Abstract:

For the attitude control of quad tilt rotor (QTR) aircraft with unknown external disturbances, a fractional order sliding mode control strategy based on the fractional order theory, sliding mode variable structure control theory and the new rapid reaching law is proposed. First, using the characteristics of information memory and forgetting of fractional calculus operator, the fractional calculus theory is introduced into the sliding mode control method, and a fractional order proportional integral sliding mode surface is designed. Second, in order to solve the problems of long convergence time and shake out serious of the traditional reaching law, a new fast reaching law model is put forward with characteristics of the second order sliding mode. Third, considering the existence of complex disturbances, the super twisting sliding mode disturbance observer is used to estimate and compensate the composite disturbance on line. Finally, by comparing with the traditional integer order sliding mode control and dynamic inverse PID control, simulation experiment results show that the proposed control scheme has good control performance.