DO_CHANGE_SPEED throttle_cruise vs airspeed_cruise with and without airspeed sensors

Posted by drone1000 on February 27, 2015 at 10:34am

I've been reading over the ArduPlane 3.2.1 code trying to dig out the difference between the airspeed_cruise_cm and throttle_cruise parameters manipulated by DO_CHANGE_SPEED while flying waypoints in AUTO.  Is there a rule of thumb in setting these terms?  Under these circumstances it would seem these terms are redundant.

Why must both of these values be specified? Is there is a difference in how these are handled based on whether an airspeed sensor exists or not?

The comments suggest airspeed_cruise_cm and throttle_cruise should be set to equate to one another here: https://github.com/diydrones/ardupilot/blob/ArduPlane-3.2.1/ArduPlane/APM_Config.h.reference#L552 Is this true?

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Replies

  • Developer
    Grant Morphett April 8, 2015 at 8:47pm

    My understanding is airspeed_cruise_cm (set via TRIM_ARSPD_CM) is the target airspeed when you have an airspeed sensor enabled and can accurately measure your airspeed.  Its in cm/s.

    When you don't have an airspeed sensor enabled then the target airspeed is set from the throttle level which is a % via THROTTLE_CRUISE.

    Thanks, Grant.

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