Han Ho Choi

Fuzzy Sliding Mode Speed Controller for PM Synchronous Motors With a Load Torque Observer

This paper investigates the robust stabilization problem of a permanent magnet synchronous motor (PMSM). A fuzzy sliding mode speed controller with a load torque observer is designed, which can effectively mitigate chattering and guarantee robust speed control of a PMSM under model parameter and load torque variations. Furthermore, the proposed control method considers the disturbance inputs representing the system nonlinearity or the unmodeled uncertainty. The proposed control algorithm is implemented using a TMS320F28335 floating point DSP. Finally, simulation and experimental results are presented to validate the effectiveness of the proposed scheme.

Sliding-Mode Output Feedback Control Design

We consider the sliding-mode output feedback controller (SMOFC) design problem for a class of uncertain multivariable systems. We first design a stabilizing SMOFC for matched uncertain systems. Using linear matrix inequalities (LMIs), we derive a necessary and sufficient condition for the existence of a linear sliding surface depending on outputs and compensator states. Using the solution of the LMI existence condition, we characterize the gain matrices. We give the nonlinear switching feedback gain guaranteeing the reachability condition. Second, we give an LMI-based design method to combine various useful performance criteria which can be used to guarantee a desired robust performance in spite of mismatched uncertainties. The performance criteria include alpha-stability, LQ performance, H 2/H infin performance, and peak-to-peak gain bound. In particular, we show that by including H infin performance constraints, we can easily solve the SMOFC design problem for challenging system models to which the previous methods are not easily applicable. Finally, we give a numerical design example showing that our method can be successfully applied to the problem of designing reduced-order SMOFCs for uncertain time-delay systems or mismatched uncertain systems.

Digital Implementation of an Adaptive Speed Regulator for a PMSM

We design an adaptive speed regulator for a permanent-magnet synchronous motor (PMSM). The proposed adaptive regulator does not require any information on the PMSM parameter and load-torque values, thus, it is insensitive to model parameter and load-torque variations. We implement the proposed adaptive-speed-regulator system by using a TMS320F28335 floating point DSP. We give simulation and experimental results to verify that our method can be successfully used to control a PMSM under model parameter and load-torque variations.

Adaptive PID speed control design for permanent magnet synchronous motor drives

This paper proposes an adaptive proportional-integral-derivative (PID) speed control scheme for permanent magnet synchronous motor (PMSM) drives. The proposed controller consists of three control terms: a decoupling term, a PID term, and a supervisory term. The first control term is employed to compensate for the nonlinear factors, the second term is made to automatically adjust the control gains, and the third one is designed to guarantee the system stability. Different from the offline-tuning PID controllers, the proposed adaptive controller includes adaptive tuning laws to online adjust the control gains based on the gradient descent method. Thus, it can adaptively deal with any system parameter uncertainties in reality. The proposed scheme is not only simple and easy to implement, but also it guarantees an accurate and fast speed tracking. It is proven that the control system is asymptotically stable. To confirm the effectiveness of the proposed algorithm, the comparative experiments between the proposed adaptive PID controller and the conventional PID controller are performed on the PMSM drive. Finally, it is validated that the proposed design scheme accomplishes the superior control performance (faster transient response and smaller steady-state error) compared to the conventional PID method in the presence of parameter uncertainties.

T–S Fuzzy-Model-Based Sliding-Mode Control for Surface-Mounted Permanent-Magnet Synchronous Motors Considering Uncertainties

This paper presents a new sliding-mode control (SMC) scheme based on Takagi-Sugeno (T-S) fuzzy model for surface-mounted permanent-magnet synchronous motors (SPMSMs). First, a global T-S fuzzy model is given to represent the nonlinear dynamics of the SPMSM. The proposed T-S fuzzy-model-based sliding-mode controller considers motor parameter uncertainties and unknown external noises, so it is robust against motor parameter and load torque variations. Also, the linear matrix inequalities with feasible performance constraints are used to design both the sliding surface and the sliding-mode controller, and the stability of the proposed controller is analytically proven. In this paper, a simple sliding-mode observer is used to estimate load torque information. The proposed observer-based control scheme is implemented by using a Matlab/Simulink simulation tool and a prototype SPMSM drive with a TMS320F28335 DSP. Finally, simulations and experiments have been performed to justify that the proposed observer-based control strategy can guarantee a better performance (i.e., faster dynamic response, less steady-state error, more robustness, etc.) than the conventional observer-based nonfuzzy SMC scheme when there exist motor parameter uncertainties and unknown external disturbances.

Suboptimal Control Scheme Design for Interior Permanent-Magnet Synchronous Motors: An SDRE-Based Approach

This paper designs a suboptimal speed controller as well as a suboptimal load torque observer based on state-dependent Riccati equation (SDRE) approach for interior permanent-magnet synchronous motor (IPMSM) servo systems. First, dynamic equations of the IPMSMs are transformed to a suitable form that makes an SDRE-based control technique applicable. Moreover, the maximum torque per ampere (MTPA) control is incorporated to improve the torque generation in the constant torque region. The asymptotic stabilities of the proposed controller and load torque observer are fully guaranteed through an extended linear quadratic regulator (LQR) theory. This proposed method is simple to implement because the SDRE solutions are approximated off-line. The proposed observer-based suboptimal control scheme can ensure faster dynamic response, smaller steady-state error, and more robust response than the LQR and proportional-integral (PI) controller under the system parameter variations and load torque disturbances. The effectiveness of the proposed control strategy is verified via experiment.

An Adaptive Voltage Control Strategy of Three-Phase Inverter for Stand-Alone Distributed Generation Systems

This paper proposes an adaptive control method of three-phase inverters for stand-alone distributed generation systems (DGSs). The proposed voltage controller includes two control terms: an adaptive compensating term and a stabilizing term. The adaptive compensating control term is constructed to avoid directly calculating the time derivatives of state variables. Meanwhile, the stabilizing control term is designed to asymptotically stabilize the error dynamics of the system. Also, a fourth-order optimal load current observer is proposed to reduce the number of current sensors and enhance the system reliability and cost effectiveness. The stability of the proposed voltage controller and the proposed load current observer is fully proven by using Lyapunov theory. The proposed control system can establish good voltage regulation such as fast dynamic response, small steady-state error, and low total harmonic distortion under sudden load change, unbalanced load, and nonlinear load. Finally, the validity of the proposed control strategy is verified through simulations and experiments on a prototype DGS test bed with a TMS320F28335 DSP. For a comparative study, the control scheme of feedback linearization for multi-input and multioutput is implemented, and its results are presented in this paper.

SDRE-Based Near Optimal Control System Design for PM Synchronous Motor

This paper presents a nonlinear optimal speed controller based on a state-dependent Riccati equation (SDRE) for permanent magnet synchronous motor (PMSM). An SDRE-based near optimal load torque observer is also proposed to provide the load torque information for the controller. In both designs, the stability is analytically proven, and the Taylor series method is used to find an approximate solution because the SDRE cannot be directly solved. The SDRE-based optimal controller and the observer can ensure better control performance such as no overshoot and fast transient response in speed tracking than the linear conventional controllers such as linear quadratic regulator and proportional-integral controller even under the variations of the model parameters and load torque. The proposed SDRE-based control strategy is implemented on a PMSM testbed using TMS320F28335 DSP. The simulation and experimental results are given to prove the feasibility of the proposed control scheme.

A Three-Phase Inverter for a Standalone Distributed Generation System: Adaptive Voltage Control Design and Stability Analysis

This paper proposes a robust adaptive voltage control of three-phase voltage source inverter for a distributed generation system in a standalone operation. First, the state-space model of the load-side inverter, which considers the uncertainties of system parameters, is established. The proposed adaptive voltage control technique combines an adaption control term and a state feedback control term. The former compensates for system uncertainties, while the latter forces the error dynamics to converge to zero. In addition, the proposed algorithm is easy to implement, but it is very robust to system uncertainties and sudden load disturbances. In this paper, a stability analysis is also carried out to show the robustness of the closed-loop control system. The proposed control strategy guarantees excellent voltage regulation performance (i.e., fast transient response, zero steady-state error, and low THD) under various types of loads such as balanced load, unbalanced load, and nonlinear load. The simulation and experimental results are presented under the parameter uncertainties and are compared to the performances of the corresponding nonadaptive voltage controller to validate the effectiveness of the proposed control scheme.

Discrete-Time Fuzzy Speed Regulator Design for PM Synchronous Motor

This paper proposes a discrete-time Takagi-Sugeno (T-S) fuzzy speed regulator system for a permanent-magnet synchronous motor (PMSM). An accurate approximate discrete-time T-S fuzzy model is first derived for a PMSM. By using the discrete-time T-S fuzzy model, a fuzzy acceleration observer as well as a fuzzy speed regulator is designed. In terms of linear matrix inequalities, sufficient conditions for the existence of the regulator and observer are derived. The exponential stability of the augmented control system is also shown. The proposed discrete-time T-S fuzzy speed regulator system is implemented by using a TMS320F28335 floating point DSP. Simulation and experimental results are given to verify that the proposed digital control method can be successfully used for a PMSM under model parameter and load torque variations.