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Students develop technology for tunnel boring machines

By Tina Hilding, College of Engineering & Architecture

A-tunnel-boring-machine-in-London-in-2012---80SEATTLE – The city’s tunnel boring project inspired nearby engineering students last year to address navigation improvements. They’ve filed a provisional patent application and are building a prototype.

Tunnel boring machines (TBMs) and specifically one of them – Bertha – have been in the news of late. The world’s largest TBM is slowly making its way through two miles of Seattle’s underground sediment as part of a $3.1 billion project to replace the Alaskan Way Viaduct. The machine stopped moving forward in December, and the project contractors are currently devising a plan to fix it.

Guidance technology outdated

Local inventor Dan Preston volunteered to work with students in Washington State University’s mechanical engineering program at Olympic College in Bremerton. An inventor who holds more than 75 patents and pending applications, Preston developed technologies used in GM’s digital OnStar system.

A tunnel boring machine in London in 2012.

Accurate navigation is critical for efficient operation of TBMs, Preston said, “but the guidance technology dates from about 1985.” Traditionally, that has meant repeated surveying – at a cost of thousands of dollars per effort.

The students spent many hours putting together diagrams of the problem.

“When all the pictures were on the board, literally in little diagrams, it was the story of the invention,’’ Preston said.

Smart sensors and redundancy

The result is a new way to guide a TBM and map the tunnel during the process. The technology uses angular rate sensors, global positioning systems and acceleration sensing devices – the same smart sensors and accelerometers used in many modern computing devices and navigation systems.

The students built redundancy into their technology: there are two measurement units that feed into a microprocessor, calculate position changes and integrate acceleration data.

Sensors collect an array of geographic positions, which are used to construct a 3-dimensional mesh of the tunnel wall and create an accurate centerline.

Students apply for patents

By combining navigation with mapping, the system reduces follow-on costs.

“The whole thing is integrated into one system,’’ said Paul Peterson, a student working for his longtime employer, Puget Sound Naval Shipyard, while pursuing a mechanical engineering degree.

Since the WSU program at Bremerton got underway in 2010 and with Preston’s support, 12 students have applied for patents on a variety of technologies. Eight more students expect to have patent applications filed with the U.S. Patent Office when they graduate in May.

“Their name is on a patent application with a guy who has done a lot of stuff. That is something you can’t take away,” said Preston.

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