Author Topic: Pos & Vel & Acc & Attiude (roll,pitch,yaw) data have a lot of vibration  (Read 2759 times)

h106frp

  • Hero Member
  • *****
  • Posts: 1811
    • View Profile
Re: Pos & Vel & Acc & Attiude (roll,pitch,yaw) data have a lot of vibration
« Reply #15 on: February 18, 2017, 06:05:16 PM »
I would expect most of this low level or high frequency (step change) could be tuned out with the servo drivers PID loop and some of it will just be lost becuase the motion platform just will not respond quick enough.

HornetMaX

  • Hero Member
  • *****
  • Posts: 5871
    • View Profile
Re: Pos & Vel & Acc & Attiude (roll,pitch,yaw) data have a lot of vibration
« Reply #16 on: February 18, 2017, 06:08:18 PM »
I would expect most of this low level or high frequency (step change) could be tuned out with the servo drivers PID loop and some of it will just be lost becuase the motion platform just will not respond quick enough.
Exactly. If you're "just" driving a servo with that signal, it is very likely the noise will be filtered out anyway.

The nois is annoying only if you do some advanced control and/or signal processing, like online identification of some bike parameters or usage of the acc signal for some estimator (e.g. lean angle estimation).

afarre

  • Newbie
  • *
  • Posts: 25
    • View Profile
Re: Pos & Vel & Acc & Attiude (roll,pitch,yaw) data have a lot of vibration
« Reply #17 on: February 19, 2017, 07:24:55 AM »
You are both right, this high frecuency & low amplitide noise is not a big issue to direct drive hardware actuators.
It does become an issue when needed to handle that data at software post-processing, like me  :-[

I recognice that when handling recorded real telemetries, I necessarily need to apply filtering becuase real telemetry is always noisy.
Even that it seems to be buggy having similar noise at syntetic data coming from physics model, mainly when noise remains when engine stalls or bike crashes

h106frp

  • Hero Member
  • *****
  • Posts: 1811
    • View Profile
Re: Pos & Vel & Acc & Attiude (roll,pitch,yaw) data have a lot of vibration
« Reply #18 on: February 19, 2017, 10:39:48 AM »
I dont know if it help but i have noted that the background vibration levels (including stationary) is bike dependant. Poorly defined bike/suspension geometry (GEOM) appears to make the problem much wose so might be worth sampling across several bikes.

HornetMaX

  • Hero Member
  • *****
  • Posts: 5871
    • View Profile
Re: Pos & Vel & Acc & Attiude (roll,pitch,yaw) data have a lot of vibration
« Reply #19 on: February 19, 2017, 11:20:18 AM »
You are both right, this high frecuency & low amplitide noise is not a big issue to direct drive hardware actuators.
It does become an issue when needed to handle that data at software post-processing, like me  :-[
But what kind of post-processing do you need ?  Didn't you say that you're "only" using this to drive the movement platform ?
Because in that case you have the filtering done by the actuators, plus the one you need to do anyway (to prevent the platform reacting too much when, let's say, the bike smashes in a wall) etc.

I recognice that when handling recorded real telemetries, I necessarily need to apply filtering becuase real telemetry is always noisy.
Even that it seems to be buggy having similar noise at syntetic data coming from physics model, mainly when noise remains when engine stalls or bike crashes
I wouldn't say buggy but I agree that it shouldn't be there, unless it comes from the engine vibrations (I have no idea if the amplitude is realistic or if GPB even "simulates" that, easy to check though: bike standing still, very the RPMs and see if the vibration is affected).

What h106 said is interesting.

Random question for Piboso (just a curiosity, not a suggestion): what would be the penalty in going from float to double ? Huge ?

afarre

  • Newbie
  • *
  • Posts: 25
    • View Profile
Re: Pos & Vel & Acc & Attiude (roll,pitch,yaw) data have a lot of vibration
« Reply #20 on: February 20, 2017, 10:15:50 AM »
Before continuing, let me apologize because I had to start by introducing myself, that was because I already did it with PiBoSo by private mail, I'm sorry again.

I am developing a simulation project with the skill of faithful reproduce all bike environment cues. Compared with any other kind of simulator here we find 2 hard nuts to crack: physics model and movement platform.

For both subsystems I would prefer to act as integrator of existing parts but, about physic model there is nothing similar to rFactor for bikes, finding that GPB closely match what I need, starting with its interfacing hardness.

About platform does not exist anything able to reproduce bike accelerations in terms of intensity and sustainability, so I am developing a new platform & ‘motion cues algorithm’, which can reproduce all bike accelerations with no limit of time.

Mentioned algorithm includes a lot of post-processing. While I have tried to use GBP output interface ‘as it is’, I found that I need some other data, or maybe I can get them by transforming available ones. Example: I would need pos & vel & acc based on ‘ground reference’ instead CG, but I hope I can get them by undoing the transform to CG.

But, in any case, a more stable data would help, do not forget that vibration occurs even with bike stopped and engine off (stalled).

From this point let me do some more tests to manage both problems: vibration and getting needed data from available ones, and I will post my results.

afarre

  • Newbie
  • *
  • Posts: 25
    • View Profile
Re: Pos & Vel & Acc & Attiude (roll,pitch,yaw) data have a lot of vibration
« Reply #21 on: February 20, 2017, 10:17:56 AM »
Just in case anybody wants to check vibrating data just follow this:

Enable telemetry output (http://forum.piboso.com/index.php?topic=19.0)
Run GPB and, as HornetMaX said, slam the bike (1st gear, having gear and clutch in manual)
Wait until bike stops; wait few more seconds to record telemetry with bike stopped.
Exit GPB
Edit file “GP Bikes\gpbikes\logdata.csv”, go to the end of file and see how numbers are dancing at columns 8 & 9 ("LatAcc","LonAcc")

NOTE: see that vibration is 10 times bigger because logdata.csv acceleration is in G’s, but it needs to be converted to m/s2, in coherence with pos & vel, for any sort of use.
« Last Edit: February 20, 2017, 10:20:07 AM by afarre »