Innovative approach to the momentum management control for Space Station Freedom

A new approach to the control moment gyro (CMG) momentum management and attitude control of the Space Station Freedom is presented. First, the nonlinear equations of motion are developed in terms of body attitude and attitude rate with respect to the local horizontal local vertical (LVLH); then, they are linearized about any arbitrary stable point via the use of perturbation techniques. It is shown that, for some assembly flights, linearization of the equations of motion about the LVLH may not be valid and that a better choice would be to linearize about a torque equilibrium attitude (TEA). Next, a three-axis-coupled control law is used and the controller gains are determined via a combination of the optimal control and regional pole placement techniques. Finally, it is shown that the proposed linearization process, together with the coupled control laws, can stabilize a previously uncontrollable space station assembly flight.