LPM TPM measures the rails worldwide

An OEM product for SPENO International SA
A customer product
The LPM TPM on-board system for Speno
Rail measurement to automate maintenance

As the train passes, the rails wear out. To maintain them, Speno designs trains fitted with grinding wheels. They use rail profile measurement systems. Grinding is carried out according to the results obtained. Previously operating contact measurement sensors, the Swiss company has modernized its measurement systems by providing them with optical technologies. She took the opportunity to develop the PXI processing and visualization platform. The application programmed in LabVIEW now runs on a single PXI controller with a multi-core processor ...

On-board rail measurement system for Speno

qmt has developed and industrialized, as part of its OEM program, the LPM TPM product for measuring the profile of the rails. The systems are installed in grinder trains which relies on the maintenance of railways around the world


The designation of transverse profile corresponds to the part of the rail potentially in contact with the wheel on a section orthogonal to the direction of the rail. The longitudinal profile is defined as the variation in height of the rail-wheel contact point with respect to a reference along the axis of the rail. The wear of the rails appears a) on their transverse profile, in which case it is a wear by friction of the edge of the wheels on the rail (mainly in bends), or by creep of the rail if excessive loads are put outstanding; b) on their longitudinal profile, forming undulations whose amplitude increases with each passage of railway convoys (mainly in the acceleration and deceleration zones).

Correcting the transverse and longitudinal profiles is essential for the safety of rail traffic (strength, grip, guidance, etc.), to reduce track maintenance costs (the less the profiles are worn and the less they wear), and finally to reduce vibration problems (loss of traction energy, reduction of noise emitted by the passage of a convoy, increase in passenger comfort).

The measurement system developed is used to determine the transverse and longitudinal profiles on the train which realizes the correction of the rails by grinding. He indicates to the conductor the areas and the intensity of grinding. This system consists of five subsystems: determination of transverse profiles by laser (KLD), comparison and management of transverse profile measurements (MPT), determination of longitudinal profiles by mechanical height sensors positioned on a rolling cart (MPL), a supervisor and a test and calibration bench.


As in any engineering project, the primary objective is to obtain the greatest number of reliable functionalities for a minimum investment. The industrial context also imposes unforgiving reliability criteria and minimal downtime, and therefore troubleshooting. Thus, in a single development, several pseudo-independent and inter-communicating sub-systems were developed using the solutions offered by National Instrument.

Longitudinal measurement module (MPL)

This subsystem integrates the acquisition of the height measured by the sensors in contact with the rails, processes the data to display the information useful to the train conductor, records it, then regenerates it on a plotter in order to have a paper copy of the measurements . This system must be able to be autonomous, print data coming from another identical subsystem, or work with the supervisor. This module has neither an output screen nor a keyboard.

Transverse measurement module (MPT)

This subsystem is composed of the laser system and the MPT management system. The MPT receives the data from a profile measurement sensor and compares it with reference profiles saved in a library to indicate which grinding wheels to use (and at what depth) to correct the profile. It then prints the cross sections on a printer. This system must also be able to stand alone or work with the supervisor.

Supervision module

This subsystem is used to configure the MPL and MPT modules, to display their measurements "on the fly", possibly to supervise other systems present on the train. It must be able to be stopped without disturbing the operation of the two subsystems.

Fit For You (F4U)
some products

some products

F4U program
Solution on

Solution according to notebook

M4U program
OEM program

Custom product
industrialized by QMT

OEM program