I’m going to pick some important points in terms of tuning the arducopter. At the time of writing, the current version is AC 3.1.
My two main problems with my tricopter are these two: maintaining Alt-Hold and wobbling oscillation while quickly descending.
So, here goes:
These two terms (Rate Control P, Throttle Rate P) go a long way to making your copter perform well, and are highly dependent on the thrust to weight ratio of your copter. More thrust = lower gains.
- My copter oscillates quickly (smaller movements) when stabilized: Lower your gain in Rate Control P.
- My copter oscillates slowly (larger movements) when stabilized: Lower your gain in Stabilize Control P.
- My copter gets wobbly when descending quickly: Raise your gain in Rate Control P. You can tune most of this out, but it’s impossible to descend into your prop wash without some wobbles.
- My copter is too sluggish : Raise your Stabilize Control P gain. These gains make ask the copter to respond faster to angle errors.
- My copter yaws right or left 15° when I take off: Your Motors are not straight or your ESCs are not calibrated. Twist the motors until they are straight. Run the ESC calibration routine.
- My copter angles back in the opposite direction I’m flying after forward flight: Raise your gain in Stabilize Control P.
- After aggressive flying my copter leans to one side 10 – 30°: Do what ever you can to remove vibrations and isolate APM. You can even try and add a small weight to APM to keep it from vibrating. Also, just land for a few seconds, then continue flying, it will give APM a chance to correct without the vibration.
- My copter won’t stay perfectly still in the air: Run the level command on a flat surface. (hold disarm for 15 seconds to invoke.) You can also fly in auto-trim mode in a windless (important!) environment. Any wind will cause the changes you make to work against you when the quad rotates 180°. You can use your radio pitch and roll trims, but remember to re-center them when you set up your radio with the config tools. Using the radio trims can have a negative effect in SIMPLE mode when yawing. Never Trim Yaw, Your copter may start spinning on it’s own. (Quads are also susceptible to drafts. They will need constant corrections unless you install an optical flow sensor. One day…)
- My copter flies well, but then dips a motor arm in a fidgety manner while hovering: Your motor may be going bad or the bullets connectors between the motor and ESC may be at fault. Vibration from a bent shaft or unbalanced props can make bullet connections fail momentarily stopping the motor. A motor with bad bearings takes more power to spin. The ESC could be cutting out to protect itself. Or it maybe flying slow enough to stall the motor. Attach a current sensor between your battery and the motor and test the difference between a good motor and the bad one. If you are seeing higher draw in the bad one, replace or fix it.
- In Loiter, my copter constantly overshoots: Try and increase your Nav_P term. You can also tune down your I terms because in some cases, the Nav_I or Loiter_I can causes overshoot. Making the Iterms 0 when in still wind is the best way to tune Nav_P.
- My alt hold above 10 feet is only about 1-2m accurate: That’s actually the best you can achieve. The baro sensor is sensitive to light and wind. Use a felt cover to protect it from wind and make sure you don’t glue the hole and seal it up.
- My copter increasingly swings up and down in alt hold. It eventually get’s down to the ground: Your THROTTLE_P is too high or low. You don’t need a lot of P to do alt hold. Think of how much you move the throttle to hold alt perfectly. Not much! That’s what you need P to do. I will ramp up as your battery goes lower to make up the difference.
- I have a sonar installed but I can’t get it to work. Your sonar may be picking up electrical noise from the ESCs. Be sure to move it a few inches from any ESCs and try a shielded cable, if possible. If it’s cold outside, your sonar may stop working.
My quad loiters by rotating in a CW or CCW circle: Adjust your compass declination until it stops circling.