Zhu Yanwei

Dynamics of tether-tugging reorbiting with net capture

To control the growth of space debris in the geostationary earth orbit (GEO), a novel solution of net capture and tether-tugging reorbiting is proposed. After capture, the tug (i.e., active spacecraft), tether, net, and target (i.e., GEO debris) constitute a rigid-flexible coupled tethered combination system (TCS), and subsequently the system is transported to the graveyard orbit by a thruster equipped on the tug. This paper attempts to study the dynamics of tether-tugging reorbiting after net capture. The net is equivalent to four flexible bridles, and the tug and target are viewed as rigid bodies. A sophisticated mathematical model is developed, taking into account the system orbital motion, relative motion of two spacecraft and spacecraft attitude motion. Given the complexity of the model, the numerical method is adopted to study the system dynamics characteristics. Particular attention is given to the investigation of the possible risks such as tether slack, spacecraft collision, tether rupture, tether-tug intertwist and destabilizing of the tug’s attitude. The influence of the initial conditions and the magnitudes of the thrust are studied.

Robust optimal guidance for hypersonic glide vehicle with hinge moment constraint

The magnitude of hinge moment is a prominent problem for rapid dive maneuver of hypersonic glide vehicles. A robust optimal integrated guidance law considering constraints of hinge moment and terminal impact angle is proposed with excellent performance. Based on the analogy relationship of hinge moment and normal aerodynamic load, the constraint of hinge moment is transformed to normal load constraint; and the optimal guidance law under nominal conditions is derived utilizing optimal control theory. A terminal sliding mode control based guidance modification is designed to eliminate the inevitable departure brought by uncertainties in finite time; and the hyperbolic tangent function is introduced to reduce the high-frequency chatting. The theoretical analysis and simulation results are conducted to illustrate the capability of the proposed integrated guidance law for hypersonic glide vehicle.