A Sensor-Less Motion Sensing Method of a 3-DOF Permanent Magnet Spherical Motor

This paper presents a sensor-less method for measuring in real-time the 3-DOF orientation as well as the angular velocity of a permanent magnet spherical motor (PMSM) using back-electromagnetic force. By utilizing the relationship between the induced voltages of the coil windings and the moving magnetic fields of rotor permanent magnets, this method can incrementally compute the 3-DOF orientation and angular velocity by measuring the induced voltages in the static electro-magnets of a PMSM without installing any sensors. This method is experimentally investigated on a prototype PMSM and the results are compared with a commercialized gyroscope sensor.