Title

Active Nutation And Precession Control For Exoatmospheric Spinning Ballistic Missiles

Abstract

Spinning a ballistic missile is a common practice to stabilize the attitude of the vehicle; however, this requires the vehicle to be accurately balanced to avoid nutation and precession due to axis misalignment. While a missile is spinning, it is subject to nutation attitude behavior depending on the non-diagonal terms of the inertia matrix. Utilizing the onboard Attitude Control System (ACS), the nutation and precession energy can be dissipated to achieve accurate spinning motion. This may be desirable if the vehicle is carrying a sensor package that needs to be pointed accurately. This paper develops the equations of motion for a spinning ballistic missile utilizing the full inertia matrix with non-zero cross products of inertia (POI). The unbalanced condition that is represented by the non-zero cross POI is also evaluated in terms of axis misalignment between principal axis of rotation and geometrical body axis. We present an active nutation control scheme using the missile's ACS to minimize the nutation and precession angles. A typical nutation control scheme can create an aberration of the precession angle and this interaction is examined with the goal of minimizing both. The proposed control scheme is based on an active combination of several control methodologies and a two control loop architecture. A nonlinear dynamic inversion control technique is used to stabilize the inner loop dynamics, which calculates torque commands from body rate errors. A linear controller that is used to calculate the body rate commands from the attitude error expressed in quaternion implements the outer loop. A key aspect of this design is the control allocation algorithm, which translates the desired body axes torque commands into thrusters firing commands. Finally, a system identification routine based on least square regression is used to estimate the mass properties of the vehicle which are used by the dynamic inversion controller and the control allocation algorithm. Furthermore, the results of 3DOF simulations, including special considerations of modeling a spinning vehicle, detailed model of an Inertial Measurement Unit, pitfalls and uncommon modeling errors are presented. In addition to the control scheme and its simulation results, this paper presents additional design trades that were considered during the design process such as: the effect of ACS capacity and sizing on total attitude controllability, the elimination of chatter and the different techniques considered, considerations of time delay and computational disturbances, attitude measurement sensor noise and error sources, and choice of control parameters. © 2008 by Ricardo Elias and Juan Vega.

Publication Date

1-1-2008

Publication Title

AIAA Guidance, Navigation and Control Conference and Exhibit

Number of Pages

-

Document Type

Article; Proceedings Paper

Personal Identifier

scopus

DOI Link

https://doi.org/10.2514/6.2008-6998

Socpus ID

78651074135 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/78651074135

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