Open-loop optimal attitude control of miniature spacecraft using MEMS actuators

A novel attitude control method based on micro-electro-mechanical systems (MEMS) actuators, developed by Li et al. Each actuator (called pseudowheel) comprises four small beams of electro-thermal materials. If these beams undergo the transverse deformation in a clockwise rotation, the spacecraft rotates in counterclockwise direction in order to conserve the system angular momentum. However, when the actuator is off, the beams come to their undeformed configurations because of their elastic properties. This problem can be overcome by employing a sequence of large rotations caused by deflecting actuators about two or three orthogonal axes to produce a net attitude change. The kinematics of all rotation sequences is considered and then the rotating angles of MEMS actuators are derived by solving a set of nonlinear equations in terms of attitude angles of the spacecraft and rotating angles of the MEMS actuators. This paper presents further researches based on the work of Li et al. Such as study of rotation sequences, kinematics analysis of spacecraft, and simulation of attitude motion. Assuming the conservation of system angular momentum and employing inverse kinematics, the time response of attitude motion of the spacecraft is simulated. This approach not only just searches a possible solution based on an open-loop control strategy, but also determines a set of optimal rotating rates of MEMS actuators, which can produce a minimum kinetic energy required for attitude control. The proposed approach may be particularly useful for the attitude control of miniature spacecraft.