Rotor position sensing apparatus and method using piezoelectric sensor and hall-effect sensor
A position observer for control-based torque ripple mitigation in permanent magnet synchronous machines (PMSMs). Rotor position is determined using data from two sources: a piezoelectric sensor for initial position and low-speed detection, and a single Hall-effect sensor for high-speed detection.
1. A method of estimating the rotor position of a permanent magnet synchronous machine, comprising:
employing a first sensor, other than a magnetic field sensor, to provide data at low operating speeds of said synchronous machine, said first sensor being sensitive to torque ripple and capable of generating a signal suitable for use as a torque ripple feedback signal in a torque ripple mitigation algorithm;
employing a second sensor, of a different type than said first sensor, to provide data at high operating speeds of said synchronous machine; and
processing said data from said first and second sensors to determine the rotor position of said permanent magnet synchronous machine over a wide range of speeds including low and high speeds.
2. The method of claim 1 , wherein said low operating speeds of said synchronous machine include substantially zero speed.
3. The method of claim 2 , wherein said first sensor is a vibration sensor.
4. The method of claim 3 , wherein said first sensor is a piezoelectric sensor.
5. The method of claim 4 , wherein said second sensor is a Hall-effect sensor.
6. The method of claim 5 , further comprising the step of integrating rotor velocity to estimate rotor position between Hall-effect sensor transitions.
7. The method of claim 6 , further comprising:
applying stator excitation to said synchronous machine at substantially zero speed to induce vibration;
sensing said vibration with said first sensor while said synchronous machine is at substantially zero speed; and
determining the initial rotor position of said synchronous machine from said induced vibration as sensed at substantially zero speed by said first sensor.
8. The method of claim 7 , wherein a sequence of stator excitations is applied to said synchronous machine to induce a sequence of torque-ripple-induced vibrations, and a ratio of sensed vibrations is used to determine the initial position of the rotor.
9. A method of determining the rotor position of an electric machine having a rotor mounted within a stator and driven by a rotating magnetic field generated by excitation of said stator with an alternating current, comprising:
applying stator excitation to said stator of said electric machine; and
using torque-ripple-induced vibration to determine the rotor position of said rotor within said stator of said electric machine.
10. The method of claim 9 , wherein said applying includes applying a sequence of stator excitations to said electric machine to induce a sequence of torque-ripple-induced vibrations, and wherein a ratio of sensed vibrations is used to determine the position of the rotor.
11. The method of claim 6 , further comprising:
applying high-frequency stator excitation to said synchronous machine at substantially zero speed to create torque-ripple-induced vibration;
sensing said induced vibration with said first sensor; and
determining the initial rotor position of said synchronous machine from said induced vibration as sensed by said first sensor.