The problem of controlling a typical nonlinear servo motor of an unmanned aercraft with non-stationary parameters using a robust PID controller is considered. The procedure for calculating the parameters of a robust PID controller based on the localization method (further - LM PID controller) for continuous and discrete control systems is studied. The influence of disturbing factors (internal and external) acting on the servo motor is considered. It is established that the main perturbations acting on the servo drive include internal perturbations, which are changes in the time constant and its gain from the temperature of the environment and the quality of the supply voltage. The simulation in the class of linear and nonlinear continuous systems showed that a servo drive with a ML PID controller has the property of robustness in the working range of changes in both the input signal and the parameters of the servo drive and controller. Simulation results showing the research are presented. When describing a servo motor with an LM PID controller in the class of linear discrete systems, its robustness is limited by a narrow range of variation of both its parameters and the quantization period of the input signal. As the degree of uncertainty in the parameters of the servo motor increases (approaching the working range of their change), the discrete system loses stability. For the synthesis of robust control circuits of an unmanned aercraft with given characteristics, mathematical dependences of the settling time and static error of a typical servo motor with LM PID controller from the quantization period of the input signal and the degree of uncertainty in its parameters are presented.