Design Of The Autopilot For A Quad-Rotor Aircraft

An overall scheme of digital flight control system is proposed, according to the characters of quad-rotor aircraft which are light, small volume, low power, high performance-to-price. The autopilot of quad-rotor aircraft is mainly composed of flight control computer. A flight control computer whose core is C8051F020, using the modular design method.For easing the way of the control, quad-rotor aircraft uses symmetrical layout. This article has analyzed the structural style and the working principle of quad-rotor aircraft. Characteristics aerodynamics and kinematics of quad-rotor aircraft are analyzed, and the nonlinear mathematical model is given. Its dynamic characteristics are discussed in detail. The nonlinear model is decoupled to four separate loops, and the increment function of small signal perturbation is derived which is regarded as the control object. On the base of work principle and linear model, the method and application of the controller are proposed. Attitude controller and position controller are designed using the classical method of PID. Finally, the feasibility of control method is verified by the digital simulation.In order to control effectively the attitude and position of the quad-rotor aircraft through the adjustment of four motors, the structural style and the experiment platform whose cores are sensor, flight control computer and actuator are designed. It concludes that the relationship between the DC motor speed and the PWM duty cycle is confirmed, the requirement of the rotor pull is satisfied, the reaction of actuator is fast and continuous, and the model of DC motor is equaled to an inertial loop. The tests have verified the function and rationality of the hardware and software, and the rationality of scheme.