AP_Scripting/AP_Vehicle/Copter/Rover: add set_desired_speed for use in scripting

[yuri-rage]

Adds a Lua binding for set_desired_speed(float) to Copter and Rover.

Allows scripting to update the nav speed in all autopilot assisted modes.

Also includes an extremely minor update to the rover-MinFixType.lua example, per Pete's request (was not incorporated in the initial commit last week).

[rmackay9]

I think we could use the is_autopilot() method here which would allow it to work in RTL, SmartRTL, etc as well.

[yuri-rage]

I looked at doing so and generally agree, but I was not confident that wp_nav->set_speed_xy(speed * 100.0f) would function predictably if the mode was not AUTO. If I was simply being overly conservative, then I'm happy to make the change!

[yuri-rage]

Change made per request. Rebase/squashed commit containing Copter.cpp

[rmackay9]

In general this looks good to me and I think we could merge it if the above suggested change is made. thanks!

[yuri-rage]

@rmackay9, I'd also like to kindly request a backport to 4.2-stable. Particularly for Rover users, I think there will be some hesitance to upgrade to 4.3 with the major nav controller changes, so I anticipate a lot of "hangers on" to 4.2 for a while. I know several of us have an immediate use case for the set_desired_speed() binding.

[IamPete1]

Would be good to load a custom param name. It would be good to be able to remove the scirpting user params at some point.

[yuri-rage]

Per Discord discussion, will make this change.

[yuri-rage]

@IamPete1, custom param set added per discussion. Might be a good example to point folks toward when discussing scripting params, since I think I did a pretty decent job of writing a short function that takes care of it.

Also added Lua docs to AP_Scripting commit.

[IamPete1]

Looks good. Needs lua docs.

I wonder if we should accept speed changes in any mode? For example I want to start my mission at speed X. Currently the script would have to keep trying until the request was accepted.

MAVLink do_change_speed works in any mode.

[yuri-rage]

I wonder if we should accept speed changes in any mode? For example I want to start my mission at speed X. Currently the script would have to keep trying until the request was accepted.

MAVLink do_change_speed works in any mode.

@rmackay9, would it be acceptable to simply remove the is_autopilot() / is_autopilot_mode() checks to accomplish this intent?

[rmackay9]

@yuri-rage, yes, I think it's ok to remove the is_autopilot() and is_autopilot_mode() checks. It should do no harm to set the value even if AR_WPNav or AC_WPNav aren't being used.

[yuri-rage]

yes, I think it's ok to remove the is_autopilot() and is_autopilot_mode() checks. It should do no harm to set the value even if AR_WPNav or AC_WPNav aren't being used.

@rmackay9, in the case of Rover, I'm not sure we'd fully accomplish @IamPete1's intent if we just remove the check. Should we instead default to mode_auto->set_desired_speed(speed) if is_autopilot_mode() returns false?

EDIT: see my next comment - behavior is not impacted by these changes.

[yuri-rage]

@rmackay9, @IamPete1,

Removing the mode checks does not result in the DO_CHANGE_SPEED behavior that Pete describes (starting an auto mission at the requested speed after set_desired_speed() is called from any other mode). Instead, the vehicle uses cruise/waypoint speed from the params (even if mode_auto.set_desired_speed() is explicitly called in the method).

For Rover, I have removed the conditional mode check statement anyway, since control_mode->set_desired_speed() returns false for non-autopilot modes, which is likely more efficient than evaluating the condition.

For Copter, recommend no changes to the implementation as written.

[rmackay9]

@IamPete1 you happy with this? If "yes" maybe put an approved on it?

[IamPete1]

Looks good, thanks.

[rmackay9]

Merged, thanks!

[yuri-rage]

Excellent! Thank you!

@rmackay9, not sure if you saw my request for a backport to 4.2, but that would be extremely helpful. Please let me know what I can do to help!

[rmackay9]

This has been included in Copter/Rover-4.2.3 except for the last commit, "AP_Scripting: rover-MinFixType example param caching fix" because of a merge conflict.