Optimal Control Of Nonlinear System Operation Under External Disturbanc

In recent years,the products of China’s paper making,steel making,mineral processing and other processing industries ranks among the top in the world,but there still have some problems such as high energy consumption,large resource consumption and low product quality.In addition,there lacks unified production and operation indicators because different industrial sectors have different characteristics.However,the manual method of determining the production target set points often has some problems such as inaccuracy,large error and insecurity.Considering the characteristics of complex industrial processes,for systems with nonlinear external disturbances,this paper studies a strategy of two-level optimal operational control.The controller is designed at the bottom loop control level without changing the structure and parameters of the controller.In the upper optimization setting layer,the disturbance observer is designed,and the setting value is dynamically adjusted to minimize the influence of the disturbance on the system,so that the loop output can achieve tracking control of the target value.Compared with the linear exogenous system,the nonlinear exogenous system considered in this paper can not only describe the unknown constant load,harmonic and other linear signals,but also describe a large class of nonlinear signals.The specific work of this paper are as follows:1.For the system with nonlinear external disturbances,on the basis of two-level optimal operational control,the upper layer determines and adjusts the target set values,while the lower layer makes the loop output track the target value.In the two-layer structure optimal setting control system,the widely used PID controller is used in the bottom layer.Firstly,the parameters of the PID controller are obtained by solving linear matrix inequalities(LMI).Secondly,for industrial processes with nonlinear uncertain harmonic disturbances,a disturbance observer is designed to estimate those uncertain disturbances.Finally,the effect of disturbances or noises are minimized by dynamically adjusting the settings points.2.For a class of nonlinear systems with input constraints and uncertain external disturbances,a two-level control strategy is studied.Different from some previous studies that ignored the existence of constraints in industrial production,this paper also considered the constraints in the operation optimization control of nonlinear systems.In this paper,the PI controller is used at the bottom of the two-layer structure optimal operational control.Firstly,the PI controller parameters are obtained by solving linear matrix inequalities(LMI)from the constrained requirements.Secondly,a disturbance observer is designed to estimate the uncertain external disturbances in the bottom loop.Finally,through dynamic adjustment of the set value,the loop output can still track the target value to minimize the impact of interference on the system performance.3.Firstly,for nonlinear systems with limited control input and bounded input rate in the bottom loop,a parameter adjustment method for PI controllers is given theoretically under the restricted conditions.Secondly,a disturbance observer is designed at the optimal setting level to estimate the external disturbances and dynamically adjust the setting value;Finally,a simulation is carried out and the results show that the control scheme can effectively suppress the influence of interferences under the control input amplitude and the rate constraints.