Sensorless Position Estimation Research Articles

A Position Sensorless Control of Switched Reluctance Motors Based on Phase Inductance Slope

A new sensorless position estimation method for switched reluctance motor (SRM) drives is presented in this paper. This method uses the change of the slope of the phase inductance to detect the aligned position. Since the aligned positions for successive electrical cycle of each phase are apart by a fixed mechanical angle 45° in the case of 12/8 SRM, the speed of the machine can be calculated to estimate the rotor position. Since no prior knowledge of motor parameters is required, the method is easy for implementation without adding any additional hardware or memory. In order to verify the validity of this technique, effects such as changes in the advanced angle and phase lacking faults are examined. In addition, an inductance threshold based sensorless starting scheme is also proposed. Experimental results demonstrate the validity of the proposed method.

Sensorless rotor position estimation of PMSM by full-order and sliding mode EMF observers with speed estimate

The paper discusses the problem of rotor position estimation for the nonsalient PMSM and presents a Full-Order (FO) observer and a Sliding Mode (SM) observer; both are constructed using a speed estimate. The observers are developed using the PMSM model in the stationary reference frame and use the motor voltages, currents and speed as inputs. The PMSM is treated as a time-varying plant. Convergence is analysed assuming that the speed signal is inaccurate - this corresponds to the situation when a speed estimate is used to obtain a sensorless observer. Under improper speed, the FO observer gives errors; however, the SM observer can be forced to converge by increasing the gains. The SM structure proposed allows design of a variety of sensorless observers.

Model Reference Adaptive System Based Adaptive Speed Estimation for Sensorless Vector Control with Initial Rotor Position Estimation for Interior Permanent Magnet Synchronous Motor Drive

The rotor position/speed sensor used to control the permanent magnet synchronous motor drive has increased size and cost, decreased reliability, and a need for shaft extension and mounting arrangements. Sensorless control is currently adopted in many industrial applications for reasons of robustness, cost, cabling, and reliability. In order to achieve correct operation from zero speed startup of a sensorless salient-pole permanent-magnet synchronous motor (the interior permanent magnet synchronous motor), the initial rotor position of the motor is required. A model reference adaptive system technique has been used for speed estimation in sensorless speed control of the interior permanent magnet synchronous motor with space vector pulse width modulation. This article presents a new approach to improved initial rotor position detection of an interior permanent magnet synchronous motor. The method uses a suitable sequence of short and long time voltage pulses applied to the stator coil at standstill. Short time voltage pulses are applied to the motor terminals to detect the initial rotor position. Long time voltage pulses are used for detection of the magnet polarity based on the effect of saturation. The measurement of the current peaks values gives information about the initial rotor position. Simulation and experimental results are presented and show the validity of the proposed method, which is capable of reliable initial rotor position detection, including the polarity of the magnet at standstill. The error initial rotor position detection is less than 5 mechanical degrees. Experimental results are presented for an interior permanent magnet synchronous motor obtained on a fixed-point digital signal processor based control system. Experimental results show that the modeled reference adaptive system technique speed estimation provides high-performance sensorless control and initial rotor position estimation algorithms of the interior permanent magnet synchronous motor drive.

Sensorless PMSM Control for Automobile Air-Condition Based on Sliding Mode Observer

The paper presents a review of the sensorless position estimation algorithms which are being adopted by Automobile Air-condition. After analyzing and introducing of the sliding mode variable structure theory and the mathematic model of PMSM, the control strategy based on SMO and its math expression are presented. The simulation model in MATLAB/SIMULINK is established, in which the real rotor position and the estimated rotor position calculated by SMO under dynamic and static state are analyzed. Besides, the principle of sliding gain selection is raised. The simulation provides the theoretical foundation.

Position Sensorless Control Based on Augmented Extended Kalman Filter for Permanent Magnet Linear Synchronous Motor

In order to achieve position sensorless control for PMLSM drive system, speed and position of the motor must be estimated. A novel sensorless position and speed estimation algorithm was designed for PMLSM drive by measuring terminal voltages and currents. That was state augmented extended Kalman filter (AEKF) estimation method. The resistance of the motor was augmented to the state variable. Then, the speed, position and the resistance were estimated simultaneously through extended Kalman filter (EKF). The influence of the resistance on the state estimation results could be reduced. As well as giving a detailed explanation of the new algorithm, experimental results were presented. It shows that the AEKF is capable of estimating system states accurately and reliability, and the proposed sensorless control system has a good dynamic response.

Position Estimation of a Matrix-Converter-Fed AC PM Machine From Zero to High Speed Using PWM Excitation

This paper describes a sensorless position estimation method for a permanent-magnet (PM) motor fed from a three-phase matrix converter using only its space-vector pulsewidth-modulation (SVPWM) sequence. The scheme employs measurements of dii/dt of the motor line currents to construct orthogonal ldquoresolverlikerdquo position signals. In principle, the SVPWM waveforms provide sufficient excitation to extract the position signal from the motor current. However, in order to improve the signal-to-noise ratio of the di/dt signals, a small modification to the SVPWM is required. Sensorless control of the PM synchronous motor at zero and high speeds is demonstrated experimentally. The use of alternative input voltage vectors is also investigated to reduce the current ripple.

Space and time harmonics related problems and their mitigation for position and speed sensorless slip-ring induction motor drives applications

There have been renewed interests in slip-ring induction machines due to their increasing use in both grid connected and stand-alone wind power generation schemes. Despite the squirrel cage induction generators’ advantages of being brushless, low-cost, needing less maintenance and having inherent overload protection, the biggest advantage of variable-speed wound rotor induction machines is in its doubled energy capture. Also in high power induction motor drives such as static Kramer drives or static Scherbius drives use of wound rotor induction motors is a must. Thus it becomes necessary to measure the speed of the machine for closed loop control for such high performance drives. Recently, a sensorless position and speed estimation scheme was proposed for wound rotor wind power generator. In this paper, the limitation of the scheme caused by space and time harmonics have been investigated. Simulation results have been presented to explain the mechanism of the space and time harmonics caused distortion of current. Experimental results showing the deterioration of speed detection scheme at light load for a slip-ring induction motor have been presented. Finally, improvements have been applied experimentally to obtain better speed estimation.

Sensorless position estimation in a fault tolerant motor drive with redundancy

This paper proposes a sensorless position estimation scheme suitable for a fault tolerant permanent magnet (PM) AC motor drive with redundancy. The proposed fault tolerant motor has an electrically and magnetically isolated configuration to improve reliability and fault tolerance. The method utilises the instantaneous currents and voltages of the windings, and a mathematical model of the motor drives to estimate the rotor position. Simulation results are shown to demonstrate the effectiveness of the proposed estimation method.

Four-Quadrant Pulse Injection and Sliding-Mode-Observer-Based Sensorless Operation of a Switched Reluctance Machine Over Entire Speed Range Including Zero Speed

The objective of this paper is to present a sensorless position estimation technique for switched reluctance machines (SRM) operating in constant dynamic mode over a wide speed range including zero speed. The technique combines two different methods to deliver high resolution position information over the wide speed range. At zero and low speeds, a voltage pulse injection method is used to estimate the rotor position in all four quadrants. For higher speeds, a sliding mode observer (SMO) based algorithm is used and combined to work with the low speed algorithm. Experimental results demonstrate the effectiveness of this new combined technique that has four-quadrant operation capability.

Novel sensorless driving method of SRM with external rotor using impressed voltage pulse

The paper presents an improved impressed diagnostic pulse-voltage method to estimate the rotor position of a switched-reluctance motor (SRM) with an external rotor. The fundamental method of impressed diagnostic pulse voltage is to impress pulse voltage at the inactive phases of a SRM that has an external rotor. Because the variations of inductance are dependent on the rotor position, and because the characteristic current values produced from the pulse voltage are dependent on the inductance, the rotor position can be inferred by observing the characteristic-current value. If the inductance of the SRM does not vary obviously, noise in the characteristic-current signal may cause failure of the sensorless-position-estimation method. Therefore, an improved impressed diagnostic pulse-voltage method is presented to increase the variations of characteristic current and estimate rotor position. First, the structure, characteristics, operational principles and mathematical model of the SRM with an external rotor are introduced. Then the improved impressed diagnostic pulse-voltage method is utilised to implement the sensorless position estimation for commutation control.

Optimized INFORM Measurement Sequence for Sensorless PM Synchronous Motor Drives With Respect to Minimum Current Distortion

In the paper a standard measurement sequence for INFORM-based sensorless position estimation of permanent magnet synchronous motors is analyzed and its properties with respect to the current deviation before and after the measurement are pointed out. Based on that a modified operating point adjusted measurement sequence with minimum current deviation and minimum time demand is introduced. Measurement results verify the improvement of the modified measurement sequence: The current distortion is reduced significantly resulting in reduced additional losses caused by the INFORM-measurement. Additionally, in the paper several measurement results concerning the performance of the sensorless position estimation under various load conditions are presented.

Sensorless rotor position and speed estimation for a synchronous reluctance motor

A method of sensorless position and speed estimation for the synchronous reluctance motor using only the measurement of current available at the stator terminals is introduced. The ability to make this estimation is due to the variation of inductance with the rotor position. The technique does not require accurate measurement of machine parameters, only that the inductance be significantly different in both the d- and q-axes. Using the estimated rotor position, rotor speed can be calculated using a modified zero-crossing technique. The results of several simulations are presented, demonstrating the algorithm's suitability for a variety of load torques, speeds and saliency ratios. The results of the practical implementation of this work using a 22 kW synchronous reluctance machine are also presented.

An approach for sensorless position estimation for switched reluctance motors using artifical neural networks

This paper presents a new approach to the sensorless control of the switched-reluctance motor (SRM). The basic premise of the method is that an artificial neural network (ANN) forms a very efficient mapping structure for the nonlinear SRM. Through measurement of the phase flux linkages and phase currents the neural network is able to estimate the rotor position, thereby facilitating elimination of the rotor position sensor. The ANN training data set is comprised of magnetization data for the SRM with flux linkage (/spl lambda/) and current (i) as inputs and the corresponding position (/spl theta/) as output in this set. Given a sufficiently large training data set, the ANN can build up a correlation among /spl lambda/, i and /spl theta/ for an appropriate network architecture. This paper presents the development, implementation, and operation of an ANN-based position estimator for a three-phase SRM.

Encoderless position estimation for symmetric cage induction machines under loaded conditions

This paper presents sensorless position estimation using a conventional or symmetric cage induction motor. The rotor position information is obtained by high-frequency injection and using the modulating effect of the rotor slots. This makes true sensorless position control possible. The deteriorating effect of saturation harmonies for operation at full flux and higher loads is suppressed by using a harmonic compensation scheme based on parameters obtained from an automated commissioning process. Experimental results are shown, demonstrating sensorless position estimation at full flux and high loads. Initial experimental results are presented for encoderless position control under full flux.

Sensorless rotor position estimation at standstill of cylindrical brushless dc motors using opened phase voltage change caused by eddy currents

Sensorless rotor position estimation at standstill of cylindrical brushless dc motors using opened phase voltage change caused by eddy currents

Sensorless rotor position estimation at standstill of cylindrical brushless dc motors using opened phase voltage change caused by eddy currents

A rotor position estimation of a cylindrical brushless dc motor at standstill has been difficult to obtain. Therefore, torque control of a motor has been difficult at starting of the motor, and realization of the position estimation at standstill has been sought. This paper proposes a simple processing of a rotor for which nonmagnetic materials are pasted on the rotor surface. This processing generates an eddy current on nonmagnetic materials and causes an opened phase voltage change according to rotor position. The experimental results using a microcomputer show that it is possible to estimate rotor position of the cylindrical motor despite a standstill by using the opened phase voltage change. ©�1998 Scripta Technica, Electr Eng Jpn, 126(1): 52–60, 1999

High-grade position estimation for SRM drives using flux linkage/current correction model

This paper proposes a principle of high-resolution sensorless position estimation for a switched reluctance motor (SRM) drive, using either flux linkage or current to correct for errors in rotor position. The estimation algorithm makes full use of the nonlinear magnetic characteristics of the SRM through correlation of current, flux linkage and rotor position. The estimation model is simple, but with no loss in accuracy, leading to few real-time computations. Furthermore, a criterion is proposed to choose the phase most suited for position estimation when more than one phase conducts. The algorithm can also correct the predicted flux linkage, which, in turn, may be used to further correct the position estimate, and the features hereof are discussed. Simulations, real-time implementation and experimental results using the algorithm are presented, and confirm the concept.