New observer-based DFO scheme for speed sensorless field-orienteddrives for low-zero-speed operation

This paper describes a new direct field orientation (DFO) scheme based on a modified flux observer using measured stator voltages and currents. The proposed approach addresses the problem of torque control of speed sensorless drives at low-zero speed, where rapid speed changes do not occur and signal frequency can approach zero. The scheme can maintain field orientation and stable torque control with simultaneous resistance and speed tuning taking place. Simulations and locked rotor experiments with torque measurements are used for verification     

采用检测信号并考虑主磁链饱和的异步电机无传感器矢量控制

异步电机无速度传感器矢量控制需要通过由定子电压和电流建立的模型来计算磁链矢量和转速。如果磁链矢量的估计中存在误差，例如由电机模型参数不准确造成的误差，那么系统的稳定性就会出现问题。本文提出了一种考虑了主磁链饱和效应的方法来辨识磁链矢量甚至是在定子频率为零时的磁链。因此保证了全速和全转矩范围内的系统的稳定运行。     

基于误差预处理技术的水下被动目标跟踪方法

针对伪线性估计器有偏性问题进行了研究,指出产生有偏性的原因是由于将测量方位误差引入了测量方程。针对潜艇测量方位的变化特点,提出了一种对测量方位分段拟合的处理方法,将处理后的测量方位用于伪线性估计器。通过仿真实验,验证了该方法不但可以大大减小有偏性,而且提高了目标要素的解算速度。     

A speed estimator for high performance sensorless control ofinduction motors in the field weakening region

The paper proposes a modified version of the model reference adaptive system (MRAS) based speed estimator, whose outputs of the reference and the adjustable model are rotor flux space vectors. The estimator is modified in such a way that the variation in the instantaneous level of the main flux saturation during operation in the field weakening is recognized and properly compensated at all times. The speed estimation scheme is equally applicable to both vector controlled and direct torque controlled induction machines, since it operates in the stationary reference frame and requires measurement of only stator voltages and currents. Verification of the proposed scheme is provided by simulation and by experimentation on an indirect feedforward rotor flux oriented induction machine for speed references of up to twice the base speed     

A simple approach to flux and speed observation in induction motordrives

The stator-flux orientation concept allows very good transient and steady-state performances in induction motor drives. However, this control strategy can be conveniently implemented only if the stator flux is correctly observed in the entire speed range. The authors have developed a simple flux observer that gives very satisfactory results, especially near zero speed, and the approach which has been followed also allows a good speed estimation. The observer has been both simulated and implemented on an experimental system that uses a single chip to control the whole drive system. The experimental results show excellent performances, despite the low computational load     

A programmable cascaded low-pass filter-based flux synthesis for astator flux-oriented vector-controlled induction motor drive

The concept of a programmable cascaded low-pass filter method of flux vector synthesis has been introduced in the literature. In this paper, the idea is expanded, analyzed, improved, and then applied to a stator flux oriented 100-kW electric vehicle drive. It was verified that the flux estimation works well at zero speed finite torque start-up mode and low- and high-speed field weakening regions, thus completely eliminating the need of a speed sensor     

Model Reference Adaptive Controller-Based Rotor Resistance and Speed Estimation Techniques for Vector Controlled Induction Motor Drive Utilizing Reactive Power

In this paper, a detailed study on the model reference adaptive controller (MRAC) utilizing the reactive power is presented for the online estimation of rotor resistance to maintain proper flux orientation in an indirect vector controlled induction motor drive. Selection of reactive power as the functional candidate in the MRAC automatically makes the system immune to the variation of stator resistance. Moreover, the unique formation of the MRAC with the instantaneous and steady-state reactive power completely eliminates the requirement of any flux estimation in the process of computation. Thus, the method is less sensitive to integrator-related problems like drift and saturation (requiring no integration). This also makes the estimation at or near zero speed quite accurate. Adding flux estimators to the MRAC, a speed sensorless scheme is developed. Simulation and experimental results have been presented to confirm the effectiveness of the technique.     

Speed-sensorless induction Machine control for zero speed and frequency

A recently introduced speed-sensorless controller structure for tracking the rotor-flux orientation of an induction motor was implemented in a laboratory setup. The controller is based on superimposing a low-frequency ac test signal on the stator current of the motor. The response in the stator voltage to the signal depends on the orientation of the signal relative to that of the rotor flux. The dependency is due to the reaction of the mechanical system, and it is used to control the orientation error to zero. In the experiments, the controller operated successfully under nominal torque both at zero speed and at zero frequency. Slow and fast speed reversals under nominal torque were also successful. In addition, the system was capable of withstanding both motoring and generating load torque steps up to 50% of nominal torque.     

Sensorless double-inverter-fed wound-rotor induction-Machine drive

The basic operation of a wound-rotor induction-motor drive fed by inverters on the stator as well as the rotor side is discussed. Different modes of operations are defined and explained based on power flow on both the sides of the machine. The sensorless motor control scheme consists of V/f-type direct frequency control on one side, with either vector control or direct torque and flux control on the other side. The machine operates up to twice the rated speed in either direction, with full flux and torque, thereby producing up to twice the rated power. Novel frequency profiles are proposed, which ensure that the frequency on either side never drops below a minimum value (set at 12 Hz in this work). Therefore, the estimation of flux can be simply and reliably carried out by integration of voltage, resulting in simple sensorless control. The drive works reliably at all speeds including zero speed and at all loads. Results from a 50-hp prototype drive are presented.     

Comparative study of adaptive and inherently sensorless observers for variable-speed induction-motor drives

State observers are key components of modern ac drives. The paper presents a comparative analysis of two state observers for induction-motor (IM) drives: the speed-adaptive observer and the inherently sensorless observer. The adaptive observer employs the time-variable full-order motor model with the rotor speed as the adaptive quantity. Thus, the speed estimation accuracy significantly impacts on the flux observer. It is shown that the popular model reference adaptive system (MRAS) speed estimator displays reduced bandwidth, and does not deliver adequate performance for the flux estimation. The inherently sensorless observer employs a full-order dual reference-frame model in order to eliminate the speed adaptation. In this way, it becomes decoupled from the speed estimator and its performance is superior to that of its adaptive counterpart. Theoretical aspects and comparative simulation results are discussed for both observers. Comparative experimental results for both observers are presented. Very low-speed-operation (3 r/min) capability of the drive with the sensorless observer is demonstrated.     

利用频谱特性的速度自适应信道估计方法

本文利用信道在移动环境下频谱带限和对称的特征,提出一种新的对移动速度自适应的信道估计方法。该方法通过寻找频谱自相关的峰值来确定频域滤波器的长度。相对传统速度自适应方法,该方法不需要估计多普勒频率或移动速度,降低了系统实现的复杂度;也不需要信道的长时统计量或信噪比信息,实时性较高。信号在频域的处理必然会有频谱泄漏问题,传统方法滤除噪声的同时也去掉了部分信号,对此本文同时还提出一种恢复泄漏的频域信号的方法,使估计性能有所提高。仿真结果显示,从步行到高速移动的环境下,本文提出的信道估计方法的均方误差(MSE)都保持在较低的水平,具有良好的对速度自适应的估计性能。     

Design and analysis of general rotor-flux-oriented vector controlsystems

Reduced-order observers for rotor flux estimation of induction motors are considered. The “current” model and “voltage” model are obtained as special cases. It is shown that the flux dynamics form a nonlinear closed-loop system when the flux estimate is used for field orientation. The observer gain selection is extremely critical for good behavior of this system. A framework is developed, in which the properties of any gain selection can easily be assessed. Four candidate gain selections are considered, two of which yield schemes that do not use the rotor speed in their equations (inherently sensorless schemes). It is also shown that for any gain selection, an equivalent synchronous-frame implementation (i.e., indirect field orientation) always exists     

A scale‐independent way for differential estimation in dynamic radio frequency identification systems

Cardinality estimation in radio frequency identification systems has been applied to estimate the population of tags in many applications. However, it is more meaningful to estimate the number of tags moved in and out in a dynamic radio frequency identification system, which is called differential estimation problem. Zero differential estimator is a newly proposed algorithm to solve this problem. However, the time slots consumed by zero differential estimator are relevant to the system scale under the accuracy constraint. This will result in low time efficiency when the system scale is very large. In this paper, we thus propose a scale‐independent algorithm for differential estimation called zero‐one differential estimator. The numbers of tags moved in and out are estimated from the idle slots in two consecutive frames. We can prove that the time slots consumed in our proposed algorithm are not relevant to the system scale under the accuracy constraint. Moreover, we conduct abundant simulations to evaluate the performance of the proposed approach. The simulation results show that the estimation error grows little as the system scale grows. It indicates that our proposed algorithm is indeed scale‐independent. Copyright © 2015 John Wiley & Sons, Ltd.     

Fuzzy logic enhanced speed control of an indirect field-orientedinduction machine drive

Field orientation control (FOC) of induction machines has permitted fast transient response by decoupled torque and flux control. However, field orientation detuning caused by parameter variations is a major difficulty for indirect FOC methods. Traditional probability density function (PID) controllers have trouble meeting a wide range of speed tracking performance even when proper field orientation is achieved. PID controller performance is severely degraded when detuning occurs. This paper presents a fuzzy logic design approach that can meet the speed tracking requirements even when detuning occurs. Computer simulations and experimental results obtained via a general-purpose digital signal processor (DSP) system are presented     

Field oriented control of induction machines employing rotor endring current detection

The usual method of induction motor torque control uses the indirect field orientation principle in which the rotor speed is sensed and slip frequency is added to form the stator impressed frequency. Unfortunately, the rotor resistance varies as the motor heats up under load thereby changing the rotor time constant which has a deleterious effect on the torque response. In this paper two new field oriented control schemes are presented which employ rotor end ring current detection and thereby remove the dependence of the controller accuracy on temperature so that the controller is entirely independent of rotor time constant variations. The field orientation schemes do not require an incremental encoder for rotor position sensing. The motor torque can be accurately controlled even down to zero speed operation     

An Adaptive Sliding Stator Flux Observer for a Direct-Torque-Controlled IPM Synchronous Motor Drive

This paper focuses on performance improvements of the stator flux estimation for a direct-torque-controlled interior permanent magnet synchronous motor drive. In this paper, an adaptive sliding observer is presented to estimate the stator flux linkage based on the motor current model. The experimental results show that the proposed observer has been able to deliver more accurate estimation than an open-loop estimator both in the steady state and during transients. The observer has better dynamic behavior, disturbance resistance, and high-accuracy estimation ability. With the integrated flux observer, the drive system can operate at very low speed down to 10 r/min (0.33 Hz) with half full load.     

High-performance induction motor speed control using exact feedback linearization with state and state derivative feedback

This paper presents a novel nonlinear speed/position control strategy for the induction motor utilizing exact feedback linearization with state and state derivative feedback. The speed/position and flux control loops utilize nonlinear feedback which eliminates the need for tuning, while ordinary proportional-integral controllers are used to control the stator currents. The control scheme is derived in rotor field coordinates and employs an appropriate estimator for the estimation of the rotor flux angle, flux magnitude, and their derivatives. The overall control scheme can be easily implemented with a microprocessor-based control platform. An error sensitivity analysis is included which proves the system to be robust to parameter variation and even more, immune to rotor resistance variation. Simulation and experimental results validate the theoretical part of the paper and reveal the high performance and advantages of the novel control scheme.     

Frame-frequency estimation in ultrawideband systems

This paper investigates the estimation of the frame frequency in ultrawideband (UWB) communication systems. An estimation method is proposed that exploits the transmission of a periodic pulse sequence at the frame frequency. The samples of the received waveform are used to compute a cost function that depends on a trial value of the incoming pulse frequency. The location of the maximum provides an estimate of the transmitted frequency. The performance of the estimator is assessed theoretically and is compared to the Cramer-Rao lower bound. It is shown that in certain conditions the estimator achieves the bound at high SNR values. Simulations validate the theory and show the degradations in the estimation performance caused by multiple-access interference. They also give an idea of the estimation accuracy needed in a correlation receiver.     

A MRAS-based adaptive pseudoreduced-order flux observer for sensorless induction motor drives

The performance of vector-controlled sensorless induction motor drives is generally poor at very low speeds, especially at zero speed due to offset and drift components in the acquired feedback signals, and the increased sensitivity of dynamic performance to model parameter mismatch resulting especially from stator resistance variations. The speed estimation is adversely affected by stator resistance variations due to temperature and frequency changes. This is particularly significant at very low speeds where the calculated flux deviates from its set values. Therefore, it is necessary to compensate for the parameter variation in sensorless induction motor drives, particularly at very low speeds. This paper presents a novel method of estimating both the shaft speed and stator resistance of an induction motor. In this novel scheme, an adaptive pseudoreduced-order flux observer (APFO) is developed. In comparison to the adaptive full-order flux observer (AFFO), the proposed method consumes less computational time, and provides a better stator resistance estimation dynamic performance. Both simulation and experimental results confirm the superiority of the proposed APFO scheme for a wide range of resistance variations from 0 to 100%.     

Real-time slip-based estimation of maximum tire-road friction coefficient

This paper presents a real-time maximum tire-road friction coefficient estimation method and field test results. The estimator is based on the relationship between the wheel slip ratio and the friction coefficient. An effective tire radius observer and a tire normal force observer have been designed for the computation of the slip ratio from wheel speed and vehicle speed measurements. The effective tire radius observer has been used so that the proposed method works for all driving situations. A tractive force estimator, a brake gain estimator, and a normal force observer have been used for the estimation of the friction coefficient. The proposed estimation method for the maximum tire-road friction coefficient has been implemented using a fifth wheel and typical vehicle sensors such as engine speed, carrier speed, throttle position, and brake pressure sensors.