Product category:
Rotary Position, Tilt and Angular Sensors
News Release from: Variohm Eurosensor | Subject: Tilt sensor
Edited by the Engineeringtalk Editorial
Team on 31 March 2000
Non-contact Sensor used in Tilting
Trains
When Siemans Traffic Division were invited to supply control gear for Germany's new tilting trains, they incorporated a novel, non-contact position sensing unit.
When Siemens Traffic Division were invited to supply control gear for Germany's new tilting trains, they incorporated a novel, non-contact position sensing unit being marketed by Variohm Components The tilting mechanism allows the trains to run faster on conventional track whilst avoiding discomfort to passengers
This article was originally published on Engineeringtalk on 30 Jun 2008 at 8.00am (UK)
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At the heart of the system is a pneumatic cylinder that tilts the carriages to reduce the effect of lateral acceleration.
The cylinder is part of a closed-loop system incorporating a tilt Sensor, an electronic servo control system and a servo valve.
To function correctly the cylinder required a positional feedback sensor capable of operating in harsh environmental conditions such as sprayed water, dust and abrasive grit and at temperatures varying between -40°C and +80°C, for the expected 20 year lifetime of the carriages.
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The M150 can be installed in a volume of less than 20 x 20 x 10mm and provides an essentially infinite linear position resolution over measurement range of 0 to 38mm
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Thin film deposits of sandwiched magnetic and nonmagnetic layers can be combined with sensors on 'spiral arms' to return an absolute position value over a single rotation.
The system was also expected to withstand shock of up to 50g when the carriage wheels passed over the gaps where one rail meets another.
From the outset it was realised that if the system was to work reliably over such a long period, the position feedback (sensing) system needed to be integrated into the pneumatic cylinder itself.
After looking at inductive and ultrasonic sensors, Siemens decided to use the new Novotechnik TLI system which is available from Towcester based Variohm Components Limited.
This revolutionary new device uses the best features of conventional potentiometric transducers married to a captive pick-up.
The potentiometric elements are manufactured from 'conductive plastic', which is a well proven and reliable technology.
The elements are linearity corrected after manufacture in order to provide high accuracy.
Unlike a conventional potentiometer, the TLI units are energised from an AC voltage which is derived from the trains' DC supply by the TLI's integral electronics.
Utilising this alternating supply means that the conventional contacting type pickups can be replaced with a new capacitively coupled pickup.
The 'raw' output from the potentiometer is an AC signal, the amplitude of which alters depending on the position of the capacitive along the potentiometers' stroke length.
The electronics convert this AC signal to an analogue voltage which is proportional to the pickup position.
To the outside world, the TLI looks like a normal potentiometer but it isn't subject to the wear associated with a sliding pickup.
The TLI is designed to be integrated in hydraulic systems used in construction machinery, agricultural machinery or in any heavy duty positioning system.
It is an absolute system so it knows exactly where it is at all times, even if the power supply is interrupted.
It can work at speeds of up to 10 metres/second whilst still offering a resolution of 0.01mm and an accuracy of 0.15%.
Lifetime exceeds 200 million operations.
Various mounting arrangements are available at measurement ranges between 50mm and 1000mm.
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