Unstable descent in SITL

Hi. I’m new to Ardupilot, and I have been using SITL with Gazebo 9 for testing a landing guidance scheme with the iris model. I’m giving velocity commands in all 3 directions.

The drone is unstable and crashes during the descent. Sometimes, there is a significant difference in commanded z and observed z velocity components. As a result, it’s never able to achieve a smooth landing. Even if given only horizontal motion, there are oscillations in the drone. Would it be possible to understand the cause of this error? Please view the video below for a better understanding. I’m allowing a maximum of 1m/s descent if the speed is less than 1 and 1.9 otherwise.

link

Update:

Please redirect to this post : Arducopter 3.6 SITL with gazebo unstable flight

This had solved the problem along with increased z-accel parameters.