Abstract
Considering the velocity of the missile cannot remain constant in most applications due to the effect of aerodynamic drag and thrust, a feasible adaptive impact angle control guidance law under varying velocity is proposed. The design of the guidance command is transformed into the design of the flight path angle, which is proposed as a general polynomial function of time-to-go with unknown coefficient. In addition, the unknown coefficient can be acquired from the boundary condition of the position. To cope with unpredictable disturbances, the adaptive scheme to initialize and recalculate the control parameter at each time step is also adopted. First, the guidance law is proposed with constant velocity. Then the law is extended to a more practical situation by considering varying velocity, and the estimation of time-to-go under varying velocity is proposed. Different simulations are carried out to verify the performance of the proposed guidance law.
Highlights
Reducing relative distance between missile and target is the primary objective for a guidance law
Among the additional constraints [3], impact angle control is of great importance and has been considered in many guidance laws
TIME-TO-GO ESTIMATION UNDER VARYING VELOCITY To calculate the guidance command in (20) and (33), we should acquire the information of time-to-go, which cannot be directly measured from any device
Summary
Reducing relative distance between missile and target is the primary objective for a guidance law. The generalized variable structure was used and an additional surface was introduced to reach a wider range of the final impact angle He et al [16] proposed a nonsingular terminal sliding mode(NTSM) guidance law, which was constructed through a combination of traditional NTSM and second-order sliding mode. The time-to-go polynomial guidance (TPG) law was first shown in [18], Lee et al [19] assumed the guidance command as a function of time-to-go with two unknown coefficients, which were determined to satisfy the specified terminal impact angle and acceleration constraints. All of the aforementioned studies on impact angle control guidance have assumed that the velocity of the missile was constant. In contrast to previous work, this note proposes an impact angle control guidance law without assuming a constant velocity. The problem of guidance command design can be transformed into the design of flight path angle
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