Sensorless Closed-loop Control Research Articles

Virtual Impedance Refined Inductor Current Observation and Current Sensorless Control for Grid-Connected Inverter

When facing the current sensor failures, the inverter system will be shut down or run in open-loop mode, and the controllability will be severely degraded. Therefore, the development of the current sensorless control strategy for the grid-connected inverter is worthy of academic attention. In order to solve this problem, a current observation method is proposed in this article, which is enhanced by the virtual impedance and operation data based error correction. The method combines the control scheme variables of dc side voltage and ac side grid voltage to observe the ac side inductor current. The output of current sensors can be replaced in the current closed-loop control, contributing to the current sensorless control. The research results show that the current observation method can effectively track the real-time current and the virtual impedance implementation ensures the accuracy of this current observation. Under the impedance refined current observations, dynamic variations in inductor current can be timely reflected, and the stable operation of the current sensorless closed-loop control can be ensured. Finally, the correctness and effectiveness of the proposed control strategy have been verified by MATLAB / Simulink simulation and experimental results.

A Position Sensorless Closed-Loop Control Mode of a Three-Phase Hybrid Stepper Motor

The demand for the high-performance and low-cost position control actuators in many applications promotes the development of three-phase hybrid stepper motors. The torque ripple, loss, and pullout torque of the motor are the key factors to be considered in the motor application. In order to solve the problems of the open-loop control mode, this paper proposes a new “sensorless closed-loop” control mode to significantly improve the performance of three-phase hybrid stepper motors. This control mode is developed by estimating the rotor position with the Extended Kalman filter observer, thereby realizing the closed-loop control of the motor with sensorless technology. This paper illustrates the effects of this control mode by analyzing motor noise, losses, and pullout-torque. The results show that the use of the “sensorless closed-loop” control mode presented can effectively improve the performance of the stepper motor while maintaining the advantages of the motor in terms of cost and size. These results have positive significance for the development, application, and promotion of high-performance three-phase hybrid stepper motor systems.

Experimental study of the combustion characteristics prediction model for a sensor-less closed-loop control in a heavy-duty NG engine

The closed-loop combustion control is an effective way to reduce the cycle-to-cycle variations of spark ignition (SI) engine. In this paper, a series of experimental tests were conducted to investigate the combustion performance and emissions characteristics in a six-cylinder natural gas (NG) engine. The correlation between combustion phasing and control parameters was analyzed under different EGR rates and spark timing (ST) at medium and low loads. Additionally, a prediction model on the basis of the correlation was developed employing artificial neural network (ANN) for a sensor-less closed-loop combustion control. After analyzing the results, it is found that a linear relationship exists between CA 50 and ST under various EGR rates. Engine out emissions (i.e., CO, THC, and CH4) are insensitively affected by the CA50. It is observed that the NOx emission is significantly higher in comparison to those under the higher EGR rate. As a consequence, CA50 is acting as the feedback signal for closed-loop combustion control with consideration of cylinder consistency. Moreover, the ANN model was proven to be an impressive way to predict the combustion characteristics, which can substitute the cylinder pressure sensor. Moreover, the prediction model can be applied in a sensor-less closed-loop combustion control, while the correlation coefficient value can reach up to approximately 1.00.

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.

Sliding-Mode-Observer-Based Position Estimation for Sensorless Control of the Planar Switched Reluctance Motor

This paper proposes a position estimation method for a planar switched reluctance motor (PSRM). In the method, a second-order sliding mode observer (SMO) is used to achieve sensorless control of a PSRM for the first time. A sensorless closed-loop control strategy based on the SMO without a position sensor for the PSRM is constructed. The SMO mainly consists of a flux linkage estimation, an adaptive current estimation, an observing error calculation, and a position estimation section. An adaptive current observer is applied in the current estimation section to minimize the error between the measured and estimated currents and to increase the accuracy of the position estimation. The flux linkage is estimated by the voltage equation of the PSRM, and the estimated flux linkage is then used to estimate the phase current in the adaptive current observer. To calculate the observing error of the SMO using the measured and estimated phase currents, the observing error of the thrust force is introduced to replace the immeasurable state error of the position and speed of the mover. The sliding surface is designed based on the error of the thrust force, and stability analysis is given. Once the sliding surface is reached, the mover position is then estimated accurately. Finally, the effectiveness of the proposed method for the PSRM is verified experimentally.

Sensorless Control of Permanent Magnet Synchronous Motors with Compensation for Parameter Uncertainty

Estimation errors of the rotor speed and position in sensorless control systems of Permanent Magnet Synchronous Motors (PMSM) will lead to low efficiency and dynamic-performance degradation. In this paper, a parallel-type extended nonlinear observer incorporating the nominal parameters is constructed in the stator-fixed reference frame, with rotor position, speed, and the load torque simultaneously estimated. The stability of the extended nonlinear observer is analyzed using the indirect Lyapunov’s method, and observer gains are selected according to the transfer functions of the speed and position estimators. Taking into account the parameter inaccuracies issue, explicit estimation error equations are derived based on the error dynamics of the closed-loop sensorless control system. An equivalent flux error is defined to represent the back Electromotive Force (EMF) error caused by the inaccurate motor parameters, and a compensation strategy is designed to suppress the estimation errors. The effectiveness of the proposed method has been validated through simulation and experimental results.

Sensorless micro-permanent magnet synchronous motor control system with a wide adjustable speed range

This study proposes a new sensorless speed control system for a micro-permanent magnet synchronous motor. Owing to the special characteristics of the micro-permanent magnet synchronous motor, a new rotor position estimator is proposed here. First, by detecting the three-phase zero-current crossing points, a low-resolution of the current position can be detected. Next, by using a Proportional Integral (PI) state estimator, the resolution of the current position can be obviously improved. After that, the deviation voltage between the ideal d-axis voltage and the estimated d-axis voltage is computed to compensate the estimated rotor position. By using the estimated rotor position, the proposed sensorless closed-loop control system, which has good performance including fast transient responses, good load disturbance responses and good tracking responses, can be realised. A digital signal processor, TMS320F28335, is used as a control centre to execute the rotor position estimating algorithm and control algorithm. Experimental results show that the sensorless micro-permanent magnet synchronous motor control system can provide a wide adjustable speed range from 5 to 40 000 r/min with satisfactory performance, which is better than the micro-permanent magnet synchronous motor using an attached 64 pulses/revolution encoder.

Adaptive-Neuro-Fuzzy-Based Sensorless Control of a Smart-Material Actuator

In this paper, adaptive-neuro-fuzzy-based sensorless control of a smart-material actuator is presented. The smart material that we used to develop a novel type of linear actuator is Terfenol-D. The peristaltic motion in the actuator is generated by inducing a traveling magnetic field inside the Terfenol-D element. The sensorless control of the actuator is based on an observation illustrating a direct relationship between the active element's position and the coils’ inductances. To detect the inductance change, the coil's current response to a pulse voltage input is monitored. Then, a fundamental relationship between the coils’ current-response pulsewidths and the active element's position is developed using a combination of a Sugeno fuzzy model and neural networks. Eventually, the closed-loop sensorless control of the magnetostrictive actuator was successfully performed. The neuro-fuzzy-based sensorless control demonstrated the position-estimation capability with a <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\pm$ </tex></formula> 0.5-mm maximum error. The sensorless control scheme combined with the unique features of this actuator is promising in the applications, where conventional actuation and sensing methods are proved inapplicable due to technical or reliability issues.

Sensorless Control of a Novel Linear Magnetostrictive Motor

In this paper, the sensorless control of a novel linear magnetostrictive motor is presented. We developed this low-power linear magnetostrictive motor with local three-phase excitation. In response to a traveling magnetic field inside the Terfenol-D active element, it moves in the opposite direction with a peristaltic motion. It is observed that there is a direct relationship between the active element's position and the coils' inductances. To detect the inductance change, the coil's current response to a pulse voltage input is monitored. Then, a fundamental relationship between the coils' current-response pulsewidths and the active element's position is experimentally developed. Eventually, the closed-loop sensorless control of the linear magnetostrictive motor was successfully performed. The sensorless control demonstrated the position-estimation capability with a <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\pm$</tex></formula> 1-mm maximum error.

Sensorless Control and Fault Diagnosis of Electromechanical Contactors

This paper describes a novel algorithm for a closed-loop sensorless control of electromagnetic devices. It integrates a novel fault diagnosis algorithm of the whole electromagnetic circuit. Applied to a contactor with a dc core, it eliminates the armature and contact bounce, whether it is ac or dc powered and at either 50 or 60 Hz. The position and velocity of the moving armature and contacts are calculated by means of the online determination of the inductance using only the measured current and voltage values of the contactor coil as control inputs. A fuzzy controller takes the position and velocity of the armature as input and provides the current set point as output, which controls the velocity of closure of the contacts. The algorithm has been implemented in a low-cost electronic module.

Adaptive controller design for a sensorless IPMSM drive system with a maximum torque control

An advanced controller design for a sensorless interior permanent-magnet synchronous motor control system is proposed. A maximum torque/ampere control algorithm is used to improve the torque performance of the drive system. In addition, an adaptive controller combined with the maximum torque/ampere control is proposed to obtain a good transient response and a good load disturbance rejection capability. The proposed control method can be applied to both a sensorless adjustable speed control system and a sensorless position control system. Using the Lyapunov stability theory and Barbalat's lemma it is shown that the closed-loop sensorless control system is an asymptotical stable system. A 32-bit digital signal processor is used to execute the rotor position estimation algorithm and the control algorithm. Experimental results validate the theoretical analysis and show the correctness and feasibility of the proposed system

A three-phase hybrid stepping motor drive system combined with position-sensorless closed-loop control

This paper proposes a drive system for a three-phase hybrid stepping motor, combining sensorless closed-loop control with conventional open-loop control. It is characterized by sophisticated control providing both prevention of pulling out from synchronism and suppression of natural rotor oscillation, without any position sensor attached to the motor shaft. A switching technique in chopper control which can enlarge the speed range controllable in the sensorless closed-loop control is described. Starting and stopping sequences are developed to reduce mechanical natural oscillation produced in the transient state. Finally, the proposed drive system is compared experimentally with a conventional constant-current open-loop drive system. It is shown that the proposed drive system can perform the switchover from starting to sensorless closed-loop operation within 20 ms, and can reduce the natural oscillation caused just after positioning. © 2000 Scripta Technica, Electr Eng Jpn, 131(3): 80–90, 2000

A Three-Phase Hybrid Stepping Motor Drive System Combined with Position-Sensorless Closed-Loop Control

This paper proposes a drive system for a three-phase hybrid (HB) stepping motor, combining sensorless closed-loop control with conventional open-loop control. It is characterized by the sophisticated control providing both prevention of pulling out from synchronism and suppression of rotor natural oscillation, without any position sensor attached to the motor shaft. Switching technique in chopper control is described, which can enlarge a speed range controllable in the sensorless closedloop control. Moreover, starting and stopping sequences are developed to reduce mechanical natural oscillation caused in transient state. Finally, the proposed drive system is compared with a conventional constant-current open-loop drive system experimentally. It is shown that the proposed drive system can perform a switchover from the starting to the sensorless closed-loop operation within 20ms, and can reduce the natural oscillation caused just after positioning.