Automatic control systems play an increasingly important role in aerospace engineering, both in view of the higher level of automation expected from flight vehicles and of the recent emergence of unmanned vehicles.

Control systems design problems in aerospace pose significant challenges because of their intrinsically multivariable nature, often associated with large model uncertainty and unstable dynamics. These are the main reasons why advanced methods for analysis and synthesis are frequently adopted in aerospace applications.

In view of the above, the course aims at the following goals: to provide a sound background on modern methods and tools for the stability and performance analysis of linear systems; to cover robust analysis and design of SISO and MIMO linear time-invariant (LTI) feedback control systems; to introduce simple methods for gain-scheduled control systems design; to apply the above methods to problems in aerospace control such as aircraft SAS and CAS design (both longitudinal and lateral-directional) and UAV control system design.

Lectures and exercise sessions will allow students to:

• Master fundamental theoretical results for linear feedback control systems
• Understand modern methods and tools for linear control systems analysis and design
• Formulate and solve advanced control systems design problems

Solve aerospace control problems using state-of-the-art methods and tools.

Systems theory – stability and performance: Equilibria of nonlinear systems; Lyapunov stability for equilibria of nonlinear systems: definition and examples; Stability for LTI systems; From classical performance indicators to modern ones; H₂ performance for linear systems; H_∞ performance for linear systems.

Linear SISO feedback systems – nominal design: Frequency-domain loop-shaping and sensitivity shaping; time-domain state feedback and observer-based output-feedback using classical methods (eigenvalue assignment, LQ control).

Linear SISO feedback systems - robust analysis and design: Uncertainty modelling in SISO systems; Robust stability analysis of SISO feedback systems; Nominal and robust performance analysis; Requirement specification; Robust design: unstructured and structured mixed sensitivity synthesis.

Linear MIMO robust analysis and design: Introduction to MIMO linear systems; Nominal stability and performance in the MIMO case; Robust stability and performance in the MIMO case; MIMO robust design.

Implementation issues: modern anti-windup methods for MIMO control systems subject to saturations; implementation of gain-scheduled controllers.

Aircraft flight control: Introduction to flight control architectures (classical SAS+CAS; dynamic inversion, model following); Aircraft SAS and CAS design (longitudinal and lateral-directional).

Rotorcraft attitude control: modelling for attitude control; rotorcraft SAS; rotor state feedback.

UAV attitude and position control: PID cascade architecture; inversion-based architectures (dynamic inversion and model following).

Structural control: active vibration control systems.

Students are required to know the principles and methods of linear systems theory and SISO linear control systems stability and performance analysis.

The students will be able to choose between a written exam and a design project which will be presented during the course.

In both cases the evaluation will be also based on the clarity of the presentation.

During the exam the students shall demonstrate that:

• they understand the theoretical fundamentals on linear feedback control systems
• they have acquired modern methods and tools for linear control systems analysis and design
• they have learned how to formulate and solve aerospace control systems design problems.