As a contractor, you know the difficulty of relying on eyesight to level your earthmoving project. For you to build a solid foundation, the ground beneath it has to be adequately compacted and leveled. But from the seat of a dozer or motor grader, it’s not easy to tell if the site is at the proper grade.
Over the years, this problem has led to the development of machine control systems. By relying on the Global Positioning System (GPS) and Global Navigation Satellite System (GNSS) to provide position and elevation reference construction sites, today’s contractor can grade accurately and position with confidence.
What Is a Machine Control System?
Machine control systems are an incredible development for the construction industry. But what is meant by machine control? Essentially, it means that the machines used in construction are more precisely controlled to work efficiently in their environment. Take leveling, for instance — a machine control system enables grading tractors to compare a digital grading map to the position of the blade and cut it to the proper elevation and position on the job site.
So how do they do this? The key to machine control systems comes down to GPS and GNSS. The short version is that GPS and GNSS signals are received by the (or antennas) on the tractor and provide position and elevation references on the job site. That position is compared to a digital terrain model of the proposed plans and automatically guides the cutting edge to grade.
The predecessor to this system was laser-based. A rotating laser transmitter was mounted above the machines on a tall tripod. The rotating plane of light could cover over 1500 feet of the jobsite accurately. The machines would have laser receivers attached to the top of a mast referencing the cutting edge of the blade. The laser signal striking the receiver would actuate the cutting edge up or down and then maintain when it reached the proper grade. This system was used in both construction and agriculture since the late 1960’s.
But that system could only do so much. Since the laser was an ‘elevation only’ reference it could only adjust up or down based on where the laser was. The laser system has no ability to know the position or where it is on the job site. The contractor would also need to move the laser transmitter each time he moved past the 1500’ range of distance.
How Does a Machine Control System Work?
For machine control systems to be so precise, they have to follow a very specific process. This process largely involves tracing and modifying from several satellites to the receivers on the jobsite.
1. Satellites and Base Stations
Since machine control generally relies on GPS, it starts with satellites in the outer atmosphere. These satellites triangulate with one another to generate a digital map of the construction site. They then send a signal down to the site itself.
At the site, the contractor sets up a base station. Base stations receive and correct the GPS signal. This correction is necessary because the satellite signal isn’t accurate enough for precision earthwork.
GPS is fine for locating things on a large scale. But in this context, the machines need to receive results down to the millimeter scale. From thousands of miles overhead, the satellites can’t measure with that degree of accuracy. The signal has to travel an incredible distance through the atmosphere just to reach the ground. At that point, the satellites can end up with a margin of error of as much as 30 feet. For leveling ground on a construction site, 30 feet is a huge amount.
That’s why the base station is necessary. It’s kept at a specific, fixed point on the site, often attached to the top of a pole inserted into the ground. It’s also programmed with the location of that specific point, allowing it to act as a reference point. When it receives the GPS signal, it compares the two locations — the place the satellites think it is versus where it knows it actually is. Then it adjusts for the difference. By lining the two up, it shifts all the information from the satellites over to the correct position.
Once the base station has modified the GPS signal, it sends the signal out to all active rovers, usually in the form of radio waves. This modified signal is called real time kinematic, or RTK. Two types of rovers are typically used — man rovers and machines. Both types have a receiver to pick up the GPS signal and an antenna to pick up the RTK. With that information, they generate a digital 3D map of the site, from which they can determine exactly where on the site they’re positioned. They can then know what they need to do in each given spot.
3. Alternative Systems
Of course, this arrangement can vary across different systems. A few different types of machine control systems are available. The standard type is the one described above, but two other prominent options exist as well — cellular systems and IMUs.
One alternative system relies on cellular signals instead of radio. These systems don’t use base stations. Instead, they connect to cellular reference stations somewhere outside the construction site.
Such stations are owned by private entities or the government, which may require special permission and possibly a fee for contractors to use them. The advantage of these systems, though, is that they don’t require a local base station. And since they use cellular modems instead of radio waves, the signal can be broadcast much farther without decreasing in quality.
A second alternative system is that which uses inertial measurement units, or IMUs. IMUs don’t measure location, but they calculate position change at an incredibly fast and accurate rate. They’re connected to the rover itself, usually two per vehicle. As the rover moves, the IMUs can determine exactly how they’re moving. They then coordinate with the location being provided by the RTK to determine precisely where the blade of the machine is at any given moment.
What Are the Components of a Machine Control System?
In the process outlined above, several different components work together to aid in the precision of the construction process. These components often take the form of technological devices, which send signals back and forth to one another to work the magic of machine control.
In the midst of the process explanation, though, it can be easy for specific terms to get lost or mixed up. For the sake of clarity and simplicity, here’s an overview of each of the individual components involved in most machine control systems.
1. External Components
One of the easiest ways to divide the list of machine control system components is by where they’re located — on the rover, or off of it. The overall system requires equipment of both types for it to function. Here are the main components located outside of the rover.
- Satellites: Like all satellites, machine control satellites orbit in Earth’s upper atmosphere. They transmit a precise clock signal over two or three frequencies back down to the earth. Signals from three or more satellites give the base station and rovers enough information to “fix” an accurate location on the earth.
- Base station: Base stations usually take the form of small boxes positioned atop poles in the ground. They receive the GPS signal from the satellites and compare it with their precise location, adjusting it accordingly to generate the RTK. They then send the RTK to the rovers.
- Cellular reference station: Cellular reference stations are an alternative to base stations. Rather than being onsite, contractor-owned and radio-based, they’re offsite, typically rented and cellular signal-based. They have a greater range than base stations.
2. Rover Components
While satellites, base stations and cellular reference stations are external installations, the other major components are connected to rovers. The first two items on this list — man rovers and machines — are themselves types of rovers. The others are attachments that often appear on those rovers.
- Man rover: Man rovers are a type of rover that contractors use to calibrate GPS signals and lay out projects on a site.
- Machine: Machines are a type of rover that contractors use to alter the ground on a site, such as leveling.
- Rover GPS receiver: Rover GPS receivers are connected to the top of poles on rovers. They pick up GPS signals to determine the rover’s location, which they then transmit to the data collector.
- Rover radio antenna: Rover antennas are attached to rovers to pick up the RTK from the base station. They transmit this information to the data collector.
- Data collector: Data collectors are consoles in rovers that receive the signals from the receivers and antennas. They bring all the information together and compare the GPS position to the map loaded on the data collector. Data collectors are typically used with handheld
rovers by the surveyor or grade checker. Control Boxes are a type of data collector used on a machine control system to automatically move the blade to grade or to monitor the elevation for manual operation.
- Machine blade: Machine blades are the parts of a machine that cut the ground into the desired shape. They appear on vehicles like dozers and leveling trucks.
- IMU: IMU stands for inertial measurement unit. IMUs are devices that measure changes in position on a precise scale. In machine control, they’re sometimes attached to rovers as a counterpart to the GPS signal, working with it for higher accuracy.
How Are Machine Control Systems Used?
We’ve now covered all the elements of machine control systems, and how they work. But what is machine control used for in the actual construction process? What equipment is it most often paired with?
Quite a few processes occur on construction sites before the building even starts. Excavating, compacting, dozing and scraping are just some of the things construction workers do before beginning to build. None of these jobs are simple under normal conditions, but they don’t have to be complicated. Here’s how machine control can be applied to several of them.
- Excavating: Excavation involves digging out slopes and trenches on construction sites, whether to even out a building surface or to lay pipes. Of course, scooping out large chunks of dirt is far from an exact process, so machine control systems can be a huge asset to excavators. These systems are capable of sensing the precise location of an excavator at all times relative to its environment, so the operator can be sure they’re digging in just the right spot.
- Paving: Paving equipment is designed to spread out and flatten concrete or asphalt. This process commonly involves laying out string as a guideline for where the concrete or asphalt needs to go. Machine control eliminates that need. With features like automatic steering, machine control can direct paving vehicles along their path at precisely the desired alignment and slope. This system saves a significant amount of time that would otherwise be spent preparing and surveying.
- Piling: Piling refers to the process of inserting large quantities of hard materials like concrete, metal or wood into the ground. These materials are meant to give extra strength to the foundation of whatever structure is built on the site. Piling equipment can use machine control to ensure that it’s inserting all materials at the right angle and in the right spot.
- Compacting: Compacting equipment performs the function of pressing down dirt, concrete and asphalt into a firm surface, eliminating any air pockets or weak connection points. Machine control is useful here because it allows you to monitor pass counts and surface temperature as you work. These are important factors to know, but hard to be sure of without machine control.
- Drilling: Often, contractors must drill deep into the ground for one purpose or another. For instance, piling requires having a deep opening in which to place the metal or concrete. For these situations, drilling equipment is a necessity. But drilling can be a delicate process. You never want to drill too deep, and certainly not in the wrong location. Machine control prevents these mistakes from happening. It can calculate just the right depth to drill to, and it warns the operator if they’re drilling somewhere they shouldn’t be.
- Dozing: Dozers are essential tools on nearly any construction site for grading and leveling sections of ground. But getting the ground to just the right level is no easy task. 3D machine control systems allow for automatic blade control, directing the dozer blade to exactly the right angle at exactly the right spots. This system improves accuracy and efficiency by a large margin. Furthermore, by ensuring level ground, it maximizes safety for workers once the building process begins.
- Scraping: If it’s important to have machine control for dozing, it’s even more important for scraping. Scraping functions somewhat like dozing, but on a much finer and more precise scale. While dozers push large amounts of dirt out of the way to even out the ground, scrapers go back over the area to fine-tune it. Machine control for scrapers functions just like for dozers, directing the blade to just the right position to achieve a perfectly level cut.
Where Can You Get a Machine Control System?
No matter what the focus of your latest construction project is, you can benefit from machine control. It can refine your leveling and hone your digging, and it can do it all while giving you feedback on where each rover is on the site at any given moment.
As an overseer, you can use the system software to see the whole site at once and observe every place that is being altered in real time. Best of all, with the amount of time and money saved by the precision and accuracy of the system, it will quickly pay for itself.
SITECH Southwest can get you the machine control system you need to revolutionize your construction process. As an authorized Trimble dealer, we offer top-quality equipment for all the construction processes listed above. Just get in touch with us today to get your machine control system!