Low-speed Sensorless Control Research Articles

Smooth Low-Speed Sensorless Control of Switched Reluctance Machine With Heavy Load

For the switched reluctance machine (SRM) with heavy load, the inductance of the conduction phase is nonlinear, which makes the sensorless control method based on the linear region of the phase inductance no longer applicable. Meanwhile, in the case of light or no load, the estimated rotor position will abruptly change at the connection points between neighboring segments, which has an impact on the estimation of the speed. In this paper, a low-speed sensorless control method for the SRM with heavy load is proposed. The idle-phase inductance is modeled over a wide rotor position range for position estimation, and a proportional gain decreasing type second-order generalized integrator based on a frequency-locked loop (SOGI-FLL) is constructed to estimate the speed while performing rotor position filtering. The effectiveness of the proposed method is experimentally verified with a 3-phase 12/8-pole SRM prototype, and the results show that the estimated rotor position and speed are accurate and smooth, which is beneficial to performance improvement of the sensorless control.

Low Speed Sensorless Control Scheme Based on Infinite Position Set in Harmonic Subspace for DTP-PMSHM

Low Speed Sensorless Control Scheme Based on Infinite Position Set in Harmonic Subspace for DTP-PMSHM

Low-Speed Sensorless Control of Switched Reluctance Motor Drives Using Random Pulse Injection for Noise Reduction

Low-Speed Sensorless Control of Switched Reluctance Motor Drives Using Random Pulse Injection for Noise Reduction

A Quasi Edge Aligned Pulse-Width Modulation to Enhance Low-Speed Sensorless Control of PMSMs With a Single DC-Bus Current Sensor

The low-speed sensorless control of permanent magnet synchronous machines (PMSMs) with a single DC-bus current sensor has not been solved thoroughly from the prior literatures. This article proposes a novel quasi edge aligned pulse-width modulation (QEAPWM) to realize this purpose. Compared with the conventional phase-shifting PWM, the QEAPWM has several advantages of the accurate reconstructed phase-current and the fixed current sampling time interval, which are beneficial to obtain the current ripple evoked by the high-frequency (HF) injected voltage to estimate rotor position. The effectiveness of the proposed method is verified on a 500-W PMSM drive and compared with three state-of-the-art methods. The experimental results verify that the QEAPWM-based sensorless control achieves satisfactory performance both in the transient and steady-state processes with the maximum 15° position estimation error without a magnetic cross-coupling saturation compensation, and nearly zero error with this compensation.

Sensorless Control of SPMSM Based on High-Frequency Positive- and Negative-Sequence Current Dual-Demodulation

In surface-mounted permanent magnet synchronous motor (SPMSM) low-speed sensorless control, the high-frequency sinusoidal voltage injection method for rotor position estimation is affected by the low saturation salient rate of SPMSM and the system delay, resulting in estimation error. This paper proposes a dual-demodulation method utilizing the high-frequency positive- and negative-sequence stator current of the motor. This method is based on the principle of maximizing the effect of the salient inductance component and minimizing the significant component of noise, which improves the utilization of the current containing angle information and increases the signal-to-noise ratio of the position angle error fed to the rotor position observer. The DC bias of the current caused by system delay is also eliminated so that the accuracy of position estimation is improved. The proposed method is verified by experiment, and the results show that the accuracy of the estimated rotor position and dynamic performance of the estimator are greatly improved compared to existing methods.

A Lean Approach to Zero and Low-Speed Sensorless Control of PMaSynRMs

A Lean Approach to Zero and Low-Speed Sensorless Control of PMaSynRMs

High-Frequency Square-Wave Signal Injection Based Sensorless Fault Tolerant Control for Aerospace FTPMSM System in Fault Condition

To enhance position detection reliability, this article proposes a new high-frequency square-wave signal injection (HFSWSI) based sensorless control for aerospace fault tolerant permanent magnet synchronous motor (FTPMSM) drives, which can be configured as the nonsimilar redundancy for a physical sensor. The novel sensorless control scheme with HFSWSI in two nonfault windings is first proposed for the FTPMSM system under each phase current independent control frame, which is free of the coordinate transformation. The HFSWSI-based position detection is then proposed for rotor position estimation via HF response currents even in phase open-circuit fault (OCF) and short-circuit fault (SCF) conditions. To enhance the dynamic performance, a novel dual-output filter is proposed for the fundamental and HF response current component extractions with almost no phase lag. To guarantee the fault tolerant performance, the optimal torque control (OTC) is utilized to ensure that the FTPMSM system generates the ripple-free torque even in fault condition. The resulting sensorless FTPMSM system has outstanding low-speed sensorless control performance both in normal and fault conditions, which is also experimentally validated on a six-phase FTPMSM platform.

HF-Based Sensorless Control of a FTPMM in Ship Shaftless Rim-Driven Thruster System

Take a dual-winding permanent magnet fault tolerant motor (FTPMM) in the ship shaftless rim-driven thruster (RDT) as the research object, the position sensorless control algorithm based on high frequency (HF) current injection is presented to estimate the rotor position and the rotor position signal is extracted from the voltage. In order to reduce influences of proportional-integral (PI) controller, current regulators and voltage calculation errors, the generalized second-order integrator (SOGI) is discussed along with how to combine with the low-speed sensorless control. And the current vector fault-tolerant control strategy is applied to compensate for the faulty phase current with other healthy phase currents. The rotor position at low speed is estimated under healthy as well as open-circuit faulty conditions by using the HF current injection algorithm based on SOGI (HF-SOGI). After simulation in Matlab/Simulink, the experimental results further demonstrate the feasibility of the HF-SOGI strategy by the FTPMM experimental setup. It can be calculated that the rotor speed ripple is decreased obviously after fault-tolerant control strategy is applied. It can be concluded that the HF-SOGI strategy can estimate the position accurately, which can further improve the reliability and application scope of FTPMM and the RDT system.

Sensorless Fault-Tolerant Control via High-Frequency Signal Injection for Aerospace FTPMSM Drives With Phase Open- and Short-Circuit Faults

The high-frequency (HF) signal injection methods have been widely used for the low-speed sensorless control of permanent magnet motors under the vector control framework. However, for the fault-tolerant permanent magnet synchronous motor (FTPMSM) system under fault conditions, the fault-tolerant control is usually based on independent control of each phase current, rather than the vector control, which prevents the existing sensorless control from being directly applied. To cope with this issue, this article proposes a novel sensorless control by HF signal injection in any nonfault two-phase windings for the FTPMSM system with no coordinate transformation, which can ensure the low- and zero-speed sensorless control performance both in fault-free and fault-tolerant operation conditions. This sensorless control scheme is based on an independent control framework of each phase current, which consists of the real-time inductance observer, the nonorthogonal phase-locked loop (NPLL), the notch filter, and the polarity discrimination of the magnet pole. The real-time inductance observer is proposed to estimate the differential mode inductances of two nonfault phases. The NPLL is proposed to achieve the rotor position and speed estimation based on the obtained two-phase inductances. To enhance the sensorless control performance, a new notch filter is proposed to filter out the injected HF response component in phase current. The proposed sensorless FTPMSM system has preeminent low-speed control performance and robustness in the nonfault and fault-tolerant operation process, which is also verified via experiments on a six-phase FTPMSM platform.

A Regional Phase-Locked Loop-Based Low-Speed Position-Sensorless Control Scheme for General-Purpose Switched Reluctance Motor Drives

In this article, a general-purpose low-speed position estimation scheme using pulse injection is proposed for sensorless switched reluctance motor (SRM) drives. For the conventional low-speed sensorless control methods, magnetic characteristics are often used for position estimation, but it requires offline measurement and reduces the generality of sensorless control algorithms. To solve the issue, a new position estimator based on a regional phase-locked loop (RPLL) is designed. The approach utilizes a self-commissioning process to capture the unsaturated inductance adaptively at the initial stage. The RPLL is then adopted to estimate the full-cycle rotor position from the idle-phase inductance during sensorless operation. The speed-reversible sensorless control capability is also realized by a simple heterodyne design. Furthermore, stability analyses and parameter design are given to prove the robust local stability and convergence. Finally, comparative experimental validation is conducted on a 5.5-kW 12/8 SRM setup to verify the proposed method's effectiveness under both no-load and load conditions.

Low speed sensorless control method of brushless DC motor based on pulse high frequency voltage injection

A low speed sensorless position control method for brushless DC motor based on pulse pulse high frequency voltage injection is proposed according to the characteristic that the brushless DC motor (BLDCM) which is produced at present makes the counter electromotive force waveform show sinusoidal waveform in view of the problem that it is difficult to accurately obtain the rotor position and speed of the brushless DC motor at zero and low speed. Its principle is to inject high frequency sinusoidal voltage signal on the estimated direct axis of the synchronous rotating coordinate system so that the motor can generate saturated salient effect, obtain the estimation error containing the rotor position information, and by detecting the output current of PI regulator of quadrature axis current loop, and then estimate the initial position of the rotor and judges the magnetic pole, realize the determination of the actual rotor position, finally, realize the non-position static low speed control of BLDCM by adding current and speed rings. According to the simulation test, it shows that this method can detect the position and speed of the motor rotor well at both zero speed and low speed.

Low-Speed Sensorless Control for the Interior Permanent Magnet Synchronous Motors with Sliding Discrete Fourier Transform

An efficient estimation of the rotor position has always been a premise of the reliable operation for the interior permanent magnet synchronous motors (IPMSM), especially for low-speed conditions because of the small back electromotive force (EMF) and low signal-to-noise ratio (SNR). The commonly used observation method, e.g., sliding mode observer (SMO), is suitable for these surface mounted motors and has no great adaptability to the saliency. In this paper, a novel rotor position (including the real-time position and initial position) estimation method was proposed based on the traditional high-frequency signal injection method. Firstly, high-frequency signals were injected to induce the high-frequency current components which contain the rotor position information. Then, the sliding discrete Fourier transform (SDFT) algorithm was used to extract the amplitudes of the induced current components which could be used to get the real-time and initial rotor positions by a proportional integral (PI) regulator and a polarity identification. Lastly, with the established experiments’ platform, the estimation tests of the rotor position at a low speed have been completed to make verification of the effectiveness of the approach studied in this paper.

Improvement of Low-speed Sensorless Control with Multi-Layer Neural Network

Improvement of Low-speed Sensorless Control with Multi-Layer Neural Network

Low-speed sensorless control of permanent magnet synchronous motors via the Cauchy–Gauss hybrid mutation particle swarm optimization algorithm

In the process of tracking the speed and rotor position of a permanent magnet synchronous motor, the conventional proportional–integral (PI) control method has difficulty satisfying the requirements of the control system. Therefore, an alternative based on particle swarm optimization is proposed in this article. To improve the optimization performance, a nonlinear differential decreasing inertia weight and an asynchronous time-varying learning factor are adopted. A Cauchy–Gauss hybrid mutation strategy is introduced to prevent the algorithm from falling easily into a local optimum. Then, the high-frequency injection method is used to estimate the rotor speed and position. Simulations and experiments show that the proposed Cauchy–Gauss hybrid mutation particle swarm optimization method has good dynamic performance and anti-interference capability and can satisfy the requirements of the system.

An Improved Sensorless Control of IPMSM Based On Pulsating High-Frequency Signal Injection With Less Filtering for Rail Transit Applications

A pulsating high-frequency signal injection-based low-speed sensorless control of interior permanent magnet synchronous motor (IPMSM) using a conventional stationary reference frame low-pass filter (LPF) may experience a phase delay. Similarly, the heterodyning process may exhibit time delay and bandwidth restriction. Thus, an improved approach with a single high-pass filter in a stationary reference frame is proposed. The rotor position error is extracted from the high-frequency current using the sign of sine of the injected signal considering the phase shift. Consequently, the estimated reference frame LPF in the heterodyning process and the delay compensator for a stationary reference frame LPF-based approach are discarded. A phase-shift tracking observer (PSTO) independent of position error is included. Meanwhile, an online d-axis high-frequency current amplitude estimation is adopted to normalize the effect of d-axis inductance variation. The comparative study with a stationary reference frame LPF and the heterodyning process has shown that the proposed self-sensing strategy delivers an excellent speed sensorless control performance. Thanks to the online d-axis current amplitude estimation, the impact of d-axis inductance variation on speed-position identification has been improved. The proposed self-sensing strategy has been validated using MATLAB simulation and Hardware-in-the-loop (HIL) with TMS320F28335 digital signal processor considering rail transit applications.

Sensorless Starting Control of Brushless Synchronous Machine (BSM) For Aircraft

In this paper, the sensorless starting control of brushless AC synchronous machine (BSM) for aircraft is studied. Low speed sensorless control technology is the key to accomplish full speed sensorless control. After injected the high frequency voltage with the three-phase AC excitation, the initial rotor position as the response is shown in this paper. On that basis, the sensorless control from starting to low-speed operation is accomplished. The performance of the starting control system is researched using MATLAB simulation software and the feasibility of the proposed scheme is demonstrated by simulation results.

A new simplified fundamental model‐based sensorless control method for surface‐mounted permanent magnet synchronous machines

For sensorless control of surface-mounted permanent magnet synchronous machines (SPMSMs), the major issue is in zero- and low-speed ranges. Since back-electromotive force (EMF) is proportional to speed, back-EMF based methods fail at zero and low speed. A solution considering the starting process and low speed sensorless control is presented. A simplified fundamental model-based method is proposed. Based on the simplified model, the measured stator currents in the stationary reference frame can be directly utilised for position estimation so that the sensorless control performance at low speed and starting is improved. Moreover, with the knowledge of rotor initial position sector information, a stable and reliable starting performance is achieved with the proposed method. The effectiveness of the proposed method is verified through experimental results.

Universal Full-Speed Sensorless Control Scheme for Interior Permanent Magnet Synchronous Motors

This article presents a general-purpose full-speed sensorless control scheme for interior permanent magnet synchronous motors (IPMSMs). By applying a quadratic extended back electromotive force (QBEMF) model, the injection-based and model-based position estimations can be combined into a universal sensorless control strategy for the full-speed operation. At low speed, the QBEMF model acts as a self-demodulator that can extract position information from arbitrary high-frequency currents without using digital filters. Therefore, it is suitable for any type of injection signals and can eliminate the adverse effect of filters. When the injection is removed at high speed, the same QBEMF model can still be used for position estimation, thereby solving the conventional transition issue from low-speed to high-speed sensorless control. In consequence, a unified algorithm is designed to achieve arbitrary injection for low-speed sensorless control and seamless transition across full-speed region. The proposed scheme is hence simpler and more effective compared to conventional full-speed sensorless methods. Finally, the feasibility of the proposed estimation algorithm is verified for a 15-kW IPMSM drive.

Simple and Effective Online Position Error Compensation Method for Sensorless SPMSM Drives

In low-speed sensorless control of surface-mounted permanent magnet synchronous machine (SPMSM), high-frequency (HF) signal injection methods are often used to estimate the rotor position by tracking the motor saliency characterized by the inductances. Cross-saturation effects caused by the load current will influence the inductances, and consequently the saliency, which will introduce position estimation error to the sensorless drive, degrading the drive performance. Such load-dependent position estimation error, which is inherent in HF signal injection sensorless methods, is difficult to be identified by the sensorless algorithm itself. This article proposes a new online method to detect and compensate the load-dependent position estimation error for SPMSM without additional devices or the knowledge of the load-dependent HF inductances. The proposed method can identify effectively the load-dependent position estimation error by simply varying the direction of the current vector. Experimental results are presented to validate the proposed solution.

Low Speed Sensorless Control Based on an Improved Sliding Mode Observation and the Inverter Nonlinearity Compensation for SPMSM

It is a difficult to accurately estimate the rotor position in a surface permanent magnet synchronous motor (SPMSM), especially for low speed conditions because the back electromotive force (EMF) is almost zero. In this paper, an improved sliding mode observer (SMO) with a continuous sliding mode switching function (which could reduce the chattering effect) is proposed to estimate the real-time rotor position at a low speed. Through the introduction of an intermediate variable H, the back EMF is extended at low speed, which could improve the estimation accuracy for the rotor position. In addition, the chattering phenomenon is reduced by redesigning the sliding switching function. On the other hand, inverter nonlinearity also results in torque ripple and deteriorates the drive performance because of the harmonic components in the three-phase stator current. Here, a generalized sliding discrete Fourier transform (GSDFT) strategy is studied to extract the harmonic components, which can then be compensated with the corresponding compensation voltage calculated from the motor mathematical model. With the proposed strategy, the estimation accuracy can be apparently restricted when the rotor speed is lower than 50 rpm, while the chattering effect is also improved. With the nonlinearity compensation, the total harmonic distortion obviously decreases, which can improve the rotor estimation and the torque performance. In addition, the GSDFT algorithm executes in approximately half the time of the SDFT compensation method.