# Starling loosing stability when switching from position mode to trajectory mode

Source: https://forum.modalai.com/topic/3433/starling-loosing-stability-when-switching-from-position-mode-to-trajectory-mode
Category: Development Drones (https://forum.modalai.com/category/44/development-drones)
Tags: starling
Posted: 2024-05-14 15:29:11 UTC by iparra
Replies: 4 · Views: 1419

## iparra · 2024-05-14 15:29:11 UTC

We are using voxl-mapper for autonomous indoor flights and we are experiencing strong height looses or even drifting sideways when switching from position mode (Drone hoovering in position hold  mode with 90-100% QVIO quality) to offboard (trajectory). Sometimes it is a short drop in height, but most of the times the drone reaches the floor or drifts sideways at a considerable speed until we switch to manual mode and land. The times it is able to regain stability, voxl-mapper works as expected. Any idea of what can cause this?

Thank you in advance

## Reply by iparra · 2024-05-16 09:53:13 UTC

@iparra I have narrowed it down a little. It has to do with apriltag detection. As soon as the service is enabled the drone looses stability even switching to figure_eight mode. The following options were enabled "en_transform_mavlink_pos_setpoints_from_fixed_frame":  true, "en_tag_fixed_frame":   true. Maybe it has something to do with the transforms. Any idea? Is the use of tag-detector in some way incompatible with autonomous navigation?

## Reply by Moderator (ModalAI staff) · 2024-05-17 02:54:10 UTC (in reply to iparra)

@iparra Have you gone through the steps in the VIO troubleshooting guide? https://docs.modalai.com/flying-with-vio/#troubleshooting-vio

## Reply by iparra · 2024-05-17 16:49:57 UTC (in reply to Moderator)

@Moderator Not all of them, recalibrated IMU, measured vibrations and some times vibrations were about 5  on the z axis. The problem happens when apriltag detection service is running.

## Reply by iparra · 2024-05-20 11:26:45 UTC

When we start voxl-tag-detector service with "en_tag_fixed_frame": true any change to offboard mode makes the drone loose the position, heavily drifting sideways. Isn't the px4 control referenced only to local frame? If so tag relocalization shouldn't affect the hold position. Is there any other configuration we are missing?