Instability during AUTO RTL in Copter T-motor M1000

Hello to the good community members,

I have assembled a quadcopter called ‘T-motor M1000’
While there are several issues still to tackle, there some of the problems that I want to highlight and want to invite you all to please suggest the changes.

Weather: Mild wind of around 2-3 m/s, clear sky, playground

  1. Please note, the copter did perform very well in POS HOLD mode (extremely beautiful I must say, as I had been struggling since long to get anything near to it). The only problem is it looses altitude by 2-3 m when I give roll/pitch of over 5m/s, the sensor reading remains constant as if its holding it but in reality it drops a lot and its scary sometimes.

  2. During RTL when the drone was coming to home I have observed a lot of instability in Attitude control, at one point it felt like it will fall from sky. It can also be seen in the graph below

  3. There is a constant oscillation (in diagonal axis), we tried to change MOT_Thst_expo to 0.4, 0.2, 0. The oscillations seems to die at lower MOT_Thst_expo but its still oscialliting although the frequency and amplitude of oscillation has reduced. Any suggestion, what other parameters we can play with to git rid of this?

  4. The Loiter flight mode is not as smooth as we had expected. There is an extra breaking at the end of every pitch and roll command. How can I make it smooth

  5. Is lowering MOT_thst_expo going to adversely effect my flight in AUTO mode. POS and Altitude hold mode seems to work good with Expo=0, It’s an integrated T-motor ESC and MOTOR combination. Antigravity MN 7005 with 24x7.9 prop.

  6. We had checked the vibes in POS HOLD and Altitude hold mode by flight at 9-10 m/s but had not crossed the barrier of 30 vibe in any axis. But today during flight we saw it shoot to 52 in z-axis, and there was also an unexpected peak in y axis (a single high peak) at 32. How can I understand this problem and which direction I should explore more in to solve this. Any hint please?

  7. Please help me explore the effect of FLTE, FLTD, FLTT parameters. As per wiki these should be half of gyro filters, but I have seen people setting it something different to achieve good tune. I had also changed it but didn’t notice any significant change.

Please find the logs in the following link

Please feel free to share your comments, I want to make it a reliable system for aerial mission. Also, am eager to explore more and experiment with it.

Thanks for all the support that I am already got. Hoping for some more. As I develop understanding I am also eager to help people like me.

Can someone please help me with this