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 Post subject: Re: Rocket Payload
PostPosted: Tue Jun 08, 2010 5:14 am 
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'Luck! Hope you break nothing but records!

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 Post subject: Re: Rocket Payload
PostPosted: Mon Jun 14, 2010 3:58 pm 
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Just shy of 33,000ft :D :D :D

I am in a hotel in Billings MT right now should be back home this evening. I will post pics and more info tonight.
I did get great video as well.


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 Post subject: Re: Rocket Payload
PostPosted: Mon Jun 14, 2010 6:55 pm 
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Six miles, plus some! :D Did the electronics survive OK?
Lookin' forward to pics and video.

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 Post subject: Re: Rocket Payload
PostPosted: Tue Jun 15, 2010 3:29 am 
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Offical Numbers:

Altitude 32,363ft
Gees 18.5
Velocity 1,367 mph


The launch went great. I recovered the rocket intact and functinal about 2 miles away.

I plan on spending all day tommarow doing data reduction and will post sometime tomarrow.

My telem project worked good. I did have an issue at apogee where power was cycled but plenty of good data to work with.

I will post more details after I get some sleep.

What is the best way to post video?

Also Ken, Kurt and Nathan I want to thank you guys for the help along the way :D


Attachments:
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comp1.JPG
comp1.JPG [ 332.89 KiB | Viewed 5864 times ]
IMG_0672.JPG
IMG_0672.JPG [ 937.11 KiB | Viewed 5864 times ]
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 Post subject: Re: Rocket Payload
PostPosted: Tue Jun 15, 2010 3:45 am 
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another shot


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 Post subject: Re: Rocket Payload
PostPosted: Tue Jun 15, 2010 4:29 am 
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Location: CA bay Area
Nice photos.
Hmmm. Video(s). :?: Post it/them on YouTube and post the link here, I would guess.
Later.

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 Post subject: Re: Rocket Payload
PostPosted: Tue Jun 15, 2010 8:00 pm 
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here is the link http://www.youtube.com/watch?v=H-u16dhb8QI


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 Post subject: Re: Rocket Payload
PostPosted: Wed Jun 16, 2010 12:05 am 
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Better video http://www.youtube.com/watch#!v=I701JpONHmk


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 Post subject: Re: Rocket Payload
PostPosted: Wed Jun 16, 2010 4:21 am 
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"Sweet! That went a lonng ... way!" :o
Awesome audio editing!
What did you put the video together with?
Later.

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 Post subject: Re: Rocket Payload
PostPosted: Sun Jun 27, 2010 9:01 pm 
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I have zipped the flight data

accel temp - output eeprom
l3gps - raw - gps file
mongoose_placemarkers - kml file to create placemarks of gps data in google earth
mongoose_path - kml file for google earth to create a path from the gps data
mongoose_flight - spreadsheet for accel data

The data from the accel has the flight going alot lower and lasting half as long as it really did. The cause of this I beleive is

1. at rest reading could be wrong (this will be saved to eeprom now)
2. using floating point then converting to int ( I have been looking at using fixed point)

GPS was lost 14 seconds into flight. Cause is believed to be wrong placement of antenna. At first it was thought that the power cycled at apogee but the accelrometer data shows this not to be true.

I have now mounted the electronics in an rc airplane and plan on a few flights in this before it goes back into a rocket.

The next rocket flights will be lower for ease. This will also make it possable to fly more often


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 Post subject: Re: Rocket Payload
PostPosted: Mon Jun 28, 2010 4:22 pm 
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So you suspect the speed of calculating the FP numbers may have been a factor in the problem?

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 Post subject: Re: Rocket Payload
PostPosted: Tue Jun 29, 2010 3:35 am 
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I beleive the problem is in rounding error caused in the last 2 lines.

Code:
flight_loop:

 adin ax1, accel            'Get accel ADC
 
 delta = at_rest - accel                'Find differance between atrest and adc accel reading
 
 accel_float = tofloat delta         'Convert delta interger to floating point 
 gees = accel_float/5.6                      'Gees = acel counts / 5.6 counts per gee
 acceleration = gees * 32.2         'Accel = gees * 32.2 for ft/sec or 9.8 for m/sec
 velocity = velocity + acceleration * 0.015                     '-----Need to get timming                                 
 
 int_velocity = toint velocity            'Convert velocity float to interger
 int_acceleration = toint acceleration         'Convert acceleration float to interger


I am looking at fixed point. From what I understand so far I run the adc through a filter(?) to get the extra bits for 16.16 fixed point(?). From what I read addition and subtraction are not hard but multiplication and division get tricky.


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 Post subject: Re: Rocket Payload
PostPosted: Tue Jun 29, 2010 4:39 am 
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Just so you know there is no rounding done in the FP library code. However there are limits to precision which could be what you are running into. You'd need to narrow down where in your calculations your data starts to drift from what it should be. That would indiciate where to start looking.

Fixed point may not give you what you want. if it's a speed issue then fixed point can be a good workaround but in general fixed point does not have nearly the precisiion you can get from FP. Basically wth 16.16 fixed point you can handle numbers from +-32767 to +-.000030(also your resolution)

If you don't need that large an integer side you can go 8.24 which gives you 1/8millionth resolution but only +-127 integer.

When adding fixed point numbers you don't need to shift. If you multiply or divide you have to shift. if you are doing 16.16 then you have to shift by 16 bits after a mul/div. Also you have to be carefully about truncated values. If you multiply two 16.16 fixed point numbers you can very easily get a number bigger than 32bits.

There is a lot to fixed point and its not something you should jump into lightly. But if you do please post any questions as you run into problems.

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 Post subject: Re: Rocket Payload
PostPosted: Tue Jun 29, 2010 8:23 pm 
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Quote:
Just so you know there is no rounding done in the FP library code. However there are limits to precision which could be what you are running into.


Correct but these two lines

Code:
int_velocity = toint velocity            'Convert velocity float to interger
int_acceleration = toint acceleration         'Convert acceleration float to interger


I added this becase of the time it took to send out the fp numbers and storage.

Code:
You'd need to narrow down where in your calculations your data starts to drift from what it should be. That would indiciate where to start looking.


This was suposed to be an easy task as one of the altimeters is supposed to output a csv file. Only problem is the data saved from this alt is wrong way wrong :( . I am working with the other data but I have to create plots by hand.


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 Post subject: Re: Rocket Payload
PostPosted: Thu Jul 01, 2010 2:13 am 
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Will pretend that last post doesn't exist. There is no problem or rounding. I have now made it through all the data.

Before this launch I changed the at_rest/aunch_detect routine to update the at rest reading while waiting for launch to be detected. This caused the last few at rest readings to be false so I buffered them through some variables.

When I was testing I had the constant "offset" set to 3 or roughly acceleration of 0.5 gee would be the threashold. Prior to launch I increased this to just over 1 gee or 6 (adc counts).

I determined the calculated at rest reading from the flight was 491 counts. Playing with the data I found that an at rest reading of 498 counts matches the data from the other altimeter REALLY close.

Out of curiosity I checked the output from the accel when held vertical = 498 counts. This leads me to beleive that my at rest reading was not old enough.

I am really happy with how this data looks once the at rest reading is fixed. I cant wait to put it up past 30k again.

I did lose lock on the way up and this is still a problem that needs to be addressed. Looking at antenna config(use a yagi currently).


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