A sensorless initial rotor position estimation scheme for a direct torque controlled interior permanent magnet synchronous motor drive

In direct torque control (DTC) scheme, the requirement of the continuous rotor position sensor and coordinate transformation is eliminated since all the calculation is done in stator reference frame. However, the DTC scheme requires the position sensor to determine the initial position of the rotor at starting. Elimination of the shaft-mounted position encoder is a very desirable objective in many applications since this sensor is often one of the most expensive and fragile components in the entire drive system. This paper presents a sensorless method of determining the initial rotor position of a direct torque controlled interior permanent magnet (IPM) synchronous motor drive. The method consists of injecting a high frequency voltage to the windings and examining the effects of the saliency on the amplitude of the corresponding stator current components. This method does not depend on the level of static load and on any motor parameters. The magnet polarity of the rotor at its initial position is also identified using the effect of saliency. Modeling and experimental results verify the effectiveness of the proposed method.     

无刷电机转子状态的无位置传感器检测方法

在无刷电机控制系统中,经常使用位置传感器对电机转子状态进行检测.而无位置传感器检测法可以简化电机控制系统的结构,提高系统的可靠性.为解决此问题,将定子电流、转子转速和位置作为状态变量,利用扩展卡尔曼滤波器对电机转子的状态做出最小方差估计,从而实现无刷电机的无位置传感器检测.通过仿真实验证明了电机运行在高速和低速时此方法都能快速、准确地检测出转子的转速.     

Direct power control of grid-connected wound rotor inductionmachine without rotor position sensors

A method is presented for fast response control of the torque and flux of a grid connected wound rotor induction machine fed by back to back connected voltage source inverters on the rotor side. It is based on the measurement of active and reactive power on the grid side where voltages and currents are alternating at fixed frequency. The active and reactive powers are made to track references using hysteresis controllers. The method eliminates the need for rotor position sensing and gives excellent dynamic performance, as shown by simulation and experimental results from a variable speed constant frequency induction generator system. It is also capable of starting on the fly. It is thus an attractive sensorless control method for drive as well as generator 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     

Indirect rotor position sensing in real time for brushlesspermanent magnet motor drives

This paper describes a modern solution to the real-time rotor position estimation of brushless permanent magnet (PM) motor drives. The position estimation scheme, based on flux linkage and line-current estimation, is implemented in real-time by using the abc reference frame, and it is tested dynamically. The position estimation model of the test motor, development of hardware and basic operation of the digital signal processor (DSP) are discussed. The overall position estimation strategy is accomplished with a fast DSP (TMS320C30). The method is a shaft position sensorless method that is applicable to a wide range of excitation types in brushless PM motors without any restriction on the motor model and the current excitation. Both rectangular and sinewave-excited brushless PM motor drives are examined, and the results are given to demonstrate the effectiveness of the method with dynamic loads in closed estimated position loop     

A novel, robust DSP-based indirect rotor position estimation for permanent magnet AC motors without rotor saliency

This paper proposes and implements a novel rotor position sensorless technique for PM AC motor drives, which allows acceleration from standstill and can operate under various practical operating conditions including transient speed changes. The technique developed here relies on the measurement of the phase voltages and currents of the motor. It uses the incremental values of flux linkage, and the back-EMF functions to estimate incremental rotor position. Using a phase-locked loop (PLL) algorithm, an internal closed-loop correction algorithm can correct rotor position estimation drift, which may be due to the motor parameter variations or measurement inaccuracies. The method is implemented in closed-loop using a digital signal processor (DSP), and details of the implementation are provided in the paper. To demonstrate accuracy, robustness and reliability of the position estimation scheme, the paper presents a number of real-time experimental results, including dynamic operating conditions.     

Fuzzy logic rotor position estimation based switched reluctance motor DSP drive with accuracy enhancement

This paper describes a novel angle estimation scheme for a real time digital signal processor (DSP) based switched reluctance motor drive using fuzzy logic where several unique techniques are implemented to improve the estimation accuracy. First, an optimized fuzzy model of the motor was created using an adaptive neuro-fuzzy inference system (ANFIS) based on accurately measured flux linkage data. Secondly, an improved fuzzy optimal sensing phase selector was developed based on the analysis of both modeling error and measurement error. Lastly, a delayless polynomial predictive filter and an online phase winding resistance estimator are also implemented to further improve the position estimation accuracy. Both simulation and experiment results on a DSP based real time drive are presented to show the effectiveness of this scheme.     

双闭环无刷直流电机驱动电路的设计与实现

在对无刷直流电动机控制系统的发展及应用综述的基础上,介绍了无刷直流电动机的结构和工作原理,给出了其数学模型,并重点分析了无刷直流电机控制技术中简单易用且鲁棒性较好的PID控制算法。对无刷直流电动机控制系统的硬件和软件设计做了详细论述。该电路是基于微芯公司的电机驱动电路专用驱动芯片DSPic30f4011而设计开发的,其中主体电路架构包括电源电路,三相逆变桥电路、转速闭环、电流闭环、线电压闭环和保护电路等。系统的软件设计中,主要包括微控制器的初始化程序、开环起动、换向控制、电流、速度采样时刻控制等。     

Implementation and experimental investigation of sensorless speed control with initial rotor position estimation for interior permanent magnet synchronous motor drive

In this paper, a new approach to sensorless speed control and initial rotor position estimation for interior permanent magnet synchronous motor (IPMSM) drive is presented. In rotating condition, speed and rotor position estimation of IPMSM drive are obtained through an extended Kalman filter (EKF) algorithm simply by measurement of the stator line voltages and currents. The main difficulty in developing an EKF for IPMSM is the complexity of the dynamic model expressed in the stationary coordinate system. This model is more complex than that of the surface PMSM, because of the asymmetry of the magnetic circuit. The starting procedure is a problem under sensorless drives, because no information is available before starting. The initial rotor position is estimated by a suitable sequence of voltage pulses intermittently applied to the stator windings at standstill and the measurement of the peak current values of the current leads to the rotor position. Magnetic saturation effect on the saliency is used to distinguish the north magnetic pole from the south. To illustrate our work, we present experimental results for an IPMSM obtained on a floating point digital signal processor (DSP) TMS320C31/40 MHz based control system.     

Comparison of two interleaving techniques for coded hybridDS/SFH-SSMA

The author presents a performance comparison of two interleaving techniques for coded hybrid direct-sequence/slow frequency-hopped spread spectrum multiple-access (DS/SFH-SSMA) systems with noncoherent DPSK demodulation, employing predetection diversity (equal gain combining (EGC)) over indoor radio channels     

Comparison of two packet-retransmission techniques (Corresp.)

Two methods of dealing with the overflow problem in packet switches are compared: switch-retransmission and host-retransmission. The comparison is based on approximate analytic models of tandem queueing networks and is verified by simulation.     

Rotor time constant updating scheme for a rotor flux-orientedinduction motor drive

This paper presents a simple online rotor time constant identification scheme of an indirect field-oriented induction motor for the purpose of improving the performance and robustness of the drive. The proposed technique neither requires any special test signal nor any complex computations. This scheme is based on a special switching technique of the current-regulated pulsewidth modulation (CRPWM) voltage-source inverter (VSI), which allows measuring the induced voltage across the stator phase. The rotor time constant is then identified directly from this measured voltage. This proposed technique provides six windows within one electric cycle to update the rotor time constant, which should be sufficient for all practical purposes. Simulated results followed by experiments are presented to validate the effectiveness of the proposed technique     

Compact triangular resonator without direct coupling between two access waveguides

Novel triangular resonators containing active and passive sections have been fabricated and characterised with various multimode-interference (MMI) lengths. The optimum MMI length and width turn out to be 108 and 9 mm, respectively. A free spectral range of approximately 228 GHz is observed near 1558 nm along with an on?off ratio of 9 dB. The proposed triangular resonator has the advantage of removing the direct coupling between the two access waveguides of the MMI coupler.     

Real-time sensing of tooth position for dental digital subtractionradiography

Dental digital subtraction radiography requires accurate repositioning of the patient and X-ray source in order to facilitate correct diagnostic of bone loss. Present mechanical repositioning systems do not allow radiography of posterior teeth, and are uncomfortable for the patient. A new repositioning system that utilizes a six degrees of freedom position sensor and a robot arm with X-ray source is proposed. A mathematical model for the system is given, and the robot arm solution is obtained based on patient position. An error analysis is performed in order to determine the influence of sensor and robot errors on system accuracy. A series of experiments to determine sensor noise and accuracy are described. These tests showed relatively small errors over the work envelope of the sensor. Further tests showed that there is no adverse effect due to the presence of metal work in the patient's mouth. The high bandwidth of the sensor may allow real time tracking of small movements of the patient's head.     

Antenna scanning techniques for estimation of spacecraft position

Scanning movements are added to a tracking antenna's trajectory to estimate the true spacecraft position. The scanning movements are composed of the harmonic axial movements of an antenna. This motion produces power variations of the received signal, which are used to estimate the spacecraft's position. Three different scanning patterns (conical scan, Lissajous scan, and rosette scan) are presented and analyzed in this paper. The analysis includes the evaluation of the estimation errors due to random or harmonic variation of the antenna's position, and due to random and harmonic variations of the power level. Typically, the estimation of the spacecraft's position is carried out after completing a full scanning cycle. Sliding-window scanning is introduced in this paper, wherein the spacecraft-position estimation is carried out in an almost-continuous manner, and it reduces the estimation time by half.     

Novel rotor position extraction based on carrier frequency component method (CFCM) using two reference frames for IPM drives

In this paper a novel interior permanent-magnet (IPM) motor's rotor position extraction method from the carrier-frequency component signal, derived from pulsewidth-modulated (PWM) inverter switching, using two reference frames is presented. This method has been utilized for IPM motor vector control without a mechanical rotor position detector, extracting rotor position angle from the switching carrier-frequency (10 kHz) component current. It is effective for IPM motors, which have magnetic saliency, sinusoidal distributed stator winding, and are supplied by a PWM voltage-source inverter. The performance of two IPM motors' vector control without mechanical rotor position detector utilizing this method has been investigated. Experimental results demonstrating good dynamic and steady-state performance achieved are presented and discussed.     

Comparison of doppler ultrasound and direct electrocardiography acquisition techniques for quantification of fetal heart rate variability

A method for comparison of two acquisition techniques that are applied in clinical practice to provide information on fetal condition is presented. The aim of this work was to evaluate the commonly used Doppler ultrasound technique for monitoring of mechanical activity of fetal heart. Accuracy of beat-to-beat interval determination together with its influence on indices describing the fetal heart rate (FHR) variability calculated automatically using computer-aided fetal monitoring system were examined. We considered the direct fetal electrocardiography as a reference technique because it ensures the highest possible accuracy of heart interval measurement, and additionally all the definitions of popular time domain parameters quantifying FHR variability formerly have been created using the fetal electrocardiogram. We evaluated the reliability of various so called short-term and long-term variability indices, when they are calculated automatically using the signal obtained via the Doppler US from a fetal monitor. The results proved that evaluation of the acquisition technique influence on fetal well-being assessment can not be accomplished basing on direct measurements of heartbeats only. The more relevant is the estimation of accuracy of the variability indices, since analysis of their changes can significantly increase predictability of fetal distress.     

A new active position sensing method for ropeless elevator

Traditional cable driven elevators perform poorly in high-rise buildings because the weight of the cable limits the payload, and its elasticity degrades control performance. Further, it is not mechanically possible to include several elevator cars in the same hoistway because of the cable. However such multi-car elevator systems are desirable since they reduce passenger waiting time and reduce the space requirements of the elevator system. A promising solution is to use long armature linear motors spanning the hoistway to directly drive elevator cages. In such applications, the mover position sensing method must be explicitly addressed since most active position sensing methods require traveling cables, which are also an obstacle for multi-car elevator systems.In this paper, the linear-motor active position sensing method is formally introduced and the principle of operation, design and real-time operation methods are presented. The proposed method is used to measure the position of the mover of a long armature permanent magnet linear synchronous motor requiring no active components on the mover, thus traveling cables are eliminated. The principle of operation is inspired by linear variable differential transformer: A magnetic shunt positioned at a fixed distance ahead of the mover deforms the magnetic field created by one of the armature coils. The deformation can be determined by measuring the induced voltages on the neighboring coils, and the position of the shunt, and thus the mover, can be calculated.A design method for the optimal dimensions of the shunt for a given armature to provide long measurement range and small maximum position error is presented, accompanied by a real-time measurement algorithm that will enable the motor to be driven using the method. Finally the method is verified by simulations and experimental results conducted on a full scale linear-motor elevator prototype that was constructed in the laboratory.     

A lateral position sensing system for automated vehicle following

This paper investigates the use of photoresistive light sensor arrays as a possible lateral position sensing system for a vehicle, or several vehicles, following a lead vehicle under separate control. A brief motivation for the use of such a sensing array is followed by a derivation of an appropriate sensor layout. It is shown that the sensing array has several benefits, including cost, simplicity, redundancy, and near linearity. Experimental results are given for a scaled vehicle following manoeuvre using a simple lateral control strategy. The results show that the sensor array may be attractive for lateral alignment in vehicle-following manoeuvres     

Initial rotor position estimation and sliding preventing for elevators with surface-mounted PMSMs

Improved methods of initial rotor position estimation and sliding prevention are presented in this paper for elevators with surface-mounted permanent magnet synchronous machines (SPMSMs). In contrast to most of the existing literature, in this paper, estimation errors caused by stator resistance and dead time are analysed in detail. The improved estimation method can reduce the errors greatly without dead-time compensations and knowledge of motor parameters. Besides, an observer-based feedforward compensation of load torque is introduced to elevator applications to prevent sliding during the starting process. Since the torque observer is widely used in other motor applications, we focus on the impact caused by the change in inertia. Finally, a series of experiments are performed on a testing system with two 13.4 kW SPMSMs and drivers to illustrate the effectiveness and improvement of the method.