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Thu 10 Sep 2009 04:00 AM

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In total control

Machine automation is here, but what productivity increases can be worth the investment in the real world? We visit a site which has switched to automatic mode.

In total control
FIXED: This transmitter is needed to maintain a fixed point on site.
In total control
ROVING: Using a GPS rover and a pickup truck is far faster and more accurate than staking.
In total control
PUTTING DOWN ROOTS: This solitary tree is the project’s emblem.
In total control
CALLING BASE: A base station is needed on site at all times.
In total control
HOTSEAT: Forward visibility from the cab is very limited on either model.
In total control
ON TRACK: The projects manager is grateful for the system.

Machine automation is here, but what productivity increases can be worth the investment in the real world? We visit a site which has switched to automatic mode.

If there is one vision guaranteed to terrify the general public, it would be the image of autonomous, robotic bulldozers grazing over the wreckage of cities once populated by humans.

Fortunately such a chilling dystopia is a little way off. While ‘total control' ‘dozers are very much a reality, they only follow the blueprints fed into the computer, rather than making their own decisions on large scale urban planning matters.

The question is, how do such machines work at all, and what advantage can they offer? Simply put, total control is a system where a site is first ‘staked' using GPS Rovers. These devices consist of a rod, a receiver and a computer. The rod holds the receiver on top and it has a ‘point' at the bottom, while the electronics sit in the middle.

There is usually a handheld device, which looks like some kind of industrial PDA, which tells an operator what the whole system is doing. A base stationis set somewhere on site and used as a reference point, and perhaps obviously, marking out a site in this way supercedes the use of posts, string, chains or any other old way of marking the ground. High stakes

Once the ‘stakes' have been set, the data is loaded onto a computer with the surveyor's original drawings. These are then passed to the computers, via radio, in the heavy machinery. The on-board computers can be fully 3D, or they can display the information in two dimensions, or even just as a string of lights, depending on which system has been ordered.

Machines that can benefit from total control include not only ‘dozers and graders, but also excavators and even road compactors.

To put this to the test, we visited a large building site in the desert, some 50 kilometers outside Abu Dhabi island. The site, named South of Shamka on completion will comprise of ten thousand new villas, taking up no less than 17 million square meters. Currently at the groundworks stage, operations have been split between Tristar Contracting and Bin Nawi Contracting. It is the latter that we are visiting today.

When a project covers this kind of surface area, the exact location of the heavy equipment can be a difficult thing to establish, which is where GPS comes in.

Smaller sites can get away with using regular surveying equipment, such as the now-common five-second Total Station, but with this amount of ground to cover, the contractor decided to try a package from electronics firm Topcon.

Initially, this comprised of a system fitted to two bulldozers, with a base station and a ‘rover' - another device which clamps to the side of a car for taking readings on the move.

The contractor has just put in an order for a further four systems for bulldozers and some for motor graders, which should be extra suitable for fine grading, as the company has just bought several of the new electro-mechanical Cat 14M machines.

Bulldozers

Mick Hales of Topcon, explains; "The two machines that have been equipped so far include a Cat D8R and a Komatsu D155A. The difference in terms of the electronics system is that in the Cat the unit calculates its position from the base of the track, while on the Komatsu it analyses the position of the blade itself."

There are different systems available, which work in 2D and in 3D, with the latter obviously displaying the topography of the ground in three dimensions. To be fair, the building site is currently so vast and barren that the display rarely shows much other than a graphic representing the machine itself.

All of the blueprints for the groundwork have been fed in the computer, which then tells the operator how much to cut and how much to fill. When the amount is within the tolerances set by the surveyor (which in this case is five centimeters for rough grading on rocky ground, while fine grading can be millimeter perfect, depending on the condition of the machines hydraulics.)The operator then just follows a ‘box' which displays the exact height of the blade in millimeters, which is green when the tip is inside the parameters and red when it is outside. The operator then just needs to make sure that the box stays ‘green' to ensure a good grade.

This works particularly well, according to Hales, as you don't need the best operators in the world to get a good finish. We are sure that there are many site owners who will rejoice at this news - as we all know, there is nothing worse than having to double-handle work, because some of the drivers can't follow the stakes.

Views

Not that such drivers should be blamed. From the cab of the D8, forward visibility comprises mostly of the exhaust stack, while the view through the angled doors is little better. Truly, it would require skill to drive this machine in the usual way. However, with the aforementioned screen, it becomes much easier for the operator. Hales says: "Different people will tell you different things (about productivity gains), but I'm sure they will get triple the production out of this ‘dozer."

He added, that even in fleets such as this, where equipment is only fitted to a number of machines, the efficiency gains can be quantified: "You might not see it with just one ‘dozer, but now everyone around him knows where elevation is they are all much improved."

Walid Daher, Operation Manager, Bin Nawi Contracting agrees with Hales.

"As many as seven bulldozers can follow the path graded by the first machine" he says, adding that he was extremely grateful for the system, having used it in the past on other sites. "On this system, you just need to teach the operator how to use it and he can do the job of both the supervisor and the foreman" he says. Recently the contracting company has placed orders for several more bulldozer and grader systems.

Satellite

Interestingly, whenever equipment that uses satellite positioning is written about, it is usually referred to as being ‘GPS', though in fact pretty much all of the systems from any of the manufacturers in construction is mentioned, what is being referred to is a technology that can not only pick up the Global Positioning System craft, but also the Russian GLONASS (derived from Global Navigation Satellite System) for increased accuracy. Hales points out that while is useful in the city, it is not so necessary in the wide open desert of this site.

Future

While not employed on this site yet, or indeed anywhere in the Emirates as far as we know, the fully automatic systems referred to at the beginning of this article is very much a reality in other parts of the world. The advantages are obvious - there is no chance of operator fatigue, and accuracy is limited only by mistakes in the original engineering drawings.

There are plans to get such a machine up and running over here. "We want to fit total control to a Cat D6T" says Hales.

 This model has modern joystick control as well as electronically controlled powershift transmission and drivetrain.

Of course, at the moment it is inconceivable that there would be no operator at all, but perhaps in the near future there is no reason why he would actually be needed to sit on the machine, as all the monitoring and adjustments can be made from the ground with a remote control unit.

One computer could be used to drive packs of machines together, so there will always be synergy across the entire fleet, as the computer will understand implicitly what the entire fleet is doing. Imagine how much more productive a road building site would be with such a package.

Back in the here and now, the systems that are available today can be further enhanced for fine grading with the addition of rotating lasers which can ensure millimeter-perfect grading, even when cutting a slope.

In short, it is a wonder that, given the obvious benefits in speed and efficiency, that more contractors are not using it already.

What is a total station?

A total station is an electronic optical instrument used in modern construction projects. It is also used by archaeologists to record excavations as well as by police, crime scene investigators and insurance companies to take measurements of scenes. The total station is an electronic theodolite integrated with an electronic distance meter to read distances from the instrument to a particular point.

Some models include internal electronic data storage to record distance, horizontal angle, and vertical angle measured, while other models are equipped to write these measurements to an external data collector, which is a PDA.

Angles and distances are measured from the total station to points under survey, and the coordinates (X, Y, and Z or northing, easting and elevation) of surveyed points relative to the total station position are calculated using complex algorithms as well as trigonometry and triangulation.

Data can be downloaded from the total station to a computer and application software used to compute results and generate an electronic map of the surveyed area.

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