An Unbiased Active Disturbance Rejection Control Approach for Near Space Vehicle Autopilot

The angular rate is the derivative of pitch angle other than the derivative of angle of attack, there determinately exists a steady-state error in the closed-loop system output with the linear active rejection control in the case that the control variable is the angle of attack. In this study, an unbiased linear active disturbance rejection control approach based on two-loop control is proposed. The internal-loop is built by angular rate feedback to improve the damping, and the external-loop is built by angle of attack feedback to realize the system output accurately reproducing the reference input. Furthermore, a linear active disturbance rejection control is applied for the external-loop controller design. The approach is employed to a hypersonic near space vehicle autopilot. The numerical simulations show that the proposed approach preserves the performance on frequency domain as good as that of the conventional active disturbance rejection control approach, the steady-state error of the closed-loop system is well removed, and the angle of attack command is tracked with better accuracy than that of some previous active disturbance rejection control approaches.