Missile flight control
The flight control system is a key element that allows the missile to meet its system performance requirements. The objective of the flight control system is to force the missile to achieve the steering commands developed by the guidance system. The types of steering commands vary depending on the phase of flight and the type of interceptor. For example, in the boost phase, the flight control system may be designed to force the missile to track a desired flight-path angle or attitude. In the midcourse and terminal phases, the system may be designed to track acceleration commands to effect an intercept of the target [www.jhuapl.edu].
The missile control system keeps the missile in the proper flight attitude. For example, the missile axis must lie along the desired trajectory rather than at an angle. The missile must be roll stabilized; a fixed plane through the missile axis must remain parallel to a fixed reference plane outside the missile. Flight attitude stabilization is necessary if the missile responds properly to guidance signals. For example, assume that the missile has rolled 90 degrees clockwise from the proper attitude. Now, if it receives a "right turn" command from the guidance system, the operation of the control surfaces will turn the missile downward rather than to the right. But if the control system keeps the missile in the proper attitude, guidance signals will be correctly interpreted and produce the desired correction in the missile flight path.
When the control system determines that a change in missile attitude is necessary, it uses certain controllers and actuators to move the missile control surfaces. When it determines that a change in missile course is necessary, the guidance system uses these same devices to move the control surface. Thus the guidance and control systems overlap [maritime.org].
Paul B. Jackson. Overview of Missile Flight Control Systems. Retrieved from: https://www.jhuapl.edu/Content/techdigest/pdf/V29-N01/29-01-Jackson.pdf
MISSILE CONTROL SYSTEM. Maritime Park Association. Retrieved from: https://maritime.org/doc/missile/part1.php