FBM227 FOXBORO
as the human-machine interface,it is also feasible to use IPC as the I/O component of software PLC;In addition,the relationship between PLC and emergency shutdown safety systems(ESD),as well as the relationship with three-dimensional warehouses,robots,CAD/CAM,and so on,must be well handled.In short,PLC should be compatible with various new technologies,making it a true”computer”.
The application field of PLC is broad,and there are many areas that urgently need to be explored,such as for customs transit vehicle certification(Shenzhen Yantian)and automatic drug sales(several traditional Chinese medicine stores),which have already been examples in China.In addition,in discrete event systems,such as highway network traffic flow(vehicle counting,passenger counting,and residence time measurement),logistics systems,flexible
manufacturing systems(agile manufacturing systems),and all non-standard on-demand service systems,PLC can be used to model,take countermeasures,and optimize.The future of PLC is promising,and all pessimistic arguments are untenable.As for technological progress,it will take some time for PLC to integrate with other technologies and even disappear!
Large systems with a single machine supporting 300 loops and 65000 I/O points correspond to medium-sized PLCs or above,all using 16-32 bit CPUs.Micro and small PLCs originally used 8-bit CPUs,but according to communication and other requirements,some have also switched to 16-32 bit CPUs.Due to the fact that PLC sales below I/O 64 account for 47%of the total PLC sales,while those between 64 and 256 account for 31%,totaling 78%of the total PLC sales,more research should be conducted on micro and small PLCs.
3.2 Hardware of PLC
The hardware of the PLC controller itself adopts a building block structure,and the product structures of various manufacturers are similar.Taking the Japanese Omron C200HE as an example,it has a bus template frame structure.The basic framework(CPU motherboard)is equipped with CPU templates,while other slots are equipped with I/O templates;If there are many I/O templates,the CPU
motherboard can be connected to the I/O expansion motherboard through an I/O expansion cable,and I/O templates can be installed on it;Another method is to equip remote I/O slave stations,etc.These all indicate that PLC manufacturers develop hardware components for users to choose from,and configure them into PLCs of varying scales.Moreover,the openness of this hardware configuration brings a lot of convenience to manufacturers,distributors(agents),system integrators,and end users,and greatly facilitates the sales supply chain.This is a great success experience.
In addition to general DI/DO,AD/DA templates,I/O templates within PLC have also developed a series of special functional I/O templates,which have opened up a way for PLC to be used in various industries,such as ASCII/BASIC
