Controlling a Biodiesel Refinery With LabVIEW

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"By partnering with Signal.X and NI, the refinery realized a safe, reliable, and configurable system with reduced hardware cost, quick development time, and significant flexibility for long-term maintenance and scalability."

- Robert Hoffman, Signal.X Technologies, LLC

The Challenge:
Developing a complete control system for a demonstration-scale biorefinery that includes distributed I/O, failsafe control systems, a rich display for operators, and a reconfigurable logic system.

The Solution:
Using the NI PXI and reconfigurable I/O (RIO) architecture to control the refinery via a ladder logic emulator that empowers engineers to modify the behavior of the system without modifying source code.

Robert Hoffman - Signal.X Technologies, LLC

This project involved a demonstration plant for the proprietary refining process of converting biomass such as woodchips and rice hulls to diesel fuel on a commercial scale. The refinery takes in up to 25 tons of biomass per day and generates a direct commercial replacement for diesel fuel from petroleum sources. Key factors in the choice of control system included reconfigurability, clear user and operator interfaces, and the ability to trend and log data during a run of the refinery at a given recipe setting with a given feedstock.

NI Gold Alliance Partner Signal.X Technologies developed a control system that combines two PXI controllers that interface with 10 EtherCAT chassis, subsystem programmable logic controllers (PLCs), and networked sensors for a total of more than 3,000 points of I/O.

Working closely with plant control engineers, Signal.X designed a comprehensive graphical interface that mimics the layout of the refinery and gives operators immediate visual awareness of process status. A number of user-configurable auxiliary screens offer a closer view of representations of the plant’s many subsystems. We introduced our proprietary Signal.X PAX technology to organize functionality over the large amount of distributed I/O. Engineers can define any number of high-level command functions, safety and fault behaviors, and automation sequences with this user-configurable automation core.

Distributed I/O and Controls

The system’s 3,000+ points of I/O are scattered throughout the refinery at distances of 500 ft or more apart, so wiring the signals back to a single enclosure would be costly and time consuming. We distributed NI 9144 EtherCAT chassis throughout the refinery to greatly diminish the wiring task with short signal runs to each chassis in the field. Ethernet was the only wire back to the main control room and the PXI chassis.

The NI 9144 chassis includes an integrated FPGA, which was also instrumental to the success of this project. System uptime and reliability were the two most critical factors when considering the architecture. We took advantage of the onboard FPGA for all critical control parameters. We developed the FPGA code so that each chassis was capable of up to 16 independent and configurable proportional integral derivative (PID) control loops, controlling and maintaining items such as chiller temperatures, valve flow rates, and fluid levels. This design ensured full control of the safeties and processes even if other primary system components such as the Ethernet cabling, PXI chassis, or PC failed.

Real-Time Functionality

  • We chose two NI PXI Express controllers for the refinery controls to fulfill the superior processing power, data storage, and memory requirements, as well as act as the EtherCAT master for the distributed I/O. The core of the control system application, written and deployed using the NI LabVIEW Real-Time Module, is responsible for the following primary functions:
  •  Acquire/log/control signals from all I/O threads:
    • EtherCAT
    • Modbus TCP from networked sensors
    • PLC via EthernetIP
    • UDP streams
  • Evaluate user-defined logic
  • Execute output control based on logic evaluation
  • Publish data for the user interface

To accomplish these tasks, we used our internal technology, Signal.X PAX, to speed development and minimize commissioning time. Signal.X PAX technology, a logic-based execution system, focuses on multithreaded embedded software development in LabVIEW. By using a defined data space from each thread of the application, Signal.X PAX created a logic engine that made decisions based on the state of the system and set outputs and sent commands to each thread.

Signal.X PAX incorporated concepts familiar to ladder logic programmers like using a simple table editor to define sequential logic rungs. The full computation capabilities of the PC were also available to define more advanced data management, display and waveform acquisition, and processing behaviors. Fundamentally, Signal.X PAX evaluated decisions based on inputs and command actions when a rung was evaluated as true. It could be structured to support various modes and evaluate actions in sequence or in parallel, accommodating continuous limit checks and sequence control in manual or automatic mode, or as a global check.

This provided customers with a sophisticated and flexible tool to serve their testing needs while helping engineers with limited or no LabVIEW knowledge configure the test system to future needs. However, experienced developers could modify the threads (loops) of their custom applications that provide data to the Signal.X PAX logic engine due to the modularity of the architecture.

A key benefit of the LabVIEW architecture was the ability to log all data relevant to the entire refining process at the real-time level. Control and chemical engineers had easy access to critical recipe quality and efficiency data in the form of data files logged by each PXI controller. The rate of acquisition could be modified on the fly based on refinery conditions or state, and the data was logged in the NI standard Technical Data Management Streaming (TDMS) format.

User Interface

We used the LabVIEW Datalogging and Supervisory Control (DSC) Module to create a user interface that closely represents the overall refinery layout. The many customizable and industry-specific images and LabVIEW controls helped us develop an intuitive and familiar environment for any user to quickly determine refinery status, navigate to trouble areas, or change process variables or recipes seamlessly.

Native multiple-monitor support in LabVIEW and Windows made it possible to produce independent displays for every monitor connected to the PC. We could add more displays by simply using video cards with more monitor outputs. A total of six high-definition displays in a pyramid configuration were used. Each 42 in. widescreen displayed and controlled refinery status in the control room simultaneously. The primary screen represented the overall refinery layout. From this screen, users could click on one of the subsection areas to automatically load detailed information on one of the subscreen monitors. Since so much information could be visible at one time, visual cues such as drastic color changes and blinking controls or indicators for alarm conditions were critical. We also included choosing color schemes that were appropriate for color-blind users.

The Bottom Line

This application realizes the vision of the NI hardware platform for distributed I/O to the fullest extent. It is a powerful example of what can be accomplished with the graphical system design approach. By partnering with Signal.X and NI, the refinery realized a safe, reliable, and configurable system with reduced hardware cost, quick development time, and significant flexibility for long-term maintenance and scalability.

Contact Information:
John Niezgoski
Applications Manager
Signal.X Technologies, LLC
15800 Centennial Dr., Suite A
Northville, MI 48168
(734) 624-1450 

Author Information:
Robert Hoffman
Signal.X Technologies, LLC
15800 Centennial Dr., Suite A
Northville, MI 48168
Tel: (734) 417-8236

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