A Rotor Posture Measurement System by Analyzing Sensed Magnetic Field from Arrayed Hall Sensors

Because spherical motors have three-degrees of freedom and can rotate in any direction, they are expected to be applied to various mechanisms such as the joints of robot arms, control mechanism of robot eyes, wheels of carts, and stirrers to mix liquids and powders. The authors study spherical motors driven by magnetic forces to rotate the rotor and developed a technique, what we call Torque Map Control, to drive spherical motors referring the data prepared beforehand of working torques to the rotor in various relative spatial relations between the rotor and an electro-magnet installed on the stator when a unit current is given to the electro-magnet. For the control technique, it is necessary to measure the posture of the rotor that is presented by the rotation axis and angle from the base spatial relation between the rotor and the stator. This study developed a rotor posture measurement system by analyzing the sensed magnetic field from arrayed 64 Hall sensors. The basic applicability of the developed rotor posture measurement system is confirmed by the measurement experiments of rotor posture for the rotations around 3 rotation axes that are mutually orthogonal although some future works are necessary to improve measurement accuracy.