Autopilot design for aerospace vehicle using GUI — A user friendly approach

Autopilot is one of the key subsystems in guided aerospace vehicle. It provides steering commands to maintain the desired trajectory along with stability. In general, aerospace vehicle dynamics (plant) changes continuously with time which necessitates the change in controller to retain stability. Hence, numbers of controllers are to be designed for the total envelope of the trajectory. In this paper parameter plane method is used for the design of two-loop and three-loop autopilots. Parameter plane method gives the region of gains satisfying the gain margin and phase margin criteria. All the gains in the region satisfy the frequency response specifications but to find the optimum point number of iterations need to be performed. Designing of multiple controllers with number of iterations is a tedious job. This paper presents a GUI in MATLAB^® to provide a user friendly environment to the autopilot designer. Based on the designer´s choice of a point from the desired region of the parameter plane this GUI provides a plot of closed loop time response and the characteristic parameters of time response and open loop frequency response of each loop. Decision on accepting these parameters with respect to specifications becomes easier in this GUI. Proper controller gains are obtained upon satisfying the desired specifications.