offboard commands relaxing logic

[aerialhedgehog]

When responding to offboard position commands, the multirotor accelerations are limited by MPC_TILTMAX_AIR. This lets the multirotor make impulsive velocity changes.

ref @AndreasAntener
https://www.youtube.com/watch?v=0hdEZQ2MAW8
ref @aerialhedgehog
https://www.youtube.com/watch?v=K-pBmei5Uso#t=9

[aerialhedgehog]

ref @LorenzMeier
#1810 (comment)

"The commanded velocity should be min(velocity_command, velocity_pos_controller_output, max_vel_param). If done this way the commanded velocity can be used to control the system response, but if its too large it won't overshoot once it reaches the desired position."

[aerialhedgehog]

here's some potential pseudo code --

if offboard position commanded:

    the_position_command = offboard_position_command

if offboard velocity commanded:

    for axis in [x,y]:
        the_velocity_command[axis] = min(
            offboard_velocity_command[axis],
            velocity_pos_controller_output[axis],
            MPC_XY_VEL_MAX,
        )
    for axis in [z]:
        the_velocity_command[axis] = min(
            offboard_velocity_command[axis],
            velocity_pos_controller_output[axis],
            MPC_Z_VEL_MAX
        )

if offboard acceleration commanded:

    for axis in [x,y,z]:
        the_acceleration_command[axis] = min(
            offboard_acceleration_command[axis],
            acceleration_pos_controller_output[axis],
        )

send (
    the_position_command
    the_velocity_command
    the_acceleration_command
)

[aerialhedgehog]

an alternative could be to clamp the magnitude of velocity_pos_controller_output with the magnitude of offboard_velocity_command

if offboard_position_command:

    the_position_command = offboard_position_command

if offboard_velocity_command:

    scale_mag = magnitude(offboard_velocity_command) / magnitude(velocity_pos_controller_output)

    if scale_mag < 1:
        the_velocity_command = velocity_pos_controller_output * scale_mag
    else:
        the_velocity_command = velocity_pos_controller_output

if offboard_acceleration_command:

    scale_mag = magnitude(offboard_acceleration_command) / magnitude(acceleration_pos_controller_output)

    if scale_mag < 1:
        the_acceleration_command = acceleration_pos_controller_output * scale_mag
    else:
        the_acceleration_command = acceleration_pos_controller_output

send (
    the_position_command
    the_velocity_command
    the_acceleration_command
)