Twisting control algorithm for the yaw and pitch tracking of a twin rotor UAV

In this paper, second order sliding mode controller is used to compensate the pitch and yaw angles of multivariable (MIMO) twin rotor system. Twin rotor has 6 state variables including yaw and pitch angles, yaw and pitch angular velocities, and armature currents. Considering the physical structure of twin rotor, the controller aims to track the mentioned angles and stabilize their angular velocities. Depending on the type of sliding control mode in the design process, the armature currents should be placed in an allowable range based on physical characteristics of twin rotor. This helps the controller to do the tracking and stabilizing in a proper way. Second order sliding control design is done based on twisting algorithm and in this regard, two sliding surfaces are defined as the sum of tracking error of yaw and pitch angles and their integrals. The controller performance is studied in the light of tracking accuracy and steady-state error, transient behavior and response fluctuations level and presence or absence of ripple in response. In all cases, the simulation is presented for first and second order sliding mode controllers and their advantages and disadvantages will be investigated.