace the module with a Canada non abs module (simple proportion valve I assume). But ABS might be nice.

 

 

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