Flexibility modeling and autopilot design of interceptor missile using multiple sensing

When addressing concerns related to an unstable interceptor missile with lightly damped structural modes, the active mitigation of structural vibrations may be unfeasible due to constraints in actuation and uncertainties in modeling. In such cases, a prevalent engineering strategy involves the use of band-stop filters to mitigate the impact of vibrations on autopilot feedback loops. This approach is commonly known as the mode cancellation technique. The paper proposes a model for flexibility and autopilot design for a highly flexible unstable interceptor missile using multiple sensors such as gyroscopes and accelerometers. The model combines interceptor flight dynamics, actuator dynamics, and air-frame elasticity in a state-space form. The order of the model is reduced to optimize sensor placement and minimize the flexibility’s impact on control. This enables autopilot design with extended bandwidth. Once the choices are made, a three-loop autopilot with multiple sensing techniques is proposed and analyzed to extend the autopilot’s bandwidth by countering air-frame deformation measured by these sensors. The simulated test cases demonstrated that significant attenuation of the first and second elastic modes can be achieved with good stability margins.