RockeTiltometer 3

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Frank,

Congrats on getting this product out to the market. I just got mine installed into my purple two-stager, and it will add tilt and motion monitoring to a Raven altimeter. Looking forward to pushing the button!

Jim
 
JimJarvis50 said:
Frank,

Congrats on getting this product out to the market. I just got mine installed into my purple two-stager, and it will add tilt and motion monitoring to a Raven altimeter. Looking forward to pushing the button!

Jim
Click to expand...
Hi Jim...thanks again for all your help and support on this project - it was very valuable feedback...looking forward to see how the new RTOM3 does on your upcoming flight...best regards, Frank
 
Frank, in the Appendix B you have the altimeter/timer being turned on before the RTOM3. That may be backwards... I'm assuming that you won't get continuity on your altimeter if the RTOM3 is powered off, so the RTOM3 may need to be powered on before your altimeter/timer. Does this sound correct to you?
 
Looks great and the size is awesome! Just ordered one. Now to figure out how to fit it in a 54mm with all the other stuff.
 
cerving said:
Frank, in the Appendix B you have the altimeter/timer being turned on before the RTOM3. That may be backwards... I'm assuming that you won't get continuity on your altimeter if the RTOM3 is powered off, so the RTOM3 may need to be powered on before your altimeter/timer. Does this sound correct to you?
Click to expand...
That sounds right to power up ROTM3 first for altimeters like ET classic with a “one and done” measurement at start-up. I am assuming there will be RTOM3 continuity once the “heartbeat” chirps start up until launch is detected; or is it possible for an out of envelope condition to be detected causing loss of ROTM3 continuity during gyro calibration?
Looking forward to getting my hands on one and trying it out!
 
Another question… if the launch rail is angled slightly down range for safety, I gather the gyro calibration will call that angle zero?
 
I have some basic information questions as well. What is the power requirements? The 'ignition circuit' is only two contacts, is one the signal from the source and the other the output? It isn't clear how the connections to the source altimeter/timer and the charge is connected.
 
I can answer a few questions based on my own testing (and discussions with Frank). You can start up either your altimeter or the RTOM3 in either order. You won't get a continuity reading from the altimeter until the RTOM3 is powered up (and vertical I think?). The tilt envelop is vertical. Setting the rail at an angle has no effect on this (i.e., it will not call an angled rail vertical). Power requirements are a minimum of 5V. A 9V battery or a 2S lipo will work. As stated in the manual, the current drain is appreciable. A fresh alkaline 9V will last 2-3 hours (over 3 hours in my test). Don't use a used 9V. For wiring, you just take one of the leads to the igniter, break it, and connect the two ends to the RTOM3. That is, one of the igniter leads comes into and then out of the RTOM3. It just breaks the circuit.

Jim
 
cerving said:
Frank, in the Appendix B you have the altimeter/timer being turned on before the RTOM3. That may be backwards... I'm assuming that you won't get continuity on your altimeter if the RTOM3 is powered off, so the RTOM3 may need to be powered on before your altimeter/timer. Does this sound correct to you?
Click to expand...
Hi Cris - good catch...probably best to state it that way...fixed...see related comments below...thanks, Frank
 
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WoShuGui said:
That sounds right to power up ROTM3 first for altimeters like ET classic with a “one and done” measurement at start-up. I am assuming there will be RTOM3 continuity once the “heartbeat” chirps start up until launch is detected; or is it possible for an out of envelope condition to be detected causing loss of ROTM3 continuity during gyro calibration?
Looking forward to getting my hands on one and trying it out!
Click to expand...
As Jim says above, you can power either device first, but if you have a device that is one-and-done, obviously you should start it initially...the RTOM3 is simply interrupting one side of the igniter output from the triggering device...

If the RTOM3 is powered up, its ignition circuit will be interrupted whenever you exceed the selected critical angle, whether the rocket is yet launched or not...

The RTOM3 knows "down", so if you tilt your rocket on the rail for launch for an off vertical launch, it's OK - the gyros will know "down" and they will report/use the actual tilt angle from vertical - i.e., they will not use pure vertical (0 degrees) as the starting angle...

The RTOM3 starts calibrating the gyros immediately after startup, whether the rocket is upright or not, but, be sure to let the rocket sit for 5 minutes after it is raised to the launch position for best tilt accuracy...

Current draw on the RTOM3 averages about 130 mA...a fresh, average 9V alkaline battery has around 450 mAh, so, as Jim says, you should get at least 2-3 hours running time - I've witnessed a lot of long waits to launch, but none that long that you wouldn't go out and shut stuff down...I suggest, like I do for all electronics, to use fresh batteries for every flight regardless if you are using an RTOM3 or not - only makes sense...who wants to take the chance...

Most of the above is documented in the manual, but I welcome the questions...we try to be clear, but hey, it's rocket science, right!

Regards, Frank
 
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Just to clarify/respond to some of the comments above...

The RTOM3 begins gyro calibration shortly after power on, regardless of its orientation...it uses the accelerometers - they know where "down" is...we ask the user to wait for 5 minutes after the rocket is placed in launch position in order to achieve the accuracy [quite remarkable] specified in the documentation...

If you offset your rocket from pure vertical for whatever reason for launch, the RTOM3 knows the offset and reports it that way - e.g., if you offset your rocket for launch at 5 degrees off vertical, the RTOM3 knows the rocket is at 5 degrees of tilt...if your rocket comes off the rail and tilts an additional 5 degrees in the same direction, the logger will report the angle as 10 degrees of tilt...

We are making no assumption that the user would be connecting the air-start motor igniter to the triggering device and then applying power to the triggering device with the rocket horizontal and checking for continuity - this is contrary to any thought of safety/rules.

During launch preparation, once powered up, the RTOM3 ignition circuit will always be disabled if the rocket is outside the selected tilt envelope. So, as an example, let's say you select a critical angle of 20 degrees. If you power up the RTOM3 with the rocket horizontal, the RTOM3 ignition circuit will be disabled since you are exceeding the selected angle (you are at ~90 degrees).

Further, once the rocket is raised to a tilt angle of less than 20 degrees from vertical, as you continue to prep for launch, the RTOM3 ignition circuit will be enabled...if you should lower the rocket for some reason with things still powered up (a definite no-no), ignition will again be disabled if you exceed 20 degrees of tilt.

Once you have the rocket at final launch position (assuming that its inside the tilt envelope!) and get to the point of connecting the sustainer/air-start igniter(s) and/or powering up your triggering device, the RTOM3 ignition circuit will have been enabled and any continuity checking by the triggering device will operate normally.
 
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How do you download the User Manual...BEFORE a purchase?
We'd like to know everything about this device before ordering.
 
Frank,
Been playing on the bench with the RTOM3 that arrived yesterday. This appears to be phenomenal tech!
A plot of the log for what looks like a manufacturing test is below and I had a couple quick questions.
  • VRR units are Deg/s?
  • If the log does not capture a motion measurement, how might one know how close a flight gets to excess motion detection? Could that be deduced from the VRR and the tilt rate of change?
1630001080238.png
 

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WoShuGui said:
Frank,
Been playing on the bench with the RTOM3 that arrived yesterday. This appears to be phenomenal tech!
A plot of the log for what looks like a manufacturing test is below and I had a couple quick questions.
  • VRR units are Deg/s?
  • If the log does not capture a motion measurement, how might one know how close a flight gets to excess motion detection? Could that be deduced from the VRR and the tilt rate of change?
Click to expand...
Yes, the VRR is in degrees per second, but it is not involved in our computation of motion since the rotation around the Z axis does not change the rocket's orientation...

Our Motion Monitoring determines the rate of change of the rocket's orientation - [quite] different from any reported change in the tilt value in the logger output...it is possible in some instance that they could coincide, but extremely unlikely - there is no way to infer the motion value from the fields in the logger output...

We do not quantify the motion value in the logger data, just the exception event as you noted...in fact, you may find that a motion event is so quick to reset that the logger's frequency of 40 Hz will not toggle the field (show up) in the logger, but you will see the ignition disabled briefly for a few log cycles due to the short built in delay...
 
RockeTiltometer said:
Yes, the VRR is in degrees per second, but it is not involved in our computation of motion since the rotation around the Z axis does not change the rocket's orientation...

Our Motion Monitoring determines the rate of change of the rocket's orientation - [quite] different from any reported change in the tilt value in the logger output...it is possible in some instance that they could coincide, but extremely unlikely - there is no way to infer the motion value from the fields in the logger output...

We do not quantify the motion value in the logger data, just the exception event as you noted...in fact, you may find that a motion event is so quick to reset that the logger's frequency of 40 Hz will not toggle the field (show up) in the logger, but you will see the ignition disabled briefly for a few log cycles due to the short built in delay...
Click to expand...
Thanks! Yeah, I saw a quick movement briefly disables ignition with no logged excess motion. Hanging the RTOM3 on a loop of monofilament so it pendulums and does off axis rotation (simulating a coning condition) does seem to set off excess motion in phase with the pendulum period during periods of higher VRR between rotation reversals. So in this case the excess motion is coming from the off-axis components (pitch and yaw) of the rotation and pendulum?
1630023635966.png
 
WoShuGui said:
Thanks! Yeah, I saw a quick movement briefly disables ignition with no logged excess motion. Hanging the RTOM3 on a loop of monofilament so it pendulums and does off axis rotation (simulating a coning condition) does seem to set off excess motion in phase with the pendulum period during periods of higher VRR between rotation reversals. So in this case the excess motion is coming from the off-axis components (pitch and yaw) of the rotation and pendulum?
Click to expand...

Hi Dave,

Very clever test! We like it - it is a good one to demonstrate/test the system performance...

You were able to pull and parse the data out of an awkward logger output for doing so - did you create an Excel macro or some such? We debated output format and I decided to present the info such that the user could dump it into any text editor and glean the info relatively quickly - usually the period of interest is pretty short...internally we have other output formats that easily lend to use in a spreadsheet to analyze data for in-house testing and such...

Yes, motion is derived from the off-axis components...as you have seen, the motion monitor will detect excessive coning or tilting motion, as well as a combination of both...

You "punished" the RTOM3 pretty good in your testing - did you notice that by the end there was little/no accumulated drift error?! Did you let it sit for 5 minutes prior to initiating the test?

As you said earlier - phenomenal tech...innovation at its finest...Dr. Premerlani has created a terrific tilt/motion detection scheme for the RTOM3!!
 
RockeTiltometer said:
You were able to pull and parse the data out of an awkward logger output for doing so - did you create an Excel macro or some such? We debated output format and I decided to present the info such that the user could dump it into any text editor and glean the info relatively quickly - usually the period of interest is pretty short...internally we have other output formats that easily lend to use in a spreadsheet to analyze data for in-house testing and such...
Click to expand...
The log format is fine. Nothing fancy needed to parse. Just copy/paste into Google Sheets, text to columns with space as a delimiter, data filter by the first column to get the vector of interest and more copy/paste for the line plot. Suppose it could be a macro, but doesn’t take that long to do manually.

RockeTiltometer said:
Yes, motion is derived from the off-axis components...as you have seen, the motion monitor will detect excessive coning or tilting motion, as well as a combination of both...
Click to expand...
Motion measurements could provide some really interesting dynamics information for data hounds like me, but I get that the sampling rates needed would make the log file a lot bigger than most folks want to deal with.

RockeTiltometer said:
You "punished" the RTOM3 pretty good in your testing - did you notice that by the end there was little/no accumulated drift error?! Did you let it sit for 5 minutes prior to initiating the test?
Click to expand...
I also did a zero input static test and there was no tilt drift over the whole 120 seconds… a perfectly flat line! Yeah, before every run I let it sit so the gyros calibrate for at least 5 minutes. I suppose the real test will come in an actual flight when the RTOM3 gets spanked with a few dozen Gs of motor thrust. It sure looks impressive in the quasi-static ground tests tho.
 
WoShuGui said:
I suppose the real test will come in an actual flight when the RTOM3 gets spanked with a few dozen Gs of motor thrust. It sure looks impressive in the quasi-static ground tests tho.
Click to expand...


Have you looked over the new RTOM3 Test Results tab on the web site? An excerpt:
Note that the absence of acceleration during the simulated flight test does not invalidate the results. There are only two potential paths for high-g acceleration to impact the accuracy of the orientation estimation. One is a direct path through the accelerometers. Since the accelerometers are not used by the RTOM3 in orientation estimation after launch, that path is blocked. The other potential path is coupling of acceleration into the gyro sensors. For the gyros used in the RTOM3, there is no coupling of acceleration into the gyros, so that path is not possible either. Therefore, high-g acceleration does not corrupt orientation estimation during accelerated flight and ground testing is adequate to verify the performance of the RTOM3.
Click to expand...

Thanks for your interest/insight! Frank
 
Now that the dust has settled a bit with the release of the RTOM3, I had a chance to go back and revise the Operating Manual...nothing major, just clean up and some editing to try and make things a little clearer...you may want to go to the web site and re-download the manual...regards, Frank
 

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