Abstract: Disturbance torque directly affects the tracking and measuring accuracies of seeker and the guidance precision. To analyze the degradation of gyro-stabilized seeker tracking accuracy due to disturbance torque, the dynamics models of seeker, seeker gimbal friction and seeker cable disturbance torques are established. To reduce the influence of disturbance torque on seeker tracking accuracy, a practical disturbance observer (DOB) is designed to compensate the disturbance torques. Multi-rate sampling problem due to the difference between sampling and hold times of seeker system and DOB is considered. A discrete DOB design method is proposed based on Nyquist stability theory, so the conservation of small gain design method can be removed. Sampling, hold and filter time constants of DOB are specified by balancing system stability, disturbance torque compensation and sensor noise reduction. An extracting method of information which is required by DOB is proposed by integrating the measurement information of missile and seeker. The mathematical simulation results show that the designed DOB can improve the seeker tracking accuracy efficiently.

Key words: control science and technology, disturbance observer, stability, seeker, disturbance torque compensation, multi-rate sampling