Input-output response based simultaneous tracking and disturbance attenuation control for helicopter image stabilizers

Image stabilizer is important for most unmanned helicopter system. Usually it should be able to drive the video sensor to track some targets precisely under heavy vibration due to the high speed rotation of the rotor. This is the so-called simultaneous tracking and disturbance attenuation control (STDA) problem. In this paper, a new 2DOF control strategy is proposed aiming at the STDA problem. The proposed control is composed of inner loop control, which is used to attenuate the disturbance due to helicopter's vibration, and a prefilter, which is outside the closed loop and used to ensure the transient performance of the whole system. One of the most absorbing advantages of the new proposed method is that the two parts are decoupled completely and thus can be designed separately. For inner loop control, an AFC enhanced PID control is proposed to realize disturbance suppression, while for the prefilter, a new parameter optimization algorithm is introduced to ensure optimal step tracking without influencing the disturbance attenuation performance. Furthermore, it should be pointed out that the whole controller is designed based on only input-output response independent on accurate model information of the system. Finally, experiments are conducted on a real image stabilizer with simulated vibration, and the results show the feasibility and validity of the proposed method.