Automating a Canning Line Using NI LabVIEW and FieldPoint

Author(s):
Christoph Widmer - Kuhn AG

Industry:
Food/Beverage

Products:
Compact FieldPoint, LabVIEW, FieldPoint

The Challenge:
Replacing an outdated programmable logic controller and a temperature controller that controls a food canning line and an autoclave with minimum software development. Improving the control of the autoclave to reduce the chance of malfunction.

The Solution:
Designing a system using NI FieldPoint and LabVIEW Real-Time for maximum ease-of-use, adaptability, and precision control.

We needed to completely replace the existing, outdated automation and control systems of our food canning line, because we no longer had adequate technical support for those systems. Because we could not reuse the existing software, we had to completely rewrite the software. Changing to a new system gave us the opportunity to implement more functionality such as controlling the autoclave programmatically.

Food Canning Process
In our food canning line, we produce mushroom cans and preserves. The mushrooms follow a whole sequence of treatment steps. First, we wash them, blanch them in a cooker, and rinse them before sending them to the slicing machine. We then automatically fill the cans with the correct weight of sliced mushrooms. We subsequently fill these cans with water and seal the cover. Finally, we sterilize the finished can in an autoclave for 30 minutes at 117 °C and a pressure of 1.5 bar. We must reach a pressure of 1.5 bar because we need to counter the pressure from inside the can. Even a short drop of the external pressure can cause the can to be deformed. Besides the cans, we also produce preserved mushrooms in nylon bags, which are even more delicate and very susceptible to pressure variations during sterilization and subsequent cool down.

System Architecture
After successfully implementing a composting plant with LabVIEW and FieldPoint two years ago 1 , we decided to again use LabVIEW and FieldPoint to replace the old PLC-based canning system. With the new FP-2000 controller and LabVIEW Real-Time, we can now run LabVIEW code embedded on an FP-2000-based distributed system. This solution effectively overcomes many of the shortcomings of the traditional PLC systems. While we have shown in our previous project that LabVIEW under Windows NT is capable of delivering response times that are sufficient for many automation tasks, using the new FP-2000 controller and LabVIEW Real-Time has several distinct advantages:
• A dedicated execution system separate from the PC for added safety
• Execution on a true real-time platform for shorter and guaranteed response times
• Much smaller packaging because the PC is needed only for visualization

Implementation
We divided the software into several distinct parts:
• The automation of the entire line before sterilization - washing, blanching, rinsing, cutting, filling and weighting, and sealing
• The automation of the autoclave - filling and emptying
• The control of the autoclave - temperatures and pressure

While in the past we needed three different control systems for the three parts, we have now reengineered the entire functionality in LabVIEW. In particular, for the first two parts, we needed PLC-type controllers and for the third part, we needed PID-controllers for temperature and pressure control. We now have implemented all these parts, such as the machine automation and the PID control in the software. In the past, we used a paper strip chart recorder to monitor the sterilization process and for quality control. With the new solution, we no longer need the paper strip chart recorder because we log the data to disk in five second intervals for later post processing, saving us time.

In the past, the old PLC controllers were capable only of the most basic fault control and correction, requiring constant supervision. Equally, in the past there was no user interface, but with LabVIEW, creating a sophisticated user interface is quite simple. We can view this data remotely. In addition, the sterilization process can now run without operator supervision because of the numerous safety features built into the software. These safety features also can automatically correct some abnormal conditions such as variations in pressure, saving us money.

Discussion
With LabVIEW, we can seamlessly integrate all aspects of an automation solution, such as control functions, process automation, error recovery, visualization, database integration, statistics, and so on. We can program with LabVIEW Real-Time directly and download the application to run independently on the FP-2000 controller. Our software engineers only have to use one system and can write the entire application with the same tool.

Even in this rather small application example, traditional automation and control solutions required two different systems. To make matters worse, these systems are always proprietary and become obsolete after a certain time. Hardware and software maintenance then becomes extremely difficult. The LabVIEW platform is very well suited for automation applications. This platform can replace all aspects of traditional automation and with an onboard, dedicated processor, the new FP-2000 is another important piece in this picture. The ability to execute the critical code on a separate hardware target under a real-time system greatly enhances the performance of our already developed PC-based solutions.

For more information, contact:

 Christoph Widmer

Kuhn AG, Alpsteinstrasse 56

9100 Herisau, Switzerland

Tel: (41) 71 353 77 77

Fax: (41) 71 353 77 76

E-mail: kuhn.champ@spectraweb.ch

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