feat(vtol_att_control): increase front transition throttle to compensate for weight ratio#27900
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mbjd wants to merge 1 commit into
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feat(vtol_att_control): increase front transition throttle to compensate for weight ratio#27900mbjd wants to merge 1 commit into
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…ate for weight ratio Currently: - VT_F_TRANS_THR is always the literal throttle used - VT_ARSP_TRANS is scaled by sqrt(weight ratio =: WR) - Transition times (VT_F_TRANS_OL_TM, VT_TRANS_TIMEOUT, VT_TRANS_MIN_TM) are only scaled with air density (^1.5) but not weight This results in quite inconsistent behaviour. A heavier vehicle will: - Need a higher airspeed by sqrt(WR), but throttle and time params are the same - Acceleration decreases by WR assuming same force, and actual time to same airspeed too - So time to reach transition airspeed actually increases by WR^1.5 To fix this: - Scale throttle with sqrt(WR). Assuming quadratic throttle->thrust force mapping, This removes most of the discrepancy and reduces it to a factor of sqrt(WR) - This remaining factor is removed by scaling all transition times with sqrt(WR) as well
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🔎 FLASH Analysispx4_fmu-v5x [Total VM Diff: 96 byte (0 %)]px4_fmu-v6x [Total VM Diff: 96 byte (0 %)]Updated: 2026-07-14T16:27:04 |
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Problem
VTOL Transitions to FW are parameterised such that a significant weight ratio change requires re-tuning of some parameters. Currently:
VT_F_TRANS_THRis always the literal throttle usedVT_ARSP_TRANSis scaled bysqrt(weight ratio)VT_F_TRANS_OL_TM,VT_TRANS_TIMEOUT,VT_TRANS_MIN_TM) are only scaled with air density (^1.5) but not weightThis results in quite inconsistent behaviour. For a heavier vehicle:
sqrt(WR), but throttle and time params are the sameWRassuming same force, and actual time to same airspeed tooWR^1.5, requiring manual re-tuning for substantial WR changesSolution:
sqrt(WR). Assuming quadratic throttle->thrust force mapping, This removes most of the discrepancy and reduces it to a factor ofsqrt(WR)sqrt(WR)as wellMain risk: Front transition is where we draw the most power, even more so at a heavy weight ratio. This increases peak power draw momentarily on those setups.
Tiltrotor and tailsitter are only affected in so far as the transition times are increased by
sqrt(WR). We add no explicit weight compensation for those vehicles, as it is already approximately done by the hover thrust estimator.Changelog Entry