The optimal design for the attitude control system of a spacecraft with on-off impulse thrusters as actuators was studied. For the spacecraft actuating a large angle rest-to-rest attitude maneuver

proper attitude control law and proper attitude commands were designed to reduce the fuel consumption of the thrusters. First

the configuration of six impulse attitude thrusters on the spacecraft was given

and a nonlinear system model to describe the large angle attitude motion of the spacecraft was established using the quaternion tool. With this model

a nonlinear PD control law was designed to steer the spacecraft in actuating large angle maneuvers

and the stability of the nonlinear attitude control system was proved by the second method of Lyapunov. Then

the allocation logic of the six impulse thrusters in the three axis attitude control system was proposed. Since the nonlinear PD control law has to be implemented with the pulse width modulation technique

three switching thresholds were introduced into the nonlinear PD control law to reduce the consumption of fuel. The switching thresholds were selected using the particle swarm optimization technique. A scheme of scheduling the quaternion command for the rest-to-rest large angle attitude maneuver was proposed by steering the Euler angles to reach their aims with uniform angular rates. The scheme was helpful for improving the transient property and reducing the fuel consumption of the control system compared with the conventional step commands. Simulation results verified the effectiveness of the control law and the scheme of scheduling the commands.