Real-Time, Mission-Critical Control and Acquisition of a High-Channel-Count Distributed and Networked System

Author(s):
François Desjardins - Averna Technologies, Inc.
Shahzad Sarwar - Canadian Space Agency

Industry:
Aerospace/Avionics

Products:
Lookout, LabVIEW, Real-Time Module, Compact FieldPoint, PXI/CompactPCI, FP-2010, DataSocket, ENET-232/2, Signal Conditioning, Distributed I/O, FieldPoint

The Challenge:
Implementing a distributed and mission-critical data acquisition and supervisory control system that integrates thousands of transducers, actuators, and thirdparty data loggers with secure system access, configurable data logging, data extraction, and display features in a short delivery time.

The Solution:
Using off-the-shelf hardware from National Instruments, including FieldPoint real-time controllers, I/O modules, PXI-based switching, and ENET modules combined with powerful software tools, such as LabVIEW and Lookout, to implement the fully integrated solution in a cost-competitive and time saving architecture.

The Need for a Quick Upgrade

Before upgrading their system using NI hardware, our customer’s test facilities used several different technologies to control the chamber environment variables and measure a multitude of physical quantities. They needed a system that incorporated thousands of single measurement points including thermocouples, voltage and current transducers, relays, digital I/O, and measurements transmitted by data logger units through serial links. The technologies that the facilities implemented in the past were controlled by applications that were limited in flexibility, ease of use, and speed. In addition, they relied on custom, obsolete signal conditioning hardware and the high-channel-count system had to operate with stable, redundant hardware. Our customer needed networked, distributed operation along with real-time control and flexible configuration capabilities. They considered replacing the existing transducers and data logger units, but our customer needed to upgrade the system within three months and this option was too time-consuming and cost-prohibitive to meet the deadline.

Implementing Flexible Technologies

After working with NI support engineers, we realized that we could address all of our customer’s system requirements with cost-effective and flexible technologies including NI FP-2010 controllers with real-time acquisition and control; FieldPoint modular I/O for distributed signal conditioning and acquisition of a variety of analog and digital signals; ENET-232 modules to integrate serial interface devices in the system without distance limitations; PXI-based switching hardware for implementing hardware redundancy; Lookout software for supervisory control and data logging support by Citadel; the LabVIEW Real-Time Module to build an embedded and easy-to-design control and data acquisition engine; LabVIEW software for implementing a flexible user interface for system configuration and data viewing and to glue other subapplications together; and support technologies such as DataSocket, VI Server, and ActiveX for ease of integration and information exchange between several different subapplications running real-time or Windows OS platforms in a networked environment.

Using Lookout, we implemented main and backup control servers that rely on the Windows NT operating system running on personal computers to provide redundant execution. We built the redundant network using switches, multiroute cabling, hubs, and best network topology practices.

We also designed internetworking and intranetworking using Microsoft security software to manage user access at the operating system level. The built-in user manager features in Lookout also helped resolve user access issues. We implemented I/O stations using firmware that runs with LabVIEW Real-Time on the FieldPoint controllers, which interact locally with the I/O modules and the control servers to integrate all of the required system inputs and outputs.

To integrate the data loggers and other control hardware with the serial interfaces, we used LabVIEW drivers running on control servers. ENET-232 interfaces connected the serial hardware to the Ethernet infrastructure while providing transparent and remote connectivity to the equipment. Furthermore, we built multiple operator consoles using Lookout, and our customer can deploy the consoles anywhere on the local network. These applications run on Windows NT installed on personal computers. Internet and intranet users gain access to the client and server applications using a Web browser and the built-in Web server features of Lookout and LabVIEW.

System Architecture Overview

We divided the system into five major subsystems on the server side:

• Lookout server
• LabVIEW servers
• FieldPoint controller applications
• PXI switch controller application
• Manual reversion application

On the client side, the operator console contains management windows and complex data viewers created with LabVIEW. We created the industrial-look graphical display for processes using Lookout.

The main Lookout server is normally active and runs on the primary server machine. The standby Lookout server that runs on the standby server machine monitors the primary Lookout server and automatically takes over if the primary Lookout server fails. When the primary Lookout server comes back on the network, the primary and standby Lookout servers return to their previous operation. The Lookout redundancy system manages these seamless control transfers.

The LabVIEW server is an application residing between the Lookout server and the rest of the system. A primary LabVIEW server is associated with the primary Lookout server, and a standby LabVIEW server is associated with the standby Lookout server. The LabVIEW server reads/writes the FieldPoint hardware I/O channels by communicating with the FieldPoint controller application that runs on the FP-2010 module and controls the FieldPoint bank. The FieldPoint controller application runs on each active and redundant FieldPoint controller bank on the network.

The PXI switch controller application executes in a PXI controller and switches the primary and redundant FieldPoint banks. The LabVIEW server sends the switching commands, and the manual reversion application executes on a PC so that the user can take local control of a FieldPoint bank through RS232 communication on the serial port in the FieldPoint controller module.

Implementing Hardware Redundancy

FieldPoint I/O devices, which we grouped in banks of three to eight modules, acquire all of the current and voltage signals. We used an NI FP-2000 controller running LabVIEW Real-Time to supervise each bank. The system implements a three-to-one hardware redundancy by routing the I/O signals to FieldPoint controllers through PXI switches. Using the redundant local area network, all of the FieldPoint controllers connect to the main and backup servers.

Intuitive and Hierarchical Access

With the LabVIEW application, the system can build disk-resident configuration sets with intuitive and hierarchical access to the system hardware. Configuration changes dynamically load to the PXI application and FieldPoint controllers and become effective in real time.

Real-time code in the FP-2000 controllers handles deterministic system control and provides the transducer data to an acquisition demon running on the server machine. The server collects the data from the serial devices and feeds it to Lookout data logging panels. Data logs to a Citadel database with a typical logging rate of 100 KB/s. The user can conduct features such as alarming, dead band for logging, and defining computed data values through the data acquisition and logging part of the system. Also, the user can implement LabVIEW VIs to take advantage of configurable data extraction and viewing with historical, real-time trend graphs with tabular data display.

In addition, we designed the system control in subcategories. Proportional integral derivative (PID) control loops running on FieldPoint controllers provide a deterministic control of sensitive system parameters. Users can optimize the PID parameters and monitor loop performance with VIs running on remote networked machines. The supervisory control and human machine interface (HMI) commands propagate through the Lookout panels to FieldPoint controllers across the network.

Successful Development of a Mission-Critical System

The main and backup servers rely on Lookout redundancy features to realize a mission-critical system that parallels the hardware redundancy while minimizing the data and control loss due to hardware or software failure on a single system element. The system operates in distributed networked modules where users have password protection and hierarchical access to single test facilities for all of the control and data viewing operations. Using NI hardware and software, we successfully implemented the fully integrated solution in a cost-competitive and time-saving architecture.

Author Information:
For more information on this Case Study, contact:
François Desjardins
Averna Technologies, Inc.
87 Prince - Suite #140
Montreal H3C 2M7
Tel: (514) 842-7577
Fax: (514) 842-7573
info@averna.com

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