THE ATTITUDE CONTROL SYSTEM OF 'KUNPENG-1B' SOUNDING ROCKET'S UPPER SERVICE PLATFORM

Sounding rocket is the only platform to explore the near space vertically. In order to create a stable and efficient platform for near space researches, the Attitude Control System (ACS) is added for the first time in the upper service platform of Chinese sounding rocket 'Kunpeng-1B'. The composition, function, and attitude control algorithm of the ACS are introduced. The actuator is Cold Gas Thruster and the solenoid valves are used to control the outlet of gas to generate thrust. After separation, the upper service platform needs to complete control sequence of de-spinning, three-axis-stabilized, pitch maneuver and spinning-up with the help of ACS. During the de-spinning phase, the roll channel's solenoid valves are actuated by the roll rate error through pseudo rate modulator (PSR). The active nutation control is implemented firstly in this phase. When the nutation angle exceeds the threshold, the pitch channel's solenoid valves are enabled to generate lateral moment to prevent nutation angle divergence. During the three-axis-stabilized phase, the pitch, yaw, roll angles maintain at 60 degrees, 90 degrees and 0 degrees, respectively. To increase the damping, both angular rate and angle error are introduced to PSR modulator. The decoupling control strategy of three-axis-stabilized control is that the roll channel has the highest priority. The pitch and yaw channel's controllers are enabled only if the absolute value of roll angle reduces below 25 degrees. The pitch maneuver phase begins when the upper service platform reaches the peak altitude. The pitch angle descends to -60 degrees during this phase. During the spinning-up phase, the roll rate maintains at 180 degrees/s for 2-dimensional space measurement. On 27th, Apr. 2016, 'Kunpeng-1B' sounding rocket equipped with the new ACS was launched successfully. The roll rate is 330 degrees/s and the nutation angle is about 75 degrees before ACS works. Even under this large perturbation condition, the ACS still completed all missions successfully. The telemetry data demonstrates the effectiveness and the robustness of the control algorithm.