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Real Time Engine Control
The U.S. Environmental Protection Agency requires large engines to meet strict pollution-emission requirements to be certified roadworthy. Engine manufacturers don't need to test every engine, just a particular design. Thus having the test equipment to perform the tests would be costly, since they would only be used when a design changes. So they ship a new engine to a test facility where such testing occurs all the time. This facility puts the engine into a test cell, and couples it to a dynamometer. By running the engine through an EPA-specified speed/torque cycle, the real world of uphill / downhill, fast / slow, continuous / irregular driving can be simulated. And by measuring the pollutant concentration in the engine's intake air and the concentration in its exhaust during this cycle, one can judge the pollution emission contributed by the engine. Since the cycle is specified, the tests are repeatable. However, it is the speed and torque which must be controlled to match the specified cycle. But the engine does not have a "torque" input: it has a throttle input. The throttle influences the torque, but does not directly control it. To resolve that, a PID (Proportional - Integral - Derivative) loop is required. This loop measures the current speed and torque values, compares them to the target values, and calculated (based on P,I, and D factors) a corrective signal to drive the throttle and dyno toward the target values. Such a control loop requires accurate timing and accurate measurements. While a desktop-based system could provide the accurate measurements, timing is another matter. Desktop Operating systems are not designed to be real-time. Screen windows coming and going, network traffic, mouse movement, all of these interrupt the data-acquisition process and disturb the timing. To get around that, Culverson recommended that a true real-time operating system be employed to perform the control loop operations (at 100 times per second). This solution worked so well that a whole PXI system was installed, and all DAQ operations (measurements of pollution concentrations, temps and pressures) were moved into the PXI. Now the host computer acts as the control center, and data reviewer, while the PXI acquires all data.
With 250 or more channels to acquire, it is essential for the configuration process to be as simple and re-usable as possible. Here is the channel configuration window, showing all possible fields. Some fields are disabled according to the channel's type. The SUMMARY window shows a list of all channels of a given type. Configuration errors (e.g., assigning two channels to one physical line) are caught here, befor a test is even started. The configuration program is stand-alone, and can be run on an engineer's office, without DAQ hardware.
The PROJECT configuration defines parameters about the project as a whole, rather than individual channels. the HIGHLIGHT DIFFERENCES feature shows differences between any given project file, and the CURRENT file. Config files are automatically backed up, and stamped with a usage date to verify what configuration was in place at what time.
A HEADER window defines parameters for this particular run, such as what ranges the gas analyzers are to expect. Cartain project config info can be overridden here.
For precise gas measurements, the gas analyzers must be calibrated often. Some analyzers are self-calibrating, others are not. Calibration involves flowing a zero-concentration gas thru the analyzer, and recording its reading, and then flowing a known-concentration gas (near full scale) thru the analyzer, and recording its reading again. This window accomplishes that.
After calibration, we are ready for a test. During the test, you can monitor up to four channels on two charts, or up to 60 channels in text indicators on the other tabs. Configuration options let you group channels together for display. Channels exceeding warning values are highlighted, channels exceeding danger limits can trigger a shutdown of the engine.
After the test, the recorded data file is automatically brought up for review. One can view any channel, make an HTML document of all channels, and print the graphs from here.
As per Culverson standard policy, the data file CONTAINS all the configuration files used to record it. This prevents any question of "which configuration did we use?", or "what was the scale factor on channel 13?". It is recorded in the data file itself, and can be easily extracted.
This window allows you to construct your own spreadsheet format. You may choose which channels to include, what order to put them in, and what time portion of the test to include. This format is saved in a separate file, so you can apply it to several data files if need be.
After formatting the spreadsheet, you may preview it and save it for importing into a spreadsheet program.
The data file can be analyzed for emissions totals, these are obtained from detailed analysis of the recorded signals, in methods defined by the EPA.

NOTE: These programs are NOT available for purchase from Culverson Software. These are examples of the type and quality of work done. All work done by Culverson Software is proprietary, and will not be sold, traded, or given away to other parties.
Some of the above pictures may have logos, program names, and other references to actual clients removed, for contractual reasons.

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