Information on the Universal Data Acquisition and Control System (UDACS)

Southwest Research Institute has developed a novel system that streamlines engine, lubricant, and emissions testing. The Universal Data Acquisition and Control System (UDACS), a combined hardware and software package, can be customized to run standard and non-standard tests on a variety of gasoline or diesel engine test stands.

UDACS provides the equipment to transduce and condition various input parameters, including temperatures, pressures, forces, speeds, and flow rates. It also contains output devices such as pressure outputs, voltage outputs for heating elements and dynamometer control, and digital outputs in the form of AC or DC relays. The system provides:

• Automatic test sequencing
• Closed loop control
• Disk logging of test data
• Data display in real-time
• Configuration by non-programmer

Software consists of a stand version (UDACS-TS) that runs only on the UDACS hardware and a desktop version (UDACS-DT) that runs on any IBM PC AT compatible with EGA or VGA, hard disk, and math coprocessor.

Flexible Hardware

The UDACS console contains a blower (or optional air conditioner), a rack-mounted CRT, an IBM-compatible industrialized PC, keyboard, UPS (uninterruptible power supply), signal conditioning, power supplies, and various transducers. The UPS not only provides power during a blackout (for 10-15 minutes) but also protects all of the electronics from power line spikes and noise. UDACS signal conditioning contains six backplanes that provide for 64 analog input channels, eight digital inputs, four frequency inputs, 16 analog outputs, and eight digital outputs. Signal conditioning modules (5B series) are plugged into the appropriate backplane positions.

The input pressure panel is pre-drilled and wired for up to 24 pressure transducers. Only the transducers required for a particular application are usually installed. Transducers can be easily installed in the field by removing the hole plug, installing the transducer, and mating the electrical connectors. The output pressure transducers (I/Ps) are similarly configured. Also supplied are 24 jacks for thermocouples or RTDs and 16 jacks for voltage inputs.

Flexible Software

The software allows a test engineer or technician to define, write, debug, and run a laboratory test. No programming language knowledge is required. The software provides a consistent and intuitive user interface and attempts to minimize the number of items that must be remembered. The test can be developed on the UDACS hardware in the laboratory or on a PC-compatible computer in the office.

A test definition file (file with .TST extension) is created by filling in several tables as shown in the large dotted box in the diagram on the next page.

Inputs

UDACS provides for two basic types of inputs, primary and derived. Primary channels are usually associated with a single hardware input while derived channels are functions of one or more primary or derived channels. The primary input channels are first defined as the test engineer selects which of the 76 input channels to use, assigns names, units, and formats to each channel, and selects the transducer type. Up to 32 calculated channels can be defined and are also assigned names, units, and formats, as are the primary channels. Additionally, a formula must be entered to define the derivation (equation).

Outputs

The output or control channel must be configured. Eight digital outputs that control the AC or DC relay modules are plugged into the digital backplane. Each output can be named and turned on or off manually or via the test sequencing tables. Sixteen analog output channels can be set directly (open loop, 0-100 percent) or via closed loop PID control. Any of the output PID channels can be assigned a process name from the list of primary and derived channels.

Test Sequencing

After the inputs and outputs have been defined, the test designer must decide the test sequence. The test sequence is basically a list of set points for the defined outputs, an acquisition list for data logging the inputs, and a list specifying what inputs should be limit checked.

For convenience, a test is divided into small parts called steps. A step can be programmed to last from a minimum of a tenth of a second to a maximum of more than 6.8 years. The actual length of a step can depend on the elapsed time, a condition of the inputs, or an operator action. It is a period in which the digital outputs are fixed and the PID set points are defined (either as constants, ramps, or profiles), and one alarm table decides which inputs are checked. A profile is a series of regularly spaced set points such as the speed and load set points for an EPA schedule. UDACS provides up to 340 steps in a test.

A test can also be divided into larger sections called phases. A phase is a collection of from one to 128 steps in which the channels logged to disk and the logging rates are fixed. Different logging rates (or different lists of channels to be logged) in sections of the test are possible by partitioning the test into phases.

UDACS digitally filters each raw channel before logging to disk to prevent aliasing. The filter cutoff for each channel can be set by the test designer to override the default valve. Phase counters are provided to allow phases to repeat in a user programmable pattern.

Certain test procedures are always required. UDACS uses five pre-defined phases -- Start, Idle, Stop, Resume, and Emergency Stop -- in every test that, although pre-defined, are still programmed by the test designer. One of these phases is branched to when the operator pushes the corresponding function key "Start," "Stop," "Idle," or "Resume."

Each step has an alarm table in which the test designer specifies whether each channel is limit checked, its Alarm limits, Shutdown limits, and Shutdown phase. The Alarm limit checks are usually used to warn the operator that the test is running out of specification and that a malfunction may exist. The channel is displayed in yellow to alert the operator.

The Shutdown limit checks are used to protect the operator or test stand and to automatically stop a test when an operating condition is severely out of specification. The test designer selects the appropriate action (Null, Idle, Stop, or Emergency Stop) based on the severity of the problem. When a shutdown occurs, UDACS displays a red alarm message on the screen and branches to the specified shutdown phase.

Operator Interface

The user designs the layout of the text mode operator display by selecting the location and color of the channels to be displayed. Six functions are always available to the operator during the test (viewing the operator display screen, entering a comment, editing the test header, editing the last manual data entry, and viewing or plotting data, and viewing a PID activity summary), and several others become available after a password is entered.

In addition to the text mode operator display, data can also be presented via a versatile interactive plotter. One or two plots of up to four channels each can be displayed on the screen. The x-axis of each plot can be an acquired channel for x-y plots or time for strip-chart style plots. The real-time plotter updates the screen at one-second intervals. When the screen edge is reached, the plots scroll to the left. The snapshot plotter plots data from a large circular buffer that holds a fixed amount of data (e.g., one minute of 10 Hz data, 10 minutes of 1 Hz data, or 100 minutes of 0.1 Hz data). Stored data (normal or burst) can be examined with the plotter or with a user-configured table viewer.

A tuning function allows adjustment of the PID parameters (proportional band, reset, etc.) while viewing the set point, output, and other PID terms in real time. The operator can also preempt the computer generated set points and/or outputs via the tune function.

Test Results

After the test is over, the raw data must be processed into an easily readable format. A translate function built into both UDACS programs will convert the binary files into ASCII text files. For most tests, however, summary statistics are much more convenient. The report generation flow diagram shows what can be done with the data. A report configuration file must be created by the user with a normal DOS text editor. This file is a list of all steps of the text which should be summarized. For each of the steps, a list of channels, control points, and deviations is included. The output of the translate function is three ASCII text files. The summary statistics file reports the average, standard deviation, minimum, and maximum for each channel in the list for all requested steps. The second file generated contains a table for each step of the number of occurrences that each channel was not within the control point plus or minus the deviation. The last file is a list of occurrences of channels that were continuously out-of-limits for a user selected number of consecutive data points. The channel name, beginning time and duration of the out-of-limits condition, and the minimum/maximum value during that interval are presented.

Network

UDACS-TS contains an embedded TCP/IP FTP (File Transfer Proctocol) server that provides conductivity to a variety of computers (PCs, minis, and mainframes). Any FTP client (including UDACS-DT) can retrieve files, list directories, delete files, and set the date and time on a UDACS test stand while a test is running. In addition, UDACS-DT can show the real-time operator display, real-time PID activity, or a real-time plot from any network stand.

Notes:

1) UDACS-DT and UDACS-TS are copyrighted by Southwest Research Institute 1988-1994.

2) DOS, IBM, IBM PC AT and VGA are registered trademarks of International Business Machines Corporation. Excel is a registered trademark of Microsoft Corporation.

3) Specifications for UDACS are subject to change without notice.

Specifications

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