Combining INFORM method, voltage model and mechanical observer for sensorless control of PM synchronous motors in the whole speed range including standstill

Abstract

The article presents the combination of a low-speed model (INFORM method) and a specially adapted high speed model (voltage model or EMF model) for covering the full speed range of sensorless permanent magnet (PM) synchronous motor drives. Both models generate ''measuring information'' for a linear observer, modelling the mechanical structure of the motor. A special feedback loop is introduced, coupling back the observer information to the integrating voltage model. Thus, a stable operation with high robustness against parameter uncertainties and low frequency disturbances is achieved. Zusammenwirken von INFORM-Verfahren, EMK-Modellen und mechanischem Beobachter bei der sensorlosen Regelung von Permanentmagnet-Synchronmotoren im gesamten Drehzahlbereich einschließlich Stillstand. In dem vorliegenden Beitrag wird die Kombination eines Tiefdrehzahlmodells (INFORM-Verfahren) mit einem adaptierten Hochdrehzahlmodell (Spannungsmodell, EMK-Modell) fü r den sensorlosen Betrieb von Permanentmagnet-Synchronmotoren im gesamten Drehzahlbereich vorgestellt. Beide Modelle erzeugen ,,Messinformation'' fü r einen linearen Beobachter, welcher die mechanische Struktur des Motors modelliert. Eine besondere Modellrü ckkopplung vom Beobachterausgang zum integrierenden Spannungsmodell wird verwendet. Damit wird ein stabiler Betrieb mit hoher Robustheit gegen Parameterunsicherheiten und tieffrequenten Stö rungen erreicht. Schlü sselwö rter: sensorlose Regelung; INFORM-Verfahren; Spannungsmodell; EMK-Modell IntroductionIn recent years, the permanent magnet synchronous machine (PSM) has got increasing importance for reliable highly dynamic drive applications. It has a lot of advantages like best efficiency as well as compact construction due to the use of rare earth permanent magnets. A problem in critical applications with respect to costs, space and reliability is the rotor position sensor, which reduces the robustness of the drive considerably. In this article, the INFORM method for sensorless torque-, speed-and position control down to standstill is used to realize cost-effective sensorless drives for reliable transient operation. It is combined with a so-called ''voltage model'' or ''EMF model'', respectively, at higher speed to cover the whole speed range. However, a performance increase can be achieved by combining the INFORM and EMF model with a mechanical observer of the motor shaft, building a new extended observer structure. A local stability analysis shows the poles of the extended observer.

Extended back EMF model for PM synchronous machines with different inductances in d- and q-axis

“…All data are given in normalized values. The following calculations deal with the classical back EMF model [1], [2] and [6]. The stator flux linkage ψ s is derived from the stator voltage equation…”

Extended mechanical observer structure with load torque estimation for sensorless dynamic control of permanent magnet synchronous machines

“…If load torque is estimated using a further state quantity, this deviation will force the estimated load to its real value. Combining the specially adapted voltage model [7], which generates "measuring information" in the high speed range, with an extended observer, reduces the speed controller to a simple proportional element. In the low speed range the well known INFORM-method gives position information to the linear observer.…”

Poles position identification of permanent magnet axial flux motor using PIPCRM sensorless method.

“…Therefore sensorless methods, which provide excitation flux position at standstill, are developed [1] [2]. Well known method, which can be used at standstill, is INFORM method [3] [4] [5] [6]. In such a method, stator windings are supplied by voltage pulses from a three phase converter.…”