Control moment gyro (CMG) based spacecraft attitude control using feedback linearization control technique

In this paper we are investigating the pointing and attitude control of a satellite in low-Earth orbit, The control system is composed of three orthogonal Single-Gimbaled Control Moment Gyro (SG-CMG) aligned with the control axes of the spacecraft and derives its control torques from precession of the gyro wheels. It is shown that this system has full Relative Degree, Hence, the feedback linearization control technique which is one of the techniques in nonlinear control design is utilized to linearize the whole dynamics of spacecraft from inputs to outputs. Since CMGs are driven by three DC motors, the controller is designed when the motor moment of inertia and damping and motor torque limitation are taken into account. The numerical simulations are performed for normal, maneuvering and safe-hold modes to show the main features of the proposed controller.