In this paper, we propose a design method of a nonlinear optimal controller for systems with rate limited actuators which are known to cause PIO of an aircraft. The PIO prevention problem is solved as a robust stabilization problem of a servo system for pilot commands. Simulation results demonstrate that the nonlinear controller achieves faster tracking performance with less oscillation and smaller input compared with an anti-windup compensator using the H∞ method. Robustness against parameter error, observation noise and time-delay is also confirmed.
This paper proposes a new attitude maneuver planning method for a spacecraft equipped with control moment gyros (CMGs). By introducing the piecewise linear gimbal angular accelerations as designing parameters, a quasi-time-optimal attitude control is achieved by a rest-to-rest maneuver. A main advantage of the proposed method is to allow the restrictions for the magnitudes of the gimbal angular velocities and the gimbal angular accelerations due to mechanical constraints. The effectiveness of the proposed method is demonstrated by numerical computations.
This paper considers an attitude estimation of flight vehicles using multiple sensors, e.g., a magnetometer and an accelerometer. Two types of estimation algorithms, the least-squares estimation and the analytic solution, are presented. Then, the stochastic error bound is evaluated by using the Cramer-Rao's lower bound. The effectiveness of the proposed methods is evaluated by numerical simulations.
The authors have developed laser ignition micro solid rocket which is a propulsion system suitable for 10-kg-class microspacecrafts. Although the specific impulse is expected to increase by reducing the throat area, higher combustion chamber pressure with the smaller throat causes a couple of serious problems. One is throat erosion and the other is break of combustion chamber. In order to prevent these difficulties, we made three improvements in design of thruster. First, we reinforced the throat, and throat erosion did not occur. Secondly, we changed the ignition surface of the propellant. As a result, peak pressure reduced, but specific impulse also reduced. Thirdly, we made the propellant to encapsulate to constrain the combustion surface, and peak pressure reduced considerably. We designed thrusters which had smaller throat than conventional, and established the increase in specific impulse by 17%. We visualized the combustion chamber, and it was found that capsule could control the combustion surface of propellant.