Divergence in Position mode, and a new mode PA.

[chestnut]

Dear all,

When we are flying in Position mode, if you fly very fast, suddenly you release stick, maybe divergence appear and crash. Example : https://www.youtube.com/watch?v=JmxGvsXB1q4.
So I have a idea, create a new mode, that i called PA mode (position and attitude), when i use my multirotor for flycam, i fly in position mode, when I push pitch and roll stick, my multirotor fly in attitude mode after that if i release stick, wait a minute when my multirotor stable so possition mode start.

I will post video in PA mode in the next week.

[SuperSharpShooter]

Would you consider trying to incorporate a wind correction into your PA mode so that it will still fly straight when flying in attitude mode? Same as how arducopter hybrid loiter works. I take it you're familiar with that?

[LPR]

Divergence has been discussed many times and there are many ways to stop the problem.

The two major causes of divergence is vibrations and under powered motors.

You can tune the AQ to stop divergence. lowering the Tilt Angle D with make a difference. Lowering the Tilt Angle P will also help but it also slows the rate of tilt which I don't like.

In most cases if you can hover with 50% throttle you should have enough power to avoid divergence.

A flexible frame or having the AQ board mounted with some type of vibration dampening can also cause divergence.

Larry

[chestnut]

Hi all,

I just added a new mode Attitude for fast flying, it's independent with Possition mode. It's very useful for FLYCAM.

[Max]

What are you referring to as divergence? In the video you linked to I don't see anything close to crashing. I've also tested releasing stick quickly or changing direction in PH mode, and have never run into any issues on properly tuned MR. Here are a couple quick examples:

http://www.youtube.com/watch?v=PvF55OWo ... page#t=324
http://www.youtube.com/watch?feature=pl ... _9nE#t=146

How is your new Attitude mode different from PH/DVH?

-Max

[chestnut]

Hi Max,

When Drone in position mode and fly very fast (about > 30 degree pitch or roll) and sundenly you release stick, if battery or motor doing close maximum power, divergence will appear. I have seen it before.
I just added stich for that :
...
else if (supervisorData.state & STATE_ARMED && RADIO_FLAPS > -250) {
if(RADIO_GEAR > 0)
{
//old code
}
else //just Altitude Hold engaged
{
if (navData.mode < NAV_STATUS_ALTHOLD || navData.mode == NAV_STATUS_POSHOLD) {
// record this altitude as the hold altitude
navSetHoldAlt(UKF_ALTITUDE, 0);

// set integral to current RC throttle setting
pidZeroIntegral(navData.altSpeedPID, -UKF_VELD, motorsData.throttle * RADIO_MID_THROTTLE / MOTORS_SCALE);
pidZeroIntegral(navData.altPosPID, UKF_ALTITUDE, 0.0f);

navData.holdSpeedAlt = navData.targetHoldSpeedAlt = -UKF_VELD;
navData.holdMaxVertSpeed = p[NAV_ALT_POS_OM];
navData.mode = NAV_STATUS_ALTHOLD;

// notify ground
AQ_NOTICE("Altitude Hold engaged\n");
}

[chestnut]

When you fly attitude mode, you can go PH mode with RADIO_GEAR, and if you want to fly very fast, you can go ATTITUDE mode. It's really cool, I will up video as soon.

[Max]

So in other words this is an altitude-hold-only mode, w/out position hold engaged?

-Max

[chestnut]

[LPR]

Chestun

Your altitude hold mode is a good addition but you might think of disabling GPS for altitude hold if you are flying in an area where there is trees. Poor GPS signals can cause a rapid altitude change and if your flying fast you could have a problem.

Larry