After setting ARSPD-USE to 1, the aircraft experiences oscillation


I am testing a 2.4-meter aerial survey aircraft. Equipped with Matek’s airspeed meter. The altitude control with ARSPD-USE=0 has been adjusted and can now fly normally. For better flight, I hope to control the throttle using an airspeed meter: ARSPD-USE=1. But after modifying the parameter, I entered cruise mode and found that the aircraft was very unstable with wavy lines in altitude. And the automatic throttle fluctuates greatly, making it almost impossible to fly. Please help me see what the problem is.

I switched to cruise mode twice between 34:20 seconds and 35:14 seconds in the log, and the issue was discovered here.

https://drive.google.com/file/d/1iHnaRo5khiJ9KfXuztw05JS_qkSMLT_x/view?usp=drive_link

I would retune the aircraft (just standard AUTOTUNE flight)

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Also make sure your airspeed sensor is properly calibrated. If you’re still experiencing the issue after that & autotune, you can reduce THR_SLEWRATE, increase TECS_THR_DAMP, and/or reduce TECS_INTEG_GAIN.

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I don’t think this will help as this is data fusion “on the desk” issue. We probably shouldn’t fuse airspeed below 3-5m/s (when near noise floor).

@1111153 Your airspeed sensor is poorly calibrated.

It shows about 12.8 m/s, but from the circling flight and the groundspeed it will be about 15.5 m/s. I would increase ARSPD_RATIO from 2.5 to 3.6. Calibrating an Airspeed Sensor — Plane documentation. You flew about 15.5 m/s with about 35% throttle. I would therefore correct AIRSPEED_CRUISE from 12 to 15.5 and then test again.

Rolf