Development of Servo-Actuator Control System for Aeronautical Applications

As sustainability gains significance in the aviation sector, the development of next-generation on-board systems is becoming increasingly vital. While significant progress has been made in recent years and many milestones have been reached, the development of these systems is still an ongoing process. To accomplish this objective, the aviation industry is transitioning away from the use of hydraulic systems by replacing them with electromechanical alternatives. The focus of this master's thesis is the development of the control algorithm for an electro-mechanical actuator, used to replace the hydraulic pistons currently used in general aviation aircraft's braking systems. In this particular implementation of the braking system, the actuator is driven by a brushless DC motor controlled by a motor driver that interfaces with a microcontroller. This system's microcontroller is part of the C2000 Texas Instrument family and is used to fully control the system's performances in real time. The work documented in this thesis consists on the porting of a previously developed control algorithm (on Matlab/Simulink) into 'C' language. During this process the algorithm has been adapted to work with the available facilities of the microcontroller and in some cases its structure has been changed. The resulting 'C' program has been compiled and loaded on the microcontroller that manages the overall braking system. Initially, the microcontroller internal structure has been studied and its internal hardware blocks have been tried individually, it's then been implemented the control algorithm and finally the code has been compared to the older version by running it on a testbed. The code structure has been designed making the most of the hardware devices included in the microcontroller and it's been tried to make the system implementation as flexible as possible. For this reason and to improve code readability it’s been implemented a set of 'C' datatypes and function (an Hardware Abstraction Layer) that can be used to handle the operations and to setup each microcontroller's peripherals. The system's recurrent tasks have been implemented exploiting interrupt and using timers to control their execution whenever possible. A particular accent has been put into making the execution of the interrupt service routines as fast as possible, by doing this the CPU's workload becomes reduced and potentially enables the implementation of the control algorithm for more than one actuator using a single microcontroller. Once completed, this system has been used to physically test some brake actuators and to determine the different system responses with different PID based controller layouts.