Altitude Regulation of Quadrotor Types of UAVs Considering Communication Delays

Estimation of transmission delays caused by wireless communication and analysis of the delay effects is one of the critical challenges to be considered in designing controllers for quadrotor types of unmanned aerial vehicles (UAVs). This paper presents an estimation method using experimental data and analytical solutions of delay differential equations (DDEs). For the approach, measured transient altitude responses are compared to time-domain descriptions obtained from the analytical solutions. That makes use of the Lambert W function for first-order DDEs. The dominant characteristic roots are obtained in terms of system parameters including the delay. Proportional controllers are used to generate the altitude responses for estimation. The effects of the time delay on the responses are analyzed. Then, proportional plus velocity controllers are designed to obtain better transient altitude responses. MATLAB/Simulink is used for simulations, experiments, and analytical solutions of the DDEs in terms of Lambert W function.