Controlling Sandia National Laboratories Thermal Test Complex Using National Instruments LabVIEW and NI TestStand

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"NI products were key to our success in developing the TTC control system. FieldPoint and LabVIEW formed the backbone of an effective distributed control system."

- Allen Smith, Ktech Corporation

The Challenge:
Developing a control system to manage the complex array of equipment needed to conduct controlled fire experiments, including fuelling and igniting JP-8 jet propellant, methanol, hydrogen, and methane fires, powering and controlling high-energy heat lamp arrays, and governing high-volume air flow in three test facilities.

The Solution:
Building programmable automation controllers (PACs) with embedded control software for facility subsystems using National Instruments LabVIEW and NI TestStand software and National Instruments FieldPoint hardware.

Author(s):
Allen Smith - Ktech Corporation

Sandia National Laboratories recently contracted Ktech Corporation to develop an integrated software control system for its a new multilaboratory Thermal Test Complex (TTC), which tests full-scale weapons systems in real-fire environments. The TTC facility offers three thermal modes – gas fire, liquid fire, and radiant heat – with systems to accurately control test conditions and analyze the fires. The seven-story building features a 60-foot-diameter fire test cell, an 84-foot-long low-speed wind tunnel, and a test cell for 5-MW radiant heat tests. The design supports jet fuel, methanol, hydrogen, and methane fires and includes water cooling and air flow equipment.

Using National Instruments FieldPoint hardware, NI LabVIEW and NI TestStand software, and a graphical object-oriented programming (GOOP) approach, Ktech developed a low-cost, integrated software control system for the TTC facility that reduces manpower needs, limits personnel exposure to electrical and fire hazards, and increases testing efficiency. We implemented PAC programming using the LabVIEW Real-Time Module and data-logging, alarm handling, and security features using the LabVIEW Datalogging and Supervisory Control (DSC) Module, and we developed a test sequence engine with in-test hot backup functionality using NI TestStand.

LabVIEW and Graphical Object-Oriented Programming

As experienced LabVIEW developers, we knew the software was up to the task. With the powerful language features and debugging tools, we quickly developed and deployed applications with the level of sophistication needed to meet our requirements. Add-ons like the LabVIEW DSC Module saved us time implementing common features. Most importantly, LabVIEW supported the necessary advanced architectures and design methods, including GOOP.

Programmable Automation Controllers

The sheer size of the facility demanded a distributed control system. We chose to build PACs using FieldPoint hardware and LabVIEW Real-Time software. We embedded most of our hardware control logic on the PACs, reducing the processor load on our control PCs and   providing autonomous control of our hardware for continuous operations like freeze protection. LabVIEW was the common programming platform for both the PACs and the supervisory control system, so they integrated seamlessly.

Distributed controllers reinforced our object-oriented approach, and we handled control of our facilities as discrete systems. Because FieldPoint controllers are much more reliable than PCs, we chose to cache state data for our facility systems on the PACs and make the PCs clients of that data. This design meant the PCs were only responsible for maintaining data about the state of a test sequence.

Supervisory Control through LabVIEW

We relied heavily on the LabVIEW DSC Module features in our control system’s supervisory segment. We seamlessly integrated our I/O into the application with the LabVIEW DSC Module data-logging and alarm package, and we used the security features to restrict access to test sequences, management functions, and individual front panel controls based on the user’s expertise with a particular test type. We also quickly developed an intuitive operator interface tailored for process automation with the DSC front panel objects.

NI TestStand as a Batch Production Engine

We decided to employ NI TestStand for test execution. The TTC creates and maintains its intense thermal environments using strictly defined test sequences that only employ equipment relevant to each test. We also expected researchers to want new test sequences as they mix and match equipment, creating future test environments. This use pattern resembled batch process control, and we realized that the NI TestStand sequencing engine made an excellent batch controller.

This decision worked well with our object-oriented design. Our top-level code objects, representing entire subsystems, exposed functions that closely matched steps in the individual test sequences. We quickly developed those sequences in NI TestStand and relied on the engine to execute them.

NI TestStand also met our requirement to provide an in-test hot backup PC that could assume control of the system in case of primary PC failure during a test, so that operators could complete the test. To meet this requirement, we configured the backup PC to track the health, state data, and sequence placement of the main PC as it executed a test. We had a way to seamlessly pass control from the main PC to the backup by caching state data on the PACs and relying on the LabVIEW DSC Module for the interface. We then used NI TestStand for pre- and post-step callback features to create a handshaking mechanism that synchronized step execution between the main and backup PCs.

NI products were key to our success in developing the TTC control system. FieldPoint and LabVIEW formed the backbone of an effective distributed control system. We rendered a solid batch production controller with the flexibility of NI TestStand, and LabVIEW supported the object-oriented approach we used to bring everything together. The combination of NI hardware and software provided significant savings in manpower, cost, and complexity. We developed this system in roughly a year with two developers – all for less than 2 percent of the facility’s total cost.

“The software is an incredible step into the 21st century,” the facility owner said. “Our past systems used toggle switch controls or even manual in-the-field adjustments. New software features like automated fuel delivery, cell wall cooling, and radiant heat array control are saving us a lot of turnaround time between tests, and we can now troubleshoot mechanical issues faster and more accurately than ever before.”

Author Information:
Allen Smith
Ktech Corporation
1300 Eubank Blvd.
Albuquerque, NM 87031
Tel: 505-254-4172
asmith@ktech.com

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