C.M. Liaw

Design of a two-degree-of-freedom controller for motor drives

A two-degree-of-freedom controller for motor drives with a first-order model is proposed. The parameters of the controller are designed using a systematic procedure to match the prescribed motor drive specifications. Very good rotor speed dynamic responses of both the command tracking and load regulation characteristics can be achieved. A theoretic basis for the design procedure is derived in detail. Simulated and experimental results are given to demonstrate the effectiveness of the controller. >

Fuzzy Control with Reference Model-Following Response

Publisher Summary This chapter discusses a hybrid controller combining the advantages of model-following controllers and fuzzy controllers. In this hybrid controller, an output linear model-following controller is first designed according to the roughly estimated plant model at nominal operating point and the chosen reference model. Then an adaptation signal is yielded by a fuzzy controller, which is driven by the model-following error and its change. The description of the systematic design of a conventional fuzzy controller and its major problems is given. Then a fuzzy model-following controller (FMFC) combining the advantages of a model-following controller and a fuzzy controller is introduced. In the design of this hybrid controller a reference model is selected and a linear model-following controller (LMFC) is designed based on the roughly estimated plant model at the nominal operating point. The proposed fuzzy model-following controller applied to the speed control of an indirect field-oriented induction motor drive is illustrated. Dynamic signal analysis of the model following behavior is made; accordingly, the procedure for constructing the control algorithms is introduced in detail. Some simulation and measured results are provided to demonstrate the performance of the motor drive controlled by the fuzzy model-following controller.

A discrete adaptive induction position servo drive

A discrete adaptive induction position servo is designed and implemented. In the proposed servo system, the dynamic model of the indirect field-oriented induction motor is estimated from measurements using the stochastic approach. Based on this model, a PI speed controller and a P position controller are designed using pole-placement and root-locus techniques. In order to reduce the effects of machine and load parameter variations on the performance of the indirect field-oriented induction motor servo drive, an adaptive controller is augmented in which a reduced reference model, which defines the desired following control performance, is chosen and the adaptive control signal is synthesized. The proposed adaptive controller has the advantages of being easy to design and implement. Simulation and experimental results show that good following and regulating control performances are achieved. Moreover, the performances are rather insensitive to parameter variations. >

Mixed method of model reduction for linear multivariable systems

A mixed method of model reduction for linear multivariable systems is proposed. The least common denominator of the elements in the reduced transfer matrix model is constructed by preserving the dynamic modes with dominant energy contributions, and the parameters of the numerators are found using the continued-fraction method. In addition, a reduced model with state-space form, having the same order as those of the reduced transfer matrix, is also found. The reduced model is always stable if the original system is stable. Moreover, the reduced model gives rather good approximations in both the transient and steady-slate responses of the original system.

A robust induction motor servo drive

A position controller, considering the effects of system dead-time and parameter variations, for induction motor servo drives is proposed in this paper. First a DSP-based computer controller indirect field-oriented induction motor servo drive is implemented and its dynamic model at the nominal case is estimated from measurements. Based on this model, an integral plus proportional (IP) controller is quantitatively designed to match the prescribed position tracking specifications. Then a dead-time compensator (DTC) and a simple robust controller (RC) are designed and augmented to reduce the effects of system dead-time on the stability and the performance degradation due to parameter variations. The prescribed drive tracking specifications can be preserved under parameter variations. Rather good load regulating response can also be obtained. Some experimental results are provided to demonstrate the effectiveness of the proposed controllers.<<ETX>>

Position Control of a LBDCM Drive

In this paper, the dynamic model estimation and quantitative position control of a linear brushless DC motor (LBDCM) drive are studied. First, the inverter-fed LBDCM drive is established and its dynamic model is estimated from measurements. Then, according to the estimated model at nominal case, a two-degree-of-freedom controller (2DOFC) is designed to meet the prescribed tracking and load regulation position control responses. As the system parameter and operating condition changes occur, an output feedback linear model following controller (MFC) is added to reduce the effects of perturbations, and hence the performance degradation can be reduced. Finally, a ramp position command with suitable changing rate is generated to avoid the occurrence of velocity limitation, and thus the overshoot of position response due to large-step command change can be eliminated.In this paper, the dynamic model estimation and quantitative position control of a linear brushless DC motor (LBDCM) drive are studied. First, the inverter-fed LBDCM drive is established and its dynamic model is estimated from measurements. Then, according to the estimated model at nominal case, a two-degree-of-freedom controller (2DOFC) is designed to meet the prescribed tracking and load regulation position control responses. As the system parameter and operating condition changes occur, an output feedback linear model following controller (MFC) is added to reduce the effects of perturbations, and hence the performance degradation can be reduced. Finally, a ramp position command with suitable changing rate is generated to avoid the occurrence of velocity limitation, and thus the overshoot of position response due to large-step command change can be eliminated.

Robust control of current-mode controlled converters

A robust controller for multimodule current-mode push-pull power converters is presented. First, the small-signal equivalent circuit and transfer function model of the converter system are found. Then the slope compensation is selected and model reduction is performed using the concept of dominant energy mode. Based on the reduced converter models, a PI (proportional-integral) controller is quantitatively and systematically designed to the prescribed specifications. A robust controller is proposed and augmented to improve the control performance when parameter variations caused by system configuration change and by operating point shift occur. The performance of the converter and the effectiveness of the proposed controller are demonstrated by simulated and experimental results.<<ETX>>

System simplification using variable structure reduced models

A practical method of model reduction for linear systems is proposed. To minimize the order of the reduced plant model and to achieve a very good approximation of the original system, the reduced model of the original system is constructed from two submodels. One model emphasizes the transient behaviour, and the other gives a very good steady-state approximation. The submodels are estimated using the techniques of frequency response matching and dominant energy modes analysis. The main features of the proposed method are that the order of the reduced model can be minimized and the reduced model can give good approximations in both the transient and steady-state responses of the original system. Moreover, applications of the proposed reduced model to control system design can lead to good performances in the transient and steady-state periods. Some simulated examples arc given to demonstrate the effectiveness of the proposed method.

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

The winding current response and the adequate commutation significantly affects 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, an intelligent commutation instant tuning technique is developed to pursue better motor torque generating characteristics of BDCM. The motor drawn line current minimization is employed as the performance index in making the commutation tuning. Then, a robust current-mode controller is proposed to 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. 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.