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This article details the design of a skid-to-turn autopilot for a 155mm spin-stabilized canard-guided projectile. The proposed concept possesses a so-called dual-spin configuration: the aft section contains the payload and is highly-spinning in order to provide the system with dynamic gyroscopic stability, whereas the forward section is roll-decoupled from the aft one by means of a coaxial motor, and includes all the necessary guidance and control software and hardware. A set of two pairs of nose-mounted rotating aerodynamic control surfaces are used to regulate the projectile airframe pitch/yaw dynamics. The autopilot design, based on an accurate linearized model, remains a challenging task because of the heavy cross-coupling between the normal and lateral axes dynamics generated by the high-spin rate of the aft section. A H∞ loop-shaping design approach is used in order to synthesize a low complexity structured fixed-order robust controller, taking into account modeling uncertainty and the limited performance of the actuators and sensors. Two kinds of autopilot feedback structures are considered such that they correspond to two different positions for the sensors. The influence of this sensor position on the open-loop projectile pitch/yaw dynamics is also emphasized.

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