Project: Biopharmaceutical filtration automation, August 25, 2005
The end user has ordered the HMI hardware, but the equipment has not yet arrived so graphic development is again delayed. As described in last week's entry, static displays were developed without the PLC controller to develop against. Once the HMI hardware is available, the HMI software will be set up to communicate with the PLC and the graphic displays will be checked out against the running logic.
Again, to keep the project moving forward, we continue working on areas that would normally occur after the basic graphic development is complete. We are currently designing and developing automatic sequences for the equipment modules. Having a working simulated process with a graphical HMI interface is extremely helpful when developing equipment modules because we can run the sequence from the HMI and observe the results on graphic displays. Since equipment modules simply manipulate control modules or other equipment modules, observing a sequence from a process graphic is infinitely easier than observing the sequence from within the programming code.
The real meat of the control application is in the equipment modules and the current design includes 51 equipment modules (roughly twice what was expected at the start of the project). Each equipment module is designed as a state machine similar to the S88 phase logic state diagram. What sets our equipment module state diagram apart from the S88 phase state diagram is that any number of states may be defined for one equipment module and state transition logic is also uniquely defined. This may seem like a very loose structure, yet it still provides a consistent, standard structure despite the number of states and state names.
We have developed a single standard equipment module HMI faceplate interface that works with all equipment modules. When the faceplate loads, it interrogates the referenced equipment module and dynamically adds state command buttons— dynamically discovering the appropriate state label to apply to each button. The equipment module includes state enabled flags maintained by state transition logic so that the faceplate may enable/disable state buttons as determined by equipment module internal logic.
Currently we have completed the design for about half of the 51 equipment modules. Equipment module code has been developed for the following 7 harvest tank equipment modules:
1. Agitation Control
2. Pressure Control
3. Temperature Control
4. Vessel Drain
5. Purified Water Drop Control
6. Tank Level Control
7. Pre-SIP Pressure Hold Test
Designing, developing, and testing equipment modules will consume the majority of the project between now and the scheduled date for code completion at the end of September.
Next week and through the month of September we will be focused on equipment module development. Additional HMI work will start when the HMI equipment becomes available.