Research on lever loop in two-loop autopilot design by pole placement

The effect of lever loop on the two-loop autopilot has been often neglected in the traditional analysis and design, actually it has a great effect on the performance of the two-loop autopilot, because it brings the body angular acceleration into the main loop. Firstly, the method of two-loop autopilot pole placement is presented in the paper, when the dynamic performance of fin actuator, angular rate gyro, filter and accelerometer are neglected. Secondly, the effect of lever loop on the two-loop autopilot important parameters is analyzed. We find that the lever loop obviously decreases the increasing velocity of the autopilot undamped natural frequency and open loop crossover frequency along with open loop gain. In the condition we can design a high enough open loop gain autopilot without compensation in engineering. Finally, the principle of lever loop effect on the performance of two-autopilot is analyzed by root-locus.