Robust Control With State-Dependent Boundary Layer: Designs And Applications

Motion control technology has been widely used in the industrial process. With the increasing requirement of fine control performance, improving the existed advance control is an approach to meet the above demand. Nonlinear robust control is an important research field in nonlinear control theory, suitable for quick-moving controlled objects. By introducing the state-dependent boundary layer, this thesis explores the improving design methods of the nonlinear robust controller. The major work of this thesis covers the following aspects:1. By reading extensive relevant literatures, the close-loop system's performance is analyzed under the effect of nonlinear robust control algorithm with a fixed boundary layer.2. To overcome the weakness of the nonlinear robust controller with a fixed boundary layer, two kinds of nonlinear robust controllers with a state-dependent boundary layer are designed including unit vector type and saturation function type. The performance of the close-loop system is investigated. It is proved that the proposed controller can alleviate the chattering phenomenon, and meanwhile the system control accuracy can be improved. The effectiveness of the proposed control strategy is demonstrated by numerical results.3. A nonlinear robust controller with a state-dependent boundary layer is designed for the mathematical model of BLDCM control system. Theoretical analysis shows that the system errors converge to an area near the origin under the proposed control input. The width of the boundary layer is related to the system state. The controller can alleviate the chattering phenomenon, and we can also obtain high control accuracy at the same time. By comparing the control results of the traditional one with the proposed one by computer simulation, the effectiveness of the proposed control strategy is verified.4. Based on the robot control systems'property and the traditional robust controller with a fix boundary layer's design method, two robust controllers with a state-dependent boundary layer are designed for the nth order robot control systems. The property of the close-loop system is analyzed under nonlinear robust control algorithm with a state-dependent boundary layer. By comparing the computer simulation results of the traditional one with the proposed one, it is demonstrated that the robust algorithm with a state-dependent boundary layer can alleviate the chattering phenomenon effectively, while the control accuracy can improved by reducing the width of the boundary layer.