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Added the minimum time to wait before transitioning from BURNOUT back… #172

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Added the minimum time to wait before transitioning from BURNOUT back… #172

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7aeed8d
Added the minimum time to wait before transitioning from BURNOUT back…
okotwal17 Oct 31, 2025
116f522
Changed the naming convention to sustainer_burnout_to_first_boost_tim…
okotwal17 Nov 3, 2025
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4 changes: 2 additions & 2 deletions MIDAS/src/finite-state-machines/fsm.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -154,7 +154,7 @@ FSMState FSM::tick_fsm(FSMState& state, StateEstimate state_estimate, CommandFla

case FSMState::STATE_FIRST_BOOST:
// if acceleration spike was too brief then go back to idle
if ((state_estimate.acceleration < sustainer_idle_to_first_boost_acceleration_threshold) && ((current_time - launch_time) < sustainer_idle_to_first_boost_time_threshold)) {
if ((state_estimate.acceleration < sustainer_idle_to_first_boost_acceleration_threshold) && ((current_time - launch_time) < sustainer_burnout_to_first_boost_time_threshold)) {
state = FSMState::STATE_IDLE;
break;
}
Comment on lines 155 to 160
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@mpkarpov-ui mpkarpov-ui Nov 4, 2025

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This logic is incorrect, this conditional is a guard against instantaneous (non-sustained) accelerations while the vehicle is on pad (or, in the IDLE state). I believe the logic here is correct as-is before, and this change should likely be reverted.

Expand All @@ -168,7 +168,7 @@ FSMState FSM::tick_fsm(FSMState& state, StateEstimate state_estimate, CommandFla

case FSMState::STATE_BURNOUT:
// if low acceleration is too brief than go on to the previous state
if ((state_estimate.acceleration >= sustainer_coast_detection_acceleration_threshold) && ((current_time - burnout_time) < sustainer_coast_time)) {
if ((state_estimate.acceleration >= sustainer_coast_detection_acceleration_threshold) && ((current_time - burnout_time) < sustainer_coast_time && ((current_time - burnout_time) > minimum_time_for_burnout_to_first_boost))) {
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@mpkarpov-ui mpkarpov-ui Nov 4, 2025

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I disagree with this logic, this will still trigger the back transition to FIRST_BOOST if the instantaneous acceleration occurs, the only thing this guards is it will prevent the FSM from doing so in the first 0.25s that the FSM is in the BURNOUT state.

What we're looking for instead is that

  1. state_estimate.acceleration exceeds the threshold
  2. The elapsed time is less than the coast time
    AND
    both of the above conditions are met for at least x seconds (in our case, 0.25s). Consider the following flight:

t-0: IDLE
t+0: FIRST_BOOST
t+3: BURNOUT
t+3.75: accel sensor issue causes it to read +16g accel
t+3.76: accel sensor issue clears and accel returns to normal

With the current code:
At 3.76s...

  • state_estimate.acceleration (16g) >= the threshold ✅
  • (current_time - burnout_time) = 0.75s, < sustainer_coast_time ✅
  • (current_time - burnout_time) = 0.75s, > minimum_time_for_burnout_to_first_boost (0.25s) ✅
    So the back transition is triggered even though it shouldn't be.

With the logic outlined above, in the same condition

  • state_estimate.acceleration (16g) >= the threshold ✅
  • (current_time - burnout_time) = 0.76s, < sustainer_coast_time ✅
  • Conditions above have been met for 0.01s, < minimum_time_for_burnout_to_first_boost ❌
    So we don't back transition

state = FSMState::STATE_FIRST_BOOST;
break;
}
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5 changes: 4 additions & 1 deletion MIDAS/src/finite-state-machines/thresholds.h
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Expand Up @@ -238,4 +238,7 @@

// The minimum expected jerk for a main deployment event (m/s^3)
// (Core Setting)
#define booster_main_jerk_threshold 300
#define booster_main_jerk_threshold 300

// Minimum time to wait before deciding to go from BURNOUT to FIRST_BOOST. (ms)
#define sustainer_burnout_to_first_boost_time_threshold 250
Comment on lines +243 to +244
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@mpkarpov-ui mpkarpov-ui Nov 4, 2025

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This comment could use some work. Nominally, the rocket should never go BURNOUT -> FIRST_BOOST, so it doesn't necessarily make sense to call it "minimum time to wait before x".

A better comment could be "Minimum duration of sustained acceleration before fallback to boost"

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