Speed-sensorless sliding-mode torque control of an induction motor

Novel induction motor control optimizing both torque response and efficiency is proposed in the paper. The main contribution of the paper is a new structure of rotor flux observer aimed at the speed-sensorless operation of an induction machine servo drive at both low and high speed, where rapid speed changes can occur. The control differs from the conventional field-oriented control. Stator and rotor flux in stator fixed coordinates are controlled instead of the stator current components in rotor field coordinates i_sd and i_sq. In principle, the proposed method is based on driving the stator flux toward the reference stator flux vector defined by the input command, which are the reference torque and the reference rotor flux. The magnitude and orientation angle of the rotor flux of the induction motor are determined by the output of the closed-loop rotor flux observer based on sliding-mode control and Lyapunov theory. Simulations and experimental tests are provided to evaluate the consistency and performance of the proposed control technique     

Vector control for induction machine on the application of optimalcontrol theory

An approach for constructing a field-oriented control system using the state-space method is proposed. The field-oriented control system can be realized by coinciding the synchronously rotating reference frame with the axes of the secondary flux linkage reference frame and by simultaneously but independently adjusting the three control inputs. A control-system synthesis method that achieves speed control, field-oriented control, and constant flux control simultaneously is presented. The control system has a full-state feedback structure and is synthesized by applying a multi-input and multi-output optimal regulator theory. The excellent robustness of the constructed system results in zero steady-state errors for changes in parameters such as rotor resistance. The validity of the control scheme is verified by simulation studies. Results are presented for a field-oriented induction motor driven by a PWM (pulse-width modulation) inverter     

A new approach to DVC combined with ROI extraction and residual video coding for multimedia sensor networks

The Wyner-Ziv distributed video coding scheme is characterized for its intraframe encoder and interframe decoder which can also approach the efficiency of an interframe encoder-decoder system. In Wyner-Ziv residual coding of video, the residual of a frame with respect to a reference frame is Wyner-Ziv encoded, which can reduces the input entropy and leads to a higher coding efficiency than directly encoding the original frame. In this paper, we propose a new approach of residual coding combined with Region Of Interest (ROI) extraction. Experimental results show that, the proposed scheme achieves better rate-distortion performance compared to conventional Wyner-Ziv coding scheme.     

基于MRAS无速度传感器矢量控制系统研究

根据异步电动机矢量控制基本原理,构建了基于转子磁链定向的模型参考自适应系统,并针对其基准模型易受积分初值和漂移问题的影响,提出了一种改进的速度辨识方法。该方法由改进的电压参考模型和电流可调模型构成。利用Matlab/Simulink对系统进行了仿真,仿真结果表明该系统能较好地估计电机的磁链及转速,收敛速度快,具有良好的...     

Active filtering function of three-phase PWM boost rectifier under different line voltage conditions

Slight hardware and algorithm modifications as well as a higher power ratio of a three-phase pulsewidth-modulation (PWM) rectifier make compensation of neighboring nonlinear power load possible. The active filtering function enlarges the functionality of PWM rectifiers, which decreases the cost of additional installation of compensating equipment. It gives a chance to fulfill both shunt active filter (SAF) and PWM rectifier tasks in a multidrive system by one advanced converter. Thanks to the idea of virtual flux, the direct power control space-vector-modulated (DPC-SVM) and new synchronous double reference frame phase-locked loop approach, the control system is resistant to a majority of line voltage disturbances. This assures proper operation of the system for abnormal and failure grid conditions. Simulation and experimental results have proven excellent performance and verify the validity of the proposed system.     

Parameter sensitivity of indirect universal field-orientedcontrollers

The universal field-oriented (UFO) controller was developed to decouple flux and torque in an arbitrary synchronous flux reference frame, realizing a high degree of generality, which makes the UFO controller compatible with all existing field-oriented controllers, including indirect and direct field orientation. This compatibility is useful to realize drives over a wide speed range using both direct UFO (DUFO) control and indirect UFO (IUFO). In this paper, generalized steady-state torque and flux expressions are derived analytically for detuned operation of the IUFO controller in an arbitrary reference frame. For a given machine (determined by its leakage factor), the expressions can be graphically represented (using only three parameters) as a function of the input command ratios. With these graphs, the steady-state performance of all indirect field-oriented controllers (controlling rotor flux, airgap flux, or stator flux) can be readily evaluated     

Adaptive Nonlinear Direct Torque Control of Sensorless IM Drives With Efficiency Optimization

Efficiency optimization of induction motor (IM) drives is a major subject based on these drives' extensive use in the industry. Among the different proposed methods, a model-based approach (MBA) seems to be the fast one. However, this method needs the motor parameters that must be correctly identified. On the other hand, a search-based approach (SBA) is a parameter-independent method but needs a greater convergence time. In this paper, a novel model-based loss-minimization approach is presented, which is combined with a backstepping direct torque control of the IM drive. An improved search-based method for efficiency optimization is also introduced. The proposed controller is realized in the stationary reference frame and has a fast-tracking capability of rotor flux and electromagnetic torque. Moreover, a sliding-mode rotor-flux observer is introduced, which is employed for simultaneous determination of rotor-flux space vector, rotor speed, and rotor time constant. The proposed control idea is experimentally implemented in real time using a field-programmable gate-array board synchronized with a personal computer. Simulation and experimental results are finally presented to verify the effectiveness of the method proposed.      

Predictive Torque Control of Induction Machines Using Immediate Flux Control

This paper proposes a new concept for the control of voltage-source inverter (VSI)-fed induction machines. The method uses a predictive algorithm and can be split into two parts. The purpose of the first part, i.e., predictive torque control (PTC), is to predict the stator reference flux vector corresponding to the reference torque at the end of the sampling interval. The second part of the method provides accurate tracing of the stator reference flux by selecting either an active or a zero voltage vector. This approach is called immediate flux control (IFC), where two possible variants are suggested. In the first variant, a simple and fast algorithm obtains minimal stator flux error by impressing either an active or a zero voltage vector throughout the entire sampling interval. Consequently, the switching frequency becomes very low, but current and torque ripple are considerable. The second IFC variant generates the stator flux more accurately by applying an active voltage vector only throughout a calculated time slot within a sampling interval, whereas, during the remaining time of the sampling interval, a zero voltage vector is impressed. As a result, higher switching frequency arises, but it is still lower than that with space vector modulation. Both IFC variants, together with PTC, require minimal processing time and were efficiently implemented in a digital signal processor, which controlled a 3-kW induction machine drive. The obtained experimental results confirm the validity of the proposed approach.     

一种新型H.264/AVC多参考帧预测方法

在H.264/AVC视频压缩标准采用的几项关键技术中,使用多参考帧预测可以增加最佳匹配块的检索概率,进而大大提高了编码效率。受B帧直接(direct)预测模式的启发,提出了一种新的基于扩展帧的多参考帧预测方法,由多参考帧中的共同位置块及其参考块扩展得到一个新的抽取帧,增加了原始序列的时域分辨率,使得扩展帧更加接近当前帧,提高了运动估计中最佳匹配的检索概率,进而提升了编码效率。仿真结果证实该方法的编码性能好于H.264/AVC参考软件。     

A new approach for minimum-torque-ripple maximum-efficiency controlof BLDC motor

Torque-ripple control of the brushless DC motor has been the main issue of the servo drive systems in which the speed fluctuation, vibration, and acoustic noise should be minimized. Most methods for suppressing the torque ripples require Fourier series analysis and either iterative or least-mean-square minimization. In this paper, a novel approach to achieve ripple-free torque control with maximum efficiency based on the d-q-0 reference frame is presented. The proposed method optimizes the reference phase current waveforms which include the case of three-phase unbalanced conditions. As a result, the proposed approach provides a simple way to obtain optimal motor excitation currents. The validity and practical applications of the proposed control scheme are verified through the simulations and experimental results     

Online identification of induction machine electrical parameters for vector control loop tuning

In a vector-controlled induction machine drive, accurate knowledge of the machine electrical parameters is required to ensure correct alignment of the stator current vector relative to the rotor flux vector, to decouple the fluxand torque-producing currents and to tune the current control loops. This paper presents a new method for online identification of the induction machine parameters required to tune a rotor-flux-oriented (RFO) vector control scheme. Accuracy of the slip frequency estimation required for RFO vector control is achieved by utilizing the parameter independent "flux pulse" rotor time constant estimation scheme, which utilizes short-duration pulses injected into the flux-producing current. The parameters required to tune the synchronous frame current control loops with a decoupling circuit are estimated using a recursive estimation scheme derived from the synchronous frame voltage equations. As the "flux pulse" scheme requires signal injection into the flux-producing current a new rotor time constant estimation scheme is presented, based on the sensitivity analysis of the recursive parameter estimation scheme. Simulation and experimental results are presented which demonstrate the effectiveness of the online parameter identification and control loop tuning technique.     

目标表面地球辐射和地球反照的均匀模拟法

对地球面元的方位角和天顶角进行了均匀采样,并将面元位置矢量由球坐标系转化到了地心赤道坐标系中.通过数值积分,计算出了地球反照和地球红外辐射对目标的辐射角系数.计算结果表明,该方法不仅在计算效率和计算精度方面都明显优于随机模拟方法,而且与辐射换热角系数手册数据十分吻合,非常适用于目标热流的计算.     

New sensorless vector control using minimum-order flux state observer in a stationary reference frame for permanent-magnet synchronous motors

This paper proposes a new sensorless vector control method that can be applied to both of salient-pole and nonsalient-pole permanent-magnet synchronous motors (PMSMs). The proposed method estimates the phase of a rotor flux by a newly developed state observer in a stationary reference frame for sensorless vector controls of PMSMs. The flux state observer has the following attractive features: 1) it requires no steady-state conditions for the dynamic mathematical model of the motor; 2) its order is the minimum second; 3) a single observer gain is simply constant over a wide operating range and can be easily designed; 4) it utilizes motor parameters in a very simple manner; and 5) its structure is very simple and can be realized at a very low computational load. The proposed speed-estimation method, which exploits the inherent physical relation of integration/derivation between phase and speed, is very simple and can properly estimate rotor speed. The usefulness of the proposed method is examined and confirmed through extensive experiments.     

Comparison of universal field oriented (UFO) controllers indifferent reference frames

The principle of the universal field oriented (UFO) controller, operating in an arbitrary reference frame, is applied to a CRPWM inverter. Due to its high degree of generality,the UFO controller is compatible with rotor, stator, and air-gap flux field oriented control. The authors compare the stability regions and the steady state performance of these three types of controllers applied to the same machine. The rotor flux based controller has been selected as the basic reference. Digital simulation results are carried out to show that the performance of the complete UFO system, i.e., combined direct and indirect UFO, in a nonrotor flux based reference frame leads to a robust high performance drive with no dependency on machine parameters in steady state     

Active and reactive power control for doubly-fed wound rotorinduction generator

A power control system for a doubly fed wound rotor induction generator has been developed. This power control system applies a control method using a rotating reference frame fixed on the gap flux of the generator, and can control active and reactive power independently and stably. The characteristics of the control system have been proved by experiment. Harmonic currents fed to the rotor windings are transmitted to the stator winding changing its frequency. The transmitting characteristics of the harmonic currents have been analyzed and verified by experiments     

Optimizing Motion Compensated Prediction for Error Resilient Video Coding

This paper is concerned with optimization of the motion compensated prediction framework to improve the error resilience of video coding for transmission over lossy networks. First, accurate end-to-end distortion estimation is employed to optimize both motion estimation and prediction within an overall rate-distortion framework. Low complexity practical variants are proposed: a method to approximate the optimal motion via simple distortion and source coding rate models, and a source-channel prediction method that uses the expected decoder reference frame for prediction. Second, reference frame generation is revisited as a problem of filter design to optimize the error resilience versus coding efficiency tradeoff. The special cases of leaky prediction and weighted prediction (i.e., finite impulse response filtering), are analyzed. A novel reference frame generation approach, called ?generalized source-channel prediction?, is proposed, which involves infinite impulse response filtering. Experimental results show significant performance gains and substantiate the effectiveness of the proposed encoder optimization approaches.     

Current controller reduced switching frequency for VS-PWM inverterused with AC motor drive applications

The current control system of the three-phase voltage source inverter used in AC motor drive application is presented in the paper. This system, operating in the rotating reference frame fixed to the motor flux, minimizes the switching frequency inverter transistors. The optimal inverter output voltage vector positions, recorded in an electrically programmable read-only memory, ensure the longest path of moving the stator current vector inside the tolerance band which is square shaped. Theoretical bases for the choice of optimal inverter output voltage vector positions are discussed     

Nonlinear sliding-mode torque control with adaptive backsteppingapproach for induction motor drive

In this paper, the nonlinear sliding-mode torque and flux control combined with the adaptive backstepping approach for an induction motor drive is proposed. Based on the state-coordinates transformed model representing the torque and flux magnitude dynamics, the nonlinear sliding-mode control is designed to track a linear reference model. Furthermore, the adaptive backstepping control approach is utilized to obtain the robustness for mismatched parameter uncertainties. With the proposed control of torque and flux amplitude, the controlled induction motor drive possesses the advantages of good transient performance and robustness to parametric uncertainties, and the transient dynamics of the induction motor drive can be regulated through the design of a linear reference model which has the desired dynamic behaviors for the drive system. Finally, some experimental results are demonstrated to validate the proposed controllers     

Implementation of a DSP based real-time estimator of inductionmotors rotor time constant

Implementation of ac drives insensitive to parameter variations is an important need in the field of high performance drives. For drives controlled by the indirect rotor flux oriented control method (IRFOC), the rotor time constant (τ_r = L_r/R_r) exerts a dominant role in the loss of dynamic performance and its variation results in an undesirable coupling between flux and torque of the machine. This paper presents a new scheme for on-line estimation of rotor time constant using dq representation of the model in the stationary reference frame and measurements of accessible motor variables only (voltages, currents and speed). The estimator is tested by simulation in the MATLAB/SIMULINK environment and validated experimentally on a 1/4 hp squirrel cage motor and a 1/4 hp wound rotor motor with implementation on a TMS320C31 digital signal processor     

Fast mode-decision for H.264/AVC based on inter-frame correlations

The H.264/AVC standard yields higher coding efficiency rates than other video coding standards. This is because it uses the rate-distortion optimization (RDO) technique, which selects the optimal coding mode and a reference frame for each macroblock (MB). In order to achieve this, the encoder has to encode a given block by exhaustively using all kinds of combinations (including different intra and inter-prediction modes). As a result, the computational complexity of video coding in H.264/AVC is extremely high. In this paper, two fast intra-/inter-mode-decision algorithms are proposed to reduce the complexity of the encoder. Both of these algorithms are based on the inter-frame correlation among adjacent pictures. For the fast intra-mode-decision, we used the intra-mode of the most-correlated MB at the reference frame to encode the current MB and the stationary property of the current MB was used for the fast inter-mode-decision. The simulation results show that the proposed algorithms significantly reduced the computational complexity with a negligible loss of PSNR and a slight increase in bitrate.