Research And Implementation Of Functional Safety Of PAC Control System

PAC (Programmable Automation Controller) has a powerful computing performance as industrial PC,and has the programming way,real-time performance and reliability of PLC. The emergence of PAC meet the increasing demands of users and demonstrates its extensive application prospect. As users increasingly concerned about the safety of equipments,IEC draw up the international functional safety standard IEC61508 and the functional safety communications standard of IEC61784-3.The standards point out the directions for the study and the development of communication functional safety. This dissertation includes the following contributions:(1).The definition and requirements of functional safety of international standard IEC615O8 and IEC61784-3 are analyzed.International Functional Safety standards of IEC615O8 and IEC61784-3 are studied to explain the main principles and important concepts such as risks,safety integrity,safety integrity level and safety life cycle. On this basis, the industrial communications requirements and related definitions in IEC6.1784-3 standard are introduced.(2).PAC controller's function security is studied.In order to solve the wrong order during the controller implementation, program flow method is presented to realize the implementation of the PAC core. In order to solve the program execution deadlock, watchdog technology is applied to achieve real-time monitoring and program reset.In order to solve the data errors during PAC controller's implementation, data checkout method is applied to assure the safety and validity of data. In order to solve the problems during the communication transmission, such as. the packet loss, delay, wrong sequence and camouflage packets, Functional safety protocol layer is designed and implemented.The layer uses the relationship key, timestamp, sequence number, CRC checksum and other functional security technologies to effectively reduce the communication error rate and meet the safety communication requirements.The above measures can ensure the security and reliability of the PAC control system.The function security methods of the PAC controller is verified through a temperature control illustration.The control functions is realized through function block configuration and the PAC controller's safety performance is studied through recording the timestamps of program blocks and grabbing communication messages.The experiment result shows that the functional safety system of PAC can reduce the error rate, detect and conduct transmission fault to protect data transmission security and improve the functional safety during the implementation and communication of PAC controller.