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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. [ABSTRACT FROM AUTHOR]

In this paper, a simple and accurate method is proposed for online estimation of the rotor permanent magnet (PM) flux linkage for surface mounted PM synchronous machines. By advantageously utilizing an injected zero-voltage vector, the effects of inductance in estimating the PM flux linkage is eliminated. The inverter voltage error and phase resistive voltage drop effects are minimized by repeating the test at different speeds. Therefore, as a result, only the voltage commands are needed for PM flux linkage estimation, resulting in great simplicity. Filtering the current ripple caused by the zero-voltage vector injection is not necessary. The proposed method can be used with sensored or sensorless field-oriented control strategies. The experimental results have shown a good accuracy of the proposed new method. [ABSTRACT FROM AUTHOR]

Improving the positioning response is one of the key goals for permanent magnet synchronous motor position servo systems. The sliding mode variable structure controller (SMVSC) is an effective method due to the advantages of strong robustness, fast response, and easy practical implementation. However, the existing SMVSCs have difficulties in optimizing the position tracking response speed and chattering performance at the same time. This article proposes an improved position speed integrated SMVSC (ISMVSC) with a new variable exponential reaching law based on position error and a saturation function, and a speed-limiting method using speed error and trajectory planning. The general design principle is given and various tests are carried out to verify the effectiveness of the proposed method. The experimental results show that compared with traditional methods, the ISMVSC can improve the positioning response speed and reduce chattering problems at the same time; it also exhibits a stronger transient speed-limiting ability. All these advantages make the proposed controller a superior method to achieve high-response positioning control of the servo system that performs point-to-point motion. [ABSTRACT FROM AUTHOR]

The effective identification of the load torque is one of the key methods to improve the positioning accuracy of the position servo system, and the sliding mode observer (SMO) is a common identification method in the speed control system because of its advantages of insensitive parameters and easy physical realisation. However, the existing SMO cannot achieve high precision and high response identification of load torque in the full speed range when the motor is running at variable-speed or variable-load, which limits its application in the position servo system. Based on the analysis of the stability and the adaptive law of feedback gain coefficient, an improved SMO for adaptive identification based on adaptive control and improvement of cut-off frequency is proposed. To verify the proposed method, the dedicated simulation model and test platform are built. The results show that the proposed observer can realize the adaptive identification of the load torque under the condition of variable-speed or variable-load, and the estimation accuracy is high. The position servo system designed by the proposed observer can improve the response against load change, which is an effective method for high-precision positioning control of the position servo system with a variable-speed or variable-load. [ABSTRACT FROM AUTHOR]

Effective identification of the load torque is one of the key aspects in improving the performance of servo drive systems against load disturbances. Sliding mode variable structure control has become a popular method in the development of a load torque identification (LTID) algorithm due to its parameter insensitivity and easy realization features. However, existing LTID sliding mode observers (SMO) with conventional structure have the disadvantages of high-frequency chattering and poor estimation accuracy, which limit its application in high-performance servo systems. In this paper, the mathematical model of the conventional LTID-SMO is deduced and analyzed. A new LTID-SMO is proposed by replacing the sign function with a saturation function and an additional feedback loop in the load torque observer. The effectiveness of the proposed observer is verified by various experiments. The results show that compared to conventional load torque observer, the proposed observer can identify the load torque with higher accuracy and faster response in different operational conditions. [ABSTRACT FROM AUTHOR]

This paper presents a new initial rotor position estimation method for an interior permanent magnet synchronous motor. The proposed method includes two steps. First, the minimum voltage vectors are injected to estimate the rotor position. Second, in order to identify the magnet polarity accurately, two opposite voltage pulses are injected on the estimated d-axis. In the proposed method, no filter is needed to draw the high frequency current signal for position estimation and no low-pass filter is required in the current control loop for extracting the fundamental current component for field-oriented control. The fast and reliable feature of this proposed method allows starting the motor with 100% load torque. The effectiveness of the proposed method is verified experimentally and the maximum position estimation error is around 6 electrical degrees. [ABSTRACT FROM AUTHOR]