Robust bounded control for nonlinear uncertain systems with inequality constraints

• Published in: Mechanical systems and signal processing Vol. 140; p. 106665
• Main Authors: Li, Chenming, Zhao, Han, Sun, Hao, Chen, Ye-Hwa
• Format: Journal Article
• Language: English
• Published: Berlin Elsevier Ltd 01.06.2020; Elsevier BV
• Subjects: Bounded control; Control systems; Inequality; Inequality constraints; Isomorphism; Nonlinear control; Nonlinear systems; Robust control; Stability; Uncertainty; Bounded control; Uncertainty; Inequality constraints; Nonlinear systems
• ISSN: 0888-3270; 1096-1216
• DOI: 10.1016/j.ymssp.2020.106665

•The inequality constraints of control input and output are taken into consideration for nonlinear systems simultaneously.•The state transformation is applied to control output for changing its domain.•The control input is regarded as a function of an auxiliary variable based on diffeomorphism.•The value of control input can be limited to a prescribed bound by choosing a proper bounded function.•Uniform boundedness and uniform ultimate boundedness are guaranteed based on Lyapunov method. A novel bounded control for nonlinear uncertain systems with inequality constraints is considered. First, a state transformation is applied to satisfy the inequality constraints of the controlled outputs. Therefore, the controlled outputs are within the desired bounds. Next, a diffeomorphism is introduced for the control inputs. Based on that, the control inputs are transformed to be bounded functions. The maximum and minimum of the control inputs can be artificially set by choosing a proper bounding function. This control scheme is able to guarantee uniform boundedness and uniform ultimate boundedness. The simulation shows that the control cost of the novel bounded control and the error of the controlled system are smaller than LQR control, regardless of the uncertainty.