1 Introduction
Track Geometry Control System (TGCS) has been designed to enhance the capabilities and improve the performance of track maintenance machines. It provides a means of acquiring track measurements, designing track adjustments, implementing the designed adjustments during track maintenance as well as performing an audit or check of the maintained track as a means of quality control.
1.1 System Requirements
The system comprises an industrial PC, high performance data acquisition sub-system and application software which is fully IBM PC and MS Windows compatible. All the application software has been designed to be used with a touchscreen but can also be used with a mouse or other pointing device. A keyboard is not required as the TGCS software provides the necessary on-screen keyboards and numeric keypads where data entry is required.
Above: A Stealth industrial Pentium PC and TGCS interface box installed on a tamping machine
The minimum system requirement is an IBM or compatible PC with 4Mb RAM and hard disc, running MS DOS and Windows 3.x, together with a VGA display, mouse, trackball, touchscreen or other pointing device. The PC must have at least one vacant ISA slot to accommodate a full length AT size expansion card. For best performance the PC should have a rugged industrial specification, a maths co-processor, a colour LCD, VGA (640 x 480 resolution) display, and an Accutouch 5 wire resistive touchscreen with Monitor Mouse driver for Windows.
1.2 System Components
The data acquisition sub-system is a Sorcus Modular 4 base board with plug-in modules to interface with a distance wheel shaft encoder, displacement transducers, and analog lining and lift controllers. the base board complete with modules is installed in a single ISA expansion slot within the PC enclosure.
The remaining components of the system are an interface box containing cable interconnection terminals, fuses and power supply modules, a Hohner shaft encoder, and Jewell servo inclinometer(s). The shaft encoder is fitted to a suitable distance measuring wheel. This can be either an independent wheel or a wheel of one of the track referencing trolleys. One inclinometer is fitted to one of the track referencing trolleys for recording cant. If required for lift and cant control, the second inclinometer is fitted to the lift referencing frame.
1.3 Machine Requirements
TGCS can be fitted to a range of track maintenance machines, having a variety of existing measuring transducers, most systems being based on measuring track displacement from a fixed reference chord. For meaningful track measurements, the displacement transducers should be related to a suitable chord geometry, so that overlapping chord measurements can be used to accurately reconstruct the track shape. Transducers can be supplied or existing transducers adapted to provide the necessary displacement measurements.
Above: A displacement transducer modified to measure both horizontally and vertically.
1.4 Track Geometry Recording
Track Geometry Recorder is used to obtain a set of measurements from which the track shape can be reconstructed, together with the locations of essential track features such as cant transitions and fixed lift and slue positions. During recording, the machine is run along the length of track being measured. TG Recorder obtains track measurements from the displacement transducers at equally spaced points, the operator has a visual representation of the track measurements as recording progresses, with graphs of cant, horizontal and vertical measured versine being displayed on the screen.
When a track feature is encountered, the machine operator logs its position by pressing the relevant touchkey. A graphical representation of all the logged features is shown on the screen. Recording can be carried out, typically, at a speed of 15 km/h. On completion of recording the measurements are stored, they can subsequently be used to compute track adjustments (slues and lifts) using Track Geometry Designer or transferred to office based systems. Usually recording is carried out the direction opposite to that of maintenance so that on completion the machine is in the right place to start implementing track adjustments.
1.5 Designing Track Adjustments
Track Geometry Designer reconstructs the track shape from the measured displacements, and computes the track adjustments required to reduce track faults up to 200m wavelength. Adjustments are calculated within a global maximum range, defined by the operator, and additionally, points where adjustment is fixed or restricted are accommodated using an optimised curve fitting process to obtain the smoothest design track shape.
The operator can view the design slue, lift and cant adjustments on screen. The design can then be saved prior to starting track maintenance using Track Geometry Adjuster.
1.6 Track Adjustment
Track Geometry Adjuster controls the lift and lining actuators during tamping and lining to apply the designed adjustments. A real-time process continuously reads the track position and updates the analog signals driving the hydraulic servo valves. The operator can monitor the control process with mimics of the standard analog meters being shown on screen.
Controls are provided to pause/resume the adjustment process when necessary and to ramp out, should work need to be completed prior to the end of the originally measured track section.
1.7 Checking after Maintenance
Complementary to TG Recorder, Track Geometry Checker acquires a re-measurement of the track to allow a comparison to be made of track qualities before and after maintenance. The machine is run along the same section of track and TG Checker obtains track measurements from the displacement transducers at the same equally spaced points. No feature logging is required. The re-measured displacements are stored together with the original recording run.
1.8 Auditing
Track Geometry Auditor acquires measurements of actual track adjustments during maintenance. TG Auditor can only be used where additional displacement transducers are fitted on the machine. The audit can either be carried out independently or in conjunction with track adjustment using TG Adjuster.
1.9 Quality Control
Track Geometry Viewer calculates and displays graphs of a variety of track parameters, either from recording runs or where designed, checked or audited track measurements are available, from the track geometry before, as designed and after maintenance.
The standard parameters are 35 and 70m filtered alignment and top standard deviation. The parameters can be calculated for standard lengths of 400m, 200m, 100m or 50m or for the entire measured site. Alignment, top and cant are displayed graphically as well as with the numerical s.d. values.
1.10 Utilities
Utilities are provided for testing the data acquisition hardware, calibrating the track measurement transducers, and downloading track geometry data to floppy disc for transfer to office based systems.
| © 1998, 1999 David C. Marriott - Track Maintenance Systems |
| TGCS logo by Amelia Did It! Custom Graphics |
| Last Updated :31/12/01 |