back-EMF Observer Research Articles

Sensorless control of permanent magnet synchronous motor based on improved sliding mode observer

Aiming at the problems of chattering and low accuracy of rotor position observation in traditional sliding mode observer sensorless control of permanent magnet synchronous motor, an improved sliding mode observer sensorless control method is proposed. First, the sigmoid function is used to replace the traditional switching function, which can effectively improve the chattering problem of the sliding mode observer. Then, an adaptive back electromotive force observer is designed to avoid the use of low-pass filter and phase compensation and reduce the high-frequency harmonics in the back electromotive force estimation. Finally, the speed and rotor position information are obtained by improving the phase-locked loop, and the fundamental harmonics caused by the inverter nonlinearity are suppressed. The simulation and experimental results show that the improved sliding mode observer can effectively weaken the chattering problem of the system, and improve the position observation accuracy and the robustness of the system.

Adaptive Robust Sensorless Control for PMSM Based on Improved Back EMF Observer and Extended State Observer

Adaptive Robust Sensorless Control for PMSM Based on Improved Back EMF Observer and Extended State Observer

A wide speed range sensorless control for three-phase PMSMs based on a high-dynamic back-EMF observer

A wide speed range sensorless control for three-phase PMSMs based on a high-dynamic back-EMF observer

Research on Position Sensorless Control of RDT Motor Based on Improved SMO with Continuous Hyperbolic Tangent Function and Improved Feedforward PLL

With the increasing use of electric propulsion ships, the emergence of the shaftless rim-driven thruster (RDT) as a revolutionary integrated motor thruster is gradually becoming an important development direction for green ships. The shaftless structure of RDTs leads to their dependence on position sensorless control techniques. In this study, a novel control algorithm using a composite sliding mode observer (SMO) with a modified feed-forward phase-locked loop (PLL) is presented for achieving high accuracy position and speed control of shaftless RDT motors. The deviation between the observed and actual currents is exploited to develop a current SMO to extract back electromotive force (back-EMF) errors. On this basis, a back-EMF observer is established to achieve accurate estimation of the back-EMF. The basic structure of the PLL was modified and incorporates a speed feedforward mechanism, which enhances the performance of rotor position estimation and facilitates bidirectional rotation. The stability of the algorithm has been verified in Matlab/Simulink for a range of steady-state, dynamic, and ship propeller loading conditions. Remarkably, the control algorithm boasts an impressive adjustment time of approximately 0.006 s and its position estimation error may be as low as 0.03 rad. Simulation results highlight the performance of the algorithm to achieve bidirectional rotation, while exhibiting fast convergence, minimal vibration, exceptional control accuracy, and robustness.

A sensorless anti-windup speed control approach to axial gap bearingless motors with nonlinear lumped mismatched disturbance observers

In this paper, sensorless robust speed control with nonlinear lumped mismatched disturbance observers for a permanent magnet type axial gap bearingless motor (AGBM) is designed. Multistage anti-windup-based dynamic surface control combined with integral backstepping control is proposed to control the motor’s axial displacement and rotor speed. The approach is against parameter uncertainties and external disturbances, improving steady-state accuracy, eliminating the derivative explosion phenomenon, no chattering problem, and reducing the magnitude of the control system when current saturation occurs. In addition, a novel nonlinear lumped mismatched disturbance observer is proposed to improve the approach under unmodeled dynamics and external disturbances. To obtain high-accuracy tracking control, the control system includes the robust controller combined with the disturbance observers and anticipatory activation of anti-windup (AW) compensation, which means the controller is more complex. Then, to design a sensorless robust speed control for the motor, the rotor position and speed observer require higher accuracy. High-gain back-EMF observer combined with an improved phase-locked loop is proposed to estimate rotor angular position and speed even when the motor speed is reversed. Overall stability of closed-loop system control, including a sensorless speed control approach for motors using back-EMF estimation combined with saturation of the currents and lumped disturbance observers, is mathematically proven. Finally, the simulation results under measurement noise show that the proposed control system are obtained the effectiveness, feasibility, and robustness.

Sensorless control of permanent magnet synchronous motor based on adaptive back-EMF observer

Aiming at the problem that the change of motor parameters in actual operation will significantly reduce the control accuracy of the motor, this paper proposes a sensorless control method of permanent magnet synchronous motor based on an adaptive back-EMF observer. Firstly, in the sensorless vector control algorithm, the mathematical model of the permanent magnet synchronous motor based on the coordinate axis transformation is established, online identification of permanent magnet synchronous motor flux linkage, and the adaptive back EMF observer is constructed. The parameters update the motor model to achieve accurate control of the rotor position and speed of the permanent magnet synchronous motor. Then the back-EMF observer and the adaptive back-EMF observer are verified in the simulation environment. Then the simulation model of the back-EMF observer and the adaptive back-EMF observer is carried out, and the comparison analysis is made. Finally, a permanent magnet synchronous motor control platform is built in the laboratory, and the method proposed in this paper is verified. The results show that, under the condition that the permanent magnet synchronous motor parameters change, the online identification of the parameters and the accurate speed of the permanent magnet synchronous motor can be realized control.

Small-signal Stability Analysis and Improvement with Phase-shift Phase-locked Loop Based on Back Electromotive Force Observer for VSC-HVDC in Weak Grids

Voltage source converter based high-voltage direct current (VSC-HVDC) transmission technology has been extensively employed in power systems with a high penetration of renewable energy resources. However, connecting a voltage source converter (VSC) to an AC weak grid may cause the converter system to become unstable. In this paper, a phase-shift phase-locked loop (PS-PLL) is proposed wherein a back electromotive force (BEMF) observer is added to the conventional phase-locked loop (PLL). The BEMF observer is used to observe the voltage of the infinite grid in the stationary <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\alpha\beta$</tex> frame, which avoids the problem of inaccurate observations of the grid voltage in the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$dq$</tex> frame that are caused by the output phase angle errors of the PLL. The VSC using the PS-PLL can operate as if it is facing a strong grid, thus enhancing the stability of the VSC-HVDC system. The proposed PS-PLL only needs to be properly modified on the basis of a traditional PLL, which makes it easy to implement. In addition, because it is difficult to obtain the exact impedance of the grid, the influence of short-circuit ratio (SCR) estimation errors on the performance of the PS-PLL is also studied. The effectiveness of the proposed PS-PLL is verified by the small-signal stability analysis and time-domain simulation.

Hybrid sensorless control of PMSM in full speed range using HFI and back-EMF

The permanent magnet synchronous motors (PMSM) are more and more used because of their high performance compared with other AC motors. The present paper proposes a hybrid controller which consists of a high frequency injection estimator and a back-electromotive-force observer in full speed range for the sensorless control of PMSM. The aim objective of the study to prevent speed overshot in startup time of the motor and provides a better dynamic response in transient and permanent states using this structure. A hybrid algorithm is applied to realize a smooth transition from low to high speed. At standstill and very low speed region, HF injection technique is used to detect the rotor initial position. In this first step study, the position estimation is derived from a HF current injection by using only one filter. When the rotor speed goes up to a certain value where back-EMF can provide adequate information, a back-EMF observer will dominate. Thanks to this structure, the mechanical sensor can be engaged using the best estimates and the developed control method is fast, simple, and flexible. The effectiveness, superiority, and performance of the proposed control method and extensive simulation results are provided on a 1 kW permanent magnet synchronous motor drive, demonstrating the expected performances.

A Lag Compensation-Enhanced Adaptive Quasi-Fading Kalman Filter for Sensorless Control of Synchronous Reluctance Motor

A novel position estimation strategy based on lag compensation-assisted adaptive quasi-fading Kalman filter (LC-AQFKF) is proposed for synchronous reluctance motor (SynRM) sensorless drive in this article. In LC-QFKF, the quasi-fading factor is derived to avoid the harsh assumptions of conventional adaptive fading Kalman filter, and accessibility of the method is improved while ensuring the estimation accuracy. The computational efficiency of LC-AQFKF is promoted by introducing the quasi-fading factor into the prediction error covariance matrix. Moreover, the frequency characteristic of AQFKF-based active back electromotive force observer is analyzed, and the phase lag problem in high-speed situations caused by the low-pass filtering property of AQFKF is overcome. In this way, the estimation accuracy of the rotor position is significantly enhanced. Besides, the double dynamic position compensation method is put forward to strengthen the position estimation performance of sensorless SynRM drive under dynamic conditions. The effectiveness of the proposed scheme is validated at a 1.5 kW SynRM drive.

A Novel Constant Power Factor Loop for Stable V/f Control of PMSM in Comparison against Sensorless FOC with Luenberger-Type Back-EMF Observer Verified by Experiments

This paper proposes a novel constant power factor loop in the V/f control strategy with stabilization for a permanent magnet synchronous motor (PMSM). The advantage of such an algorithm is the independence of the machine parameters, which vary under different operational conditions, e.g., with temperature, magnetic core saturation, and skin-effect. Furthermore, it is a low-cost and simple-to-implement sensorless solution. The proposed strategy is compared against traditional sensorless FOC with a Luenberger-type back-electromotive force (EMF) observer, which can be designed based on the machine model. The output of this kind of observer is typically an error signal, which can be specified for position deviation, requiring phase-locked loop (PLL) algorithm implementation. Employing PLL, a rotor speed and position can be estimated from such an error. Therefore, it is a complex sensorless technique with high-performance microcontroller unit (MCU) requirements. Both strategies are deeply analyzed, mathematically described, and compared within the paper. At the end of the paper, these sensorless strategies are supported by experimental verification with a traction PMSM designed for golf cart applications, and the pros and cons of both techniques are discussed.

A composite sliding-mode observer with PLL structure for a sensorless SPMSM system

To achieve high-precision speed and position control for the surface-mounted permanent magnet synchronous motor (SPMSM), this paper proposes a sensorless vector control strategy based on a composite sliding-mode observer (SMO) and an improved phase-locked loop (PLL) structure. Different from the existing sensorless methods, the proposed control strategy can further improve the accuracy of observation position and speed. First, a new sliding-mode function and the equivalent control are introduced to weaken the chattering and accelerate the reaching rate. Then, a sliding-mode current observer based on an adaptive law control is designed to observe the back electromotive force (back EMF). Meanwhile, the adaptive law can ensure the stability of the system in different states and reduce the system chattering. Second, an adaptive back EMF observer is presented to accurately observe the estimated back EMF. Furthermore, the stability of the two observers is proved by employing the Lyapunov second method. Next, the variable gain PLL with the signal suppressor is used to obtain an accurate rotor position and speed. Finally, the simulations and experiments are implemented to validate the performance of the proposed control strategy, in terms of speed and position tracking as well as anti-disturbance ability.

IF 기동방식 센서리스 압축기의 소음 및 진동 저감 제어

This paper presents a simple mechanical vibration and acoustic noise reduction of IF(current-frequency) starting sensorless controlled compressor. The adopted compressor is controlled by the sensorless estimation using back EMF observer in the normal speed range. In order to increase the speed up to normal sensorless speed range, the IF open-loop starting method is used. At the IF starting, the speed variation from the fluid load makes a mechanical vibration and acoustic noise. In order to reduce the mechanical vibration and acoustic noise, a simple variable torque slope with initial rotor position estimation method is proposed in this paper. The proposed method uses an initial rotor position estimation than a conventional rotor alignment method. And, the torque reference slope according to the increased open-loop speed is changed by the hysteresis error between the open-loop reference speed and the estimated speed. Because of the initial rotor position and the variable current according to the speed can reduce the collision of the compressor at standstill and low-speed region. Consequently the mechanical vibration and acoustic noise can be reduced.BRThe proposed simple variable IF starting method is verified 2.2kW IPMSM driven HVAC(Heating, Ventilation & Air conditioning) compressor. Experimental results shows the reduced vibration and acoustic noise at the starting to normal speed range.

Sensorless Control of Outer Rotor Brushless DC Motor With Back-EMF Observer for Drone

The outer rotor brushless direct current motor, which is a highly speed, efficiently, silence and long-life motor, is the most popular motor for drones. Control methods of this type of motor is the most important parameter to be considered. The hall effect sensors, that used in BLDC motor, are not trustable in control applications therefore the back-EMF observer method can be operated for sensorless control. Reducing the production cost of the drive for drone applications is one of the primary goals of manufacturers. Manufacturing cost reduction is often achieved by eliminating driver auxiliary components such as sensors. The use of these sensors, which are important for the detection of rotor position, has been eliminated with sensorless driver designs. This study presents a sensorless outer rotor BLDC motor driver algorithm with back-EMF observer with motor input terminal current and DC bus voltage independent of rotor speed. The sensorless driver model proposed in the study was implemented for a 330W drone motor with a rated voltage of 14.8V. The proposed sensorless control algorithm is proved by MATLAB/SIMULINK results

Extended Back-EMF Based Industrial Sensorless Drive System for PMSMs

Field oriented control (FOC) of Permanent Magnet Synchronous Motors (PMSM) is utilized in many industrial applications due to its high performance. Semiconductor manufacturers provide specialized solutions and tools for this technique. However, such solutions are protected with closed source codes. This reduces the flexibility and the performance of such systems. This paper presents the conducted studies of controller and embedded software design for FOC of a PMSM using extended back-electromotive force (EMF) observer. Observer is derived from motor analytical model. Accurate position and speed estimations are observed using the simulations. An inverter board is obtained from market and a controller board with microcontroller is designed. Extended back-EMF observer model is implemented in embedded software. Performance in nominal speed range with no-load and full-load along with transient loading is tested with a 3000 rpm industrial fan motor. The developed drive system is capable to operate down to 200 rpm and maintain stability under load disturbances, compensating the 10% speed error during nominal load transitions in one second. The developed drive system is fully capable to replace the existing closed source solutions with the benefits of having a robust and flexible structure that can be fine-tuned according to the application.

Symmetrical Components Observer for LPMM Back EMF Based on Negative-Sequence Current Injection

Thrust force ripple, including no-load detent force and electromagnetic thrust ripple, worsens the precision of the linear permanent magnet machine (LPMM) control system. This article focuses on the elimination of electromagnetic thrust ripple caused by the finite length of the LPMM mover core. On the basis of the asymmetrical current controller for suppression of thrust ripple, the observation of asymmetry plays an important role. The extraction strategy, including the extraction of fundamental frequency current/voltage symmetrical components and an observer for positive- and negative-sequence back electromotive force (EMF), is derived. Compared with off-line data, the proposed control strategy has wider application. Experimental results based on an LVPMM are presented. It verifies that the asymmetrical current control strategy based on the back EMF observer reduces electromagnetic thrust ripple by more than 66%.

A Newly Designed VSC-Based Current Regulator for Sensorless Control of PMSM Considering VSI Nonlinearity

A novel d-axis variable-structure control (VSC) current regulator is proposed for realizing fast and accurate sensorless control in the surface-mounted permanent magnet synchronous motor (SPMSM) in this article. In this proposed regulator, the sigmoid function is employed as a switching control law to reduce the chattering effect and increase the degrees of freedom in tuning the regulator. The sensorless control performance under the d-axis VSC current regulator is testified by using the model reference adaptive system (MRAS) and sliding-mode control (SMC) method. In the MRAS observer, the adaptive law of speed and resistance is designed so that resistance, speed, and position can be estimated simultaneously, which can eliminate the influence of the resistance variations theoretically. In the sliding-mode observer, the back electromotive force observer is employed to estimate the speed and position of PMSM so that the estimation can cover a relative low-speed range because pure integration is not employed. Furthermore, the dead-time compensation voltages (DTCV) strategy is employed to online estimate disturbance voltage in a feed-forward manner, which can improve the sensorless control performance of PMSM. Experimental results obtained from an SPMSM drive system validate the superiority of the proposed d-axis VSC current regulator.

An Improved Adaptive Sliding Mode Observer for Middle- and High-Speed Rotor Tracking

In this article, a sensorless field-oriented vector control strategy combined with an improved adaptive sliding mode observer and a back electromotive force (back EMF) observer is presented for a surface permanent magnet synchronous motor. First, based on a sliding mode, a current adaptive observer with estimation of back EMF is proposed to obtain the error of the back EMF, which can reduce system chattering. Then, a back EMF observer based on the back EMF error is constructed to adaptively track the rotor speed and position, which avoids complicated computation. Moreover, the stability of two observers is proved by using the Lyapunov stability theory. Finally, some simulations and experiments are given to show that the proposed method can track the changes of rotor speed and position with good characters, such as fast convergence, little chattering, and good robustness.

Sensorless Position Estimation for Slotless Surface Mounted Permanent Magnet Synchronous Motors in Full Speed Range

This paper presents a scheme for rotor position estimation from standstill to nominal speed. The proposed scheme is particularly suited for surface mounted permanent magnet synchronous motors and for slotless permanent magnet synchronous motors with completely smooth cylindrical rotor, which cannot be operated with state-of-the-art sensorless methods seamlessly from standstill. At standstill and very low speed, the position is estimated by using signal injection. A systematic distortion in the position estimation that is due to asymmetries in the motor parameters is identified and compensated. The rotor polarity is identified by a special process based on the estimation of the back electromotive force (back EMF) induced by a minimal rotor motion. At high speed, the position is estimated by using a linear back EMF observer. Different observer gains are used at different speed ranges, so that the position estimate is reliable even at low speed. The combination of these two approaches enables sensorless motor control in the full speed range including standstill. Experiments demonstrate the accuracy of the proposed estimation scheme and its robustness under different thermal conditions. This paper is accompanied by two videos demonstrating sensorless operation.

Optimal Gain Selection Strategy in Back EMF Observer for Position Sensorless Operation of BLDC Motors

This article presents the design and realization of a new unknown input back EMF observer for position sensorless operation of brushless DC motor. In the proposed observer, the back EMF is considered to be an unknown interaction input from the system structure and has been estimated as a state. In the observer structure, a combination of linear and nonlinear error feedback has been used. The observer gain is the key determining factor for the fast convergence and stability of the observer. A bio-inspired optimization algorithm called Differential Evolution Krill Herd, an efficient and novel algorithm rarely used in drives application, is further developed in this work to determine the optimal value of the observer gain. Observers with optimized gains have enhanced performance in reducing the absolute mean and peak errors in the estimated speed compared to conventional back EMF observers. This can ensure a more accurate and error-free operation of the closed-loop controllers used in the process. The operating performances are verified by ways of simulation and experiment to demonstrate the convergence, robustness, as well as the effectiveness of the observer. The sensitivity of the observer with parameter variation has also been verified, and the results favour the suitability of the observer in sensorless operation.

Comparison analysis of low‐switching‐frequency‐based IPMSM sensorless drives considering regulators, observer and inverter non‐linearity

This study proposes an integration design of sensorless closed-loop drives for rail transit application employing interior permanent magnet synchronous machine (IPMSM), which works under low switching frequency. Due to the long signal sampling period in high-speed region, the individual back-EMF observer cannot ensure the sensorless closed-loop control stability. In order to increase the speed dynamic response and decouple the d - q axes currents accurately, a fast non-singular terminal sliding mode control is designed. It combines a linear sliding mode factor with conventional non-singular terminal sliding mode and is applied uniformly to position observer, speed and currents regulators. Then, considering the effect of inverter non-linearity on position observer, the observed position error caused by dead-time is analysed, and a compensation method based on q -axis voltage error is proposed. Based on the above methods, a comparison analysis of position observer, speed and currents regulators is given. Finally, a 3.7 kW IPMSM is tested to verify the feasibility of the improved sensorless method.