Fixed-time trajectory following for quadrotors via output feedback

Area of Science:

• Robotics and Control Systems
• Nonlinear Control Theory
• Quadrotor Dynamics

Background:

• Quadrotor trajectory following is challenging due to under-actuation and external disturbances.
• Existing methods often require full state information (including velocities), which are difficult to measure.
• Achieving fixed-time convergence, where the system settles within a predefined time, is desirable for practical applications.

Purpose of the Study:

• To develop a fixed-time output feedback control strategy for quadrotors.
• To address the challenges of unmeasured velocities and external disturbances.
• To ensure fixed-time stability and robustness for trajectory regulation.

Main Methods:

• Inner-outer separation design philosophy to decompose quadrotor dynamics.
• Fixed-time extended state observers (FTESOs) with polynomial feedback to estimate velocities and uncertainties.
• Velocity-free fixed-time control protocol synthesis.
• Analysis of bi-limit homogeneity properties for convergence proofs.

Main Results:

• Successfully estimated unavailable velocity states and unknown uncertainties in fixed-time.
• Developed a velocity-free control protocol achieving trajectory regulation with uniform fixed-time convergence.
• Demonstrated chattering-free inputs and enhanced system robustness.
• Validated the fixed-time convergence of all error variables through theoretical analysis.

Conclusions:

• The proposed output feedback control strategy effectively achieves fixed-time trajectory following for quadrotors.
• The method enhances robustness against disturbances and eliminates the need for velocity measurements.
• The algorithm guarantees fixed-time stability and chattering-free performance, validated by simulations.