Study on autopilot PI compensator optimal parameter design with phase lag constrain

PI compensator is used widely in autopilot design in order to eliminate response error, but as a price to pay the autopilot will have a slower time response or smaller stability margin. Firstly base on the analysis of PI compensator fundamental in frequency-range and root-locus, optimal parameter design principle is given. Then constructing the nonlinear equation which taking the time constant of PI as variable and the phase lag of compensator at crossover frequency as constrain. Through iterative design of compensator gain base on the solution of equation, the optic parameter of PI compensator can be got, both satisfy autopilot speed and stability requirement. The validity of method can be proved through example finally.