Home  
Site Partners: SpotterGuides Veloce Books  
Related Sites: Your Link Here  

Go Back   TenTenths Motorsport Forum > Racing Talk > Racing Technology

Reply
 
Thread Tools Display Modes
Old 11 Aug 2007, 17:07 (Ref:1986141)   #1
jetto
Rookie
 
Join Date: Aug 2007
Posts: 5
jetto should be qualifying in the top 10 on the grid
The General PI help thread

Hi,

I'm stuck creating some math channels. I've sort of got a wheel slip ratio channel sorted but I also want to have an acceleration channel (not the longitudinal G but one from differentiating the wheel speed traces).

How do I go about making the differential of the speed trace in a Pi Math Channel?

Thanks
jetto is offline  
Quote
Old 14 Aug 2007, 11:02 (Ref:1988266)   #2
tobias_funke
Rookie
 
Join Date: Aug 2007
Posts: 13
tobias_funke should be qualifying in the top 10 on the grid
In Pi Maths make a new channel with whatever channel name and units you want. Set the frequency rate to the same as the 'Speed' sampling rate. The channel 'code' only needs:

deriviate ([Speed] , ignore)

NB: It's case sensitive. And make sure you get the units right. If speed is in km/h you need to divide it by 3.6 to get it to m/s and by 9.81 to get the resulting trace go G.
tobias_funke is offline  
Quote
Old 14 Aug 2007, 21:51 (Ref:1989163)   #3
jetto
Rookie
 
Join Date: Aug 2007
Posts: 5
jetto should be qualifying in the top 10 on the grid
Tobias,

Thanks for that, its plotted a graph now, whats the reason for the "ignore" part? That's what I was missing.

It's brought up a graphical result showing a wavy line (like water ripples) for the acceleration trace. The speed channel its derived from shows a linearly increasing speed however the acceleration trace has these ripples of fluctuating acceleration (goes from about 8 to 4 back to 8m/s^2 and so on for the main part of the data I'm looking at).

What would be the reason for this as to me it should show a more constant acceleration?

Thanks,
Oli
jetto is offline  
Quote
Old 18 Aug 2007, 17:24 (Ref:1991456)   #4
Rubinho
Racer
 
Join Date: Aug 2003
United Kingdom
Cambridge, UK
Posts: 167
Rubinho should be qualifying in the top 10 on the grid
Quote:
Originally Posted by tobias_funke
In Pi Maths make a new channel with whatever channel name and units you want. Set the frequency rate to the same as the 'Speed' sampling rate. The channel 'code' only needs:

deriviate ([Speed] , ignore)

NB: It's case sensitive. And make sure you get the units right. If speed is in km/h you need to divide it by 3.6 to get it to m/s and by 9.81 to get the resulting trace go G.
The actual syntax is:

derivative([Speed], Ignore)

The Ignore tells Toolbox what to do in the case of a discontinuity in the data. Not so much of an issue in logged data but there may well be missing data points in live telemetry streams for example. In this case it interpolates the missing points and carries on calculating the derivative. Your other options for the second argument are Reset i.e. stop calculating the current derivative and start again when there's a discontinuity or NoData i.e. return no derivative at all when the data is missing but hold the value and continue calculating it when the data "reappears".

Rather than putting "fudge factors" in the channel to account for units, Toolbox can do all that for you. If you open the advanced maths channel options you can tell Toolbox to automatically convert [Speed] into metres per second when it reads the input channel. If you set the Quantity of the math channel to be Acceleration and Unit to be metres per second^2 then all the units issue is taken care of. Then if you want to see it in G for example you can tell Toolbox to display the output of your math channel as a different unit by setting it in the Channel Properties. It is much better to let Toolbox handle your units "under the hood".
Rubinho is offline  
__________________
"Ah," said Dirk "it is a rare mind indeed that can render the hitherto non-existent blindingly obvious."
Quote
Old 14 Aug 2007, 22:38 (Ref:1989192)   #5
tobias_funke
Rookie
 
Join Date: Aug 2007
Posts: 13
tobias_funke should be qualifying in the top 10 on the grid
To tell you the truth I dont remember the reason for the ignore, I just always do it. I think it has something to do with the signal type but for a logged trace I have always used ignore.

Try applying a 0.1 or 0.2s moving average filter to it and make sure the sampling rates for the deriviative channel are the same as the input channel.
tobias_funke is offline  
Quote
Old 14 Aug 2007, 22:44 (Ref:1989198)   #6
tobias_funke
Rookie
 
Join Date: Aug 2007
Posts: 13
tobias_funke should be qualifying in the top 10 on the grid
Oh yeah the peaks/troughs will probably be gearshifts?
tobias_funke is offline  
Quote
Old 15 Aug 2007, 00:00 (Ref:1989232)   #7
jetto
Rookie
 
Join Date: Aug 2007
Posts: 5
jetto should be qualifying in the top 10 on the grid
The data I'm looking at is for a 1st gear launch start acceleration so no gear changes.

I applied a 0.2s moving average filter and nothing much changed but then at a filter of around 0.4 or 0.5s the acceleration trace ripples dissapear and it gives a tace more like what I'd expect.

What is the moving average filter and what problems do I get with higher values of filter?

Thanks
jetto is offline  
Quote
Old 15 Aug 2007, 07:35 (Ref:1989329)   #8
tobias_funke
Rookie
 
Join Date: Aug 2007
Posts: 13
tobias_funke should be qualifying in the top 10 on the grid
Essentially moving average filter is a 'smoother' if the trace and is good for damper speed and accelerations which have a very high frequency rate.

Im pretty sure that a moving average filter of 0.1s applies a linear (i think) average to 0.1 seconds of samples for every data point. So if you sample at 10 Hz with 0.3 MAF it will for a data point it will take the average of the actual values for the point you want, the point before and the point after and so on for the next point. If that makes any sense..

The problem with having too high a value for the MAF is you throw the baby out with the bath water. You can miss a heap of information as, with a big enough filter, you end up averaging samples over a long period of time. I'd imagine if you applied a 100s moving average filter to the speed trace of a 100s lap you'd simply get the average speed for the lap.

Also what sampling rate did you log the speed at? If the sample rate is too low it could throw some important data out (aliasing). For looking at normal speed traces 20 Hz is probably enough but to derive it like you have done, you would probably need at least 50 Hz though 100 Hz would be more.

It sounds silly, but its better to log at 200 Hz and filter a trace than it is to log and view at 50 Hz.
tobias_funke is offline  
Quote
Old 19 Nov 2010, 03:42 (Ref:2792962)   #9
sonic_87
Rookie
 
Join Date: Nov 2010
Posts: 2
sonic_87 should be qualifying in the top 10 on the grid
*Help with Pi Toolbox Maths channels*

Hi,
im looking for a channel in Pi Toolbox that will determine slip ratio for a given wheel i know slip ratio is: (wheel speed-vehicle speed)/vehicle speed, but how do you create this as a maths channel? i assume you use XKart speed for vehicle speed but wheel speed im not so sure?

My aim is to plot a graph of longitudinal force (fx) against slip ratio for different wheel loads, any ideas would be appreciated.
Also how do you export data from a Pi toolbox graph into excel???
sonic_87 is offline  
Quote
Old 23 Jan 2011, 18:27 (Ref:2819584)   #10
Belatti
Racer
 
Belatti's Avatar
 
Join Date: Aug 2007
Argentina
Argentina
Posts: 394
Belatti should be qualifying in the top 10 on the grid
I guess you will use wheel speed from an inductive sensor and vehicle speed from a GPS antenna, right?

Go to "tools" => "Pi Math" => "edit..."

In the window, click on the "gree plus" and you have created a new channel, name it and in the window you will type the formula, eg:

[FL Wheelspeed]-[Speed]/[Speed]

Then check the units, date rates and you are ready.

NOTE: if you use the "speeds" I mentioned, the calculation may be wrong because of the way wheel speed is calculated (everchanging diameter of the tyre is involved). Anyway, it worths a try
Belatti is offline  
__________________
Racing is in my blood.
Quote
Old 27 Jan 2011, 05:17 (Ref:2821163)   #11
Casper
Veteran
 
Join Date: May 2007
Posts: 3,210
Casper should be qualifying in the top 10 on the gridCasper should be qualifying in the top 10 on the grid
Quote:
Originally Posted by Belatti View Post
I guess you will use wheel speed from an inductive sensor and vehicle speed from a GPS antenna, right?
I have found that GPS speed has a definite lag against the physical speed using an MXL.
Casper is offline  
Quote
Old 7 Jan 2012, 08:07 (Ref:3008517)   #12
Umerkhan
Rookie
 
Join Date: Jan 2012
Posts: 1
Umerkhan should be qualifying in the top 10 on the grid
Hi guys, i am new to Ten-Tenths and Pi toolbox. I am working on cruden in my university, I need a little help in math channels, I have done the compare time, steering angle.

would you please help me telling what other mass channels will be helpful in making my driver faster?
thanks.
Umerkhan is offline  
Quote
Old 18 Apr 2011, 13:58 (Ref:2865735)   #13
Nolly227
Rookie
 
Join Date: Mar 2011
Posts: 7
Nolly227 should be qualifying in the top 10 on the grid
The General PI help thread

Hi folks,

I’m new to Tenth Tens, and was wondering whether I could pick some brains from some of the experienced techs here.

I'm currently in my Final Year Degree studying BSc Motorsport Tech, and am using Pi toolbox as part of my analysis. Basically What I need to do is calculate the WT of the vehicle.

I know how I can calculate it using Pi but what I need to know is it possible to convert Damper Pots that are read as a voltage, and convert them to damper Loads as I need to know the force acting upon them to get any further. Any help would be greatly appreciated!
Nolly227 is offline  
Quote
Old 18 Apr 2011, 15:44 (Ref:2865810)   #14
Nolly227
Rookie
 
Join Date: Mar 2011
Posts: 7
Nolly227 should be qualifying in the top 10 on the grid
Sorry I meant how do you convert Damper pots which is a measurement of mm to force?
Nolly227 is offline  
Quote
Old 18 Apr 2011, 19:18 (Ref:2865989)   #15
Nolly227
Rookie
 
Join Date: Mar 2011
Posts: 7
Nolly227 should be qualifying in the top 10 on the grid
Bump!
Nolly227 is offline  
Quote
Old 18 Apr 2011, 20:10 (Ref:2866029)   #16
greenamex2
Veteran
 
Join Date: Aug 2002
England
Hertfordshire
Posts: 1,686
greenamex2 should be qualifying in the top 10 on the grid
You need to know the spring rate and the damper position (for each damper) that the spring is just about to start to be compressed by the weight of the car. Possible but tricky and will need constant resetting. That would give you static load at any point, is that what you are after?
greenamex2 is offline  
Quote
Old 18 Apr 2011, 20:16 (Ref:2866032)   #17
Nolly227
Rookie
 
Join Date: Mar 2011
Posts: 7
Nolly227 should be qualifying in the top 10 on the grid
Yeah thats what I thought was the case. I have calculated the spring rate and have static damper pot values as they are now, but im uncertian what the next stage of calculating WT is.
Nolly227 is offline  
Quote
Old 18 Apr 2011, 20:26 (Ref:2866041)   #18
jeebz
Rookie
 
Join Date: Apr 2011
Posts: 5
jeebz should be qualifying in the top 10 on the grid
http://blackboard.smu.ac.uk/@@B49222...tribution.pptx

if you can download that file it might help you, its pretty simply explained. hope its the right stuff
jeebz is offline  
Quote
Old 18 Apr 2011, 20:31 (Ref:2866047)   #19
Nolly227
Rookie
 
Join Date: Mar 2011
Posts: 7
Nolly227 should be qualifying in the top 10 on the grid
Quote:
Originally Posted by jeebz View Post
http://blackboard.smu.ac.uk/@@B49222...tribution.pptx

if you can download that file it might help you, its pretty simply explained. hope its the right stuff
Just downloaded it cheers for that will have a gander now!

Just noticed your a swansea met student, me too! What year and course you on?
Nolly227 is offline  
Quote
Old 6 Aug 2011, 07:09 (Ref:2936365)   #20
Matti Allemakki
Rookie
 
Join Date: Dec 2008
Posts: 7
Matti Allemakki should be qualifying in the top 10 on the grid
Quote:
Originally Posted by jeebz View Post
http://blackboard.smu.ac.uk/@@B49222...tribution.pptx

if you can download that file it might help you, its pretty simply explained. hope its the right stuff

Could you place the link again? this one isnt working anymore.

many thanks
Matti Allemakki is offline  
Quote
Old 18 Apr 2011, 20:17 (Ref:2866036)   #21
greenamex2
Veteran
 
Join Date: Aug 2002
England
Hertfordshire
Posts: 1,686
greenamex2 should be qualifying in the top 10 on the grid
One for the PI match guru's

For reasons I won't go in to (unless you push me) I need to calculate the distance so far of the current lap.

I have a formula for the total distance so far but don't know how to 'reset' it for each lap.

Any ideas?

My current formula thingy is -

register @R;
@R=@R+([CAN Car Speed]*1609.34*0.1*5/(60*60*8));
@R;

Any guidance appreciated.
greenamex2 is offline  
Quote
Old 19 Apr 2011, 10:58 (Ref:2866381)   #22
Nilzz
Rookie
 
Join Date: Apr 2011
Posts: 1
Nilzz should be qualifying in the top 10 on the grid
Pi Toolbox: Advanced Math

I am looking for someone who is able to help me out starting up with Advanced math scripts in Pi Toolbox.
Is there perhaps some kind of startup guide available somewhere?

I found the help function not very usefull on this particular subject.

I have to note that I basically have no real programming experience with C#.
Nilzz is offline  
Quote
Old 20 Apr 2011, 09:03 (Ref:2866839)   #23
Chris Y
Nature's servant
Veteran
 
Chris Y's Avatar
 
Join Date: May 2000
United Kingdom
Over there, over here
Posts: 4,380
Chris Y has a real shot at the championship!Chris Y has a real shot at the championship!Chris Y has a real shot at the championship!Chris Y has a real shot at the championship!Chris Y has a real shot at the championship!Chris Y has a real shot at the championship!
I've merged a couple of PI threads into one, to stop this forum becoming the PI support forum

Please post questions/answers about PI toolbox here, and nowhere else.
Chris Y is offline  
__________________
This planet is mildly noted for its hoopy casinos.
Quote
Old 20 Apr 2011, 09:14 (Ref:2866844)   #24
Matti Allemakki
Rookie
 
Join Date: Dec 2008
Posts: 7
Matti Allemakki should be qualifying in the top 10 on the grid
Hello,

In our championship we need to make pitstop that last a certain period of time. Now we are working with a stopwatch mounted on the steering wheel. I want to make a math channel that starts a timer at the moment the driver pushes the pit limiter button. I want to place the outcome of this channel as an alarm or something in the display so we can remove the stopwatch and make it easier for the driver.

This for PI offcourse

Matti
Matti Allemakki is offline  
Quote
Old 20 Apr 2011, 09:21 (Ref:2866846)   #25
greenamex2
Veteran
 
Join Date: Aug 2002
England
Hertfordshire
Posts: 1,686
greenamex2 should be qualifying in the top 10 on the grid
Quote:
Originally Posted by Matti Allemakki View Post
Hello,

In our championship we need to make pitstop that last a certain period of time. Now we are working with a stopwatch mounted on the steering wheel. I want to make a math channel that starts a timer at the moment the driver pushes the pit limiter button. I want to place the outcome of this channel as an alarm or something in the display so we can remove the stopwatch and make it easier for the driver.

This for PI offcourse

Matti
PI Toolbox generally works from downloads after the event and so would not be of much use. Are you using telemetry?
greenamex2 is offline  
Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
General motorsport placement / graduate thread [merged] Jamesd Racing Technology 99 1 Dec 2009 23:08
Renault World Series 2009 (Off season/General thread) JamesRamone National & International Single Seaters 288 22 Sep 2009 13:52
Superleague Formula - background and general discussion thread JimW National & International Single Seaters 471 4 Sep 2009 14:20
GP2 Series R06 Nürburgring - Racing weekend thread & general philosophising Mekola National & International Single Seaters 102 4 Aug 2007 09:14


All times are GMT. The time now is 03:09.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Original Website Copyright © 1998-2003 Craig Antil. All Rights Reserved.
Ten-Tenths Motorsport Forums Copyright © 2004-2021 Royalridge Computing. All Rights Reserved.
Ten-Tenths Motorsport Forums Copyright © 2021-2022 Grant MacDonald. All Rights Reserved.