REAL-TIME CONTROL OF SPOOLED FIBER-OPTIC FPV MULTIROTORS: ANALYSIS OF CONTROL METHODS, LOOP TIMING, INERTIA AND DELAY SENSITIVITY, AND LINK-LOSS DETECTION

Spooled optical fiber removes the radio path from first-person-view (FPV) multirotors, but the vehicle loses mass and inertia as fiber pays out, and link loss takes on a different meaning. This paper analyzes real-time control of such vehicles at the onboard, vertical-motion, and operator levels. A single-axis rate-loop model shows that in the studied configuration a 3 km spool changes the total inertia by 6%, which shifts the phase margin by at most 0.3°, whereas each millisecond of onboard delay costs about 2.1°; the delay budget, not gain scheduling, is the primary concern. In a simulation, mass feedforward lowers the altitude error from 1.21 cm to 0.65 cm RMS and tolerates a ±15% error in the payout coefficient, although the absolute benefit is small. A crossover model shows that fiber propagation delay is negligible, whereas 100 ms of added radio delay removes 23° to 34° of phase margin. At the same mean loss rate, correlated losses raise the required link-loss detection time from 35 ms to between 399 ms and 826 ms, and a closed-form approximation of this effect is derived. All results are analytical or simulated; no flight data are used.