Simplified Anti-Disturbance Control for the Roll Channel of a Low Cost Short Range Weapon

Versions of anti disturbance control for improving the disturbance rejection properties of the roll control channel of low cost tactical missiles with limited actuator bandwidth are presented and characterized. It is argued that though for a homing missile it is important to maintain a steady roll attitude (or at least a very small roll rate) the task is made difficult due to the cross channel effects (lateral manoeuvres coupled with missile body asymmetry) and an affordable actuator with limited bandwidth and non-negligible backlash. It is pointed out that the bandwidth of the roll attitude control channel is typically a decade less than the actuator bandwidth whereas the disturbances due to lateral manoeuvres may be in the lateral autopilot bandwidth which is typically larger than the roll attitude bandwidth resulting in poor disturbance rejection. The bandwidth of the roll attitude channel remains constrained due to stability robustness considerations (i) in presence of backlash and (ii) to accommodate large variations of effector gains over the flight regime. Several possibilities of anti-disturbance control configurations are mentioned and tabulated. It is shown that a particular version of anti disturbance control scheme, which is simple to implement, can successfully mitigate cross channel disturbances in roll rate due to lateral manoeuvres. A case study with reasonable values of parameters is used to demonstrate the efficacy and robustness of the suggested schemes. The results are encouraging and application to actual systems is advocated.