Design and implementation of sensorless techniques for switched reluctance drive systems

This article proposes two different methods for estimating the shaft position for a switched reluctance motor (SRM). Method 1 uses the self-inductance estimation technique to obtain the rotor position. First, by on-line measuring the slope of the stator current and compensating for the back electromotive force (EMF) effect, the self-inductance of the SRM can be detected. Then, the shaft position of the motor can be estimated according to the self-inductance. Method 2, on the other hand, uses the phase-locked loop technique to generate high-frequency signals. These signals can be used to estimate the shaft position of the SRM. The two proposed methods are compared and discussed in the article. Several experimental results are shown to validate the theoretical analysis. The adjustable speed range of the system is from 10 to 3000 rpm. Additionally, the proposed drive system can automatically start from a standstill to a setting speed.     

Bifurcation and chaos analysis of power converter for switched reluctance motor drive

Bifurcation and chaos characteristics of single phase power converter in switched reluctance motor (SRM) drive system are studied by establishing its corresponding discrete iterative map model in this article. The discrete iterative map model of the converter is first derived. The stability theoretical analysis shows that the system may lose stability as the variation of system parameters in periodic-1 operation. With the bifurcation diagrams and Lyapunov exponents’ analyses, the operation state regions of current-controlled single phase of SRM drive can shift among stable periodic-1 region, chaos region and multi-periodic region. To verify the theoretical analysis results, time-domain waveforms and power spectra of current-controlled single phase of SRM drive are obtained by Runge–Kutta algorithm. Moreover, theoretical analysis and simulation results are verified by experimental circuit.     

Automatic control of excitation parameters for switched-reluctance motor drives

This paper presents a new approach to the automatic control of the turn-on angle used to excite the switched-reluctance motor (SRM). The control algorithm determines the turn-on angle that supports the most efficient operation of the motor drive system, and consists of two pieces. The first piece of the control technique monitors the position of the first peak of the phase current (/spl theta//sub p/) and seeks to align this position with the angle where the inductance begins to increase (/spl theta//sub m/). The second piece of the controller monitors the peak phase current and advances the turn-on angle if the commanded reference current cannot be produced by the controller. The first piece of the controller tends to be active below base speed of the SRM, where phase currents can be built easily by the inverter and /spl theta//sub p/ is relatively independent of /spl theta//sub m/. The second piece of the controller is active above base speed, where the peak of the phase currents tends to naturally occur at /spl theta//sub m/ regardless of the current amplitude. The two pieces of the controller naturally exchange responsibility as a result of a change in command or operating point. The motor, inverter and control system are modeled in Simulink to demonstrate the operation of the system. The control technique is then applied to an experimental SRM system. Experimental operation documents that the technique provides for efficient operation of the drive.     

Inductance model-based sensorless control of the switched reluctance motor drive at low speed

A sensorless control scheme for the switched reluctance motor (SRM) drive at low speed is presented in this paper. The incremental inductance of each active phase is estimated using the terminal measurement of this phase. The estimated phase incremental inductance is compared to an analytical model, which represents the functional relationships between the phase incremental inductance, phase current, and rotor position, to estimate the rotor position. The presented sensorless control scheme requires neither extra hardware nor huge memory space for implementation. It can provide accurate rotor position information even as the magnetic characteristics of the SRM change due to aging. Combined with other inductance model-based sensorless control techniques, the proposed method can be used to develop an inductance model-based sensorless control scheme to run the SRM from standstill to high-speed. Simulation and experimental results are presented to verify the proposed scheme.     

Position control of a sensorless synchronous reluctance motor

This paper presents a novel position control for a sensorless synchronous reluctance drive system. By measuring the three-phase currents of the motor, a rotor position estimator is achieved. Then, a velocity estimator is derived from the estimated rotor position by using a state estimating technique. The estimated velocity tracks the real velocity well. Next, a robust position controller is designed to improve the transient and load disturbance responses. By using the proposed estimating techniques and control algorithm, a high-performance sensorless synchronous reluctance drive is obtained. A digital signal processor, TMS-320-C30, is used to execute the estimating and control algorithms. No hardware circuit or external signal is added as compared with the traditional drive system with an encoder or resolver. To evaluate the performance of the position control system, a moving table is connected with the drive system. The drive system can precisely control the moving table. Experimental results show that the proposed system has good performance. Several experimental results validate the theoretical analysis.     

Variable structure control of an SRM drive

The applications of a variable-structure system (VSS) to the control of a switched reluctance motor (SRM) drive is presented. After reviewing the operation of an SRM drive, a VSS-based scheme is formulated to control the drive speed. The scheme is then designed and tested by simulation. The results show that the VSS control is effective in reducing the torque ripple of the motor, compensating for the nonlinear torque characteristics, and making the drive insensitive to parameter variations and disturbances     

Robust speed control of a switched reluctance vector drive usingvariable structure approach

The robust speed control of a switched reluctance vector drive is presented in this paper. An approximate sliding-mode input power controller and another feedforward sliding-mode speed controller are combined with space voltage vector modulation. The resultant drive has rapid and robust speed response. In addition, a switched reluctance motor (SRM) drive incorporating the proposed controller requires only one current sensor and can be implemented in a low-cost 8-bit microcomputer and a few discrete integrated circuits. Furthermore, the controller does not require any offline characterization of the motor or load characteristics and could easily be applied to SRMs with any number of phase windings. A 4 kW four-phase SRM drive is constructed to test the performance of the controller. The results show that a step response from 200 to 1980 RPM needs only 2-3 s, even when driving a high-inertia load, and that the speed error can be controlled below 1%, even under unknown and dynamic loads. It is concluded that modified sliding-made controllers are effective in dealing with the highly-nonlinear characteristics of the SRM drive system     

永磁同步电机矢量控制系统的EKF无传感器控制策略

介绍了一种基于扩展卡尔曼滤波的永磁同步电机无传感器转子位置与速度估算方法,并以此为基础实现了永磁同步电机的无传感器矢量控制系统。通过测量流过电机定子电流和电机端电压在线估计电机转子的位置和速度,实现永磁同步电机的无传感器控制策略。仿真和实验结果验证了该方案的可行性及有效性。     

A novel sliding-mode observer for indirect position sensing ofswitched reluctance motor drives

A switched reluctance motor (SRM) drive generally requires a rotor position sensor for commutation and current control. However, the use of this position sensor increases both cost and size of the motor drive and causes limitations for industrial applications. In this paper, a novel indirect position sensing technique, namely, the sliding-mode observer, is proposed for SRM drives. The corresponding design approach and operating performance are provided to illustrate the fast convergence and high robustness of the observer against disturbances and variations     

A torque estimator using online tuning grey fuzzy PID for applications to torque-sensorless control of DC motors

DC motors are used indispensably in industrial applications because they provide such advantages as small size, high speed, low construction cost, and safe operation. A major area of research in DC motors is to determine a better method to measure the torque of motor shaft. The traditional way to measure the mechanical torque of a rotating shaft is attachment a torque transducer in the transmission system between the driving motor and the load. However, this technique requires additional parts for the transmission system, which makes the design more complicated, time consuming, costly in construction, and in many cases impossible to achieve.The purpose of this paper is to present a new method for estimating the load torque of a DC motor shaft by using a novel modelling method based on an adaptive control technique, named as online tuning grey fuzzy PID (OTGFPID). A test rig using a DC motor is setup to investigate the torque behaviour as well as to evaluate the developed estimator. Firstly, mathematical model is developed for the motor. Secondly, the experimental speed-torque data and the optimized motor model is used to optimize the torque estimator. Then the optimized estimator is used to estimate accurately the load torque. Finally, the capability of the optimized torque estimator has been validated with the practical experiments in comparison with a typical estimation method.     

New approach for high-performance PMSM drives without rotationalposition sensors

A new approach to the position sensor elimination of permanent magnet synchronous motor (PMSM) drives is presented in this paper. With the help of the modern drive technique, the actual rotor position as well as the machine speed can be estimated accurately even in the transient state using the “electrical steady-state” operation concepts. Due to the angle-modification scheme with error-tracking function, the sensorless drive system has robustness to parameter variations. As well as giving a detailed explanation of the new algorithm, the paper presents a wide range of experimental results, demonstrating the feasibility of the proposed method under full operating conditions in the ±50~±2000 [RPM] speed range and 0~1 per unit (p.u.) load conditions     

Four-quadrant position sensorless control in SRM drives over the entire speed range

Proper synchronization of the excitation with respect to the rotor position is essential in optimal control of switched reluctance motor (SRM) drives. To avoid additional cost, size, and unreliability caused by the external position sensors, magnetic status of the SRM can be directly monitored to detect commutation instants. A one-to-one correspondence between magnetic status of the SRM and rotor position removes the need for an explicit access to the rotor position. In order to obtain a good precision over the entire speed range, educated modifications on the structure of the sensorless strategy is necessary. This is due to the impact of the operational regions on dynamic behavior of the SRM. In addition, introduction of SRM technology to industrial and domestic applications has raised the need for four-quadrant operation of the SRM drives. The present paper introduces a range of strategies that are necessary to accommodate this requirement in a sensorless format. Our experimental findings indicate that high-grade sensorless operation in a four-quadrant SRM drive is possible and can be integrated in a variety of applications.     

Error analysis in indirect rotor position sensing of switchedreluctance motors

The phase excitation pulses of a switched reluctance motor (SRM) drive need to be properly synchronized with the rotor position for optimum torque production. Accuracy of this position information determines the efficiency and smoothness of the drive operation. This paper presents a method of analyzing the errors inherent to indirect rotor position sensing schemes. The error analysis in this paper breaks down the position error to its fundamental components in the position sensing system. As an illustration, the method is applied to two different indirect position sensing schemes. The same basic approach can be applied to evaluate other SRM position sensing schemes. The results are helpful in comparing the various sensing schemes, as well as focusing improvement efforts on the appropriate segment of the system     

A current-controlled quasi-resonant converter forswitched-reluctance motor

A current-controlled quasi-resonant power converter suitable for switched-reluctance motor (SRM) feeding is presented. The converter operation is analyzed and its characteristics are determined in terms of the system parameters. The converter control strategy is studied for different operating conditions. Current control operation is considered and discussed. Theoretical predictions are verified and validated by experimental results obtained with a prototype SRM drive     

Analysis and performance of a novel two-phase drive for fan andwater-pumping applications

The authors describe a novel form of drive, comprising a two-phase induction motor fed by a two-phase inverter, for use in heating, ventilating, demisting, engine-cooling, and water-pumping applications in public service vehicles and passenger cars. A theoretical analysis of the arrangement is presented and a comparison is made between a number of predicted and experimental characteristics for two practical designs. One of these is a fan drive for engine-compartment ventilation and the other a motor-pump drive for a water-cooling system. In both cases, an acceptable range of speed control is achieved (i.e. ±10% of the normal full-load speed of 3300 r/min.), and an accurate prediction of the performance is provided     

Torque-ripple minimization with indirect position and speed sensingfor switched reluctance motors

A torque-ripple-minimization controller is realized along with indirect position and speed sensing for switched reluctance motors (SRMs). The position and speed estimations are derived from a sliding-mode observer that requires terminal measurements of only phase voltages and currents. The research shows that position- and speed-sensorless observers can be reliably used for control of an SRM. Experimental results using a four-phase, 8/6 SRM and the TMS320C30 digital signal processor are presented. The results demonstrate position- and speed-sensorless closed-loop operation of a torque-ripple-minimized SRM drive     

New approach to SRM drive with six-switch converter

This paper presents novel topologies implementation for Switched Reluctance Motor (SRM) drive used in commercial applications. For effective utilization of the developed system, a novel direct current controlled PWM scheme is designed and implemented to produce the desired dynamic speed characteristic. In comparison to conventional asymmetric converter topology, it can minimize entire system costs by reducing numbers of power semiconductors. Therefore, it may open up investigation of a new way for SRM to compete with other ac motors such as induction motors, brushless dc motors, etc. The validity of the proposed method is verified through theoretical explanation and experimental results.     

Direct torque control induction motor drives withself-commissioning based on Taguchi methodology

This paper presents the analysis and design of direct torque control (DTC) induction motor drives with self-commissioning. Neither motor parameters nor controller parameters are known a priori. The self-commissioning process consists of the calculation of motor parameters, including stator resistor, inertia and friction coefficient, as well as the design of the controller. The effects of several factors, including test conditions for deriving motor mechanical parameters and natural frequency for controller design, on the performance of speed response are investigated using Taguchi's method which is widely used in quality engineering to significantly reduce the number of experiments. Therefore, the presented drive system cannot only provide self-commissioning but also dramatically improve the performance of speed response, which is evaluated using the performance index of root-mean-squared error (RMSE) of speed. Experimental results derived from a PC-based experimental system are presented to fully support the theoretical development and analysis     

Direct torsion control of flexible shaft in an observer-baseddiscrete-time sliding mode

This paper presents a new speed control method for a two-mass system coupled by a flexible shaft. Two control loops are proposed; the outer angular speed control loop calculates the reference signal for the inner loop, where the torsion of the shaft is handled as a variable under control. In this paper, the observer-based discrete-time sliding-mode (ODSM) control implementation and experimental verification of direct torsion control is presented. The experimental system consists of a conventional DC servo gear motor with encoder feedback and inertia load coupled by a flexible shaft. The controller was implemented using a transputer as the computation engine     

Sensorless position measurement in synchronous reluctance motor

A new discrete position sensor elimination technique for a sinusoidally wound synchronous reluctance motor drive is presented. The proposed technique determines the rotor position at zero crossing of the phase currents. The rotor position between the zero crossings is determined by applying extrapolation. The proposed technique works well at all speeds, including zero speed. This technique can be used in both vector controlled and conventional constant volts/Hertz type of motor controllers