Moving-mass-based station keeping of stratospheric airships

Stratospheric airships are lighter-than-air vehicles that work at an altitude of 20km in the lower calm portion of the stratosphere. They can be used as real-time surveillance platforms for environment monitoring and civil communication. Solar energy is the ideal power choice for long-endurance stratospheric airships. Attitude control is important for airships so that they can point at a target for observation or adjust the attitude to improve the output performance of solar panels. Stratospheric airships have a large volume and semi-flexible structure. The typical actuators used are aerodynamic surfaces, vectored thrust and ballonets. However, not all these actuators can work well under special working conditions, such as low density and low speed. In this study, moving-mass control is introduced to stratospheric airships because its control efficiency is independent of airspeed and atmospheric density. A nonlinear feedback controller based on generalised inverse with a nonlinear mapping module is designed to implement moving-mass control. Such a new station keeping scheme with moving masses is proposed for airships with different working situations.

Stability of Moving Mass Control Spinning Missiles with Angular Rate Loops

Moving mass control (MMC) is a new control method in control field. It is a potential way to solve the problem of aerodynamic rudder control insufficiency caused by the low density of upper atmosphere, to reduce the high speed missile aerodynamic thermal load, and to solve the problem of rudder surface ablation. However, the spinning of the airframe and the movement of internal moving mass induce the serious dynamic cross-coupling between pitch and yaw channels, which may lead to system instability in the form of a divergent coning motion. In this paper, the mathematical model of the MMC missile is established, and the angular motion equation is finally obtained by some linearized assumptions. Then, the sufficient and necessary conditions of coning motion stability for MMC missiles with angular rate loops under fast and slow spinning rates are analytically derived and further verified by numerical simulations. It is noticed that the upper bound of the control gain is affected by the location of the moving mass and the spinning rate of the missile.

Novel Moving Mass Flight Vehicle and Its Equivalent Experiment

This paper presents a novel configuration of flight vehicle with moving mass control. We focus on the development of the proposed control mechanism and investigate the feasibility of an equivalent experimental setup. First, the effect of the moving mass parameters on the control authority is investigated. Then, a control law based on immersion and invariance (I&I) theory is presented for the moving mass control system. In the design process, we select a first-order target system to reduce the difficulty of controller design. To deal with the coupling caused by the additional inertia moment, which is generated by the motion of the moving mass, the extended state observer (ESO) is designed. The proposed adaptive controller is simulated and tested on the experimental setup. Finally, the simulation results validate the quality of the proposed adaptive controller, which ensures a good performance in the novel configuration with internal moving mass.