Attitude control law design for moving mass control reentry vehicle based on sliding mode
Due to issues of aerodynamic ablation, complicated mechanical environment and serious nonlinear dynamics, the control system is difficult to achieve high accuracy. For nonlinear dynamics of moving mass control reentry vehicle, a design method based on sliding mode for pitch-yaw channel attitude control is proposed, which improves control accuracy and anti-disturbance capability. According to a reentry vehicle attitude control system, the pitch-yaw channel dynamic model of the nonlinear system is firstly given. Secondly, designed by using backstepping theory, a sliding mode controller with approach law is proposed. Besides, in order to reduce chattering of sliding mode control, an improved sliding mode controller is presented, in which relay characteristics is replaced with continuous functions. Finally, simulation results demonstrate the validity and feasibility.
Integrated Guidance and Control of Moving-Mass Actuated Kinetic Warheads
Abstract : Modeling, simulation, and integrated guidance-control of a kinetic warhead utilizing moving- mass actuators are discussed. Moving masses can be used in any speed range both in the atmosphere as well as outside it, as long as there is a force, either aerodynamic or propulsive, acting on the vehicle. Since they are contained entirely within the airframe geometric envelope, and because no mass expulsion is involved, moving-mass actuation technique offers significant advantages over conventional aerodynamic control surfaces and reaction control systems. The present research developed a high fidelity, nine degree-of-freedom simulation model of a kinetic warhead with three moving-mass actuators. This simulation model is used for actuator sizing and in the development of flight control systems. A software package for performing numerical feedback linearization technique is employed for the design of nonlinear flight control systems. Interception of non-maneuvering and weaving targets in both atmospheric and exo-atmospheric conditions are demonstrated.
Influence of filler addition, storage medium and evaluation time on biaxial flexure strength and modulus of adhesive systems
Abstract Objective. This study evaluated the effects of filler addition, storage medium and time on biaxial flexural strength and flexural modulus of six adhesive systems. Materials and methods. The adhesives were either unfilled resins: Single Bond, Prime&Bond 2.1 and One-Step; or filled resins: Single Bond Plus, Prime&Bond NT and One-Step Plus. Resin discs of each product (0.5 mm thick × 6.0 mm diameter) were prepared using silicon molds (n = 10). The discs were stored dry, in water, mineral oil or ethanol for 1 week or 3 months before biaxial flexural testing. Data were statistically analyzed by 3-way ANOVA and Tukey's post-hoc test (α = 0.05). The specimens were tested in a universal testing machine at 1.27 mm/min until failure occurred. Results. In general, the storage in ethanol led to significantly lower flexural strength and flexural modulus values than the other storage conditions for all adhesives in both storage periods. Filler addition increased flexural strength and flexural modulus for Prime&Bond NT, when it was stored dry or in water for 1 week. For Single Bond Plus, the filler addition resulted in higher flexural modulus, when it was stored for 1 week in oil and in ethanol. No significant differences in flexural modulus were observed between One-Step and One-Step Plus in any storage medium. Conclusions. Results suggested that filler addition does not necessarily have to increase the flexural strength and flexural modulus. Ethanol and oil storages tended to yield opposite effects.