Feb 13, 2012, 03:49 PM
Sopwith Camel's Cousin
Between my tx and crashed aircraft
Joined Mar 2006
3,824 Posts
Quote:
 Originally Posted by jasmine2501 ... I still don't like this usage of the term accelerometers. The component measures acceleration, not orientation - so what about an accelerometer would suddenly make orientation meaningful? I now understand there is a difference between gyros and accelerometers and that the latter can be used to implement the former, so the difference isn't exclusive, but I still don't understand the usage of the word accelerometer when what you mean is "something which measures orientation" ??? I'm not trying to cause an argument here, I'm just trying to figure out our language so we can use it consistently. If we can also be correct within the larger industry that would be cool too...
It is correct as far as I can tell. Even the wikipedia talks about it this way:
http://en.wikipedia.org/wiki/Accelerometer
"However, the proper acceleration measured by an accelerometer is not necessarily the coordinate acceleration (rate of change of velocity). Instead, it is the acceleration associated with the phenomenon of weight experienced by any test mass at rest in the frame of reference of the accelerometer device. For an example where these types of acceleration differ, an accelerometer will measure a value of g in the upward direction when remaining stationary on the ground, because masses on earth have weight m*g. By contrast, an accelerometer in gravitational free fall toward the center of the Earth will measure a value of zero because, even though its speed is increasing, it is at rest in a frame of reference in which objects are weightless.
"

As far as I can tell, this works with orientations that have to do with the earth's gravity (pitch and roll), so to speak. This will not work with orientation in the yaw direction (all directions experience the same "acceleration" from the earth's gravity). And in fact, for measuring yaw direction, multi-copters often use magnometers (compasses), not accelerometers.
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Feb 13, 2012, 04:03 PM
Gopher huntin' stick jockey
East Bethel, MN USA
Joined Jul 2009
13,684 Posts
Quote:
 Originally Posted by jasmine2501 But not all components which are given the name "accelerometer" can do that function. It just seems like there ought to be a more specific name for the thing, so we can tell the difference between accelerometers which only measure acceleration in their own frame of reference, and those which measure acceleration in other ways. Don't worry about it, it's just my personal malfunction. I don't like non-specific language in technical stuff.
That seems to be the case, as most people seem to have have no trouble with the term.

Semantics aside....

As I stated - with the mQX, orientation does not matter at all during initialization. The only thing that matters is that the bird remains motionless during the process.

Joel
Feb 13, 2012, 04:07 PM
Registered User
Joined Feb 2012
87 Posts
Quote:
 Originally Posted by turboparker That seems to be the case, as most people seem to have have no trouble with the term. Semantics aside.... As I stated - with the mQX, orientation does not matter at all during initialization. The only thing that matters is that the bird remains motionless during the process. Joel
I read your post saying that earlier. When I went out to fly I left it upside down and on a bit of an angle after connecting the battery and it worked just fine. Thanks!
Feb 13, 2012, 04:10 PM
Sopwith Camel's Cousin
Between my tx and crashed aircraft
Joined Mar 2006
3,824 Posts
Quote:
 Originally Posted by Tres Wright Same here, I knew about them for quite some time and had even snooped around this forum now and then. But all the threads seemed to be buried neck-deep in techno-geek-talk that made it seem like an electrical engineering degree was a prerequisite to owning and flying one ...
For me, one nice thing about some of the flight controllers, like the multiwii and kk: the computer/controller source code is available for them.
You can use as is, if you do not want to customize.
Or if you do want to customize, all the code is available on the web (but you really better know what you are doing ).
Looking at that source code gives me a sense of what may be stuffed into the program code for an AS3X controller (true, with some differences: most planes do not have compasses, and tip stall is not really a worry with heli's).
Feb 13, 2012, 04:15 PM
Motto - fly it, crash it = fun
United States, GA
Joined Jul 2007
101 Posts
Quote:
 Originally Posted by Ed Couch Another take on Sparky's pod fuselage. Royce did his own thing and loves the shark mouth from the old Curtis P-40 that flew in China during early WWII. Carried the theme over to the little pod for the MQX. Results are attached. ed
You guys are driving me nuts....ordered my MQX today and can't wait. Been flying my yellow and blue S107G and S033G and it sounds like they'll go on the back burner when the MQX gets here. Gotta do the fuselage changes, too. Tell me the source of these things.
 Feb 13, 2012, 04:39 PM STOP DUMBING DOWN MY SKY Joined Dec 2010 391 Posts Is this the "new" MQX? Got my camera working so now I can ask if other new MQX's are coming with the plugs to the board held on by a dab of white plastic, and the motors held in with a dab of black plastic? My MPX was the Dutch shop's second batch.
 Feb 13, 2012, 04:44 PM Registered User North Richland Hills, Texas USA Joined Aug 2000 1,906 Posts Sparky's site is at the following: http://parkflyerplastics.com/cart/in...ain_page=index. Please, please read the instructions and abide by them it makes a major difference in the rigidity of the pod to leave a small gluing ridge around the pod halves. Makes for a much stronger pod and easier to assemble. The instructions are offered on Sparks site. ed
Feb 13, 2012, 04:51 PM
Motto - fly it, crash it = fun
United States, GA
Joined Jul 2007
101 Posts
Quote:
 Originally Posted by Ed Couch Sparky's site is at the following: [url]http://parkflyerplastics.com/cart/index.php?main_page=indeed
Thanks, Ed. Two pods are ordered.
Feb 13, 2012, 04:52 PM
Registered User
Joined Feb 2012
87 Posts
Quote:
 Originally Posted by docinfrance Is this the "new" MQX? Got my camera working so now I can ask if other new MQX's are coming with the plugs to the board held on by a dab of white plastic, and the motors held in with a dab of black plastic? My MPX was the Dutch shop's second batch. Attachment 4631756 Attachment 4631757
Mine is like that too.

A few posts up Stresscracked says that some of the connectors haven't been fully seated before the "RTV" has been dabbed on, I assume he is talking about the same white goop.
Feb 13, 2012, 05:05 PM
Motto - fly it, crash it = fun
United States, GA
Joined Jul 2007
101 Posts
Quote:
 Originally Posted by Stresscracked Rob G ... I also found that poor assembly of my craft left them not fully inserted before the "RTV" was dabbed on to prevent them creeping out from vibration.
So, what's the solution?....remove the ATV and re-seat, or re-seat without removal?...or, what?
Feb 13, 2012, 05:38 PM
Rocket Programmer
United States, AZ, Mesa
Joined Jul 2007
25,789 Posts
Quote:
 Originally Posted by turboparker That seems to be the case, as most people seem to have have no trouble with the term.
Most people don't particularly care about accuracy in their writing and are more than comfortable with using ambiguous terminology. As long as they understand what they mean, they don't really care if anyone else understands it. Sometimes that is ok. When it is not ok is when someone is legitimately confused by this inaccuracy, and is not afraid to admit it, and is begging to have it clarified, and then instead of helping the person, people just use their confusion to attack them with under-handed insults. That is not cool. Nobody deserves to be treated that way.
 Feb 13, 2012, 05:51 PM Registered User Joined May 2007 145 Posts Hi fs2flyer ! On my craft, the connectors could not be fully seated because the material had intruded into the mating surfaces. In order to seat fully, the "goop" needs removal. I made the posting in order to address an issue due to a possible intermittent contact. At these low voltages, poor contacts become significant. If your craft does not exhibit problems, I would not worry, because the connectors need something to prevent movement. A better solution than the "goop" would be a small section of shrinkwrap, used in the same manner as when securing servo extension connectors to prevent them from disconnecting.
Feb 13, 2012, 06:00 PM
Gopher huntin' stick jockey
East Bethel, MN USA
Joined Jul 2009
13,684 Posts
Quote:
 Originally Posted by jasmine2501 Most people don't particularly care about accuracy in their writing and are more than comfortable with using ambiguous terminology. As long as they understand what they mean, they don't really care if anyone else understands it. Sometimes that is ok. When it is not ok is when someone is legitimately confused by this inaccuracy, and is not afraid to admit it, and is begging to have it clarified, and then instead of helping the person, people just use their confusion to attack them with under-handed insults. That is not cool. Nobody deserves to be treated that way.
'Accelerometer' is the industry-accepted term. Their function has been accurately explained by a number of people on this thread - with links, even. You seem to be one of the few (possibly the only one?) on here who has a problem with this.

Point is - the accelerometer debate started a bunch of pages ago when some people were claiming all sorts of things about the mQX that were 100% wrong - such as the self-stabilizing myth, and that the bird had to be level during the initialization process.

1) We know that the mQX doesn't use accelerometers.

2) We know that it has absolutely zero self-stabilizing capability.

3) We all know that it can be initialized in any orientation.

These are the facts.

What do you hope to accomplish by continuing to argue semantics every time someone (quite correctly) uses the word 'accelerometer' in this thread?

Joel
Feb 13, 2012, 06:18 PM
Sopwith Camel's Cousin
Between my tx and crashed aircraft
Joined Mar 2006
3,824 Posts
Quote:
 Originally Posted by jasmine2501 ... I still don't like this usage of the term accelerometers. The component measures acceleration, not orientation - so what about an accelerometer would suddenly make orientation meaningful? I now understand there is a difference between gyros and accelerometers and that the latter can be used to implement the former, so the difference isn't exclusive, but I still don't understand the usage of the word accelerometer when what you mean is "something which measures orientation" ??? ...
In one sense though, "something which measures orientation" is also ambiguous, as it does not say how you are going to measure it.
In the multi-rotor copters, one typically uses accelerometers for measuring the roll & pitch orientations, and a magnometer (compass) for the yaw orientation.
In looking at some of the multi-rotor copter flight controllers, they tend to refer to all possible sensors (and there are quite a few: I can recall gyros, accelerometers, magnometer, barometer, sonar, "gps") by the type of sensor and not by what they are "trying" to measure,
which I think is, respectively: change in orientation, XY axis orientation, Z axis orientation, Z position (height), relative position of nearby obstacles, XY position.
Last edited by flying-llama; Feb 13, 2012 at 06:23 PM.
Feb 13, 2012, 06:20 PM
Registered User
Toronto Canada
Joined Dec 2002
5,605 Posts
Quote:
 Originally Posted by turboparker 'We know that it has absolutely zero self-stabilizing capability.
Because of the previous discussions in this thread about self-stabilization, a few weeks ago I flew my MQX outside.

I discovered that if I quickly blipped the right stick, the heli would move a distance away, but would self-stabilize. I attributed this to pendulum behaviour with the majority of the mass of the copter under the thrust line.

When the copter was flipped, it also managed to return to a level position with minimum input.

A longer input and the release of the right stick would make the copter continue on the intended path.

In the mSRX thread there has been considerable discussion of the behaviour of the AS3X system.

In the mSRX heli, quick rudder input doesn't significantly affect the heading hold behaviour of the swash gyros.

Longer rudder inputs (1/2 second), switch the swash gyros from heading hold mode to rate mode.

My reason for mentioning this is that I am now curious to compare how the AS3X gyros behave in the MQX with quick stick inputs and longer control stick inputs. Is the sytem designed such that quick inputs leave the gyros in heading hold mode and longer inputs switch to rate mode?

The only reason that I bring the matter up is because of the differences that I observed with the copter behaviour when using quick blip inputs and longer inputs.

One test might be to connect a servo to the receiver output and examine its behaviour instead of using the ESC and motor.
Last edited by Martyn McKinney; Feb 13, 2012 at 06:39 PM.

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