An adaptive pitch axis autopilot design for an unstable nonminimum phase pitch axis model

• Main Author: Chen, Long Ren
• Other Authors: Saugen, John L.
• Language: en_US
• Published: 2013
• Subjects: Automatic pilot (Airplanes) > Design; Airplanes > Control systems > Mathematical models
• Online Access: http://hdl.handle.net/1957/38014

An adaptive pitch axis autopilot design procedure is presented. The design procedure is applicable to both stable and unstable pitch axis models and to those having nonminimum phase. The design approach assumes the adaptive autopilot is activated after achieving level flight. It is shown a rate-feedback compensator can be designed to ensure stable level flight pitch axis operation for the entire desired flight regime. The adaptive control loop design utilizes a pole-placement algorithm. The closed-loop characteristic polynomial is designed to have dominant poles of that of an ideal second order system to obtain the desired transient response. The identification of the system uses a modified least-squares algorithm with a variable forgetting factor. The nonlinear pitch axis model is used in simulations to evaluate the design. Command response tests include the step response and the ramp command response. Simulation results indicate that the adaptive pitch axis autopilot is capable of tracking altitude commands after activation. The closed-loop system response is close to that of the ideal second order system having the dominant poles. === Graduation date: 1991