There are many advanced control techniques developed over last years. Only few of them found their way to industrial implementation. The paper presents Predictive Functional controller (PFC), which has many implementa...
详细信息
There are many advanced control techniques developed over last years. Only few of them found their way to industrial implementation. The paper presents Predictive Functional controller (PFC), which has many implementations, however is rarely presented in publications. That type of control is used as a standard PID control replacement to meet higher quality demands of controller performance. The paper presents example of implementation of PFC in Allen-Bradley Control-Logix platform. Complexity of considered problems includes non-linearity, constrains, feedforward action, integrative effect. The paper generic control scheme was designed to facilitate industrial implementation where tuning is very simple and only concerns one parameter. That simplicity of tuning makes model-based predictive control accessible to non-experts. Results of PFC controller are compared to the results of standard PI controller used for the same process.
Today, remote control of PLC is a common requirement in a control system development. A remote control structure reflects both used components and a price of the designed system. Remote monitoring of a technology stat...
详细信息
Today, remote control of PLC is a common requirement in a control system development. A remote control structure reflects both used components and a price of the designed system. Remote monitoring of a technology state (visualisation) represents an integral part of a remote control design.
This paper introduces a scheduling method for a programmable logic controller (PLC) working under a multi-tasking, multi-processor and network-based I/O subsystem environment. We construct a generic architectural and ...
详细信息
This paper introduces a scheduling method for a programmable logic controller (PLC) working under a multi-tasking, multi-processor and network-based I/O subsystem environment. We construct a generic architectural and behavioral model of a PLC and extract precise timing constraints. A heuristic algorithm is developed to satisfy the two objectives, timing constraints and low resource occupation at the same time. A synchronization scheme between program execution and data transmission is also developed, which enables the developed algorithm to accommodate multi-processor PLCs. We analyze the performance and implement the proposed method to demonstrate feasibility.
Currently, thermal power plants adopt in most cases a throttle-governing mode for regulating the flow rate of circulating water. Such a regulating method suffers from poor control effectiveness and is incapable of ens...
详细信息
Currently, thermal power plants adopt in most cases a throttle-governing mode for regulating the flow rate of circulating water. Such a regulating method suffers from poor control effectiveness and is incapable of ensuring that a steam condenser operates at a most favorable vacuum. Moreover, it also results in a high power consumption of circulating water pumps. In view of the above, the authors have developed a variable-frequency speed-governing system, using a programmable logic controller (PLC) to design a rational control logic. This makes it possible to realize a stable start-up, shutdown and the switching-over of the circulating water pumps, thus providing a steam turbine unit with an optimum vacuum for its economic operation. The economic operating modes of the steam turbine unit are analyzed and a method for calculating optimum vacuum values is given along with a detailed description of the system control theory, hardware configuration and PLC program design. Furthermore, some fruitful application results are presented.
Eight 500 MHz cavities are applied in the storage ring of the Shanghai Synchrotron Radiation Factility (SSRF). In order to tune the cavities for different changing parameters and operation modes, the control system is...
详细信息
Eight 500 MHz cavities are applied in the storage ring of the Shanghai Synchrotron Radiation Factility (SSRF). In order to tune the cavities for different changing parameters and operation modes, the control system is essential for operations. The tuning is achieved by synchronizing the drive signal and the cavity probe signal. The error signal defined as their subtraction is amplified and used to drive a stepping motor, which in turn moves a metallic plunger in or out of the cavity by programmable logic controller (PLC). The tune speed is set to be 1 kHz/s.
Distributed control system on mixer ingredient is introduced,It has a management server,upper machine is PC,lower machine is SIMAT1C S7-200 programmable logic controller(PLC).One PC can control and manage several *** ...
详细信息
Distributed control system on mixer ingredient is introduced,It has a management server,upper machine is PC,lower machine is SIMAT1C S7-200 programmable logic controller(PLC).One PC can control and manage several *** hardware sets of the system,the design of the software and the method of the communication of computer are *** the actual production,ingredient accuracy and product quality is improved,productivity is expanded and worker's circumstances are improved.
This paper presents a fully automated programmable logic controller (PLC) based direct load control system. Unlike other existing systems, it gives the consumer the privilege to share in the load shedding policy. Afte...
详细信息
This paper presents a fully automated programmable logic controller (PLC) based direct load control system. Unlike other existing systems, it gives the consumer the privilege to share in the load shedding policy. After receiving the warning alarm from the PC at the utility control center, the consumer has the chance to switch off any desired load. If he does not act within a predefined period, the PLC will take the required action based on the scenario decided by the utility. Having the consumer decide his own priorities release the utility company from blind decisions. This is one of the most important contributions of the proposed system. Also the load restoration process is scheduled to avoid the creation of a new peak during re-energization. This is done using 48 built-in timers with an accuracy of less than one cycle (10 ms). The hardware at the customer side may be integrated with a digital energy meter to form a complete energy management system. (C) 1999 Elsevier Science S.A. All rights reserved.
An apparatus to automate completely the processing of Western blots is described. The prototype is based on a popular rotisserie system design. The incubation chamber consists of an inner cylinder that rotates inside ...
详细信息
An apparatus to automate completely the processing of Western blots is described. The prototype is based on a popular rotisserie system design. The incubation chamber consists of an inner cylinder that rotates inside an outer cylinder (incubation chamber). The blot is contained in the inner cylinder. Two magnets are mounted at one end of the inner cylinder, and rotation of the inner cylinder is effected by two magnets mounted on a motor drive outside the incubation chamber. Movement of chemicals into and out of the incubation chamber is driven pneumatically, and the entire process is controlled by a computer. Processing a blot for chemiluminescent detection takes 7 h to complete without human intervention. The quality of the resulting image is comparable to or better than a blot using manual processing. In addition, the prototype is capable of re-collecting all three antisera. for future use.
Discrete part manufacturing systems consist of numerous machines working together in a coordinated and sequential fashion. programmable logic controllers (PLC's) are widely used in the implementation of control al...
详细信息
Discrete part manufacturing systems consist of numerous machines working together in a coordinated and sequential fashion. programmable logic controllers (PLC's) are widely used in the implementation of control algorithms for these machines. The PLC's have been modeled as Discrete Event Systems (DES's) using formal control theories like Petri Nets and Finite Automata. Though such methods have received wide attention within academia, their industrial implementations are scarce. The work reported in this paper aims identify the reasons for the gap between academia and industry in implementing formal control methodologies for PLC's in Industrial manufacturing and to provide solutions to reduce the identified gap.
Petri nets have been extensively applied for specification, design, verification, performance evaluation, and simulation of the DECS. A real-time Petri net is a further improvement over timed Petri net. It is aimed fo...
详细信息
ISBN:
(纸本)0780370872
Petri nets have been extensively applied for specification, design, verification, performance evaluation, and simulation of the DECS. A real-time Petri net is a further improvement over timed Petri net. It is aimed for both control and simulation of the system under study. This paper proposes to use a real-time Petri net to represent the stage programming of a programmable logic controller for a discrete-event control system. An illustrated example is used to explore the Petri net-based PLC stage programming methodology.
暂无评论