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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 rotor position estimation for Switched Reluctance Machines (SRM)
Abstract:	A Flemish research institute developed a sensorless rotor position estimation technique for Switched Reluctance Machines (SRMs). 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 the replacement of classic AC drives by cheap and robust SRMs in many applications. The research institute is looking for industrial partners interested in licensing or (joint) further development.
Description:	A Switched Reluctance Machine (SRM) drive requires a rotor position sensor to achieve stable and efficient operation. Although SRM drives in itself offer significant advantages for many demanding applications, the extra sensor requirement (as compared to classical drive systems) increases cost and space requirements, and decreases the robustness of the system. This technology offer relates to a sensorless technique for the rotor position estimation for SRMs. 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 SRMs. The research institute is looking for industrial partners interested in licensing or (joint) further development. SRM drives are commonly used in high-speed applications and can for example be used in electric/hybrid cars but equally in e.g. compressors and consumer goods. State-of-the-art sensorless techniques for SRMs can be divided into several categories, being the ones using test vectors, the ones using flux estimators and the ones using induced voltages. If standstill operation is required, it turns out that only techniques with test vectors are actually competitive with the proposed technique. State-of-the-art techniques using test vectors, however, typically introduce load ripples, additional vibrations and sound, are difficult to implement at high speeds or require very accurate measurements. The proposed method does not show these disadvantages. Just like other methods, the proposed method exploits the property that the inductance of a motor phase changes as a function of the rotor position. However, for the technology of this offer this change in inductance is detected in an innovative way. To achieve this, the reaction of the motor phases on the converter voltage is observed. This reaction, which is a harmless (very low energy) high frequency damped oscillation in voltage, is measured by sampling and used to estimate the rotor position. The figure shows the measured response for a full revolution of the rotor of a 6x4 SRM. Such response is perfectly suitable for torque or speed control of the machine. Innovative Aspects: Besides the fact that the proposed method requires a measurement of the voltage (which, in some cases, might require some additional hardware), the method has several advantages. First of all, it allows rotor position estimation starting from standstill up to and above the nominal speed without using a shaft position sensor, which in addition means that robustness is increased over techniques using a sensor. Furthermore, a major advantage of the method is that it can be integrated seamlessly in existing SRM drive schemes. Moreover, the technique does not contribute to additional torque ripple resulting in an unaffected operation of the machine and causes no additional generation of vibration and sound. The technique eliminates the effects of magnetic coupling between the motor phases and is insensitive to the influence of saturation in case of heavily loaded machines. Using the proposed technology, classic AC drives may be conveniently replaced by SRM drives, which are known to be small, cheap and robust. 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 --------------------------- National Programmes 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: (High-speed) drive applications such as electric/hybrid cars, compressors, consumer goods (washing machines, vacuum cleaners), ... . 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 for specific applications Country of origin --------------------------- Belgium
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