Study Of Active Disturbance Rejection Controller Based On Field-bus

Traditional PID control is dominant in the field of industrial control. The industrial and scientific technologies have been developed rapidly. All kinds of improved PID control algorithm have been used, however, the PID control is far from been enough to satisfy the increasingly high requirement of industrial control system for the control accuracy, speed, and the adaptability of the environment. There is urgent need for a new efficient control method convenient for engineering application to substitute the PID control method as the mainstream control method of industrial control. The active disturbance rejection controller is an important method that appears in recent years. This method combines the recognition of modern control theory and modern signal processing technology, absorbs the typical PID ideological essence, improves the deficiency of"simple processing", and constructs a new controller better than the PID controller. Meanwhile, with the rapid development of modern communication technology, the modern field-bus technology tends to be more mature and is promoted rapidly. More and more controllers integrate one or more field-bus technologies. The distributed control system based on field-bus will become a new generation of control system following the distributed control system. The field-bus will become a worldwide technology revolution tide. Therefore, this paper suggests combining the active disturbance rejection control technology with the field-bus technology to design a new controller with large control scope and strong disturbance rejection capacity and convenient for application promotion.In order to design and develop the new controller, this paper studies systematically the field-bus technology, PID control technology, active disturbance rejection control technology, hardware and software design of active disturbance rejection controller, control system design, and experimental tests.1. Field-bus technology studyDepending on the features and advantages of the field-bus, system structure of the field-bus, and the classification of the field-bus and citing the example of the Modbus in the 485 bus, this paper analyzes the transmission mode, message frame format, function code, cyclic check code, and generation algorithm. This paper also analyzes the application occasions of different field-bus and their advantages and disadvantages in order to choose the extensive and prospective field-bus from the active disturbance rejection controller based on field-bus as the communication bus of this controller. The extensively used field-bus is Modbus, Profibus, FF, and CAN buses.2. PID control technology study The study in this section primarily states the practical control structure of the typical PID controller , provides the practical and typical PID controller algorithm, introduces the typical object scope controlled by the PID, analyzes the advantages and disadvantages of the PID controller and the reasons, points out that the control essence of the PID is"to eliminate the error based on the error feedback", defines that the primary reason for all deficiencies of the PID controller is the"simple processing"of signals, and points out the research direction to solve the typical PID deficiencies for the active disturbance rejection controller.3. Study on the active disturbance rejection control technologyAiming at critical defects and their reasons of the PID controller that require to be solved, this paper analyzes the evolution process from the tracking differentiator to the generator of the transient process and their functions, discusses functions of the non-linear feedback effect and the functions of the observer of the expansion state, analyzes the construction, transformation, and application of the active disturbance rejection controller, and derivates the active disturbance rejection control algorithm, parameter transformation, and setting method for an object with first-order inertia link with timelag, points out that in addition to the algorithm, the setting control parameters and optimization method are also the key of the technology of active disturbance controller. Good or bad parameters affect the control effect of controllers. After defining the algorithm of the active disturbance control and the method of parameter setting for an object with first-order inertia link, the Matlab software is used to compile corresponding simulation procedures and provide the flow diagram to educe the control curve of the active disturbance rejection setting. It is discussed in several aspects that the algorithm of active disturbance rejection controller excels the regular PID control algorithm. Key points of active disturbance rejection controlling technology are also introduced to provide theorical basis for compiling the software of the active disturbance rejection controller.4. Study and implementation of the active disturbance rejection controller based on field-busBased on the theory and the simulation result of the active disturbance control technology and actual operation requirements of the active disturbance rejection controller based on field-bus and taking the C8051F060 of Cygnal company as the control core, the 485 communication circuit, CAN communication circuit, analog quantity signal collecting front-end and amplification circuit, 4~20mA current output circuit, power supply, JTAG interface circuit, LC driving circuit, and ferroelectric memory interface circuit. The LC driving circuit and ferroelectric memory interface circuit are the backup for perfecting the controller in the future. Designs of communication procedure, analog quantity signal collecting procedure, 4~20mA signal output procedure, algorithm procedure of active disturbance rejection control, main procedure for these hardware have been finished. The internal core control algorithm of controller uses the active disturbance rejection control algorithm of the object of first-order inertia link with timelag. The communication protocol uses the Modbus communication protocol (CAN communication protocol only compiles the sending, receiving, and initiating procedures, which will be the backup for perfecting the communication protocol). The debugging of hardware circuit and corresponding procedures is also finished. During the procedure compiling, there are problems on three aspects which are the"transition process while given value varing"and"control of simulated sampling time and actual sampling time"and"range planning"from the simulated control to the actual control of the active disturbance rejection controller. Corresponding solutions have been given. After the controller is experimentally, all indexes of the hardware circuit and the controlling indexes of the controller satisfy the requirements.5. Study on the control system of the active disturbance rejection controller based on field-busThe active disturbance rejection controller based on field-bus is the lower computer. The Kingview 6.52 software is used to design the water temperature controlling-based experimental test system for the software of the host computer. This paper introduces the design method and content of the host computer software of the controlling system in brief, discusses the system structure of the controlling system and the selection and confirmation of the object of first-order inertia link object with timelag. The paper focuses on analyzing advantages and disadvantages of the simulated running result of the active disturbance rejection controlling and the simulated running result of the object through the improved PID control. Actual object construction is conducted according to the selected objects. As for the object of typical first-order inertia link: water temperature control device. Compare the controlling effect curve of two controlling running. Analyze the advantages and disadvantages of the two. Therefore, the accuracy of the simulated result of two controlling methods is verified. In conclusion, the controlling effect of the active disturbance rejection controller is more optimized than the improved regular PID controller. The overshoot of the whole system is little. The residual hardly exist. It is provided with high anti-interference ability and robustness. The controller is easy for promotion.6. Research and development direction in the futureThe research development direction of the active disturbance rejection controller based on field-bus can be divided into three aspects: First, enrich the field-bus protocol; second, enrich the algorithm of active disturbance rejection controller; third, the commercialization of the controller. As for the first aspect, driving circuit is designed and communication protocol is formulated for different field-bus. Modularize the protocol and enlarge the application scope. For the second aspect, it is important to design the controlling algorithm software package of the active disturbance rejection controller, which is to design the active disturbance rejection controlling algorithm and parameter setting for typical controlled objects. It is extremely important in the actual application in the future. For the third aspect, design the controller according to industries. The commercialization of the controllers has set the foundation for replacing the regular PID controllers.