Accuracy Of Rotor Position Estimation Research Articles

Research about the Sensorless Vector Control of Permanent Magnet Synchronous Motor Based on Two-stage Filter Sliding Mode Observer

In order to overcome the disadvantages of installing mechanical sensors and the problems of chattering and low observation accuracy in traditional sliding mode observer sensorless control, a two-stage filter Sliding Mode Observer (SMO) is proposed in this paper. By collecting the current and voltage of the Permanent Magnet Synchronous Motor (PMSM), the SMO algorithm is realized by using the state equation of the motor in the synchronous stationary coordinate system; the position of the rotor is estimated by the arc tangent function, the observation accuracy of the rotor position is improved by increasing phase compensation; the variable cut-off frequency filter is introduced to make the Low Pass Filter (LPF) cut-off frequency can be self-adjusted with the change of rotational speed, which improves the estimation accuracy of rotor position at different rotational speeds. Kalman filter is introduced to form a two-stage filter with variable cut-off frequency LPF, which greatly weakens the chattering of the motor and reduces the observation error. Finally, the simulation is carried out under MATLAB/Simulink. The simulation results show that the PMSM vector control system with two-stage filter sliding mode observer has high estimation accuracy, good dynamic and steady-state performance, strong anti-jamming ability and robustness.

Improved sensorless control scheme for PMSM based on high-frequency square-wave voltage injection considering non-linear change of inductance in D-Q axis

Aiming at the position sensorless control system of permanent magnet synchronous motor (PMSM), an improved high-frequency square wave (HFSW) signal injection scheme considering nonlinear inductance variation in d-q axis is proposed and implemented in this paper. Compared with the existing model, the modified scheme can take the dynamic variation of d-q axis inductance under different operation conditions into consideration by offsetting the resulting high-frequency incremental (HFI) current harmonic components, thus effectively suppressing the estimation error of the rotor position. The experimental results verify that the improved scheme proposed in this paper can not only improve the estimation accuracy of rotor position impaired by the non-linear variations of d-q axis inductance but also maintain the good steady-state and dynamic performance of traditional schemes.

Speed Sensor‐Less Control System of Surface‐Mounted Permanent Magnet Synchronous Motor Based on Adaptive Feedback Gain Supertwisting Sliding Mode Observer

Aiming at the problems of severe chattering and difficulty in low‐speed operation of the surface‐mounted permanent magnet synchronous motor (SPMSM) sensor‐less speed control system based on the traditional sliding mode observer (SMO), this paper proposes a sensor‐less control strategy of supertwisting sliding mode observer based on adaptive feedback gain (AFG‐STA‐SMO). This strategy combines the supertwisting algorithm (STA) with the equivalent feedback principle and designs an adaptive law to compensate for the rotor position error by adjusting the feedback gain coefficient online. Secondly, considering the ripple component in the back electromotive force (back‐EMF), the Kalman filter gets a smoother back‐EMF signal, further improving the rotor position estimation accuracy. The stability of the system is proved by using the Lyapunov function. Finally, the feasibility and effectiveness of the proposed control strategy are verified by MATLAB/Simulink simulation.

Reduced-order resonant regulator-based position harmonic error suppression for sensorless permanent magnet synchronous motor drives

In this article, to improve the accuracy of rotor position estimation in sensorless permanent magnet synchronous motor drives, a reduced-order resonant regulator for the rotor position sliding mode observer is proposed. Since fundamental back electromotive force can be utilized to calculate the rotor position, a mathematical model for the observer is first established based on the analysis of estimation fluctuation error, where a reduced-order resonant regulator is applied to extract the fundamental back electromotive force. Then, the phase-locked loop with back electromotive force normalization is used to compute the rotor position and speed. Finally, the experimental bench of permanent magnet synchronous motor driving system is built. The experimental results verify that the proposed strategy can effectively reduce the estimation error and meanwhile improve estimation accuracy.

Speed and Rotor Position Identification of Permanent Magnet Synchronous Motor Based on ADRC

Aiming at the accurate estimation of rotor speed and position of surface- mounted permanent synchronous motor, a scheme using extended state observer in the two phase static frame is constructed. The conventional method estimating the rotor speed and position in two phase synchronized rotation reference frame has the problem of error accumulation of the estimated rotor position which was calculated by angular velocity estimated value integral. This method avoids those problems and has advantages. The speed and current closed loop control system is constructed by using the auto disturbance rejection controller to replace the PI regulator. The simulation results validate the accuracy of the rotor speed and position is higher, and the system is stable and has good disturbance rejection performance.

Integration of Improved Flux Linkage Observer and I–f Starting Method for Wide-Speed-Range Sensorless SPMSM Drives

This article aims to improve the sensorless control performance of surface-mounted permanent magnet synchronous machine drives in the whole speed range. Based on the thought of speed partition optimization and smooth transition, a hybrid sensorless control strategy integrating with an improved flux linkage observer and the current–frequency ( I–f ) starting method is proposed. At zero–low speed, the I – f control method is utilized for the stable startup and strong antijamming capability. At medium–high speed, an improved flux linkage observer based on the sliding-mode compensator is designed for the closed-loop sensorless operation. Taking advantage of the sliding-mode compensator, not only the position estimation errors caused by the adopted filter can be compensated effectively without any speed iteration to improve the system stability, but also the suitable cutoff frequency of the filter can be selected for the fast system dynamic response. Meanwhile, the influence of machine parameter variations on the rotor-position estimation accuracy is discussed. Furthermore, in order to achieve the smooth operation between two different control schemes, an adaptive transition algorithm is described in detail. Experimental results indicate that the proposed hybrid sensorless control strategy can show an excellent performance for both steady-state and dynamic operations during full-speed range.

A Rotating Restart Method for Scalar (v/f) Controlled Synchronous Reluctance Machine Drives Using a Single DC-Link Current Sensor

This paper presents a rotating restart method for $v/f$ scalar controlled Synchronous Reluctance Machines (SynRMs) using a single DC -link current sensor. In such a case, the initial rotor position and speed are required to restart the machine due to the absence of a position sensor. The method proposes to inject three active voltage vectors in the stationary reference frame to induce the phase currents required for estimating the rotor position and speed. In addition, the phase current reconstruction method is proposed to reduce the distortion of the measured phase currents caused by adopting a single DC -link current sensor and to consequently enhance the rotor position estimation accuracy. With the proposed method, the appropriate voltage vector can be applied to the machine, thus minimizing the inrush current during the restart. Furthermore, the proposed method only requires the machine parameters on the nameplate, and it does not require any additional machine-specific tuning processes. This paper proposes a simple restart method suitable for scalar-controlled SynRM drives with a single DC -link current sensor. The effectiveness of the proposed restart scheme is validated through the simulation and experimental results.

Research on sensorless control method of permanent magnet synchronous motor based on iterated cubature Kalman filter.

Aiming at the problems of high cost, increased volume, low reliability, and environmental interference caused by sensor installation on permanent magnet synchronous motor, estimation method for motor speed and rotor position is proposed based on iterated cubature Kalman filter algorithm and applied to permanent magnet synchronous motor sensorless control. First, discrete mathematical model of permanent magnet synchronous motor in α-β coordinate system is established. Then, based on cubature Kalman filter and iterated cubature Kalman filter, simulation model of sensorless vector control system with dual closed-loop of permanent magnet synchronous motor speed and current is established. Also, simulation verification of two working conditions with given rotation speed and load is carried out. Finally, hardware experimental verification platform is built based on TMS320F28335 chip. Both simulation analysis and experimental results show that iterated cubature Kalman filter application to sensorless control of permanent magnet synchronous motor demonstrates good anti-load variation interference, stable motor operation, high motor speed and rotor position estimation accuracy, which suits the application with high requirement for precise motor control and mean important reference value and promotion significance.

High Frequency Square-Wave Voltage Injection Scheme-Based Position Sensorless Control of IPMSM in the Low- and Zero- Speed Range

In this paper, a new sensorless control scheme with the injection of a high-frequency square-wave voltage of an interior permanent-magnet synchronous motor (IPMSM) at low- and zero-speed operation is proposed. Conventional schemes may face the problems of obvious current sampling noise and slow identification in the process of magnetic polarity detection at zero speed operation, and the effects of inverter voltage error on the rotor position estimation accuracy at low speed operation. Based on the principle analysis of d-axis magnetic circuit characteristics, a method for determining the direction of magnetic polarity of d-axis two-opposite DC voltage offset by uninterruptible square-wave injection is proposed, which is fast in convergence rate of magnetic polarity detection and more distinct. In addition, the strategy injects a two-opposite high-frequency square-wave voltage vectors other than the one voltage vector into the estimated synchronous reference frame (SRF), which can reduce the effects of inverter voltage error on the rotor position estimation accuracy. With this approach, low-pass filter (LPF) and band-pass filter (BPF), which are used to obtain the fundamental current component and high-frequency current response with rotor position information respectively in the conventional sensorless control, are removed to simplify the signal process for estimating the rotor position and further improve control bandwidth. Finally, the experimental results on an IPMSM drive platform indicate that the rotor position with good steady state and dynamic performance can be obtained accurately at low-and zero-speed operation with the sensorless control strategy.

Sensorless current model control for permanent magnet synchronous motor based on IPID with two‐dimensional cloud model online optimisation

In this study, a sensorless current model control algorithm for permanent magnet synchronous motor (PMSM) is investigated based on intelligent proportion integration differentiation (IPID) with two-dimensional cloud model online optimisation. To obtain a relatively accurate rotor position and speed estimation, in virtual γ-δ rotating coordinate system, estimation of the position and speed is performed using a current error between an actual current and the model current obtained from a current model of the motor. Simultaneously, a type of IPID with parameter dynamic real-time self-tuning function is designed to adjust the speed and current loop in the current model control. By introducing the chaos particle swarm optimisation (CPSO) algorithm to optimise the control parameters offline, the entire control system is in the optimised state, then the two-dimensional cloud model online adjustment module is used to perform real-time tuning. The experimental results show that the new control algorithm proposed can accurately estimate the real-time rotor position and speed, which effectively avoids the influence of back EMF harmonics, and it has the robustness to motor internal parameter perturbation and external load disturbance.

Sensorless control for surface mounted PM machine with a high inertial load

PM machine or Permanent magnet synchronous motor (PMSM) is a nonlinear system with multivariable couplings. To achieve the sensorless control of a PMSM with high inertial load, a modified current observer, using PI regulator instead of sliding mode switching function, is proposed in this paper. The modified current observer can solve the chattering and phase delay problem while still maintaining the robust advantages of sliding mode system in position estimation. In addition, a new phase-locked loop (PLL) based angle switching strategy is designed to ensure the motor can smoothly switch from I-F control to closed-loop sensorless vector control in startup stage with a high inertial load. The simulation and experimental results show that the control system of PMSM with proposed ideas has fast response speed, accurate rotor position estimation, stable state switching and good system robustness under high inertia load.

A Back-EMF Estimation Error Compensation Method for Accurate Rotor Position Estimation of Surface Mounted Permanent Magnet Synchronous Motors

This paper proposes a back electromotive force estimation error compensation method for accurate rotor position estimation of surface mounted permanent magnet synchronous motors. When estimating the rotor position of surface mounted permanent magnet synchronous motor sensorless drives, a direct current offset error component occurs in the voltage sensor. As a result, the rotor position is distorted and the sensorless control in surface mounted permanent magnet synchronous motor is degraded. In addition, the dq-axis voltages in the synchronous reference frame have the direct current offset error component, ripples compared with the motor frequency under the distorted rotor position. In this paper, the effects of the direct current offset errors are analyzed based on the synchronous reference frame phase locked loop. To remove this direct current offset error component, a d-axis voltage is converted into a synchronous reference frame again to compensate. In other words, it is a dual synchronous coordinate conversion compensation method. The compensator utilizes a proportional-integral controller that compensates by estimating the direct current offset error component. The proposed method is useful for the improvement of surface mounted permanent magnet synchronous motor sensorless control and operating performance. The effectiveness of the proposed algorithm is verified through PSIM simulation and experimental results.

Improved Rotor Position Estimation Accuracy by Rotating Carrier Signal Injection Utilizing Zero-Sequence Carrier Voltage for Dual Three-Phase PMSM

In this paper, the rotor position estimation accuracy of rotating carrier signal injection utilizing zero-sequence carrier voltage method for dual three-phase (DTP) permanent-magnet synchronous machines (PMSMs) is investigated. When utilizing the zero-sequence carrier voltage, the system bandwidth and rotor position estimation accuracy can be significantly enhanced. However, undesirable sixth harmonic estimation error occurs for single three-phase PMSM with rotating signal injection due to multiple saliency components in the zero-sequence carrier voltage. To solve such a problem, the existing methods require time-consuming offline measurements and complex structures. Fortunately, for the case of DTP-PMSM drives, thanks to the existence of additional degrees of freedom, two high-frequency signals can be injected independently for two winding sets. Therefore, by applying the optimum phase shift angle between the injected signals, a modified rotating carrier signal injection using zero-sequence voltage-based sensorless control strategy is proposed to suppress the sixth harmonic position errors. In addition, a new simple measurement method of zero-sequence carrier voltage is proposed where one voltage sensor is placed between the two isolated neutral points. The proposed method can achieve improved rotor position estimation accuracy with low computational burden. The experimental results verify the effectiveness of the proposed strategy.

Improved Pulsating Signal Injection Using Zero-Sequence Carrier Voltage for Sensorless Control of Dual Three-Phase PMSM

The sensorless control performance of pulsating carrier signal injection employing zero-sequence voltage for dual three-phase (DTP) permanent magnet synchronous machine (PMSM) drives is investigated in this paper. This method has the synergy of high bandwidth of zero-sequence voltage method and high position estimation accuracy of pulsating injection strategy. However, such a method for single three-phase PMSM exhibits large oscillation in position estimation error due to undesirable harmonic components in the zero-sequence carrier voltage, and the existing compensation methods usually require complex structures or intensive offline measurements. As for DTP-PMSM, the undesirable harmonic components for the pulsating injection can be suppressed with an optimum phase shift between the two injected high-frequency signals. Besides, a new simple measurement method of zero-sequence carrier voltage is proposed with only one voltage sensor placed between the two isolated neutral points. As a result, the rotor position estimation accuracy can be significantly improved. The experimental results verify the effectiveness of the proposed method for DTP-PMSM.

PMSM Sensorless Control by Injecting HF Pulsating Carrier Signal Into ABC Frame

Spatial-saliency-tracking-based high-frequency (HF) pulsating carrier injection method is widely employed in permanent-magnet synchronous machines sensorless control. In order to avoid the problems of long convergence time, potential start-up failure and limited system stability existing in tracking observers, a strategy to inject three HF pulsating voltages with different frequencies and amplitudes into ABC frame is proposed in this paper. With the proposed method, three frequency components in the response current signals are demodulated and then combined together to calculate the rotor position directly. Different from the conventional method, the proposed solution utilizes both d- and q-axis carrier current instead of only the q-axis carrier current to enhance the acquisition of the rotor position information. Meanwhile, a new signal processing strategy is developed to completely eliminate the effects of system delay. Furthermore, the compensation of cross-saturation effect is deduced in detail to improve the accuracy of rotor position estimation. In addition, magnetic polarity detection is implemented with the same proposed solution by demodulating the second harmonic components from the response current signals, which simplifies the magnetic polarity process. Finally, the experimental results demonstrate that the proposed strategy can obtain an accurate rotor position with good steady-state and dynamic performance.

Research on Initial Rotor Position Estimation and Anti-Reverse Startup Methods for DSEM

Based on the finding that the inductance of doubly salient electromagnetic motor varies according to its rotor position, a new method to determine the initial rotor position is introduced in this paper. With no extra test pulses needed, this method detects the sector where the rotor is at by comparing the three-phase induced voltages during the excitation field building, significantly cutting down the time required for this procedure. Then, an equation expressing the relationship between rotor position and the three-phase terminal voltages is developed based on geometrical relations of “inductance rectangle” composed of mutual inductances, which gives a more accurate estimation of the initial rotor position. Moreover, in order to avoid the occurrence of rotor jitter or even reverse when the rotor is initially in the boundary of neighboring sectors, the first acceleration pulse for sensorless startup is distinguished from the ordinary ones, and the first acceleration pulse is studied in detail regarding the injection method, pulse width, and a new division of sector boundary. Further experiments confirmed the feasibility of the proposed methods concerning the estimation of initial rotor position and the assurance of anti-reverse rotation startup.

A New Rotor Position Estimation Method of IPMSM Using All-Pass Filter on High-Frequency Rotating Voltage Signal Injection

In this paper, a new rotor position estimation method of an interior permanent-magnet synchronous motor (IPMSM) is proposed. It is motivated by a conventional sensorless control based on the high-frequency rotating voltage signal injection in the stationary reference frame, but extracts the rotor position information from the relation between injection voltages and induced currents in the high-frequency voltage model of an IPMSM. The rotor position can be directly calculated from currents obtained by transforming the rotation matrix in the stationary reference frame. It is also calculated by using the induced current envelope through the all-pass filter. Unlike the conventional heterodyning demodulation process, the proposed method provides the accurate rotor position information without a time delay of the rotor position by the band pass filter or low pass filter. Thus, the overall dynamic performance of IPMSM is enhanced by the accurate rotor position estimation than conventional methods. The various experimental results confirm the effectiveness of the proposed method.

PMSM Sensorless Control by Injecting HF Pulsating Carrier Signal Into Estimated Fixed-Frequency Rotating Reference Frame

For permanent-magnet synchronous machines (PMSMs) sensorless control, the widely employed high-frequency (HF) pulsating carrier signal injection method is based on tracking the rotor saliency. It may face the problems of long convergence time, potential start-up failure, and limited system stability. Different from the conventional schemes, the proposed strategy is a direct estimation method. In which, a HF pulsating carrier voltage is injected into the estimated fixed-frequency rotating reference frame other than the estimated synchronous reference frame (SRF). With this approach, spatial saliency tracking observer, which is necessary in the conventional sensorless control, is removed to simplify the control structure and improve the system stability. Furthermore, the rotor position information is directly obtained from the response of injected HF pulsating carrier signal, which can avoid potential convergence failure of tracking observer. In addition, the compensation of system delays existing in the proposed sensorless control strategy is deduced to improve the accuracy of rotor position estimation. For magnetic polarity detection, a new method which has the advantages of high signal-to-noise ratio and low vibration is also investigated. Finally, the experimental results on a PMSM indicate that the rotor position with good steady state and dynamic performance can be obtained accurately with the proposed sensorless control strategy.

Influence of back-EMF and current harmonics on sensorless control performance of single and dual three-phase permanent magnet synchronous machines

Purpose – The purpose of this paper is to investigate the influence of back-EMF and current harmonics on position and speed estimation accuracy for single and dual three-phase (DTP) permanent magnet synchronous machines (PMSMs) with two fundamental-model-based sensorless control strategies which are widely utilized for AC machines, i.e. flux-linkage observer (FO) and simplified extended Kalman filter (EKF). Design/methodology/approach – The effect of distorted back-EMF is studied for sensorless vector control of single three-phase PMSM. For the influence of current harmonics, unlike the existing literature where the current harmonics are deliberately injected, in this paper, sensorless switching-table-based direct torque control (ST-DTC) strategies for DTP-PMSM which inherently suffer from non-sinusoidal stator currents in addition to the distorted back-EMF, are investigated experimentally. Findings – By employing the FO and simplified EKF-based sensorless vector control of single three-phase PMSM, it can be concluded that the rotor position estimation accuracy is less affected by the back-EMF harmonics when the simplified EKF method is utilized since it is less sensitive to such noises. When the influence of non-sinusoidal stator currents together with back-EMF harmonics is investigated for the conventional and modified ST-DTC of DTP-PMSM, it is indicated that the simplified EKF exhibits better position and speed estimation accuracy in both the conventional and modified ST-DTC strategies. In addition, its steady-state performance shows a slight superiority over that based on FO, in terms of flux and torque ripples, and THD of phase currents. For the dynamic performance, the estimated speed of simplified EKF shows less phase lag and fluctuations compared to that of FO. Originality/value – This paper introduces the influence of back-EMF and current harmonics on sensorless control performance for single and DTP PMSMs. Detailed experimental results show that the simplified EKF exhibits better rotor position and speed estimation accuracy compared to that of FO due to its higher noise-rejection ability.

Improved Sensorless Control of Switched-Flux Permanent-Magnet Synchronous Machines Based on Different Winding Configurations

In switched-flux permanent-magnet machines, winding coil connections can be rearranged into several types of machine winding configurations (MWCs), such as all poles wound, alternate poles wound, and single and dual three-phase windings. This paper investigates the influence of machine saliency on a sensorless control operation based on different MWCs. First, by injecting an HF carrier signal, the machine saliency level can be evaluated experimentally. The influence of saliency on an HF-signal-injection-based sensorless operation for different MWCs can be then investigated irrespective of any information of machine parameters. However, the secondary saliency caused by magnetic saturation or current harmonics may exist in a machine, due to which the sensorless control performance will deteriorate. Hence, an orthogonal signal-based position tracking observer is proposed to improve the accuracy of rotor position estimation rather than utilizing an existing position observer. Furthermore, experimental results confirm that a prototype machine exhibits different saliency characteristics and apparent saliency, in which the HF-injection-based sensorless control technique can be applied. Moreover, better steady and dynamic state performance can be achieved by the improved position estimator compared with using an existing position observer.