Nonlinear Disturbance Observer-Based Sliding Mode Control for the PMSM with Matched and Mismatched Disturbances

Chaolong Zhang,Tiankuo Liu,Huifang Kong,Yao Fang

doi:10.1155/2020/8837101

Abstract

High-efficiency permanent-magnet synchronous motor (PMSM) is a key technology to improve the driving range of batteries in electric vehicles, while the mismatched disturbance that is caused by external disturbances and parameter perturbation may easily result in speed fluctuations and overshoot of the PMSM, which further deteriorate the performance and efficiency of batteries. To solve the problem, a novel nonlinear disturbance observer-based sliding mode control (NDO-SMC) is proposed. Compared with the traditional SMC method, the NDO-SMC scheme has better disturbance rejection ability in the presence of matched and mismatched uncertainties and disturbances by introducing the estimation value of the nonlinear disturbance observer in the sliding surface. Furthermore, owing to the compensation of the disturbance observer, the switching gain is only required to be greater than the bound of the disturbance estimation error rather than that of the disturbance; thus, the chattering problem is substantially alleviated. A rigorous stability proof of the whole closed-loop system is given in detail using Lyapunov theory by designing an appropriate Lyapunov function. The simulation results demonstrate the feasibility and superiority of the proposed NDO-SMC strategy.

Highlights

Driving range of batteries is a key problem restricting the development of electric vehicles [1, 2], permanent-magnet synchronous motor (PMSM), as a high energy-consumption component, whose efficiency becomes the decisive factor for the driving range of batteries [3].To achieve high-performance control of the PMSM, two current controllers are employed in the FOC mechanism to allow a PMSM to achieve similar torque control performance to a separately excited dc motor, where torque and flux can be controlled separately [4]
On the one hand, mismatched disturbances are always unknown or very difficult to obtain, during the operation of electric vehicles; on the other hand, the traditional sliding mode control methods are insensitive to the mismatched disturbances. erefore, dealing with the mismatched disturbance and improving control accuracy have been a critical issue in electric vehicles
Due to the fact that the mismatched disturbance caused by parameter perturbation always exists in practice, the traditional sliding mode control (SMC) control methods are insensitive to mismatch the disturbance. erefore, we first develop a nonlinear disturbance observer (NDO) for estimating matched and mismatched disturbances, which is the foundation of controller design

Summary

Introduction

Driving range of batteries is a key problem restricting the development of electric vehicles [1, 2], permanent-magnet synchronous motor (PMSM), as a high energy-consumption component, whose efficiency becomes the decisive factor for the driving range of batteries [3]. An integral sliding surface with a high-frequency switching gain is designed, and integral action in the sliding surface drives the system states to the desired equilibrium in the presence of mismatched uncertainties; it should be pointed out that the integral action brings some adverse effects into the control system, such as large overshoot and long response time [14] Another method for handling mismatched uncertainties is focusing on the robustness of the system by Riccati control scheme, which is built on the premise that the mismatch disturbance satisfies H2-norm bound [15].

Problem Formulation and PMSM Model

Sliding Mode Controller Design Based on the Nonlinear Disturbance Observer

Findings

Simulation and Results’ Analysis