Cubic Transportation Systems Inc is a leading designer and manufacturer of mass transport ticketing systems, including the access control gates that collect travellers’ electronic fares using high-speed ticket encoding from magnetic strip or contactless smart cards to validate and allow entry and exit. Cubic’s Universal Gate range can be adapted to meet diverse requirements of ticketing and gate siting, and form an integral part of the combined software, hardware and communications systems that have revolutionised mass transportation ticketing around the world. One of Cubic’s major customers is Transport for London whose ticketing system makes full use of the technology, allowing the Capital’s travellers to use just one smart card for tube, over-ground rail and bus services.
The Universal Gate has two paddles to provide dual opening for travellers. Each gate flap is independently driven via a motor gearbox with a fixed rotation of up to 180 degrees, controlled using a feedback voltage set between an upper and a lower value, the position information being provided by potentiometers. But high traveller throughput rates require rapid accelerations and fast settling times, placing high demands on all of the system’s components. Cubic realised it needed an alternative sensor arrangement to improve the reliability and reduce the maintenance requirement of its Universal Gate.
Following a search of the market, engineers at Cubic’s UK-based product development centre worked alongside technical staff from Variohm Eurosensor to see if the Swiss-made Contelec Vert-X 13 series Hall effect sensor could help improve performance. This two-part Hall effect/magnet non-contact device can be delivered with a pre-programmed angular range between 5% and 95% of rotation. Variohm was able to supply the replacement sensor with exactly the same output characteristics as the original potentiometer version, and thanks to its small size (13mm diameter by 20mm nominal length), it was easily installed within the existing space. Moreover, the sensor’s durable stainless steel housing and integral ball bearing system were able to meet the tough environmental specifications.
The true linear output and improved accuracy of the Vert-X 13 also proved of benefit. Rather than a working tolerance of +/-10mV to set up the potentiometer, Cubic engineers found they could achieve almost pin-point accuracy, which considerably improved in-position stability. The superior linearity, moreover, had a big impact on the control system smoothness. Colin Peacock of Cubic’s UK engineering department, takes up the story:
“The Vert-X was tested during 2007 at a new rapid transit system project in Atlanta-Georgia and it quickly proved successful. The reliability gains and improved life of the non-contact device has considerably reduced the Universal Gate maintenance burden and it is now the design choice for new and retrofitted access gates worldwide.”
The Vert-X range is available with IP69 rated housings, redundancy options and with a choice of limited angle or full rotation sensing with SSI, incremental encoder or analogue outputs. Its non-contact design, compact dimensions and rugged construction provide exceptionally long life and high reliability for angular position feedback in many environmentally challenging applications.