GPS RIDER Ride Quality Measurement
GPS RIDER is a vibration recording system which obtains geographical position and speed information using the Global Positioning System or GPS. It is designed for use primarily in the Rail industry as a quick and convenient method of locating track faults and for assessing passenger comfort indices.
GPS Rider is used on high speed in-service trains and requires no connection to the train's systems.
The GPS RIDER recorder is a portable battery powered unit that measures and records vibrations in 3 axes. Data is downloaded to a PC where it can be examined in both graphical and text report format. The data is used to locate track defects, identify vehicle suspension faults and for ride quality measurement. The system produces a map of the actual surveyed route with the location of likely track faults and areas of poor ride quality highlighted.
With GPS RIDER for Windows, you can get
a report giving track jolt locations and severity
a comfort report based on UIC513
a map showing the route taken, highlighting jolts and areas of poor ride quality
graphs showing the speed profile, the raw and the averaged rms vibrations
Raw data from the accelerometers is first weighted to ISO 2631 in the frequency range 0.5Hz to 80 Hz before rms averages are calculated. The rms values are averaged over between 1 and 60 seconds. A short averaging period of 1 second allows discrete track defects to be identified. Longer periods of 2 - 5 seconds can be used to investigate suspension or vehicle/track interaction problems, and longer periods of 10+ seconds are used for evaluating passenger comfort or ride quality. Raw data can be displayed as a trace graph. Concise and easily understood reports can be produced from the data in each recording.
The recorder has no moving parts and contains 3 high quality accelerometers. The case is made from stainless steel and has a gasketed cover, closed by lockable toggle latches. This cover gives access to an LCD and keypad that control the operation of the recorder.
The recorder displays vertical, lateral and in-line vibrations as moving traces on the LCD. RMS levels are also displayed as digital values and analogue bar graphs. Recordings are stored in memory and are downloaded with GPSRIDER for WINDOWS. This software displays recordings as graphs on the computer and also produces reports by analysing the data.
The recorder is powered from rechargeable batteries that can be recharged via a low voltage adapter or by connecting an external 12v supply.
Speed and position is obtained using a GPS antenna the size a computer mouse. For optimum performance, the antenna is mounted where it has a clear view of the sky. However, it may also work satisfactorily even if the view is slightly restricted. Ideally, the antenna should be mounted on the roof, or under a non-metallic panel in the roof of the train. Depending on terrain it can sometimes give satisfactory performance on the inside of a side or front/rear window.
Speed and position information is embedded in the recording and enables vibrations or jolts to be located on a geographical basis. Speed information is accurate to about 1 mph and location accuracy to around 10 metres (2DRMS)
An optional external accelerometer can be used where space is at a premium or where high levels of vibration occur. Typically, this is used when measurements are being on suspension components. The 3-axis accelerometer is housed along with signal conditioning cuitry in a robust, compact, stainless steel enclosure with fixing holes in its base plate.
The range of the accelerometer is selected to suit where the device is used.
Taking a recording is simple!
The GPS antenna is positioned where it has a clear view of the sky and is connected to the recorder. The recorder is placed on the floor of the car with the connectors facing the front, and with the cover opened, the RECORD button is pressed to start the recording. A red LED flashes to show that it is recording. When the train has travelled over the area of interest, the RECORD button is pressed again to stop the recording. The recorder is connected to the serial port of a PC and with GPS RIDER for Windows, downloading is a simple one click operation.
GPS Rider for Windows 95/98/Me/NT/2000
GPS RIDER for Windows is a specially written package, which stores and analyses data from the recorder. It can be run on a colour Notebook PC so that analysis of a recording can be undertaken on the train. It produces detailed colour graphs, concise text reports and a map of the route over which the recording was taken. The map is produced automatically from co-ordinates that were stored in the recorder from the GPS antenna. Areas that exhibit levels of vibration above a user programmable threshold are highlighted by a change in colour and the jolts by marks. A cursor can be moved along the route to examine values at any point. Stations, level crossings, junctions, etc. can also be displayed on the map.
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