Sensorless Rotor Position Detection Research Articles

A Novel Sensorless Rotor Position Detection Method for High-Speed Surface PM Motors in a Wide Speed Range

In order to improve the performance of surface permanent magnet synchronous motor drives, a novel sensorless drive scheme is proposed in this paper, which is based on the virtual third-harmonic back EMF incorporating a fractional-N phase-locked loop (FN-PLL) and a synchronous frequency-extract filter (SFF). A simple low-pass filter based circuit is used to obtain the commutation points through the virtual third-harmonic back EMF. After that, an FN-PLL is applied to obtain continuous rotor position angles. On this basis, the SFF-based compensation is proposed to compensate the detecting error adaptively. Meanwhile, the field vector control loop for surface PM motor is proposed, which is based on the proposed rotor position detection link and compensation link. An experimental high-speed magnetically suspended blower platform is built. The effectiveness and the feasibility of the proposed method are validated with experimental results.

駆動電流の影響を受けないSRMのセンサレスロータ位置検出法

駆動電流の影響を受けないSRMのセンサレスロータ位置検出法

Effect of Stator and Rotor Saturation on Sensorless Rotor Position Detection

This paper investigates the impact of the geometry of a permanent-magnet (PM) motor on the capability to detect the rotor position without sensors by means of a high-frequency signal injection. An interior PM motor with three rotor flux barriers is considered, which is characterized by a magnetic saliency, necessary for the sensorless rotor position detection. The objective is twofold: 1) to keep an adequate saliency in all the operating range of the motor, including operations at high current, and 2) to limit the angular error of the rotor detection, which is due to the effect of the cross-saturation between the d- and the q-axes. The phenomenon of iron saturation is deeply analyzed, highlighting how the saturation of both the stator and rotor affects the machine performance, in terms of sensorless rotor position detection capability. To this purpose, the motor geometry is modified so as to achieve a higher iron saturation in the stator and, then, in the rotor. Then, the volume of the PM is changed so as to emphasize the impact of the PM flux. Different rotor geometries are finally compared with the initial one.

Sensorless Capability of Fractional-Slot Surface-Mounted PM Motors

This paper investigates the capability of sensorless rotor position detection by means of injection of a high-frequency (HF) signal of fractional-slot surface-mounted permanent-magnet (PM) motors. In order to create an HF anisotropy, such motors are characterized by the presence of a ring around each pole. For the sake of completeness, different windings are considered: a distributed coil winding and a concentrated coil winding. The effect of eddy currents in the magnets, due to the HF signal, is also considered. The effect of the slot opening is also taken into consideration. Finally, the comparison with two different PM rotor topologies is addressed: an interior PM motor and an INSET motor.

A Composite Approach of Sensorless Rotor Position Sensing for Brushless DC Motor

The principles and characteristics of the sensorless brushless DC motor rotor position detection were analyzed by using inductive method and third harmonic back-EMF detection method. A composite rotor position detection method was proposed in full speed range (including zero speed). At zero speed (static state) inductive method was used to determine the initial rotor position, and it was bases of starting and controlling for the brushless DC motor; at low speed third harmonic back EMF detection method was used. Analysis shows that the composite test method can estimate the rotor position, and it is to achieve the position sensorless brushless DC motor to run a viable method.

Sensorless Rotor Position Detection of PMSM for Automotive Application

For correct operation of the permanent magnet synchronous motors is essential the knowledge of the rotor position, which is usually given by Hall-sensors, encoders or resolvers. The aim of the present work is to set up such a general motor model, which takes into consideration the anisotropies in the magnetic structure of the motor.

Sensorless-Oriented Design of PM Motors

This paper deals with the design of a permanent-magnet (PM) motor for zero-speed sensorless rotor position detection, by means of injection of a high-frequency signal. Various aspects are investigated: influence of the rotor structure, stator and rotor saturation, reliability of finite-element analysis to predict the motor performance, and influence of rotor iron bridges and of rotor eddy currents induced. The results presented in this paper give the key rules to designing a PM motor suitable for sensorless rotor position detection.

Comparison of PM Motor Structures and Sensorless Control Techniques for Zero-Speed Rotor Position Detection

The rotor position of a synchronous permanent magnet (PM) motor can be detected by means of the injection of a high-frequency stator voltage superimposed to the fundamental component. Thanks to the rotor anisotropy, the corresponding high-frequency current is modulated and used to determine the rotor position. Two techniques are considered: the first one adopts a pulsating voltage vector in the estimated synchronous reference frame, while the second one adopts a rotating voltage vector. These techniques are effective at zero and at low motor speed. The accuracy of the rotor position detection depends strictly on the rotor saliency, that is, on the geometry of the PM rotor. In fact both saturation and d-and q-axis cross-coupling have a heavy influence on the correct rotor position detection. The aim of this paper is to compare the two sensorless control techniques, together with two rotor geometries, that is, IPM and inset rotor. In order to highlight the effectiveness of the sensorless technique, the tests are carried out at various operating conditions. It is found that the effectiveness of the sensorless rotor position detection strongly depends on the PM rotor geometry. Conversely, the choice of the sensorless control technique affects slightly the rotor position detection.

Influence of Rotor Geometry of an IPM Motor on Sensorless Control Feasibility

The sensorless control technique based on the superimposition of a high-frequency stator voltage is commonly used to detect the rotor position of a synchronous interior-permanent-magnet (IPM) motor. This technique is effective at zero and low motor speed, where back electromotive force is null or extremely low. Then, the accuracy of the rotor-position detection depends strictly on the rotor saliency, that is, on the geometry of the IPM rotor. This paper aims to determine some IPM rotor-design criteria so as to improve the sensorless rotor-position detection. Since the design has to be effective in different operating conditions, both saturation and cross-coupling effects have to be taken into account. It is found that the effectiveness of the sensorless rotor-position detection can be improved by means of a proper design of the IPM motor geometry even under heavy operating conditions

Sensorless rotor-position detection from zero to rated speed for an integrated PM synchronous motor drive

By integrating the motor, the converter and the control circuits of electrical drives into one casing several advantages are obtained. The drive becomes compact, the amount of wiring is significantly reduced, and the control of the inverter and the motor can be designed to better utilize their respective characteristics. The paper presents an integrated permanent magnet synchronous motor drive (IPMSM) using complete digital control. The control includes a simple sensorless estimation of the rotor position both at standstill and at rotation. The algorithm for the initial rotor position detection is based on the saliency of the rotor at no load and it provides both the location as well as the direction of the magnetization. At rotation the rotor position is estimated by a predictor-corrector-based observer. The integrated concept makes it simple to include accurate values of the machine parameters.