Design And Implementation Of Digital Flywheel Controller

Flywheel, as one type of actuators of the spacecraft attitude control system, has a number of advantages that other types of actuators do not have. Therefore, its control design and development have been widely investigated. In recent years, flywheel size, weight and energy consumption demands becomes a critical problem with the development of multi-function spacecrafts, and the previous control scheme of flywheel based upon analog circuits can not satisfy our application. Fortunately, with the development of electronic technology and even the emergence of large scale programmable devices, it is possible for us to design digital controller for flywheel to meet the requirement of small size and so on. In this dissertation, controller design of reaction wheels is deeply studied, in which SPARTANII XC3S250 chip of Xilinx Inc. is selected as its digital controller, and the main contents of this dissertation are presented as follows:Firstly, the development of digital control system and its advantages are presented, and the development of digital flywheels controller is also analyzed. Moreover, the advantages of digital flywheels controller comparing with other traditional controller are also given in this dissertation.Secondly, the dynamic model of flywheel control system is derived, and the whole control system has ultimately been transformed into a rate feedback control system. Moreover, a fuzzy self-tuning PID control approach is developed based on the analysis of flywheel friction torque and noise. Numerical simulation results of a type of flywheel are also presented by comparing with traditional PID control scheme. It is shown that with our proposed controller, not only smaller steady state error and short response time can be achieved, but zero overshoot and the interference to noise and external disturbances can also be effectively guaranteed. Further, the size of the flywheel can be reduced largely, and thus the requirement of medium sized flywheel momentum can be meet.Based on the synthesized control law, the hardware of the flywheel is designed in this dissertation, which is based on the FPGA core. All the hardware includes: serial communication, current detection protection, electrical power drive, optical encoder signal processing, power supply circuit and other major unit. In addition to these work, PCB board and experimental board production are also finished. Finally, the main function of the above designed FPGA are implemented with the Verilog language, which include the serial communication module, the signal through the optical encoder speed and sentenced to the module, the motor drive signal module, the digital PID algorithm module and the fuzzy control rule module as well. Moreover, experiments are also done to verify and demonstrate our proposed control law and the designed hardware correspondently.