Velocity-Free Attitude Control with Actuator Constraint

In addition to the interest in ensuring attitude control with high performance based on “velocity-free” output feedback, there is a practical motivation in introducing control input constraints nested into the closed loop. From the viewpoint of control law design, due to physical limitation, momentum exchange devices and/or thrusters as actuators for the satellite attitude control fail to render infinite control torque, and thus the actuator outputs are constantly bounded or constrained. Once the actuator reaches its constraints, the efforts to further increase the actuator output would not result in any variation in the output, and then this usually deteriorates the system performance or even results in system instability. Hence, it is very necessary to take actuator constraints into account during attitude controller design.