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Targeting accuracy and precision with laser sensors

laser sensors

Bestech is providing the local rail industry with access to products such as laser sensors that are used in driving advanced solutions.

The fundamentals of rail wheel interaction have been established for many decades. The conical shape of the wheels allows for the wheel set to shift while rounding a curve, and for the train to stay on track. These engineering principles have served railways well for centuries, however engineers are now looking for a way to reduce rail wear, allowing the tracks to operate longer without maintenance.

In a trial underway in the UK, an array of optoNCDT 1420 compact laser triangulation sensors from Micro-Epsilon have been installed to provide the measurement behind the ActiWheel solution. The sensors guide the ActiWheel traction system to produce more driving force on one side of the wheelset to ensure the train travels down the centreline of the track. The solution would overcome the compromises and issues that result from the combination of a solid axle and wheel coning and reduce wear on the wheel and the rail.

ActiWheel relies upon precise and accurate measurements from the optoNCDT sensors to provide the information for the artificial intelligence software that drives the motors that are individually affixed to each wheel. The optoNCDT sensors measure the lateral position of the wheel, relative to the rail, and according to Neil Cooney, technical director at the UK company behind ActiWheel, SET, the particular specifications of the sensor made it the perfect fit.

“We initially approached Micro-Epsilon for a suitable sensor and were very impressed with the application engineer who demonstrated the optoNCDT 1420 sensor to us. The sensor met all our technical requirements in terms of its flexibility, resolution and robustness. We are measuring down to 0.1mm accuracy and lateral movement can be up to a maximum of 20mm,” said Cooney.

This is not the only application of laser sensors in the rail industry. Sensors such as the optoNCDT have been widely used for maintenance of rail tracks and to measure wear and tear. This is in addition to track guiding devices that are installed below the train, which also use laser sensors. The conditions within these applications require a certain kind of sensor.

“These require a compact sensor that can be easily installed and provide accurate and reliable measurement at high speed,” said Wirhan Prationo, marketing engineer at Bestech, which distribute sensors from Micro-Epsilon in Australia.

As seen in its adoption for the innovative ActiWheel solution, the compact optoNCDT is optimised for the rail industry as a laser triangulation sensor.

“It combines speed, size, performance and versatility for measurement applications in the rail industry. This compact laser triangulation sensor is suitable for measuring distance and displacement up to 500mm with maximum sampling speed of 4kHz. It also can be easily integrated in restricted and narrow installation space,” said Prationo.

In the ActiWheel case, the sensor was particularly useful when it came to ensuring that the data collected was only that which was required, said Cooney.

“We’ve also been impressed by the filtering function, which filters out noise from dirt, dust, grease and pieces of bent metal on the rail head, which means we can trust the measurement data,” said Cooney.

To use the sensors, SET created a frame that lies beneath the wheel axle of the train, 400mm from the rail head. The sensors are located in front of the flange and point towards the rail head. The data from this assembly is then transferred to the ActiWheel control system via a 4-20mA analogue signal. Operation and configuration can be done using the web- based interface. While these are the settings used by the ActiWheel team there are other information channels available.

“The optoNCDT laser triangulation sensor offers a range of different output signals that enable easy integration of the sensor into any industrial control system,” said Prationo. “The sensors are operated through the web interface and they also have additional analysis features, such as video signal display, signal peak selection, background noise filtering and signal averaging. A mobile data acquisition unit can be used to collect the data, which can be connected to the computer on board.”

With the trial ongoing in the UK, the optoNCDT’s technical specifications have been tested in a variety of environments. Rated to an IP65 protection level, the system is housed within a casing that is impenetrable by dirt and dust.

During the demonstration, the optoNCDT sensors were able to read accurate data in the harsh environment underneath the train, where dust, dirt, and moisture are present. They also delivered consistent reading irrespective of whether it’s a cold, wet, rainy or bright sunny day. After running for a couple of thousand miles the sensors did not need cleaning.

While the further development of ActiWheel promises much for reducing rolling contact fatigue, this is only one potential application of the optoNCDT sensors.

Located in Australia, Bestech is able to collaborate with rail organisations seeking to leverage the precision and accuracy of laser sensor technology.

“Bestech have more than 40 years of experiences in sensors and instrumentation for solving test and measurement challenges in the industry,” said Prationo. “We offer not only high-quality products, but also our technical expertise and support to assist with real-time application to correctly gather the data you require. Bestech can also customise the product to fit into certain requirements, such as different cable length, integration with mobile data acquisition system or signal conditioning to fit into the existing devices.”

“Our team is supported by highly- trained applications engineers and product specialists with a wealth of experience in sensor applications for measurement of physical parameters in the industry.”

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