| Ventilator, a device which can control patients’breath as well as assist them when breathing, holds a significant position in the modern medical field with its wide use in the treatment of respiratory failure, respiratory diseases, and the resuscitation. The research of high-performance, non-invasive ventilator was selected as a national key project at the conferencethe 13th Five-Year Plan. The household portable ventilator adopts the electronically controlled pneumatic drive mode, whose airflow is produced by its internal turbine pump, and its pressure can be controlled by adjusting the pressure valves as well as the volume of the airflow. So, researching the theory of the motor is of high importance. The main content of this project is to design a brushless DC motor controller which has high control precision, stable operation, fast adjustment and perfect fault protection function, which will be applied to the smart household ventilator project. The thesis is divided into the following sections:First, put forward the overall design scheme according to the development of BLDC as well as current research both in china and abroad, build a mathematic model of BLDC by the knowledge of its inner structure and basic operational principle, analyze its performance characteristic theoretically. On this basis, propose the adaptive fuzzy PID control strategy under the knowledge of fuzzy control theory to let the motor break as soon as possible.Then, in accordance with the design requirements STM32F103 is selected as the micro controller of the control system to complete the data processing, signal acquisition, output driving, interactive communication and other functions. STM32F103 has abundant and powerful peripherals, and integrates the internal Flash and RAM. The basic timer of STM32F103 is taken as the interface to capture and analyze Hall signal. The 6 channels of PWM complementary output is used to control the commutative process of the full-bridge circuit, in order to realize the commutation of the motor bus. The speed feedback of the controller is realized by the input capture of the Hall signal. The speed of the motor can be calculated according to the frequency of the Hall signal. In the period of speed down, a braking circuit of energy-consumed is designed to realize the prompt breaking action.Next, programs are designed which include speed measurement, speed regulation, commutation process, fuzzy PID program and communications procedures based on the hardware platform. The control strategy of adaptive fuzzy PID is adopted in the speed governing system to achieve an excellent speed regulation performance. The controller can monitor the system status periodically, by protection circuits and detection circuits. The sampled signal of the motor is filtered by the digital process such as the arithmetic mean filter algorithm and low-pass filtering algorithm. And get the average value of sampled signal by the sliding window algorithm, as well as one over-current protection.At last, conduct an experiment of the controller’s control accuracy, efficiency as well as the whole machine. Results show that the controller has good adjustment effects, which satisfy the design requirements. |
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