Robust $\mathcal{H}_\infty$ Controller Design For INDI-Controlled Quadrotor Using Online Parameter Identification

2026-05-06

AI Summary

This work addresses the degraded attitude control performance of quadrotors under parametric uncertainties by proposing a robust cascaded controller that integrates online parameter identification with $\mathcal{H}_\infty$ gain scheduling. The inner loop employs incremental nonlinear dynamic inversion (INDI), while the outer loop is designed using signal-based $\mathcal{H}_\infty$ loop-shaping augmented with feedforward filtering to enhance dynamic response. Notably, this approach is the first to combine online system identification with $\mathcal{H}_\infty$ gain scheduling, enabling adaptive robust control over a wide range of parameter variations. Simulation and flight experiments demonstrate that the system maintains excellent tracking accuracy and stability even when identified parameters fall outside the predefined uncertainty set, provided the actuator time constant remains below 40 ms.

Abstract

It has recently been shown that all physical parameters of an Incremental Nonlinear Dynamic Inversion (INDI) controller can be estimated onboard a multirotor within half a second, which is fast enough to do the full identification during a throw in the air. However, a robust method to tune outer loop gains for this feedback-linearizing INDI controller depending on the model parameters is still missing. This work presents the design of a robust gain-scheduled controller for attitude control of quadrotor, using an INDI-based inner loop with online identification of its system parameters. A gain-scheduled cascaded attitude controller with a feedforward filter is synthesized for a symmetric quadrotor using signal-based $\mathcal{H}_\infty$ closed-loop shaping. The resulting controller exhibits good stability margins, with nonlinear simulations confirming effective tracking performance under uncertainty. Experimental evaluation is also conducted through flight tests with full online parameter identification. Even though the identified parameters during these tests are far outside the defined uncertainty range, acceptable flight performance comparable to simulation results is maintained for actuator time constants below 40 ms.

Problem

• robust control
• INDI
• quadrotor
• online parameter identification
• attitude control

Innovation

• Incremental Nonlinear Dynamic Inversion (INDI)
• online parameter identification
• robust gain-scheduling
• H-infinity control
• quadrotor attitude control