A speed-sensorless IM drive with decoupling control and stabilityanalysis of speed estimation

A new sensorless drive based on a decoupling control and an adaptive full-order observer is developed. A modified decoupling control is introduced and integrated with the adaptive observer to reduce the complexity of the whole system. The speed estimation based on adaptive control theory is analyzed and the necessary and sufficient conditions for stability of the speed estimation are analytically derived. It is indicated that the system can be unstable in the low-speed region with regenerative loads. However, assigning an appropriate feedback gain to the adaptive observer can restore the stability and reduce the unstable region. Sensitivity of the sensorless drive against parameter and measurement errors is also qualitatively discussed. Simulation and experimental results are then given to verify the validity of the theoretical results     

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.     

Adaptive pseudoreduced-order flux observer for speed sensorlessfield-oriented control of IM

An adaptive pseudoreduced-order flux observer for speed sensorless field-oriented control is presented. In comparison with the adaptive full-order flux observer, the proposed method consumes less computational time and illustrates better speed performance. Simulations and experiments on a 3-hp induction motor verify the validity of the proposed method     

Suppression control method for torque vibration of three-phase HB-type stepping motor utilizing feedforward control

This paper proposes a method to reduce the vibration of the three-phase HB-type stepping motor with cogging torque by the feedforward compensation control. The compensation signal to suppress the vibration of the motor frame is obtained by the repetitive controller installing an online Fourier transformer and utilizing an acceleration sensor attached to the motor frame or an acoustic sensor such as a microphone placed close to the frame. The sensor is used only for the acquisition of the feedforward compensation data. The feedforward compensation signal at an arbitrary operating point is derived from the amplitude and phase data of the frequency components and the operating point data. Compensation data obtained by the repetitive controller is applied to the operating point changed by reference frequency and load condition in steady state. The compensation signal for the new operating point will be generated from compensation data utilizing polynomial equation approximation and linear interpolation method. The effectiveness of this proposed method is confirmed by the experimental results.     

Robust speed control algorithm with disturbance observer for uncertain PMSM

This article suggests a robust cascade speed control algorithm for a permanent magnet synchronous motor (PMSM) combining the classical feedback linearising (FL) method and the disturbance observers (DOBs) without the integrators. The contributions of this method are twofold. The first one is to provide the simple DOBs for not only guaranteeing the closed-loop performance recovery property but also removing the steady-state errors without the integrators with respect to the tracking errors. The second one is to prove that the inner and outer loops are stabilised by the proposed cascade-type controller, simultaneously. The simulation and experimental results reveal that the proposed method maintains the speed tracking performance to be satisfactory for a wide operating region with the fixed control gain despite a plant-model mismatch where a 3-kW interior PMSM is utilised.     

Reference feedforward in the idle speed control of a direct-injection spark-ignition engine

The direct-injection spark-ignition engine has emerged as a focus of research in improving fuel economy and controlling emissions. This engine can operate in multiple modes, including a stratified charge mode with an air-fuel ratio as large as 50:1. Operating in stratified mode results in improved fuel economy and reduced CO/sub 2/ emissions. The stratified charge mode is employed during low speed and load conditions, such as during engine idle. The idle speed control problem is cast as a two-input-two-output control problem and a baseline feedback controller is developed based on an existing topology from the literature. Significant delays, however, inhibit our ability to improve the transient response via feedback alone. An improved scheme employing reference feedforward is proposed and several potential topologies are presented. A reference feedforward algorithm is derived and nonlinear simulation results are shown in which the system transient responses are improved considerably.     

无刷直流电机调速系统转矩脉动抑制方法研究

通过对无刷直流电机开通期间的相电流和关断期间的相电流分析,经过实际计算得到电磁转矩的表达式,得到相应的电磁转矩脉动曲线。基于电流预测方法通过将预测模型分为模型建立、反馈调整和性能优化3步,通过控制换相电流保持在稳定的状态,从而实现对转矩脉动的抑制。通过仿真和实际实验表明,该无刷直流电机调速系统在实际运行中具有转矩脉动小、响应速度快等优点。     

基于神经网络的可调模型直接转矩控制速度辩识

在传统的模型参考自适应(MRAS)速度辨识模型的基础上,用神经网络理论对其可调模型进行了改进。并在无速度传感器直接转矩控制系统中对该速度辨识模型进行了研究,仿真结果验证了该速度辨识模型具有满意的辨识精度和动态性能。     

Novel switching techniques for reducing the speed ripple of AC drives with direct torque control

The main theme of this paper is to present novel switching techniques, which insert zero-voltage vectors and/or more nonzero-voltage vectors to the conventional switching table, for AC drives with direct torque control. For the same sampling frequency of a drive controller, the proposed techniques are quite effective in reducing the torque pulsation and the speed ripples of the motors, as demonstrated in several experimental results. Moreover, the experimental confirmations have been made not only on an induction machine but also on a permanent-magnet synchronous machine.     

Nonlinear adaptive speed and torque control of induction motorswith unknown rotor resistance

In this paper, we propose a nonlinear adaptive speed and torque controller of induction motors with unknown rotor resistance. All the system parameters except rotor resistance are assumed to be known, and only the stator currents and rotor speed are assumed to be available. The desired speed and torque should be a smooth bounded function. A complete proof of the global stability without singularity is given, and the output error will converge to zero asymptotically. Finally, the simulation and experimental results are given to demonstrate the effectiveness of the proposed controller     

A torque and speed coupling hybrid drivetrain-architecture, control, and simulation

In this paper, a speed and torque coupling hybrid drivetrain is introduced. In this drivetrain, a planetary gear unit and a generator/motor decouple the engine speed from the vehicle wheel speed. Also, another shaft-fixed gear unit and traction motor decouple the engine torque from the vehicle wheel torque. Thus, the engine can operate within its optimal speed and torque region, and at the same time, can directly deliver its torque to the driven wheels. This paper discussed the fundamentals architecture, design, control, and simulation of the drivetrain.     

An MRAC-based nonlinear speed control of an interior PM synchronous motor with improved maximum torque operation

A model reference adaptive control (MRAC)-based nonlinear speed control strategy of an interior permanent magnet (IPM) synchronous motor with an improved maximum torque operation is presented. In most servo systems, the controller is designed under the assumption that the electrical dynamics are neglected by the field-oriented control. This requires a high-performance inner-loop current control strategy. However, the separate designs for a high-performance current regulator and a robust speed controller need considerable effort. To overcome this limitation, an MRAC-based nonlinear speed control strategy for the IPM synchronous motor is presented, considering the whole nonlinear dynamics. Nonlinear speed control is achieved by an input–output linearization scheme. This scheme, however, gives an unsatisfactory performance under the mismatch of the system parameters and load conditions. For the robust output response, the controller parameters are estimated by an MRAC technique in which the disturbance torque and flux linkage are estimated. The adaptation laws are derived from Lyapunov stability theory. In view of the drive efficiency, the motor has to provide the maximum torque for a given input. To drive the IPM synchronous motor under improved maximum torque operation, the estimated flux linkage is employed for the generation of the d-axis current command. The robustness and output performance of the proposed control scheme are verified through simulation results.     

Robust speed control of DC servomotors using modern twodegrees-of-freedom controller design

The authors propose a robust speed control system for DC servomotors based on the parametrization of two-degree-of-freedom controllers. The servosystems can dramatically improve the characteristics of the closed loop systems, i.e. the disturbance torque suppression performance and the robustness to system parameter variations, without changing the command input response. The excellent control performances obtained during laboratory experiments by using a microprocessor-based controller are shown     

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     

Robust torque optimization for BLDC spindle motors

A robust design for torque optimization of brushless DC spindle motors applied in a hard disk drive, using the Taguchi method, is described and illustrated in this paper. The optimal design process takes into consideration noises that arise in the manufacturing process, such as manufacturing tolerances for the stator tooth shape and variation of the rotor magnet magnetization distribution due to the magnetization fixture and process. The objective of the optimal design using the combined Taguchi's design of experiment (DOE) and finite-element analysis (FEA) approach is to ensure that the spindle motor torque performance is insensitive to the noise, with moderate computational effort. The optimization is realized by a simulation and analysis tool that integrates Taguchi's DOE with the FEA. In this paper, the design optimization process is described and the results are presented     

Cascomp feedforward error correction in high speed amplifier design

The authors discuss practical implications of cascomp feedforward error correction in high-performance transconductance amplifier design and a method of extending cascomp's thermal distortion cancellation to include overdriven or common-mode inputs. The authors also briefly describe a new low-power highly integrated vertical deflection system IC using the improved cascomp that approaches the gain accuracy and thermal distortion of highly degenerated feedback designs while retaining the good overdrive recovery and speed of simple cascode differential pairs.     

Moving-window spectral neural-network feedforward process control

Unlike reactive feedback control, feedforward control is a proactive method by which information about a measurable disturbance is fed, ahead of time, to the manipulated inputs of a process, the output of which is to be controlled, so as to counteract the effect of the disturbance. Discretized observations on the process variable are indexed to form a time series. A time-series model is fitted to the series. The ultrahigh signal-to-noise ratio fitted values are examined by a neural network, for patterns which detect when the future process is expected to become out of control. The neural-network diagnosis forms the basis for corrective action, prior to the process becoming out of control. In principle, this goes beyond SPC to achieve a process which is never actually out of control     

Direct torque control of induction machines with constant switching frequency and reduced torque ripple

Direct torque control (DTC) of induction machines is known to have a simple control structure with comparable performance to that of the field-oriented control technique. Two major problems that are usually associated with DTC drives are: switching frequency that varies with operating conditions and high torque ripple. To solve these problems, and at the same time retain the simple control structure of DTC, a constant switching frequency torque controller is proposed to replace the conventional hysteresis-based controller. In this paper, the modeling, averaging, and linearization of the torque loop containing the proposed controller followed by simulation and experimental results are presented. The proposed controller is shown to be capable of reducing the torque ripple and maintaining a constant switching frequency.     

复数前馈神经网络的全局最优和快速学习算法

提出了一种新型复数前馈神经网络的学习算法。当输入层和隐层之间的权值计算出来后，就可以通过求解线性方程组得到隐层和输出层之间的权值。这些权值是全局最小点。另一方面，本文算法很容易确定全局最小点时隐层神经元的个数。本文算法具有很高的训练精度和学习速度。     

Robust speed control system considering vibration suppressioncaused by angular transmission error of planetary gear

This paper proposes a new robust speed control to suppress vibration caused by angular transmission error of planetary gears. For this purpose, this paper first constructs a new numerical simulation model of angular transmission error of planetary gear, which is confirmed by experimental data from a robot arm. Next, in order to suppress the vibration caused by angular transmission error, we propose a robust speed control system based on disturbance observer and coprime factorization. Numerical simulation results show that the proposed system regulates the angular speed of motor satisfactorily, and it suppresses the vibration caused by angular transmission error