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1、A Sliding Mode Observer Based Controllerfor Switched Reluctance Motor Drives#Iqbal HusainMember, IEEESameer SodhiStudent Member, IEEEMehrdad EhsaniSenior Member, IEEE#Power Electronics LaboratoryDepartment of Electrical EngineeringTexas A&M UniversityCollege Station, TX 77843Tel: (409)-845-8775Fax:
2、(409)-845-6259#AbstractIn this paper a second order sliding mode observer is proposed for state estimation in a switched reluctance machine (SRM). The estimated rotor position obtained from the observer is used for the electronic commutation of the machine phases. The proposed sliding mode observer
3、provides a robusi method of indirect rotor position sensing using terminal measurements of phase voltage and currents The paper incudes detailed simulations of a closed loop controller based on the proposed sliding mode observer.IntroductionThe inherent simplicity, low-cost, faulttolerance and safet
4、y of the switched reluctance motor (SRM) drive have made it an attractive candidate for replacing many adjustable speed ac and de drives in aerospace, manufacturing and consumer products. The SRM is a doubly salient machine with unequal number of stator and rotor poles (6-4, 8-6, 12-8 arc common con
5、figurations) 1. When a stator phase is energized, an adjacent rotor pole pair is attracted towards the energized stator phase in order io minimize the reluctance of the magnetic path. The phase inductance of the SRM varies from a maximum when the rotor poles are aligned to the stator poles of the en
6、ergized phase, to a minimum when the corresponding poles are unaligned as shown in Fig.la. The machine torque is positive (motoring) when the phase current is switched such that it flows during the rising inductance period as shown in Fig.lb On the other hand, the machine torque is negative (generat
7、ing) when the phase current flows during the decreasing inductance region The phase excitation pulses must be properly synchronized with the rotor position for proper operation of (he motor. For example, phase demagnetization must beFig. 1(a) Idealized inductance profile for one phase of an SRM; (b)
8、 Idealized motoring torque T(+) and generating lorque T(-) for constant phase current.started some period before the end of the increasing inductance region to allow the current to decay completely to zero before the region of decreasing inductance is reached For precise control of the machine opera
9、tion it is always necessary to have accurate rotor position feedback information. In this paper a sliding mode observer is proposed to perform the task of predicting the rotor positionRotor Position SensingThe rotor position feedback information can be obtained using either discrete rotor position s
10、ensors or indirect position sensing techniques. Discrete position sensors, such as an incremental encoder or a resolver with resolvcr-to-digital converter, can give position information continuously, but the cost and requirements of these components often become prohibitive The four-quadrant drives
11、reported in 23 used mechanical sensors like Hall effect devices with a magnetized ring or opto-interruptors with a slotted disc. Discrete sensors are not suitable for space restricted applications, because a sealed endbell is often required to mount the sensors Furthermore, these sensors add cost an
12、d complexity io the system, and also tend to reduce the reliability of the system. The current trend in research is to obtain the rotor position in an indirect way using information of motor parameter variation with respect to rotor position. Almost all of the existing indirect rotor position estima
13、tion techniques arc based on the principle of inductance measurement in one of the unenergized phases since the unsaturated motor inductance in an SRM varies significantly between the aligned and unaligred position of the stator and the rotor. One way to obtain the position information is io monitor
14、 the phase current waveform and determine the position by calculating the phase inductance from the rate of change of current information. This waveR)rm detection technique was first suggested and implemenled by Acamley et al. 4 and was later used by Harris et al,Ehsani et al. 6 and MacMinn ei al. 7
15、 These techniques require active probing of the unenergized phases with a diagnostic pulse which may result in the generation of a negative torque Also, speed limitation is a factor since with increase in speed the window of lime available for injecting diagnostic pulses decreases An alternative app
16、roach of employing a model-based estimator, which uses the motor parameters and terminal measurements of phase voltages and currents have been reported by Lumsdainc et al. 8 The estimator type position sensors eliminate the need for injecting the diagnostic pulses and associated circuitry, but lay the constraints on accurate modeling and real time computations An attract
