SPHERICAL MAGNETIC DIPOLE ACTUATOR FOR SPACECRAFT ATTITUDE CONTROL

This paper develops an analytical force and torque model for a spherical magnetic dipole attitude control device, along with a control scheme that includes singularity avoidance. The device proposed consists of a non-contact spherical dipole rotor enclosed in an array of coils that is fixed to the spacecraft body. Excitation of the coils as prescribed by the control law rotates the dipole rotor in such a manner as to produce a desired reaction torque for orienting the spacecraft. The coils also control the rotor's position inside the spacecraft body via a separate control law because of the non-contact nature of the device. Due to the axisymmetric field of the dipole rotor, underactuation is possible with one device and therefore two spherical actuators are needed for full attitude control.