In recent years, the strapdown system has become the significant trend of the development of precision guided weapons. In order to effectively hit the lightly armored targets, researchers have done a series of studies on the impact angle control. However, most of them ignored the field-of-view constraint of the strapdown seeker. The existing impact angle control guidance laws with the field-of-view constraint have obvious drawbacks to some extent. For example, most of them are only applicable against nonmaneuvering targets and some of them suffer sudden hopping of guidance command due to the use of switching logic. Taking the strapdown seeker missile as the research object, this paper studies the field-of-view constrained impact angle control guidance problem against stationary targets, constant speed targets and maneuvering targets. According to the sliding mode control theory, two kinds of sliding surfaces are designed to make the missile achieve high precision attack under a desired impact angle within the field-of-view constraint. A quadratic barrier Lyapunov function and a logarithm barrier Lyapunov function are used to guarantee that the sliding surfaces designed for the impact angle constraint and the field-of-view constraint can converge to zero in finite time respectively. Then, a nonlinear extended state observer is proposed to estimate the unmeasurable disturbance of the system and alleviate the undesirable chattering by compensating it with the estimation of the disturbance. Finally, the feasibility of the proposed law is verified by numerical simulations.INDEX TERMS Field-of-view constraint, impact angle control, logarithm barrier Lyapunov function, nonlinear extended state observer, sliding mode control.
Recently, multiple constraints have been considered in the design of guidance laws. Most of the existing impact angle control guidance laws considering the seeker's field-of-view constraint are only applicable to constant speed missiles and have other limits to some extent. This paper is concerned with the field-of-view constrained impact angle control guidance law applied to variable speed missiles based on the sliding mode control theory. In the design of the sliding mode controller, we use a quadratic Lyapunov function to achieve the impact angle control. Moreover, we introduce an integral barrier Lyapunov function with an adaptive control item to address the field-of-view constraint and prevent the undesirable chattering caused by the disturbance of the nonlinear system. Then, the asymptotic stability of this close-looped system is verified. Eventually, numerical simulations are provided to demonstrate the performance of the proposed guidance law. INDEX TERMS Adaptive control, field-of-view constraint, impact angle control, Lyapunov function, sliding mode control.
A high efficient current control strategy of the Stirling linear generators was investigated in this paper. The structure of the linear generator was introduced and mathematical model was built. The efficiency of the system is compared in different current modes. The highest efficiency control strategy is calculated in the conditions of without magnetic saturation, iron-loss, mechanical loss and treating inductance as a constant. At the same time, the maximum ratio of the electromagnetic power to current control is realized. Finally, this algorithm was validated in the simulation and experiment.
The torque ripple is the important restriction affecting the promotion and application of switched reluctance motor, the analytic expressions to calculate switched reluctance motors tangential force and radial force are derived in this paper, based on analyzing the cause of switched reluctance motor vibration and torque ripple. By improving the stator poles structure, the torque near the commutation points is compensated, which smooth the wave of air gap magnetic field to reduce torque ripple when the stators and the rotors salient poles coincide. In this paper, three structures that puts wedge angle on both sides of the stator poles is presented, and analysis of torque ripple is made. Studies shows that the right size of wedge angle can effectively inhibit the switched reluctance motor torque fluctuations.
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