data acquisition sensors for braking system

[solex]

which all sensors can be used to optimise the braking system??????? few of them i have listed below pls add more
-temperature (IR) sensor
-pressure sensor
-accelorometer
-weigth sensor
-wheel speed sensor
-temperature strips or paints(which ones better???)
-a sensor for getting readings of the pedal travel(PLS SUGGEST A SENSOR )how abt a capacitive sensor fixed on the chassis rigth adjacent to the pedal??????

pls add more if reqd ..thanku

[solex]

which all sensors can be used to optimise the braking system??????? few of them i have listed below pls add more
-temperature (IR) sensor
-pressure sensor
-accelorometer
-weigth sensor
-wheel speed sensor
-temperature strips or paints(which ones better???)
-a sensor for getting readings of the pedal travel(PLS SUGGEST A SENSOR )how abt a capacitive sensor fixed on the chassis rigth adjacent to the pedal??????

pls add more if reqd ..thanku

[exFSAE]

Well.. what are you trying to optimize exactly?

[BillCobb]

Ground speed / distance sensor (Not the same as wheel speed). Yaw velocity. Pedal force.
Forget the weigth. What exactly is that, anyways. Sounds exotic. Weigth, don't tell me....

[solex]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by exFSAE:
Well.. what are you trying to optimize exactly? </div></BLOCKQUOTE>

well we r looking at obtaining the optimum brake bias reqd.....unfortunately uptil now we have never used DAQ to get real time data of the car...
m needing the value force coming on my pedal box mounts
to better the mounts...(thus readings of weigth being transfered to the front)....selection of brake lines(diameter)....as of now we r using 6mm diameter lines.....IR sensor for selection of material of hubs,disc also IR sensor for calculations of heat transfer rate...pedal seem tobe a bit spongy... these r the issues we r facing for this years car.our discs r not being overheated but since we r going for Al hubs,so just wanna keep a chek on der expansion

[solex]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by BillCobb:
Ground speed / distance sensor (Not the same as wheel speed). Yaw velocity. Pedal force.
Forget the weigth. What exactly is that, anyways. Sounds exotic. Weigth, don't tell me.... </div></BLOCKQUOTE>
sorry by weigth sensor i meant sensor for giving out realtime weigth transfer to the front under braking condition....hey thank you for the Ground speed / distance sensor.......
wudnt i the speed from my wheel speed sensor itself?????
wud der be a sensor for getting friction coefficient between the pads and the disc and tire and track ??????

[vandit]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">
....selection of brake lines(diameter)....as of now we r using 6mm diameter lines..... </div></BLOCKQUOTE>

by 6 mm you mean outer diameter of the lines right? While the internal diameter will be 2-3 mm.

[solex]

-yes vandit.....3mm ID
where can i fix a pressure sensor to get the pressures generated in the lines?????
are pressure strips(they r to b wound around the lines) good enuf for atleast obtaining highest pressure generated(they wud expand the furthest wen highest presuure is generated and remain in that state.)

[vandit]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by solex:

where can i fix a pressure sensor to get the pressures generated in the lines????? </div></BLOCKQUOTE>

Regarding where you can measure - http://www.markwilliams.com/detail.aspx?ID=1148
(kindly copy and paste in browser. didnt feel like waiting for moderator to approve the link)

Theoretically there shouldn't be difference in the pressure reading in the system. But one reason why it might be helpful to take pressure reading at caliper is that if there are some problems in brake lines (e.g. expansion) which is affecting pressure transmission, will be easy to identify. The pressure gauge discussed in the link, certainly does not help if you want pressure recording during running car. But like discussed in the link, you can setup a static measurement test. You can take readings at all four calipers at various levels of driver actuation of brake pedal. I will wait for other's reply to educate myself about dynamic reading of pressures.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">
are pressure strips(they r to b wound around the lines) good enuf for atleast obtaining highest pressure generated( they would expand the furthest wen highest presuure is generated and remain in that state.) </div></BLOCKQUOTE>

I dont have experience with the functioning of pressure strips and I am not sure if brake lines are supposed to expand. This would be serious loss in pressure. I would never want my brake lines to undergo expansion and contraction cycles with every actuation.

[vandit]

Oh yeah, by pressure strips you meant Strain gauges.

But my previous reply is still pending for approval.

[Zac]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by solex:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by BillCobb:
Ground speed / distance sensor (Not the same as wheel speed). Yaw velocity. Pedal force.
Forget the weigth. What exactly is that, anyways. Sounds exotic. Weigth, don't tell me.... </div></BLOCKQUOTE>
sorry by weigth sensor i meant sensor for giving out realtime weigth transfer to the front under braking condition....hey thank you for the Ground speed / distance sensor.......
wudnt i the speed from my wheel speed sensor itself?????
wud der be a sensor for getting friction coefficient between the pads and the disc and tire and track ?????? </div></BLOCKQUOTE>

The "best" way to measure weight transfer in real time is to run wheel force transducers. Unfortunately, those are beyond the budget of 99.9999% of FSAE teams, and add enough unsprung mass to severally compromise the system you are trying to study. Other things that could work (as long as you understand other parameters on your car) are linear pots on your dampers, laser ride height sensors, and/or an accelerometer.

The reason you can't trust a wheel speed sensor to give you an accurate ground speed is that the tire slips and will travel faster than the vehicle during acceleration and slower during braking. I think most testing these days uses a GPS signal to measure speed, though if you wanted to kick it old school you could also use a fifth wheel. or if you wanted to kick it really old school you could use a pitot tube.

you likely won't be able to find a sensor that can measure friction in real time. But if you are clever, you probably can make some assumptions and estimate friction from other logged channels.

But my suspicion here is that you really have no idea what you're trying to figure out or how to go about it. My advice, figure out what your goal is (hopefully something "smarter" than "optimize brakes"), design an experiment to help you reach that goal, and then figure out what sensors you need based on the experiment that you intend to run.

[solex]

@vandit-we r using 6mm outer dia lines.

[Adambomb]

The most efficient "sensor" I've seen for optimizing brake bias in FSAE is a good driver. http://fsae.com/groupee_common/emoticons/icon_wink.gif

As for mounting pressure transducers in the lines, best solution I've found with that is if you're using a pressure-activated switch, just get a pressure transducer with the same thread and swap it in.

[2BWise]

To measure wheel pressures add a tee between the caliper and brake line and run a pressure transducer off the third branch. Or splice the line at the most convenient point and add a tee. You could also just tee off each master cylinder and get the pressure for each axle.

To measure brake temp the best solution is to mount a thermocouple in/on the backside of the pad.

For braking DAQ in general you'll want wheel speeds, ground speed (GPS is great for this), Ax, and wheel pressure. You can use those to approximate the preferred slip level of the tire for purely longitudinal braking maneuvers and train your driver to work to that. You can also change your brake bias to fit your goal (max decel or drivability). You don't necessarily need to log weight transfer, but should easily be able to calculate it based on your decel level.