| With the development of the agriculture aviation, various aircrafts like fixed wing aircrafts and helicopters are gradually used in plant protection. Quadrocopter,a kind of four rotor helicopter without any human interaction, can adapt to complex environment in plant protection with the characteristics of short-takeoff and vertical-landing, flight stability, flexible control, simple structure, easy maintenance, etc; Next, quadrocopter can mount a variety of equipment and finish monitoring, soil moisture acquisition, seeding, sprinkle pesticide, fertilizer and other agricultural project efficiently. Therefore, to strengthen the study and application promotion of quadrocopter has very important significance.The article mainly focuses on the small quadrocopter which has some ability with load. Aircraft control system is designed by researching on flight principles of quadrocopter. First,through learning about the mechanical structure, and the change of aircraft structural features in the process of operation, we design a vehicle test platform and establish a relevant mathematical model. Second, based on the control principle of quadrocopter, the software control system is designed and fabricated with the STM32 Micro Control Unit(MCU) as the core processor, combined with a variety of attitude sensors and wireless data transmission equipment. Third, the system controls the vehicle’s attitude by calculating sensor data, obtaining the real time attitude data correctly and using fuzzy PID control algorithms. During the trial, the simulation of the plan is carried on under MATLAB first. In order to further test the superiority of the vehicle control algorithm, we test it on the experimental study platform again after simulation. Based on the above, the design and manufacture of quadrocopter are accomplished.The MATLAB software was used in this study to simulate the conventional PID and fuzzy PID control algorithms and the simulation results were analyzed and compared. For the conventional PID algorithm, the overshoot of the system was 41.9% with the rising time of 0.78 s. With the fuzzy PID control algorithm, the overshoot of the system was 28.6% and the rising time was 0.69 s. With fuzzy PID control algorithm, the overshoot of the system decreased 13.3% and the rising time reduced 0.09 s compared with the conventional PID algorithm with the scaling factor as 5, integral coefficient as 0.03, differential coefficient as 1 and system gain as 1.Using other parameters have also led to similar results, which indicated that fuzzy PID control algorithm had a better control performance. Moreover, experiments were conducted to verify the simulation results. The results showed that, the system performed in a stable way under a small load with the control of the fuzzy PID algorithm; however, this cannot be achieved by using the conventional PID algorithm under same condition. With the conventional PID algorithm, the overshoot of the system was 37.5% and the rising time was 0.62 s with a heavy load. While, the overshoot of the system was 22.5% and the rising time was 0.57 s when the fuzzy PID control algorithm was adopted. The overshoot of the system decreased 15.0% and the rising time reduced 0.05 s, which agreed well with the simulation results. The results show that, after debugged steadily,traditional PID control algorithm has better control quality only with fixed aircraft structure parameters. If the external environment or the spacecraft themselves institution characteristic changes, the quality of control become deteriorated. Compared with the conventional PID algorithm, the fuzzy PID algorithm can optimize control coefficients on line with excellent anti-jamming capability and stability when load changing. Through measured on the experimental platform, it has further proved the feasibility of the algorithm. The field experiments further show that plant protection quadrocopter can achieve the stability of flight attitude control very well. |
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