An Investigation into the Performance of Control Fin Drives.

Document Type : Original Article

Author

Egyptian Army.

Abstract

The control system of a guided missile is composed of the missile itself equipped with an automatic pilot and of a guidance system which is either on the missile or outside of it. The guidance system measures the missile's coordinates and out of them in addition to the target coordinates creates the control signals for deflecting the fins in such a direction that should result in the minimum deflection of the missile from the required trajectory. To control the missile during its flight in space, two control signals are sufficient. However, in some cases it might be required to control also the rotation of the missile around its longitudinal axis in which case there should be three control signals. The direction of the missile's motion most often takes place in two mutually perpendicular planes. In order to ensure correct functioning of the control fins in flight, the missile must not rotate around its longitudinal axis using a gyroscopic stabilization channel within the missile. Therefore, the missile autopilot has three channels two of them serving for control and one for stabilization. The main requirement imposed on the autopilot is the transfer of the control signals into mechanical rotation of the control fins. Therefore, each autopilot channel always contains a control fin drive, mainly of the servo-amplifier and the servomotor (actuator). During missile flight it is necessary to keep the missile's dynamic properties approximately fixed or slowly varying. Thus, any undue changes in the missile's maneuverability can be avoided using feedbacks from the angular speed and from the missile's normal acceleration to stabilize and to improve the dynamic properties of the missile and of the whole control circuit. Therefore, this paper is devoted to investigate the performance of the control fin drives in a guided missile including the effects of hinge moments upon its dynamic properties. The dynamic pressure had changed between three values to investigate the fin performance during minimum, medium and maximum loading conditions. Then, necessary feedbacks and cascaded correction networks are designed and analyzed to improve the system performance.

Keywords