Saturday, August 13, 2011

Programmable Logic Controller and EPICS Tools

Until now, only a little of the many existing tools of EPICS have been utilized expansively. As the main device for EPICS database building was chosen the schematic drawing of CAPFAST package. Additionally to the graphically visualizing possibility of the IOC code functionality they were involved by supporting for the schematic of multi-level hierarchies which they practiced in the form of Sub-system, device, component, EPICS traditionals.

Every schematic drawing is symbolized at the subsequently higher level by a matching symbol. Functionality of device is built from reusable components wherever probable. To identify device particular working parameters, type of hardware, etc. large-scale substitution is utilized at the symbol level of device.

Development of code
One of the EPICS attractive features is the conventional code decrease development during the control system building. Only 2200 C code lines and 160 assembler code lines required to be written for the below areas:

Integration of Modicon PLC
The PLC Quantum of Modicon 160 is a module of VME master which has instructions of ladder logic to duplicate data, to and from the dual port memory VME of MVME162.

Embedded code of CAN-bus controller
Incorporation of the supply of CAN-bus controllers into EPICS was immediately as driver and device support for the TIP810 industry pack and CAN-bus were existing from the collaboration. A layer protocol of simple application for interaction of peer to peer between EPICS and the controllers was realized. The embedded microprocessor code on the controllers of power supply was built in C with portions of minor assembler.

The existing drivers of EPICS for the serial branch driver of HYTEC 2992 were adapted to support the crate controller of JORWAY 73 SCSI which was applied in this system. This was done by substituting the inline code of hardware reliant with calls to the SCSI driver.

A few apparatus of the test place required faster controls than given by the standard classes of EPICS scan. Fast read-out loops were applied to obtain data from scanners of free-running beam profile wire at 3 as fast drive loops for the stations of admittance measurement.

Programming of PLC
The PLC was programmed in ladder logic, using programming tool of Modicon's MODSOFT. For simplicity of program state visualization in mode of on-line, the program was realized no subroutine programming and as a linear ladder was used. A simple protocol hand-shake and watchdog was realized to guarantee safe startup and synchronization between the EPICS and PLC. The program of PLC can be turned between mode of simulation and mode of run by the system of supervisory. This is realized variables of with intermediate instead values of hardware input or output in the ladder logic.


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