This allows the desired speed limiting (by acceleration) to be done before the speed-to-throttle PID controller is run.
This is required so the avoidance calls (which work on the desired speed) can be run after limiting but before the PID controllers
This limits the change in desired turn rate to reduce impossible requests which should help avoid overshoot
Also add rotation rate limit to turn-rate controller
AFAIK there is still a bug in ArduPilot where subparams should not start at index 0. This is due to the way the index math and bit shifing works as it incorrectly offsets all 0 index params to 0. We allow 2 levels of sub params - 3 levels in total. So params, sub params and sub sub params. The 0 parameter in all those is unfortunately always references param[0]. So param[0] and subparam[0] and subsubparam[0] will reference the same parameter value. Its why we always say start the index from 1 as the math and bitshifting then works correctly.
Yeah this is worded badly - hard to explain.
this fix ensures the output throttle is never in the opposite direction from the desired-speed
there is a possibility that this could lead to rougher throttle response when the vehicle is transitioning from forward to backwards motion because the throttle response will immediately go to zero when the desired speed cross over zero
Throttle controller has these advantages over existing controller:
based on velocity in vehicle's forward-back axis rather than ground-speed
straight-forward PID controller using speed error as input
speed control acceleration limts
stop control slows vehicle smoothly
configurable filtering
Steer controller has these advantages over existing controller:
output scaled properly for skid-steering vehicles
layered P and PID controller for angular error and rate control
configurable filtering
Randy Mackay
Daniel Widmann
Peter Barker
Michael Oborne
Grant Morphett
khancyr