Skip to content

6_Vicon_PX4.md

Latest commit

 

History

History
112 lines (66 loc) · 4.23 KB

6_Vicon_PX4.md

File metadata and controls

112 lines (66 loc) · 4.23 KB
Raw

Configure PX4 to perform indoor flights with Vicon

1. Basic configuraiton of PX4

First read prearm,arm and disarm specified by PX4. How can I comment on this: it is not better than shit.

Arming and disarming decides what cases will stop drones. One of the cases is that should a drone be stopped, or disarmed, if it cannot receive RC signals for a certain amount of time.

  1. Allow arming drones without RC signal We allow drones armed in offboard modes by setting COM_RCL_EXCEPT=4 like Explanation of COM_RCL_EXCEPT

Only setting this if we want to keep our drone armed when there is no RC input.

  1. Change timeout parameters to allow more time to take actions

    COM_OF_LOSS_T = 10
COM_DISARM_LAND =10 
COM_DISARM_LAND = -1 #means disable this

2 Use Vicon information in PX4

Indoor flights need Motion Capture System to provide pose information for drones in order to switch to the mode OFFBOARD. Check Using Vision or Motion Capture Systems for Position Estimation.

EKF2_AID_MASK and EKF2_HGT_MODE are the parameters to be tuned first.

We need to configure PX4 such that it takes navigation information from Vicon instead of GPS or IMU. Tutorials are given by PX4, i.e. EKF2 Tuning/Configuration, Using Vision or Motion Capture Systems for Position Estimation

  1. Set EKF2_AID_MASK = 24 which means 3: vision position fusion + 4: vision yaw fusion, we set position information is from Vicon.

  2. Set EKF2_HGT_MODE = 3: Vision, we set height information is also from Vicon

Reference:

  1. Indoor flying, RISC Lab Documentation, https://risc.readthedocs.io/1-indoor-flight.html.

  2. https://docs.px4.io/main/en/advanced/switching_state_estimators.html

  3. https://docs.px4.io/main/en/ros/external_position_estimation.html

  4. https://docs.px4.io/main/en/ros/external_position_estimation.html#reference-frames-and-ros

  5. https://docs.px4.io/v1.12/en/computer_vision/motion_capture.html

  6. https://docs.px4.io/v1.12/en/tutorials/motion-capture-vicon-optitrack.html

  7. https://docs.px4.io/v1.12/en/ros/external_position_estimation.html#reference-frames-and-ros

3 Tune EKF (Optional)

Choosing instances of EKF depends on the number of IMUs and the number of magnetometers. For pixhawks 5x, there are

  • 3 IMUS,
  • 1 magnetometer,

therefore, we should set

  • EKF2_MULTI_IMU = 3,
  • EKF2_MULTI_MAG = 1,

which leads to

    N_instances = MAX(EKF2_MULTI_IMU , 1) x MAX(EKF2_MULTI_MAG , 1) = 3

Following the guide https://docs.px4.io/v1.12/en/advanced_config/tuning_the_ecl_ekf.html, we should set - SENS_IMU_MODE = 1 as 1: Publish primary IMU selection, - SENS_MAG_MODE = 1 as 1: Publish primary magnetometer

https://docs.px4.io/v1.12/en/advanced_config/tuning_the_ecl_ekf.html.

Source: 1. External Vision System, PX4, 2. EKF2_AID_MASK, https://docs.px4.io/v1.12/en/advanced_config/parameter_reference.html#EKF2_AID_MASK.

Set frame transmition

SYS_MC_EST_GROUP


https://404warehouse.net/2015/12/20/autopilot-offboard-control-using-mavros-package-on-ros/

2 Communication schematic among MoCap, drone and base station

2.1 State estimation operated by PX4

https://docs.px4.io/v1.12/en/advanced_config/tuning_the_ecl_ekf.html

EKF in PX4 ECL