Development of a control system with soft Programmable Logic Controller (I/O) compiling function embedded and applying into automatic optical inspection system

Programmable Logic Controller (PLC) is one of the controllers which are widely used in industry. The I/O control function can generate nearly all the motion behavior required in the practical applications. To consider different formats of different PLC languages, the IEC 61131-3 language will be adopted here. The IEC 61131-3 language has a unified syntax which is defined by the International Electro-technical Commission. The C# programming language is used to develop a window environment for compiling IEC 61131-3 language to perform the related I/O control. Nowadays, most of PC-based system with soft PLC function module embedded is a close structure type system. So that any I/O point broken, it must be returned to manufacturer to re-define the I/O point. It is very inconvenient and time consuming. Therefore, an open structure control system with soft PLC function module embedded will be developed to solve this problem. The objective of this study is to develop a software system which soft PLC language can be created and complied. An execution file will be obtained after the compiling process and will be downloaded to a motion control card to generate the designed motion path. Standalone mode of the motion control system is adapted to perform the experiments for verifying the feasibility of the developed soft PLC system. A warning function generated by an automatic optical system are further arranged to test and verify the correctness of the developed soft PLC system. The results show that 100% correctness is achieved.