1,720,979 research outputs found
Rotorcraft Trim by a Neural Model-Predictive Auto-Pilot
No full textModern comprehensive finite element-based tools for the aeromechanic analysis of rotorcraft require the ability of accurately computing the model trim settings. Proportional control laws (auto-pilots) have often been used in many practical instances, because this technique is not directly related to the complexity of the system. On the other hand, classical auto-pilots must be carefully tuned for every desired flight condition. This work focuses on improving the auto-pilot technique by means of non-linear model-predictive control. A reference model of the system augmented with an adaptive neural element is used to predict the system response and solve an optimal control problem, which in turn produces the control strategy that is used for regulating the system. The adaptive element allows for the identification and correction of the mismatch between reduced model and controlled system, thereby improving the predictive capabilities of the controller. Tests on the wind-tunnel trim of a rotor multibody model and comparisons with an existing implementation of a classical auto-pilot are discussed
Tackling the Simulation of Multibody Rotorcraft Models in Maneuvering Flight by Parameter Identification
No full textn this work, we explore time-domain parameter identification approaches to generate reduced models of a comprehensive UH-60-like multibody model. Data required for the identification are gathered performing a few virtual experiments, in which the full system is perturbed about the hover condition, in either open-loop or closed-loop conditions. We validate the identified reduced models against a different set of experiments, discussing the main drawbacks of the employed methods. Moreover, we show some preliminary tracking results, where the comprehensive model is steered along a Category A continued take-off maneuver by a simple LQR controller synthesized from the identified models
Trim of Rotorcraft Multibody Models Using a Neural-Augmented Model-Predictive Auto-Pilot
No full textEffect of Modeling Approximations on the Stability of Autopilot Controllers
No full textThe classical autopilot control law is extensively used for trimming rotorcraft models in comprehensive analysis codes. It consists of a simple control law that constructs a map relating the inputs and outputs of the system, based on a static approximation to its behavior. It is then easy to compute suitable filter time constants and control gains such that a closed loop controller will steer the system to its trimmed configuration with a desired performance. However, when this control law is used to steer complex rotorcraft models, such as those used in comprehensive analysis codes, stable behavior is only observed for judiciously chosen values of the controller parameters. Three major sources of error are responsible for the observed discrepancy, in the design of the controller, 1) the dynamic characteristics of the plant are ignored, 2) the non-linear behavior of the plant is not taken into account, and 3) the Jacobian of the system is assumed to be known exactly. This work focuses on the implications of these three assumptions on the behavior of the classical autopilot, by studying their effect through both numerical closed-loop experiments on a realistic UH-60 multibody rotor model (the plant), and eigenvalue analysis of the closed-loop characteristics of different reduced order models of the full plant
Optimization of Critical Trajectories for Rotorcraft Vehicles
No full textThis paper focuses on the development of computational procedures for the trajectory management of maneuvering rotorcraft vehicles. The flight mechanics models are based on classic blade element theory, and are applicable to both helicopters and tilt-rotor aircrafts. The computation of an optimal maneuver is viewed here as an optimal control problem, where the solution minimizes an appropriate cost function subjected to constraints that translate the flight envelope limitations of the aircraft and all the necessary safety and operational requirements. A finite element based transcription process is used for discretizing the problem, obtaining a finite dimensional parameter optimization problem. Ad hoc procedures are proposed for ensuring flyable and realistic computed control time histories, that are compatible with the hidden (unmodelled) actuator dynamics. The methodology is used for developing and studying various models of the take-off of helicopters and tilt-rotors in the one-engine failure case under Category-A certification requirements
Adaptive Planning and Tracking of Trajectories for the Simulation of Maneuvering Rotorcraft with Comprehensive Models
No full textProcedures for Enabling the Simulation of Maneuvers with Comprehensive Codes
No full textWe describe a computational procedure for the simulation of maneuvers with comprehensive rotorcraft models. Our current approach uses model-based trajectory planning followed by model-based predictive tracking. We describe the predictive tracker and the adaptive reduced model on-line identification procedure. Numerical examples show that rapid and good quality reduced model identification can be achieved by the proposed scheme
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