A low-cost sensorless technique for load torque estimation in ahybrid stepping motor

This paper presents a method of torque measurement in a hybrid stepping motor without the use of speed or position sensors. It is shown that torque ripple can be minimized by appropriate shaping of the phase-current pulses and that efficiency can be maximized when the level of mechanical load applied to the shaft is known. A controller is described which generates a signal related to the mechanical load by observation of the phase-current profile using a novel low-complexity technique. Practical results are presented, showing the torque estimation relative to measured torque     

Disturbance torque estimation in a sensorless DC drive

The estimation of the disturbance torque in a sensorless DC motor drive is carried out by extending the classical observer theory. Three estimation schemes are formulated according to the representation of the disturbance torque and the processing of the observer states. In addition to the disturbance torque, all the schemes deliver an estimation of the motor speed. Steady-state accuracy and dynamics of the schemes are first determined in nominal conditions, identifying the scheme with the best performance. The effects of variations in the motor parameters are then analyzed, with the finding that a proper modeling of the motor makes the steady-state estimation of the disturbance torque insensitive to any variation. As a test, the schemes are applied to a sensorless DC motor drive for both compensating for the disturbance torque and closing the speed loop. The responses obtained with the best-performance scheme are reported     

无位置传感器直流无刷电机的DSP控制

本文介绍了无位置传感器直流无刷电机的一些位置估算方法,并着重介绍了一种利用DSP完成变频空调直流无刷压缩机的控制方法.     

基于改进型滑模观测器的永磁同步电机控制

传统基于反电动势的滑模观测器采用Sign函数来作为开关函数,因为Sign函数的开关特性,使系统存在抖振大的问题。在传统滑模观测器的基础上,通过采用Sigmoid函数代替Sign函数,改善了开关特性,大大地减少了抖振,并去掉了滤波器和转角补偿器,简化了系统,提高了反电动势的估算精度,从而得到更精确的转速和转角位置信息。在Matlab/Simulink平台基础上建立控制系统仿真模型,对该方案做了验证。仿真结果表明:该方法提高了滑模观测器的精度,降低了系统的抖振,提高了系统的性能。     

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.     

A nonlinear state observer for the sensorless control of apermanent-magnet AC machine

This paper presents a sensorless speed regulation scheme for a permanent-magnet synchronous motor (PMSM) based solely on the motor line currents measurements. The proposed scheme combines an exact linearization-based controller with a nonlinear state observer which estimates the rotor position and speed. Moreover, the stability of the closed-loop system, including the observer, is demonstrated through Lyapunov stability theory. The proposed observer has the advantage of being insensitive to rotation direction. It is shown how a singularity at zero velocity appears in the scheme and how it can be avoided by switching smoothly from the observer-based closed-loop control to an open-loop control at low velocity. The system performance is tested with an experimental setup consisting of a PMSM servo drive and a digital-signal-processor-based controller for both unidirectional and bidirectional speed regulation     

A modular control scheme for PMSM speed control with pulsating torque minimization

In this paper, a modular control approach is applied to a permanent-magnet synchronous motor (PMSM) speed control. Based on the functioning of the individual module, the modular approach enables the powerfully intelligent and robust control modules to easily replace any existing module which does not perform well, meanwhile retaining other existing modules which are still effective. Property analysis is first conducted for the existing function modules in a conventional PMSM control system: proportional-integral (PI) speed control module, reference current-generating module, and PI current control module. Next, it is shown that the conventional PMSM controller is not able to reject the torque pulsation which is the main hurdle when PMSM is used as a high-performance servo. By virtue of the internal model, to ify the torque pulsation it is imperative to incorporate an internal model in the feed-through path. This is achieved by replacing the reference current-generating module with an iterative learning control (ILC) module. The ILC module records the cyclic torque and reference current signals over one entire cycle, and then uses those signals to update the reference current for the next cycle. As a consequence, the torque pulsation can be reduced significantly. In order to estimate the torque ripples which may exceed certain bandwidth of a torque transducer, a novel torque estimation module using a gain-shaped sliding-mode observer is further developed to facilitate the implementation of torque learning control. The proposed control system is evaluated through real-time implementation and experimental results validate the effectiveness.     

永磁同步电机的零低速无传感器控制研究

文中介绍了基于高频注入法的无位置传感器控制实现了永磁同步电机初始位置的估计,控制系统采用了先进的控制策略:矢量控制策略和SVPWM(电压空间矢量脉宽调制技术),基于MATLAB/SIMULINK搭建了仿真模型,结果证明了基于高频注入法实现永磁同步电机无位置传感器控制系统算法上的有效性。     

A sensorless optimal control system for an automotive electric power assist steering system

This paper considers the analysis and design of a double-pinion-type electric power assist steering (EPAS) control system. A simplified model of the augmented steering assembly-electric motor system is developed using Lagrangian dynamics, and an optimal controller structure for the model is proposed. Three main advances to the state of the art are presented in this paper. First, a state-space design model is used rather than an input-output model. A state-space formulation for a system model that incorporates motor electrical dynamics is obtained with the assist motor angular position as the output. Second, linear quadratic regulator (LQR) and Kalman filter techniques are employed to arrive at an optimal controller for the EPAS system. The selection of weighting coefficients for the LQR cost function is discussed. Finally, the authors present a control strategy that eliminates the steering column torque sensor, a critical component in existing EPAS controller designs. The proposed control strategy presents an opportunity to improve EPAS system performance and also reduce system cost and complexity.     

Overmodulation strategy for high-performance torque control

In the overmodulation region, the operation of the electrical drive system with a current controller is characterized by a rapid deterioration of motor torque and speed. It is desirable to use the overmodulation strategy, which guarantees the fast response even in transient state and satisfies the overall closed-loop control performance. In this paper, in order to improve the dynamic characteristics of the electrical drive, a new overmodulation technique is proposed. Considering the current transition characteristics, an efficient overmodulation strategy is introduced to achieve better transient performance through an adequate voltage selection. With the help of a new overmodulation strategy, required electrical torque can be directly produced as quickly as possible, and stable drive characteristics can be achieved in the transient condition. The proposed method has been implemented on an actual inverter system and thoroughly tested on a 900-W interior permanent magnet synchronous machine (IPMSM) to confirm its feasibility     

A position-and-velocity sensorless control for brushless DC motorsusing an adaptive sliding mode observer

The sliding mode observer is robust to measurement noises. Since the switching signals of the sliding mode observer contain the induced voltages of the motors, it is possible to obtain the position and velocity of the motors directly from the switching signals. Although the estimated position can be used for locating the position of the rotor, the estimated velocity is heavily contaminated by noises from the switching signals. This direct method nullifies the merit of the sliding mode observer. Thus, the authors also present an adaptive scheme for robust estimation of the velocity of brushless DC motors. Stability of the adaptive scheme is assured, and estimation errors due to parameter deviations are analyzed. A method of parameter adjustment is described     

A novel voltage sensorless control technique for a bidirectional AC/DC converter

A novel voltage sensorless control technique for a bidirectional AC/DC converter is presented. Only a single current sensor that measures the inductor current is needed in the whole system. The sensed inductor current is used for two functions. The first one is for shaping the current waveform at the AC side and the second one is for deriving the inductor voltage by determining the rate of change of the inductor current. The AC-side and DC-side voltages, which are used for AC current synchronization and DC voltage regulation, respectively, are obtained by extracting the envelopes of the derived inductor voltage. Apart from reducing the number of sensing elements, the proposed method has additional advantages of: (1) inherent electrical isolation and reducing noise coupling between the power circuit and the controller; (2) wide operating range. Design criteria for the differentiator and the envelope detector circuit has been described. The applicability of the proposed method is verified with the experimental results of a laboratory prototype.     

Torque sensorless control in multidegree-of-freedom manipulator

A torque sensorless control for a multi-degree-of-freedom manipulator is described. In the method, two disturbance observers are applied to each joint. One is used to realize a robust motion controller. The other is used to obtain a sensorless torque controller. A robust acceleration controller based on the disturbance observer is shown. To obtain the sensorless torque control, it is necessary to calculate the reaction torque when the mechanical system performs a force task. The calculation method for the reaction torque is explained. Then the method is expanded to workspace force control in the multi-degree-of-freedom manipulator. Several experimental results are shown to confirm the validity of the proposed sensorless force controller     

Low-speed sensorless control of induction Machine

Induction motor (IM) speed sensorless control, allowing operation at low and zero speed, optimizing torque response and efficiency, will be presented in this paper. The magnitude and the orientation angle of the rotor flux of the IM are determined by the output of the closed-loop rotor-flux observer based on the calculation of the extended electromotive force of the machine. The proposed rotor-flux-oriented control scheme is robust to parameter variations and external disturbances. Both observer and controller utilize the continuous sliding mode and Lyapunov theory. A smooth transition into the field-weakening region and the full utilization of the inverter current and voltage capability are thus possible. The produced torque is a continuous output variable of control. The performance of the proposed method is investigated and verified experimentally on a digital signal processor.     

双向驱动的柔顺结构微动平台的设计与测试

针对微纳操控技术对微动平台提出的大行程、高精度、多自由度和输出位移解耦等要求,设计了一种基于两级放大机构的xy两自由度双向驱动微动平台。分析了微动平台的运动及放大原理,建立了微动平台结构的理论模型和有限元模型,并对其进行了测试。平台输出特性测试结果表明,微动平台的放大倍数可达8.5倍,与仿真值误差为6.9%,同时耦合位移控制在0.82%内;平台在150 V三角波信号驱动下,x方向上正、负向输出位移分别为84.6μm、-84.2μm;y方向上正、负向输出位移分别为85.0μm、-84.5μm。不同频率下的最大位移只在极小范围内波动,在x、y方向的正、负向输出具有很高的相似性和稳定性,实现了双向驱动,大行程、高精度的目的。     

A sensorless vector control system for induction motors usingq-axis flux with stator resistance identification

This paper presents a sensorless vector control system for general-purpose induction motors, which is based on the observer theory and the adaptive control theories. The proposed system includes a rotor speed estimator using a q-axis flux and stator resistance identifier using the d-axis flux. The advantages of the proposed system are simplicity and avoidance of problems caused by using only a voltage model. Since the mathematical model of this system is constructed in a synchronously rotating reference frame, a linear model is easily derived for analyzing the system stability, including the influence of the observer gain, motor operating state, and parameter variations. In order to obtain stable low-speed operation and speed control accuracy, an algorithm for compensating for the deadtime of the inverter and correcting the nonideal features of an insulated gate bipolar transistor was developed. The effectiveness of the proposed system has been verified by digital simulation and experimentation     

Field-programmable analogue arrays for the sensorless control of DC motors

This work presents the analogue implementation of a sensorless controller for direct current motors based on the super-twisting (ST) sliding mode technique, by means of field programmable analogue arrays (FPAA). The novelty of this work is twofold, first is the use of the ST algorithm in a sensorless scheme for DC motors, and the implementation method of this type of sliding mode controllers in FPAAs. The ST algorithm reduces the chattering problem produced with the deliberate use of the sign function in classical sliding mode approaches. On the other hand, the advantages of the implementation method over a digital one are that the controller is not digitally approximated, the controller gains are not fine tuned and the implementation does not require the use of analogue-to-digital and digital-to-analogue converter circuits. In addition to this, the FPAA is a reconfigurable, lower cost and power consumption technology. Simulation and experimentation results were registered, where a more accurate transient response and lower power consumption were obtained by the proposed implementation method when compared to a digital implementation. Also, a more accurate performance by the DC motor is obtained with proposed sensorless ST technique when compared with a classical sliding mode approach.     

A new torque and flux control method for switched reluctance motordrives

Switched reluctance (SR) motors have an intrinsic simplicity and low cost that make them well suited to many applications. However the motor's doubly salient structure and highly nonuniform torque and magnetization characteristics lead to the inability to excite the motor using conventional AC motor waveforms, or apply established AC motor rotating field theory to the motor. Furthermore, high torque ripple is inherent in the motor unless a torque ripple reduction strategy is employed. Thus, control of the motor is difficult and complex compared to other machines. Previous methods of control have fallen into two main categories: those which use a simplified linear model and those which account for the motor saturation. The simplified linear model schemes have the advantage of simplicity and tractability but are inaccurate in most practical SR drives, whereas the nonlinear schemes have the problem of high complexity and computational expensiveness which makes real-time implementation difficult. To overcome these problems, in this paper, a novel control method for the SR motor is derived from analysis of the nonuniform torque characteristics of the motor. The control method applies the philosophy of direct torque control (DTC). Unlike previous direct torque control schemes for the SR motor drive, the new method does not involve short flux patterns, a change of the motor winding configuration, or the use of a bipolar current drive. Thus, the scheme can be conveniently implemented on any normal type of SR motor drive. In addition, the scheme overcomes the problems associated with torque ripple control in the SR motor by regulating the torque output of the motor within a hysteresis band. Furthermore, the scheme is very simple and can be implemented in real-time with low cost microprocessor hardware     

Current-mode control for sensorless BDCM drive with intelligent commutation tuning

The winding current response speed and the adequate commutation significantly affect the control performance of a sensorless brushless dc motor (BDCM) drive. In this paper, the studies about these two issues to enhance the performance of BDCM drive are made. First, the sensorless inverter-fed BDCM drive with a proposed current command generation scheme is established. An intelligent commutation instant tuning technique is developed to pursue better motor torque generating characteristics. For achieving this goal, the motor drawn line current minimization is employed as the performance index in making the commutation tuning. After generating the current command with adequate commutation, a robust current-mode controller is further developed and applied to greatly speed up the square wave current tracking response and the response is rather insensitive to the machine parameter and back electromotive force (back-EMF) changes. In Addition, a simple starting method and a speed estimation approach are also proposed. Some experimental results are provided to demonstrate the validity of the proposed control method.