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HelicopterRadio - Servo - Gyro - Gov - Batt › Gyro with the most amount of gain?
01-15-2011 06:55 PM  7 years agoPost 81
DS 8717

rrProfessor

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The ATV in your transmitter has a big influence on the gyro but not on the end points of the servo. In heading hold mode the ATV in the transmitter controls the maximum rate of rotation or sensitivity if you will. The servo end points is set on the gyro and not on the transmitter using ATV. You have to refer to the gyro manual for setting these.
The atv does have influence on the end points up tp the travel limits set in the gyro. when you move the stick from center you override the gyro and give the TR more pitch up what you have in the ATV,not the gyro limits. what he wants is more movent of the servo off center,just turnig up the atv wont do that unless he reaches the limit of travel set in the ATV. what he wants is more or quicker travel around centerlike less expo so the servo travels more with less stick movement. more gain is going to take more stick movement to over come the gyro.Even in HH it might need more servo travel to keep the plane steady in hover,more gain would help in HH if the servo has enough travel.

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01-15-2011 08:34 PM  7 years agoPost 82
Eddy

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My gyro is the g501 it does not have heading hold

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01-15-2011 09:54 PM  7 years agoPost 83
ChristianM

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My gyro is the g501 it does not have heading hold
My bad, I though you meant the Gy501 gyro which does have heading hold. Any way, I would change out the G501 with a heading hold gyro. I do not think you are going to have much success with a rate gyro here.
The atv does have influence on the end points up tp the travel limits set in the gyro. when you move the stick from center you override the gyro and give the TR more pitch up what you have in the ATV,not the gyro limits.
Yes, this is true for a rate gyro but not for heading hold gyro. When in heading hold the gyro will feed in as much throw as need to maintain the commanded rate of rotation up until it reaches the end points. So if the system has little power on the controls then the gyro can command the servo to the end point even when you are only commanding a small rate. This is why I would suggest going with a heading hold gyro as it will give the increased sensitivity.

As I previously mentioned I would also go with the CSM SL720 gyro as you can change all the PID controller parameters and I suspect that you have to play with those in this application as based on the described response of the Harrier it behaves very differently from our tail rotor systems.

Best of luck with your search for a solution.

Christian

Burn fuel, be happy

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01-15-2011 10:22 PM  7 years agoPost 84
DS 8717

rrProfessor

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It s the same for HH as it is for Rate mode,the stick still overrides the gyro and give the TR as much travel as needed to spin the tail s fast as you want it too. it takes the same amount of travel to spin the tail at teh same speed for HH or rate mode,the amount of travel doesnt change just because its in HH mode vs rate mode....

YOU ONLY LIVE ONCE..IF YOU LIVE IT RIGHT THATS ALL YOU NEED

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01-15-2011 11:40 PM  7 years agoPost 85
HeliAdict

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Texas

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In heading hold the stick input sets the rate of motion. It does not override the gyro.

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01-16-2011 03:36 AM  7 years agoPost 86
human213

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Eddy

Is this the pride of Guelph?

michael

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01-16-2011 04:16 AM  7 years agoPost 87
Eddy

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Not sure

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01-16-2011 06:26 AM  7 years agoPost 88
ChristianM

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It s the same for HH as it is for Rate mode,the stick still overrides the gyro and give the TR as much travel as needed to spin the tail s fast as you want it too. it takes the same amount of travel to spin the tail at teh same speed for HH or rate mode,the amount of travel doesnt change just because its in HH mode vs rate mode....
Sorry but this is flat out incorrect, there is a fundamental difference between normal and heading hold mode in how they respond to stick input. You can see how the normal and heading hold mode behaves differently on the bench. In normal mode if you give a small input the the servo will only move a small amount but in heading hold the servo will slowly move out to the end point. The speed a which it moves to the end point is dependent upon the amount of input and how high the gain is.

In flight, a gyro in normal mode will try to counteract any movement whether it is input from the pilot or external forces. So if external forces causes a rotation of X degrees then the gyro will try to counteract this movement but once the movement has occurred it will not bring aircraft back to the original position. However, a correctly set-up heading hold gyro will and it will use the full range of servo travel if needed regardless of what input the pilot gives (could be zero input for that matter).

Christian

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01-16-2011 03:15 PM  7 years agoPost 89
DS 8717

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Hh doesnt act the same on the bench because it cant sense rotation,2 different animals. it takes the same amount of TR pitch to rotate the tail at the same given rate in both HH and rate mode.
In heading hold the stick input sets the rate of motion. It does not override the gyro.
its the same for both HH and rate mode...

YOU ONLY LIVE ONCE..IF YOU LIVE IT RIGHT THATS ALL YOU NEED

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01-16-2011 05:14 PM  7 years agoPost 90
Eddy

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Ok I figured out whats going on. You guys are talking the ATV for the gyro set up, I am talking ATV for pitch and roll channel 1 and 2.
Due to channels being so valuable on a test platform that eats channels up, I have almost always done gain tuning manually due to being short on channels. So when you are using 3" long arms you can imagine the ATV for channel 1 and 2 need to be turned way down due to the travel of the long servo arms.

Its nice that people get all huffy on these forums before figuring out what the disconnect is.

And yes the gyros were all maxed out manually in these tests, that's why the servo arms are so long, as an extension of increasing gain.

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01-16-2011 06:03 PM  7 years agoPost 91
Eddy

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oh by the way, I am using gyros on pitch and roll, yaw is stable on its own.

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01-17-2011 01:09 PM  7 years agoPost 92
ChristianM

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Hh doesnt act the same on the bench because it cant sense rotation,2 different animals.
The HH gyro senses rotation just fine on the bench but since the heli is not moving then the gyro keeps increasing the servo output in order to try to get the commanded rotation. The same thing happens in flight, when you give a stick input (commanded rate of rotation) the gyro will do an initial estimate of the servo output and the measure the rate of rotation again and increase the output if the commanded rate of rotation is not reached. A normal mode gyro will not do this.
it takes the same amount of TR pitch to rotate the tail at the same given rate in both HH and rate mode.
This is true if you have no external forces. Try doing a knife edge fall with your heli, with the gyro in normal the heli will weather wane while a good heading hold gyro will keep the boom horizontal by changing the TR pitch as air speed of the heli increases.
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In heading hold the stick input sets the rate of motion. It does not override the gyro.

its the same for both HH and rate mode...
It most definitely is not the same for HH and normal mode. That is the fundamental difference bet the two.

Christian

Burn fuel, be happy

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01-17-2011 01:14 PM  7 years agoPost 93
DS 8717

rrProfessor

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This is true if you have no external forces. Try doing a knife edge fall with your heli, with the gyro in normal the heli will weather wane while a good heading hold gyro will keep the boom horizontal by changing the TR pitch as air speed of the heli increases.
It requires the same amount of TR pitch as it does in HH,the only difference is you have to input the pitch in Rate mode instead of the gyro doing it for you.

YOU ONLY LIVE ONCE..IF YOU LIVE IT RIGHT THATS ALL YOU NEED

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01-18-2011 02:13 AM  7 years agoPost 94
McKrackin

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Whoa....wrong thread...backing out slowly....

I literally never use the word literally right.

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01-19-2011 06:58 AM  7 years agoPost 95
ChristianM

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It requires the same amount of TR pitch as it does in HH,the only difference is you have to input the pitch in Rate mode instead of the gyro doing it for you.
Well the tail rotor is the same but I thought we were talking about the gyro and the way the gyro controls the TR is very different and the required tail rotor pitch varies depending on the external forces action on the aircraft. The heading hold gyro maintains a constant rate of rotation by changing the pitch while in normal mode it doesn't. That is all there is to it.

All I am saying is that heading hold will most likely resolve the issues in this application provided it is setup mechanically correctly but a normal mode gyro will not perform well as Eddy is experiencing. It is not a question of not having enough gain on the gyro but rather the mechanical and gyro setup.

Christian

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01-19-2011 03:11 PM  7 years agoPost 96
DS 8717

rrProfessor

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HH might not help if it cant get enough throw from the servo,which is what hes talking about..He wants more throw,since its not a TR but thrust vectoring it must require more control movment off center.

YOU ONLY LIVE ONCE..IF YOU LIVE IT RIGHT THATS ALL YOU NEED

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01-19-2011 04:14 PM  7 years agoPost 97
pH7

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I really hate jumping into this explosive thread. I was pushed. Honest.

I think you really need to pay extra attention to the first 2 posts by ChristianM (from 1-15). I think he is right on with his recommendations.

I am confused by 2 things that seem to be contradictory. First you feel you need long servo arms to get the throw you need (and want more) then you back off your ATV in the Tx because it needs to be low due to the long arms. So I have trouble understanding which it is you need.

For the moment, I am going to assume that you need the correction input from the gyro to make large movements. But then I also assume that your stick movements on the Tx are making the control much too sensitive to your stick movements. If these assumptions are wrong, then just throw away the rest of this post, since I will be suggesting things to correct these "assumed" problems.

Most current gyro products let you set up the servo limits by going into a setup mode, and then using the stick on the Tx to set the limits. If you have ATVs of only 14 in the Tx at the time you do this programming, then the servo limits will be quite small. Instead, you want to crank the ATVs up to the maximum while doing this setup. If the setup is correct you should have a total of 60 degrees or more of movement. AFTER doing the setup you can lower the ATVs back to your low value, or leave the ATVs alone and use the dual rate setting to set the stick sensitivity as you wish. (The dual rate method has the advantage that you tweak one number to change stick sensitivity, instead of needing to change 2.) This should give the gyro output you need.

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01-20-2011 07:45 AM  7 years agoPost 98
ChristianM

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HH might not help if it cant get enough throw from the servo,which is what hes talking about..He wants more throw,since its not a TR but thrust vectoring it must require more control movment off center.
My understanding is that he is using a long servo arm to increase the mechanical gain but then he is redusing the ATV to 14% to avoid servo binding at the extremes. The point about HH is that it will use all available travel (if needed) to achieve the commanded rate of rotation and normal mode will not. Thus the gyro will automatically provide more throw around center if needed.

I understand that it is a thrust vectoring system and not a tail rotor. Based on Eddys description it seems like the aircraft has limited control authority which means that it will respond differently from a heli TR. This is why I suggest using the CSM SL720 since you can adjust all the PID controller parameters and not just the overall gain.

Eddy
If you still want to try to use your current gyro then I suggest that you increase the ATV significantly. Although the servo may bind when testing it on the bench it will typically not do so in flight. The same trick was used by many heli pilots in the old days when using these type of gyros in order to improve the response. But as I have stated for best result you should upgrade your gyro.

Christian

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01-20-2011 05:21 PM  7 years agoPost 99
Eddy

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"My understanding is that he is using a long servo arm to increase the mechanical gain but then he is reducing the ATV to 14% to avoid servo binding at the extremes."

This is correct. I have been say ATV I meant to say drive, ATV is maxed out.
It has tons of control authority, like I say I can roll it right over on its back, I just need the gyro to be more sensitive.

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03-02-2011 10:19 PM  6 years agoPost 100
Eddy

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La Ca

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So I finally got a gyro amplifier made, this amplifies the gyro sensitivity 10 times, it only took roughly 70% to make it stable, but this is still far more than a stock gyro will deliver. In this you tube video you will see two GY401 gyros on the same plane, one with the amplifier one without, you will see that commanded servo movement is the same but the gyros out put on one is far more, this is the exact gain setting used to make the Harrier stable. The other gyro is at 100% gain, roughly 30 or 40% more gain than you would use on your heli. So at least now you can see how much moment it takes to operate the puffers as apposed to a tail rotor. I hope this clears things up

Anyways, bottom line is, it works, the aircraft is stable and hopefully I can start flight testing soon.

http://www.youtube.com/watch?v=dWHFvKWcOjA

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HelicopterRadio - Servo - Gyro - Gov - Batt › Gyro with the most amount of gain?
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