The Study On Root-locus Analysis Of Dahlin Controller And Its Applications

The basis of computer control method is control theory and computer technology.Computer control methods are widely used for achieving better performance ofcontrol systems and higher efficiency of industrial processes.The Dahlin controller is a controller which belongs to the classical computercontrol methods. It has simple structure and is easily to put into use. The Dahlincontroller has good performance in controlling the first-order and second-orderprocesses with time delay. But ringing always occurs in the controller output, it leadsto sacrifice the system's performance.The root-locus method is a geometric method which can be used to analyze thesystems behavior. The static and dynamic performances can be determined bystudying the poles location of the closed–loop systems. Compared with the traditionalroot-locus method, the root-locus method proposed in this dissertation has thefollowing characters:1 The poles location is expressed by polar coordinates.2 The poles location is computed directly.3 The object includes the closed-loop systems and controllers.4 The influence of the parameters on the polar radius and angle can be studied mainly by differential operation.5 The relationship between the polar radius and angle can be studied mainly by differential operation.This dissertation originates from the study on the cause and elimination ofringing. The main contents of it can be described as follows:The dynamic performance of the Dahlin controller can be analyzed by theroot-locus method. Based on the properties of the root-locus, it can be proved that forall values of controller order, the Dahlin controller contains ringing poles if theclosed-loop time constant is smaller. If there exists a plant-model mismatch, ringingwill occur in the controller output. Ringing can be eliminated by increasing theclosed-loop time constant. Also it can be qualitatively explained that if the closedloop time constant is decreased, the robustness of the Dahlin controller will becomeworse.Another type of ringing has been studied. The cause of it is that the time delay isnot the integral multiple of the sampling time. Three types of modified Dahlin...