Some time ago, we debated what the future might hold if automation really took over in a big way.
We found the subject so fascinating, we took a look at what could be the future of mechanised construction – and we found the concept of autonomous robotic bulldozers was not as chilling as we first thought. Here, we revisit the sites to find out what ‘total control’ really means.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’ by using GPS Rovers. These devices consist of a rod, a reciver 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.
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 kilometres outside Abu Dhabi island. The site, named South of Shamka on completion will comprise of ten thousand new villas, taking up no less than seventeen 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 technology 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 contactor 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 the surveying equipment company Topcon, who have supplied the equipment to this site 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 tells the operator 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, as according to Hales, 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 seem to follow the height of the stakes.
VIEWS
And who can blame them? 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, but I’m sure you 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 improved.”
Walid Daher, Operation Manager, Bin Nawi Contracting agrees: “As many as seven bulldozers can follow the path graded by the first machine.” He added 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 systems as well as some for graders.
VILLAS
On a different site, known as Al Reef, there are more villas springing up with the assistance of satellite technology. Like South of Shamka, the Al Reef project is also situated miles from anywhere in the interior of Abu Dhabi, but on completion will be its own self contained ‘community’. The most clever part of this project, though is the way the surveying equipment works.
Regular villa construction is most closely associated with the traditional method of the surveyor using a theodolite to measure distance and angles. This took time, and the data needed to be recorded manually. The last few years, particularly as projects have got bigger, have seen a shift away from this type of technology and on to what are known as ‘total stations’. These devices can read the horizontal and vertical circles electronically.
Understanding how these new machines work exactly is something an engineer might be able to explain, but suffice it to say they don’t rely on bands of light seen through prisms, rather on digital imaging as new technology takes over.
The newest technology to be embraced by the region is satellite positioning. This technology can incorporate distance, direction and difference in height between survey points.
A satellite-based surveying system is simply using an electronic distance measurer that does not need direct line of sight between survey points. Instead, a GPS receiver needs to have a direct line of sight to a sufficient number of satellites.
Although the term ‘GPS’ is used as a sort of generic trademark to describe satellites in orbit, it actually refers to a ring of devices put in space by the Americans, and allowed to be free for civilian use.
In fact, any brand of surveying equipment could equally be using the Russian GLONASS system, or the soon to be launched European Galileo network, which counts Saudi Arabia among its backers.
Fibrex have chosen to buy its surveying equipment from Japanese company Topcon. Eng. Ibrahim pointed out that the company had been impressed with the technology after a demonstration.
“About two and a half years ago, Topcon showed us a machine – a 752 – and we thought it had very good speed and efficiency” he explained. Since then, the firm have invested heavily in the equipment, having bought a Hiper GA base station, two rovers total stations, along with five laser levels.
As the site is in Abu Dhabi, Fibrex opted to have its own base station. Other sites in Dubai though can take advantage of centrally located base stations. Topcon’s Talal Hanna explained; “In Dubai we have what we call reference stations, which means that the municipality is handling these. What you have to do is to subscribe and you get the correction through your phone card.”
He explained that depending on location and what the customer has ordered, there were a number of ways of linking to the base and obtaining corrections automatically, with Bluetooth and GRPS links as possibilities.
The readout is done by rotary encoder which can be absolute or incremental using light and dark radial bands. In the latter case, the circles spin rapidly, reducing angle measurement to electronic measurement of time differences.
The base station can run on large car-type batteries, meaning the surveyor can leave it anywhere on site and then come back later to find that the corrections have been done.
SATTELITE
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 having the extra satellites is useful in the city, it is not so necessary in wide open desert, as this site is, because the receivers can easily ‘see’ the sky, and so track the satellites.
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. Of course, at the moment it is inconceivable that there would be no operator, 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.
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.
