Embedded Control System for a Multi-Rotor Considering Motor Dynamics
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Fecha
2020-12
Autores
Mayorga-Macías, Walter A.
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ITESO
Resumen
Descripción
This dissertation aims to design and implement an embedded control scheme for trajectory tracking in multi-rotors. The first objective to tackle is the state of the art about the vertical take-off and landing (VTOL) devices, furthermore, the document defines the available VTOL types in the field. With the previously mentioned, the thesis defines the problematic about the available hardware and software schemes for research and development for unmanned aerial vehicles (UAVs). Therefore, a control scheme proposal is described for this type of aircrafts, which includes a nested double loop cycle that considers the control of the vehicle and the speed control of the actuators.
The research proposal considers the hypothesis of small angles approximation, which simplifies the mathematical analysis of the system, and the obtaining of a state-space model, by reducing the impact of the rotation matrix over the vehicle. The simplification of the model represents an advantage during the process of controller design for the system. This model is validated with the use of open-loop simulations (without considering the controller) in Matlab/Simulink. Such process consists in defining different motor speeds inputs, displaying the behavior of the model states and corroborate that the model behavior is the expected when compared with the real system. Given that the model requires the parameters of the system during the simulations, the methods for obtaining such information are developed since that data is not commonly provided by the brushless motors manufacturers or VTOL structures developers.
Once the dynamic model of the VTOL to control is validated, the external and internal control loops with error feedback are designed using the backstepping and PID (Proportional-Integral-Derivative) schemes. Furthermore, the stability validation for each scheme is developed in two ways: by mathematical demonstration using Lyapunov’s theorem, and by numeric results from simulation.
For the real-time implementation, one of the designed control schemes is implemented in an embedded system, and numerous experiments are performed using a commercial VTOL with the same configuration and motor arrangement considered during the mathematical modeling process. Furthermore, the hardware and software architectures used are described for the implementation of the control algorithms and for the sensor signal conditioning. The results for the experiments are reported and analyzed, and the respective conclusions are presented.
During the validation process, the use of test devices is pertinent with the purpose of allowing the developer to tune the system controller gains safely. This opens the door to the consolidation of a complete validation system that allows the modification and evaluation of new parameters and research proposals, with the purpose of adding intelligence abilities to VTOL, providing fault detection capabilities, adding support for new technologies, or for developing educational methodologies.
Palabras clave
UAV, VTOL, Multi-rotor, Error Feedback, Embedded Control, Backstepping Controller, Test-bench, Brushless Motor, Speed Sensor, Mathematical Model
Citación
Mayorga-Macias, W. A. (2020). "Embedded Control System for a Multi-Rotor Considering Motor Dynamics," Tesis de Doctorado, Doctorado en Ciencias de la Ingeniería. Tlaquepaque, Jalisco: ITESO.