Implementation of Embedded Magnetic Encoder for Rotor Position Detection Based on Arbitrary Phase Shift Phase-Lock Loop
ABSTARCT :
Rotor position is essential in control of permanent magnet synchronous motors (PMSMs). In terms of resolution, structural complexity, occupied volume, anti- interference ability, environmental adaptability and cost, embedded magnetic encoder based on linear Halls owns strong competitiveness. When linear Hall sensors are selectively installed at stator slot openings in extremely compact scenario, signal phase-shift asymmetry between two or three Hall sensors is inevitable. Conventionally, pre-filter synchronous reference frame phase locked loops (SRF-PLLs) exhibit excellent phase-lock ability at fixed frequency (50/60Hz), but become ill when frequency changes especially at zero frequency. In this paper, a novel transformation matrix is derived to map the asymmetric phase-shift signals onto two-phase stationary coordinate system. Then, an arbitrary phase-shift phase locked loop (APS-PLL) is formed by replacing Clark transformation with the proposed transformation matrix, which can accurately extract rotor position and speed information in a simple and effective way, avoiding the utilization of complex notch filter. Simulations in continuous domain based on MATLAB and experiments in discrete domain based on an 18-slot/20-pole prototyped PMSM both confirm the effectiveness of the proposed method.
EXISTING SYSTEM :
? Permanent magnet synchronous machines (PMSM) are used to an increasing rate in a wide rage of industrial applications due to their very appealing properties.
? Among them are the high efficiency and dynamics, the high torque inertia ratio, the small size and the very low torque ripple.
? Efficient operation of synchronous machines implies very low energy losses compensating their higher initial cost.
? In a high-performance PMSM operation, advanced control methods are applied, such as field oriented control (FOC), aiming to achieve smooth rotation over the entire speed range, fast response and full torque control.
DISADVANTAGE :
? However, the use of mechanical position sensor may cause some problems, such as extra cost, increase in system complexity, and reduction in system reliability.
? To overcome the above problems, in, the influence of both the flux switching motor poles and winding layers on back-EMF harmonics was analysed and a modified fluxlinkage observer with an adaptive notch filter is proposed to eliminate harmonics to improve the accuracy of estimated rotor position.
? To overcome the above problem, the software quadrature PLL can be used since it can synchronise the output signal with the input signal in frequency as well as in phase .
? Both the rotor position and speed can be calculated from the estimated equivalent back-EMF with the PLL.
PROPOSED SYSTEM :
• The control strategy is principally based on the adequacy of the proposed modified model and on the appropriateness of the SMO structure to successfully track the rotor flux position with the required stability and accuracy.
• Moreover, the proposed PMSM model plays a key role in the proposed sensorless approach.
• In this work, a new mathematical model of PMSM is proposed expressed in a modified form for rotor flux equations and referred to the ?d estimated rotating frame.
• Among the proposed observer schemes, the sliding mode observers (SMO) are widely studied in the literature and applied on a plethora of industrial applications.
ADVANTAGE :
? To achieve high-performance sensorless control of permanent magnet motors with non-sinusoidal back electromotive force (EMF), an improved sliding mode observer (SMO) adopting synchronous rotating low-pass filter (SRLPF) is proposed.
? In order to achieve high-performance control of the permanent magnet (PM) motors, both the rotor position and speed are essential.
? Compared with other strategies, the SMO is widely used because of its simple algorithm, high robustness, and excellent dynamic performance.
? As a new type of PM motor, the stator PM motors have both PMs and armature windings in stator, which exhibit better performance than the traditional interior permanent magnet synchronous motors (IPMSMs).
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