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Input date:	Tuesday, November 10, 2009	Last update:	Wednesday, August 18, 2010
Deadline:	Saturday, January 01, 2011
Type of profile:	TO
Title:	Sensorless vector control for Permanent Magnet (PM) machines
Abstract:	A Flemish research institute developed a sensorless vector control scheme for Permanent Magnet (PM) machines. The technique can be used from standstill up to and above nominal speed, and shows several advantages over the existing state-of-the-art. This allows for a convenient replacement of classic AC drives by small, fast and efficient PM machines in demanding applications. The research institute is looking for industrial partners interested in licensing or (joint) further development.
Description:	Classical Permanent Magnet (PM) machine drives require a rotor position sensor to achieve stable and efficient operation. Although PM machines in itself offer significant advantages for many demanding applications, the extra sensor requirement (as compared to classical drive systems) decreases the robustness of the system. This technology offer relates to a sensorless vector control in which the rotor position is estimated for PM machines. The technique can be used from standstill up to and above nominal speed showing several other advantages over the existing state-of-the-art. A PCT-patent has been filed. The research centre has a long experience in the design and control of electric drive systems, and offers both its general expertise as well as its dedicated expertise in sensorless control and PM machines. The research institute is looking for industrial partners interested in licensing or (joint) further development. PM machines are commonly used in many applications including drives requiring a high torque to volume density, a low inertia or a high efficiency. State-of-the-art rotor position estimators, developed for low speed operation, achieve an accuracy of about 3 to 5 electrical degrees at no-load operation. By using conventional sensorless strategies, increasing estimation errors (up to 40 electrical degrees) are observed for higher loads. Consequently, stable control of the PM machine is obtained for standstill and low speed steady-state operation up to about 100 rpm, but due to the increased estimation error, the efficiency of the drive drops significantly at increasing loads. These disadvantages are avoided using the technique of this technology offer. In order to estimate the rotor position, the proposed method slightly adapts the Pulse Width Modulation (PWM) switching scheme of the electric power converter supplying the PM machine. However, this is done without affecting the conventional control loops. It has been shown that by injecting test vectors in this way and by sampling the resulting motor current response at well-chosen moments in time, the rotor position can be accurately estimated. The estimation can then be used for the purpose of vector control. The figure shows preliminary measurement results of the estimated position and estimation errors on a laboratory prototype. Innovative Aspects: The proposed method has several advantages. First of all, it allows rotor position estimation and vector control from standstill up to and above nominal speed without using a position or speed sensor, which in addition means that robustness is increased over techniques using a sensor. Furthermore, it is a major advantage of the proposed method that it can be integrated seamlessly in existing control loops for PM machines. As the injection of test vectors does not interfere with the control loops, accurate rotor position estimation is also possible during current transients. The technique even provides the possibility to compensate the influence of heavy loading and cross-saturation. Using the proposed technology, classic AC drives may be conveniently replaced by PM machine drives, which are known to be small, fast and efficient. Application is possible in both retrofit and new applications, while offering a highly dynamic drive system without the need for a shaft position sensor. Current Stage of Development --------------------------- Development phase - Laboratory tested RTD programme --------------------------- Private Research Intellectual Property Rights --------------------------- Patent(s) applied for but not yet granted Organisation/Company Type --------------------------- Research institute/University Organisation/Company Size --------------------------- 11-50 Application Domain(s) --------------------------- Market Applications --------------------------- MA Keywords: Process control equipment and systems; Robotics; Other industrial automation; MA Keyword Codes: 008002003; 008002004; 008002007; MA Highlights: Vector control of PM machines including applications requiring a high torque to volume density (e.g. automotive applications), a low inertia (e.g. highly dynamic textile machines) or a high efficiency (e.g. wind generators). Collaboration Type --------------------------- License Agreement; Joint further development; Adaptation to specific needs; Collaboration Comments --------------------------- - Type of partner sought: research institute, industry - Specific area of activity of the partner: electric motor control - Task to be performed by the partner sought: industrialisation, (joint) further development Country of origin --------------------------- Belgium
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