Easily Detecting and Addressing Faults on Denver’s Light Rail Vehicles

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"Before the Optimation and NI solution was incorporated into the train, the driver was only provided with a single warning light that illuminated when the train was not capable of moving, and the driver would have to search the whole train for the cause. The new system drastically reduces troubleshooting time by telling the driver specifically which car and signal is malfunctioning."

- Levi Gustin, Optimation

The Challenge:
The Regional Transportation District (RTD) of Denver maintains and operates a fleet of Light Rail Vehicles (LRV) for public transportation in the Denver metro area. The existing LRV train cars operate as intended, but do not provide ample feedback to operators while in use, or to mechanics about causes of failure.

The Solution:
RTD approached NI and Optimation about incorporating a data logging, communication, and display system into the trains.

Author(s):
Levi Gustin - Optimation

System Design

An RTD Supervisor provided a description of the project requirements, including incorporation of GPS satellite data and TTL/RS232 communications with existing control equipment, as well as a graphical user interface (GUI) for the LRV operator. The GUI screens were defined so an operator could quickly determine the source of problems and correct them if possible. If problems were beyond the abilities of the operator, maintenance could be summoned without delay.

Since Optimation, an NI Gold Alliance Partner with Certified LabVIEW Architects and Certified LabVIEW Developers, has a strong history of working with LabVIEW software, our system developers easily created a data logging system for individual cars. The individual systems read and record digital and analog signals that are unique to each end of the car. This data is then transferred via Ethernet Modbus communication between the two cRIO-9074 and cRIO-9075 devices in the car and logged locally to one of the two TPC-2206 touch screen computers in the car. Besides the acquisition of data, the individual systems can receive a GPS signal to accurately set and synchronize system clocks throughout the train. This allows data acquired on two different pieces of hardware at opposite ends of the car to be related to each other through this GPS timestamp. The system also writes this GPS time to the train car’s internal computer system through serial ASCII communication. This is helpful for the RTD personnel when trying to correlate a generic error signal in the train’s existing computer with a more detailed signal-by-signal record of events logged in the NI hardware.

A Communication Challenge

The most impressive and challenging portion of the system was communicating data through the entire length of the train. Car-to-car communication is accomplished through Serial Modbus via the couplers that join two individual cars together. For a piece of data to make it from the back car of a train to the front cab where the operator display resides, it had to alternate between Ethernet communication internal to the cars and serial communication between the ends of two adjoining cars. An additional communication challenge was that the RTD’s LRVs can be driven or coupled from either end in either direction. This means that the software had to be flexible enough to propagate data in the correct direction—Modbus slave vs. Modbus master.

Reducing Troubleshooting Time

When the complete set of data is delivered to the lead cab of the train, it is displayed on an NI Touch Panel Computer. In the event of an equipment failure, the GUI allows the driver to quickly determine what possible cause would be keeping the train from successfully moving. Before the Optimation and NI solution was incorporated into the train, the driver was only provided with a single warning light that illuminated when the train was not capable of moving, and the driver would have to search the whole train for the cause. The new system drastically reduces troubleshooting time by telling the driver specifically which car and signal is malfunctioning.

Benefits and Results

The Optimation system has greatly benefitted RTD’s mechanical operations by providing more information related to mechanical failures through utilization of the data logs. RTD has also noted a gain in efficiency and as well as a decrease in downtime by providing trainwide signals to the driver.

Author Information:
Levi Gustin
Optimation

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