Offboard speed control in ROS2

ROS / MAVROS / MicroDDS
1

hi,
I am trying to achieve simultaneous position and velocity control in ROS2, using micrortps_bridge
Separately i can do position, and velocity, but when together, i think i am missing some control theory fundamentals

here is what i am doing

  1. prearm:

send a continuous stream of
Off-board control mode with only position set to true
and Trajectory set point msg with x = 0, y = 0, and Z = - ALTITUDE.

  1. Arm
    I arm the vehicle after 20 setpoint messages

  2. takeoff :
    send a continuous stream of
    Off-board control mode with only position set to true
    and Trajectory set point msg with x = 0, y = 0, and Z = - ALTITUDE

at this point vehicle takes off

  1. trying to move towards a point (2, 26) with slow speed :
    send a continuous stream of
    Off-board control mode with position and Velocity set to true
    and Trajectory set point msg with x y z, and vx vy vz,

the drone moves towards the waypoint, but at a very high speed, where as i have set vx vy and vz to 2m/s.

According to this link

Position setpoint and velocity setpoint (the velocity setpoint is used as feedforward; it is added to the output of the position controller and the result is used as the input to the velocity controller).

so i started assigning negative values to the vx, vy. It is now moving slower. but the local position message still shows around 9m/s in y axis… what am i missing here

@TSC21 @JulianOes @dagar

2

as suggested here,

MPC_XY_VEL_MAX
message has to be used to control the max speed. What is the equivalent in ROS2 micrortps message?

i could do it through Qgroundcontrol though. but there has to be a better way…

3

For anyone reading this later. The position and velocity setpoint often creates some confusion. The way it works is that the most “outer” setpoint is used, so in this case position. The velocity setpoint is used as a feed-forward for the controller but not as a limit.

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