Modeling and Control of a Haptic Feedback Aeronautical Actuator

Helicopter flight safety critically depends on pilot awareness of control limits and aircraft state, in particular during challenging flight conditions where traditional visual and auditory feedback may be insufficient or saturated. Integrating haptic technology into flight control systems represents a promising method to improve pilot situational awareness and reduce the risk of exceeding limits. This thesis presents the modeling, parameter estimation, and control design of the Haptic Parallel Actuator (HPA), a haptic feedback electromechanical actuator specifically designed for integration into the Pitch, Roll, Yaw, and Collective command chains of a helicopter fixed flight control assembly. The proposed actuator system provides dual functionality depending on flight mode: in hands-on conditions, it delivers active spring-like force cues that support pilot awareness, assist in adherence to control limits, and enhance overall flight safety; in hands-off conditions (autopilot engaged), it provides mechanical anchoring and precise actuation of the flight control inceptors to execute autonomous flight commands. A mathematical model describing both the mechanical and electrical subsystems of the actuator is developed, incorporating realistic nonlinearities and non-ideal dynamic effects. The modeling process involves accurate friction characterization, as friction forces significantly impact actuator performance and control precision. The friction model parameters are identified using a Genetic Algorithm (GA) optimization approach, utilizing experimental data collected during test activities to ensure model fidelity and predictive accuracy. Two distinct torque control strategies are designed and implemented to explore different performance objectives and design philosophies. A Super-Twisting Sliding Mode Controller (STSMC) is developed to investigate the actuator's capability for precise tracking of reference torque signals, enabling accurate replication of spring-like behavior and providing insights into the system's dynamic response characteristics. In contrast, a Proportional-Integral-Derivative (PID) controller is designed to balance tracking performance with tactile feedback quality, recognizing that perfect adherence to spring dynamics can introduce undesirable effects such as resonance peaks that degrade pilot perception. While the STSMC design prioritizes mathematical performance metrics and theoretical tracking accuracy, the PID controller development incorporates subjective feedback from experienced pilots who evaluated the tactile sensations during testing, thus considering human factors in haptic interface design. The control architecture utilizes a cascaded structure where the outer torque controller generates reference signals for an inner current control loop, which is implemented using a Proportional-Integral (PI) controller to ensure precise current tracking and actuator response. Controller performance is finally evaluated through both frequency domain and time domain analysis, obtained via experimental testing on a dedicated test bench that replicates the operational conditions and load characteristics expected in helicopter applications.