Add heading (degrees) to programming flight parameters

[dcan999]

I'm working on a pan/tilt that keeps pointed in one direction and I'd like to have the heading available to augment it's position the yaw doesn't seem to work and floats around too much.

[sensei-hacker]

Yaw in the PLC is the direction the aircraft is pointed. I added that a year or so ago and use it.

If you don't have a compass properly configured then of course you don't know which direction the nose is pointed.

Otherwise, if your aircraft wags around in a yaw a lot ...

[dcan999]

Thanks, I was still in the bench test phase and assumed the yaw reading was only from the IMU and worked like a gimbal which seem to be pretty accurate at holding yaw but the FC one drifts a lot. So with a compass active, the values for Yaw in the drop down in PLC are actually in degrees heading and not just the degrees yaw from power on that it does without a compass?

[sensei-hacker]

Exactly, with the mag, the yaw values are actual compass headings.

Without a compass, it starts out assuming due north (zero). The accelerometer, measuring gravity, can't measure anything in yaw of course. So without a compass, you're left with only the gyro, which measures how fast it's spinning in each axis, up to 2000° per second.

If the gyro noise is 0.1° per second, it'll be 30° off after five minutes. The compass overcomes that long term drift. While the gyro does a good job of responding immediately to the current rotation.

[dcan999]

Thanks for the explanation! I figured that's how it worked since the heading responds immediately to FC movement but slowly to compass movement. I originally was just going to use a gimbal like the GM3 but I think it would have the same yaw drift issue over time since it doesn't have a compass, so I am stuck using the PLC. With my basic/limited knowledge of the programming and math, for now I just have 8 quadrants set up, 0-45, 45-90, 90-135 and so on, with greater than and less than for each, so it will over ride the RC channel controlling the pan servo when it's in each quadrant heading, to stay pointed at least within 45* of the setpoint, and same with pitch. I'm sure there might be a more precise/smoother way to do it with the various math settings or PID's but it's above my knowledge grade hah.

This is for keeping a directional antenna on the plane pointed at home at all times, I wish we had an "antenna tracker" option for on-plane like we do on ground, but that seems a bit complicated to do.

[dcan999]

Ok I am back, I realized I can just use the yaw output to scale a servo output to have continuous yaw tracking with 1* resolution with only a few lines of programing, derp. So that solves that.

I realized from the start this crud approach will only work when I'm flying directly away and back towards myself, since my yaw tracking scale (home heading) is fixed and depends on what I programed before the flight.

That being said, if we had access to home heading, I could program it to track the home position no matter the position of the plane (basically have the gimbal always pointing where the home arrow is pointing), I think all the home arrow uses is home heading, do you think that's a possibility?

[dcan999]

Should I update request to say "add HOME heading to PLC"?

[MrD-RC]

Isn't Azimuth already in PLC?

[dcan999]

It is not, just yaw is. Does INAV use azimuth + heading to get the home arrow direction or home heading? I guess azimuth would let me do what I want too just with extra math vs having the home heading number INAV is using for the arrow, right?

[sensei-hacker]

This is for keeping a directional antenna on the plane pointed at home at all times

Ah, so what you really want is "direction to home", like the home arrow?

You did say "pointed in direction" though - home isn't always the same direction, of course. So do you want to point toward home, or do you want it to always point east (or west or whatever you choose)?

[dcan999]

yes, home heading, so I can keep the antenna pointed at home/launch point. I think I need vehicle heading as well as azimuth for that, correct? Is that what INAV uses for the home arrow?

I initially said "pointed in direction" since my original idea was much simpler and would only work flying directly away and towards myself (so azimuth never changes) since only Yaw is available and I can do that with the current PLC. If Azimuth and/or direction to home was added though, the antenna pointer would work in any vehicle position.

[MrD-RC]

Azimuth is the heading to home from the aircraft. So you would need to do the azimuth vs yaw calc in the PLC. The Flight operand should just return the azimuth without changes.

[dcan999]

So I would just need azimuth added to PLC then, and add/subtract the yaw value to get pointing direction needed, as as home arrow does?