An Improved Modulation Algorithm to Drive Magnetorquers

A Magnetorquer, or a Magnetic Torque Rod, is a satellite equipment that is used for angular momentum management, detumbling and reaction wheel desaturation on Low Earth Orbit (LEO) satellites. It is usually consists of copper windings around a ferromagnetic core with low remanence. When the input voltage is applied, the current flows through the coil and produces a magnetic dipole moment. It interacts with the Earth's magnetic field in such a way that the torque is produced. The most common way to drive a Magnetorquer is to vary the input voltage with Pulse Width Modulation. The classic modulation technique neglects the inductance of the magnetorquer and the discharge occurs slowly. However, especially when a faster discharge is needed, the classic modulation fails to deliver the required magnetic dipole moment. For that reason, in this study, a novel modulation technique is proposed that takes into account the exponentially convergent inductive behavior of the Magnetorquer. The proposed method produces more exact magnetic dipole moment in both fast and slow discharge conditions.