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Analysis of PN Guided Missile Systems in the Frequency Domain
Published in Rafael T. Yanushevsky, Modern Missile Guidance, 2019
The delayed response of the tail controls can be compensated by employing an additional forward control device, using either divert thrusters or aerodynamic canard fins. Missiles with forward control fins, or canards, have been used for many years. However, this type of missiles can suffer from adverse induced rolling moments. The use of grid fins, or “lattice controls,” for the tail control surfaces instead of conventional planar fins was recently proposed as a possible remedy for the roll control problems. Studies have shown that when compared to conventional planar fins, grid fins have certain advantages, such as effective aerodynamic control at high angles of attack and high Mach number, attenuated body-vortex interference and improved roll control. The primary disadvantage of the grid fin concept is a higher drag than conventional planar fins. The canard fins, located in the front part of the fuselage, generate an aerodynamic force that is in the same direction as the required maneuvering force, thus generating an immediate response in the correct direction. Canard missiles have forward and aft control systems. In contrast to (4.12) and Figure 4.6, the flight control system dynamics of this type of missiles can be represented by two transfer functions: a minimum phase transfer function for the forward control and a non-minimum phase transfer function for the aft control. The use of two control systems offers new capabilities, e.g., the ability to generate a very high angle of attack for fast and large turns. The additional degree of freedom offered by the dual control system requires special consideration in the guidance and control design. The appropriate blending of the two controls can significantly improve the performance of canard missiles. The material of this chapter allows readers to obtain the analogous equations for this type of missiles.
The numerical investigation on the rolling decoupling of a canard-controlled missile using the jet control system
Published in Engineering Applications of Computational Fluid Mechanics, 2020
Jiawei Zhang, Juanmian Lei, Jintao Yin, Jianping Niu
Many pieces of research are conducted on the aerodynamic decoupling methods between the canards and the fins. Researchers pursue to reduce the reverse rolling moment by optimizing the aerodynamic configuration or to enhance the rolling efficiency by adding an assistant control system. Three common methods are as follows. The first method is the free-spinning tail missile (Hardy, 1977). The afterbody of the missile is decoupled from the forebody by a bearing, thus avoiding the transmission of the reverse rolling moment of the tail section to the forebody, which can effectively solve the reverse rolling problem. However, because of the Magnus effect of the spinning afterbody, the missile has yaw motion (Morote, 2005; Yin et al., 2017). Moreover, the free-spinning tail missile has obvious nonlinear aerodynamic characteristics, which have a high requirement on the missile control system (Lesieutre et al., 2002). The second method is to amend the geometric parameters or aerodynamic shapes of the fins. Most decoupling designs of changing geometric parameters are to decrease the fin span (Blair et al., 1983; McDaniel et al., 2010), while this measure would reduce the lifting characteristics and static stability of the missile. Some special shapes of the fin are designed to reduce the reverse rolling moment, such as the ring fin (Burt, 1976) and the grid fin (Spirito et al., 2003). The special shapes of the fin can reduce the rolling coupling effectively, however, both of them have large drag characteristics and poor lift-drag ratio. The third method is adding a flow control system at the fins to assist in roll control (Blair, 1978). By installing diversion tubes at the tip of the fin, the mainstream flow will be guided to the fin normal direction and generates jet flow for roll control using the reaction force. However, this method can significantly increase the axial force and the complicated diversion structure decreases the system reliability.