Design and simulation of longitudinal autopilot modes for a conventional aircraft

This paper is concerned with design of an autopilot for longitudinal flight control of a conventional airplane. There are different modes of automatic longitudinal flight controls. Among those pitch attitude hold, altitude hold and vertical speed hold mode autopilots are implemented in which controller is designed for each of these modes. By the use of this controller, the system performance is improved. The performance requirements such as the peak overshoot to be less than 15% and the rise time to be less than 1 second has been achieved by the use of each controller in different modes. Traditional control techniques such as PID controller and Lead-Lag controllers are designed to each of these autopilot modes. Root-locus design technique is applied for tuning the parameters of each controller. Simulation of autopilots in the presence of three different types of atmospheric disturbances such as Dryden wind gust, Vertical wind gust model and turbulence are also observed. As in effect due to disturbance on each mode, a pitch rate feedback is applied in the inner loop of pitch controller. So a feedback control loop is developed to design the autopilot.