Wide Running Control Design Integrated On Bang-Bang Control And Regulatory Control

Despite the various advanced control methods that have continuously emerged in the past decades,the regulatory proportional-integral-derivative control remains most widely used in practical industrial areas.Its control quality is not sensitive to the change of the controlled object.So it is well used in practical control process.However,when wide running changes occur,such as the start-up process,a satisfactory result may not be obtained using the traditional PID control.Because it is hard to balance the regulation time and overshoot.The deterioration of the control process affects the economic efficiency and production safety of enterprises.The application of PID control has been quite mature.If we can continue to use the small-range adjustment ability of PID control and improve it only for wide running changes,then all condition control can be implemented with lower cost.According to the above ideas,this paper deals with the integrated control scheme called wide running switching control.Wide running control,integrated Bang-Bang control with regulatory control,is used as a complementary strategy in this study.Proportional-integral-derivative control is used to handle the smaller changes.The primary problems of the control scheme are twofold.The first point is to compute the switch point of Bang-Bang control.The second point is to judge the change of the current conditions,also to choose one from wide running control and conventional control.The calculation of the switch value or moment in nonlinear systems continues to be a difficult issue.The problems in the analytical form are difficult to solve.Thus,the study and application of numerical solutions have become increasingly extensive.Taking the second-order nonlinear system as example,we use the phase locus graphic method to compute the switch point of the Bang-Bang control.This method has the advantages of time controllability,high precision and online applicability.It also applies to the non-steady starting point control which may occur in the actual operation.No comprehensive precedent exists in the related literature for the comparison of Bang-Bang control and PID control.On the one hand,PID control is currently rather mature in the industrial fields.Other methods should not be used if PID control can achieve satisfactory results.On the other hand,Bang-Bang control requires a high-precision switching action to achieve a rapid dynamic performance.A minimal error in the switch point may cause significant deterioration.Based on the above consideration,the selection between Bang-Bang control and PID control is determined in this study by analyzing the measurement error of the controlled variable.Taking into account the equipment loss,operational accuracy and other factors,the controller switching actions should not be too frequent.Based on the above consideration,we design the start threshold of wide running control and propose the computing methods from two aspects.The final start threshold is the smaller one.The determination of threshold value made the combination of wide running control and conventional control possible.Although various control methods have been developed greatly,their control effect is subject to such as the accuracy of object model and measurement,and other interference factors.In practical industrial system,the implementation of control scheme should not be too complex.It will be lose more than gain if the implementation of complex control scheme influences the stability of the whole system.In view of this,this paper proposes the selective control structure to implement the switching control effect.Considering the problems occurred in the operation of the actual control system,a comprehensive analysis and processing is carried out.The simulation and experiment results show that the integrated control strategy can be used to complete the adjustment of full working condition of nonlinear object.