Point Mass Planning and NMPC Tracking for Time-Optimal Agile Quadrotor Gate Navigation
Journal
IEEE Access
Date Issued
2026
Author(s)
Guevara, Bryan S.
Brandao, Alexandre Santos
Type
Article
Abstract
Time-optimal agile flight through a sequence of three-dimensional gates requires a consistent coupling between trajectory planning and tracking control. Point-mass planners offer fast numerical solutions for free-final-time optimisation, but the value of progressively enriching the reference fed to a nonlinear model predictive control (nmpc) tracker through a differential flatness bridge has not been clearly characterised on multi-gate circuits. This paper presents a modular three-stage pipeline: an offline time-optimal point-mass model (pmm) planner solved with CasADi and IPOPT; a differential flatness bridge that maps the flat outputs and their time derivatives to a full quadrotor reference comprising desired position, velocity, attitude quaternion, body angular rate, and collective thrust; and a body-rate nmpc tracker implemented on the acados SQP-RTI scheme with an SO(3) logarithmic-map external cost. Two reference configurations are compared in a software-in-the-loop setup that drives the MuJoCo physics engine through ROS 2 under a randomly seeded external-force disturbance. The baseline, nmpc-Att, uses only a yaw-only attitude reference derived from the velocity heading and carries no angular-rate or thrust feedforward. The proposed configuration, nmpc-Full, activates the complete flat reference, including the full attitude quaternion, body angular rate, and thrust feedforward. Results on a seven-gate figure-8 and an eight-gate vertical loop show that reference enrichment yields a categorical improvement in gate crossing and a systematic reduction of tracking error without increasing solver cost. The loop circuit further highlights a structural limitation of the common practice yaw-only reference: it cannot represent inverted attitudes, and only the flatness-based reference resolves this case