Discrete-time LQG/LTR design and modeling of a disk drive actuatortracking servo system

This paper presents the discrete-time LQG/LTR design of a disk drive track following servo system. The servo compensator designed through linear-quadratic Gaussian control combined with loop transfer recovery (LQG/LTR) consists of a Kalman filter for state estimation and state feedback for control. The desired tracking servo performance is first formulated through a frequency shaped return ratio of the Kalman filter and subsequently recovered at the output of the plant/compensator loop through the automatic design of a discrete-time linear quadratic (LQ) regulator. Particular attention has been given to modeling the calculation time delay and bias force estimation. The excellent robustness and performance characteristics of a continuous time LQG/LTR design are theoretically unachievable due to the extremely low sampling rate and nonminimum phase plant characteristics. However, both time and frequency domain simulations show that reasonable stability margins and performance can still be recovered. This technique nearly eliminates all the trial and error typical of a conventional pole placement design of a similar system. The direct discrete-time design can handle extremely low sampling rates associated with embedded servo systems. The technique can also be used for designing multi-rate and multi-input servo systems     

Variable slope pulse pump controller for stepping position servocontrol system using frequency-locked technique

A stepping position servomotor system based on frequency-locked technique is proposed for high-performance incremental position control. A novel microcomputer-based variable slope pulse pump controller (VSPPC) using multi-rate sampling technique is exploited. The proposed VSPPC can adaptively generate motor motion profile, and it can replace the traditional PID controller for applications in stepping motor position control. System models are constructed for stability study and computer simulation. A prototype is designed and implemented to verify the theoretical studies and examine the performance of the proposed system. Position and speed responses of a realized system for 0-50 cm movement with 10 mm resolution is investigated. With the variable slope technique employed in VSPPC, the acquisition time for long-distance movement is reduced significantly and is close to that of short-range movement. In particular, the position acquisition time has improved about 67-79% compared to the conventional position control system     

Linear quadratic Gaussian control of 2-dimensional systems

The linear quadratic Gaussian (LQG) control for one-dimensional (1D) systems has been known to be one of the fundamental and significant methods in linear system theory. However, the LQG control problem for two-dimensional (2D) systems has not been satisfactorily solved due to their structural and dynamical complexity. In this paper, sufficient conditions for evaluation of the quadratic performance indices of 2D systems in terms of the system state and control variables are proposed. Using these conditions, systematic design methods for finite horizon and infinite horizon LQG controls of 2D systems are developed using a convex optimization method.     

Fuzzy adaptive vector control of induction motor drives

This paper deals with the design and experimental realization of a model reference adaptive control (MRAC) system for the speed control of indirect field-oriented (IFO) induction motor drives based on using fuzzy laws for the adaptive process and a neuro-fuzzy procedure to optimize the fuzzy rules. Variation of the rotor time constant is also accounted for by performing a fuzzy fusion of three simple compensation strategies. A performance comparison between the new controller and a conventional MRAC control scheme is carried out by extensive simulations confirming the superiority of the proposed fuzzy adaptive regulator. A prototype based on an induction motor drive has been assembled and used to practically verify the features of the proposed control strategy     

Using Stabilizer Dynamic Pre-Compensator to Design Robust Controllers for an Unstable MIMO System

This paper addresses the problem of designing LQG/LTR controllers for unstable multivariable systems. Its main proposal is to design a stabilizer dynamic pre-compensator to stabilize the system before designing the final LQG/LTR controller. This approach overcomes the problems that the This paper addresses the problem of designing LQG/LTR controllers for unstable multivariable systems. Its main proposal is to design a stabilizer dynamic pre-compensator to stabilize the system before designing the final LQG/LTR controller. This approach overcomes the problems that the original procedure can not avoid when it deals with unstable systems, but the order of the overall controller gets increased.     

A discrete model of induction motors for real-time controlapplications

The real-time digital control of induction motors and AC servomotor drives often involves estimation, identification, and adaptive control algorithms. An efficient and numerically stable discrete model of the induction motor is required to implement these algorithms in real time. A predictor-corrector discrete model of induction motors is developed here for real-time model is analyzed by a discrete root locus technique. The digital simulation of the model is presented and compared with a rigorous solution, and satisfactory results are obtained     

Neural-network-based adaptive control for induction servomotordrive system

A neural-network-based adaptive control (NNAC) design method is proposed to control an induction servomotor. In this NNAC design, a neural network (NN) controller is investigated to mimic a feedback linearization control law; and a compensation controller is designed to compensate for the approximation error between the feedback linearization control law and the NN controller. The interconnection weights of the NN can be online tuned in the sense of the Lyapunov stability theorem; thus, the stability of the control system can be guaranteed. Additionally, in this NNAC system design, an error estimation mechanism is investigated to estimate the bound of approximation error so that the chattering phenomenon of the control effort can be reduced. Simulation and experimental results show that the proposed NNAC servomotor control systems can achieve favorable tracking and robust performance with regard to parameter variations and external load disturbances     

Adaptive decoupling control of induction motor drives

A novel control approach for a robust induction motor drive system with a voltage source inverter has been developed. In the scheme, the induction motor and its corresponding inverter gating signal are controlled using the decoupling control theory. In addition, an adaptive optimal speed regulator employing the model reference adaptive control (MRAC) is incorporated into the drive system to compensate for unfavorable errors. The principles and special features of the control scheme are discussed, and the configuration of the drive system is presented. Comparison is made between conventional proportional plus integral (PI) control and the MRAC. Test results show the robustness and superior dynamic performance of the proposed control system     

异步电机矢量控制系统的仿真建模与实现

异步电机矢量控制是在交流电机的双轴理论、机电能量转换和坐标变换理论的基础上发展起来的。为了实现对异步电动机磁场和转矩的解耦控制的目的;采用交流电机的磁场定向控制(即矢量控制)的方法;建立了一种在转子坐标系下异步电机的矢量控制系统仿真模型;仿真结果表明,基于矢量控制的方法能够实现对异步电机的解耦,即通过控制励磁电流分量和转矩电流分量的大小直接控制异步电机磁场和转矩,使交流异步电机获得和直流电机相媲美的控制性能。     

Design, modeling and control of a hybrid machine system

A hybrid machine is such a machine where its drive system integrates two types of motors: the servomotor and the constant velocity (CV) motor. The existing research on the hybrid machine prototypes usually uses two servomotors, of which one “mimic” the CV motor by prescribing a constant velocity trajectory profile. It is obvious that this departs away from the real situation where a CV motor is in place. The CV motor will bring in the velocity fluctuation which can not be attenuated by the CV motor itself due to the lack of a control mechanism in the CV motor, yet be propagated to the servomotor, and further to the end-effector of the machine. The general strategy for controlling the hybrid machine is therefore to model this propagated fluctuation and incorporate it into a controller for the servomotor. A controller based on the sliding mode control technique is proposed for the hybrid machine in this paper. The stability analysis shows that the controller is asymptotically stable. Simulation with a preliminary test demonstrates the effectiveness and robustness of this controller. Finally, we examine further performance improvement through attaching a flywheel on the CV motor to demonstrate the effectiveness of the synergy of the integration of mechanical and electrical means.     

A simple direct-torque neuro-fuzzy control of PWM-inverter-fedinduction motor drive

In this paper, the concept and implementation of a new simple direct-torque neuro-fuzzy control (DTNFC) scheme for pulsewidth-modulation-inverter-fed induction motor drive are presented. An adaptive neuro-fuzzy inference system is applied to achieve high-performance decoupled flux and torque control. The theoretical principle and tuning procedure of this method are discussed. A 3 kW induction motor experimental system with digital signal processor TMS 320C31-based controller has been built to verify this approach. The simulation and laboratory experimental results, which illustrate the performance of the proposed scheme, are presented. Also, nomograms for controller design are given. It has been shown that the simple DTNFC is characterized by very fast torque and flux response, very-low-speed operation, and simple tuning capability     

深空站大天线抗风扰LQG最优控制器设计

针对深空大天线阵风扰动引起天线指向不准、接收信号抖动等问题,提出了基于最优控制策略的天线抗风扰LQG控制器设计方案。从控制对象建模、线性二次型最优控制和卡尔曼最优估计等方面详尽阐述了LQG最优控制器设计。借鉴国外DSN(深空网)相关工程经验与MATLAB工具对LQG控制器性能做了仿真分析。对LQG工程设计值得注意的问题进行了简要说明,目的旨在分析与解决相关工程技术问题,提高天线指向控制精度。     

Control design of a novel compliant actuator for rehabilitation robots

Rehabilitation robots have direct physical interaction with human body. Ideally, actuators for rehabilitation robots should be compliant, force controllable, and back drivable due to safety and control considerations. Series Elastic Actuators (SEA) offers many advantages for these applications and various designs have been developed. However, current SEA designs face a common performance limitation due to the compromise on the spring stiffness selection. This paper presents a novel compact compliant force control actuator design for portable rehabilitation robots to overcome the performance limitations of current SEAs. Our design consists of a servomotor, a ball screw, a torsional spring between the motor and the ball screw, and a set of translational springs between the ball screw nut and the external load. The soft translational springs are used to handle the low force operation, while the torsional spring with high effective stiffness is used to deal with the large force operation. It is a challenging task to design the controller for such a novel design as the control system needs to handle both the force ranges. In this paper, we develop the force control strategy for this actuator. First, two dynamical models of the actuator are established based on different force ranges. Second, we propose an optimal control with friction compensation and disturbance rejection which is enhanced by a feedforward control for the low force range. The proposed optimal control with feedforward term is also extended to the high force range. Third, a switching control strategy is proposed to handle a transition between low force and high force control. The mathematical proof is given to ensure the stability of the closed-loop system under the proposed switching control. Finally, the proposed method is validated with experimental results on a prototype of the actuator system and is also verified with an ankle robot in walking experiments.     

异步电机的无速度传感器控制系统

根据空间矢量脉宽调制技术和无速度传感器矢量控制原理,提出了电压与电流互补模型的磁链估计,能在全速度范围内得到较好的磁通及转速估计。采用TMS320F2812实现了异步电机无速度传感器矢量控制系统,给出了硬件和软件设计方案。实验表明系统动态性能强,稳定性好,具有很好的应用前景。     

基于模糊控制的定子电阻辨识研究

定子电阻的变化对异步电机矢量控制系统的性能具有重要的影响,准确获取定子电阻值在高性能电机控制系统中具有十分重要的意义。本文基于模糊控制理论,设计了一种结构简单的模糊定子电阻辨识器。在此基础上,根据矢量控制理论,采用Matlab/Simulink软件设计了异步电机矢量控制系统。仿真结果表明,辨识的定子电阻误差较小,系统响...     

Variable structure current control for induction motor drives byspace voltage vector PWM

In this paper, a variable structure current controller based on a space voltage vector PWM scheme is presented for induction motor drives. In this current controller design, only the current sensors are employed and we attempt to force the stator currents to be exactly equal to the reference currents rapidly. This proposed current controller, which is based on the space voltage vector PWM drive, exhibits several advantages in terms of reduced switching frequency, robustness to parameter variations, elimination of current/torque ripple, and improved performance in induction motor drive. It shows that the current control laws can be demonstrated in theory. Finally, simulation and experimentation results verify the proposed control scheme     

基于全阶观测器的异步电动机矢量控制系统

磁链观测一直是异步电机无速度矢量控制的难点,本文以异步电动机本身为参考模型,设计了全阶观测器的可调模型来估算异步电机的磁链和速度。利用Matlab软件构造了按转子磁场定向的矢量控制系统的仿真模型,采用全阶观测器的方法在逆变器仿真平台和实验平台上实现了异步机的无速度矢量控制。通过仿真和试验验证了模型的正确性,结果表明所建立的调速系统具有良好的动态性能。     

A new scheme for speed-sensorless control of induction motor

Various control algorithms have been proposed for the speed-sensorless control of an induction motor. These sensorless algorithms are mainly based on the speed feedback with the flux and speed estimations. This paper proposes a new scheme for the speed-sensorless control of an induction motor. The proposed scheme is based on the current estimation without the flux and speed estimations, in which the controlled stator voltage is applied to the induction motor so that the difference between stator currents of the mathematical model and motor may be forced to decay to zero. The performance of the proposed scheme is verified through simulation and experiment.     

Stator flux controlled V/f PWM inverter withidentification of IM parameters [induction motors]

A V/f PWM inverter control algorithm based on controlling the stator flux vector of an induction motor is presented. The algorithm permits an automatic boost of inverter voltage in such a way that the stator flux magnitude is kept constant. The voltage autoboost method is based on knowledge of the IM equivalent circuit parameters and given load characteristics. An offline auto measurement of the equivalent circuit parameters using a PWM inverter is described. The technique consists of performing the no-load and single-phase tests when the motor is connected to the inverter. The complete control system has been constructed and tested and the experimental results have been found satisfactory. The proposed method has achieved a considerable improvement of IM torque-speed characteristics under optimal slip frequency operation     

Design of a general purpose 6-DOF haptic interface

A general purpose six degree-of-freedom haptic device is newly designed, which can be used as a general motion commander as well as a force reflector. The structure features the large workspace and easy analysis of a serial structure and the compactness and durability of a parallel structure at the same time. The study analyzed kinematics of the proposed device to obtain the optimal device parameters in terms of kinematics and derived dynamics to form a linear control system through the feedback. In calculating the optimal design factors of the haptic device in terms of kinematics, this study employed the global isotropy index. The proposed structure has high manipulability within the workspace, which is an essential factor for a motion generator. Also the study proposed a force controller featuring an inner nonlinear loop designed to compensate the nonlinear dynamics of the device and an outer linear control loop aimed to compensate un-modeled dynamics and disturbance. For an outer linear controller, the study adopted an LQG/LTR controller that can systematically take into account stability, robustness and frequency characteristics in the design process. The performance of the proposed device was verified with its efficiency through simulation and experiments.