Opc Communication in Real Time

Control of real systems in practice brings many complications. The control algorithm is usually implemented directly in the control system connected to controlled system by using of conventional controllers. In practice at the lower level are most often used control systems based on PLCs (Programmable Logic Controllers). However implementation of modern control methods (adaptive control, predictive control, etc.) includes increased computation demands, therefore the realization of the algorithms in PLCs is difficult or almost impossible. One of the possible solutions is to use other control system, e.g. computer with running control algorithm. In this case we need to provide feasible communication between both control systems. In our case we used the well-known communication standard called OPC (OLE for Process Control) for communication between PC and PLC. In this paper we provide testing of this communication standard with reference to quality of control of real system. 1 PLC and PC in control process Control of industrial processes is often realized using small digital computers called the programmable logic controllers (PLCs), where the hardware and software are specifically adapted to industrial environment. PLCs represent a cost effective solution for control of complex systems. They offer many advantages, such as flexibility (they can be reapplied to control other systems quickly and easily) and reliability (immunity to electrical noise, resistance to vibration and impact). However, this type of controllers usually offers only simple control structures, such as on-off control or PID control loops. [2] However implementation of modern control methods (adaptive control, predictive control, etc.) includes increased computation demands, therefore the realization of the algorithms in PLCs is difficult or almost impossible. One of the possible solutions is to use other control system, e.g. PC with running control algorithm. In this case we need to provide feasible communication between both control systems. In our case we used the well-known communication standard called OPC (OLE for Process Control) for communication between PC and PLC. In this paper we provide testing of this communication standard with reference to quality of control of real system.