Pros and Cons of Machine Control

Pros and Cons of Machine Control.

There are pros and cons to everything in life, and the same is for machine control in construction. It is also easy to think that there are way more pros to machine control than there are cons. Especially if you are just getting your information from the manufacturers or websites that are selling machine control.

But as with everything in life, it is just not that simple. The reality is, is that it is not as easy or as straightforward as you might have been led to believe.

For sure, machine control systems are the way forward and they offer great benefits. But there are also some pitfalls along the way to avoid. And hopefully through this article I will help you see the pros and the cons of machine control.

The Pros of Machine Control.

  1. Less people needed to work around the machine.
  2. Easier for the machine operator to see what they need to achieve.
  3. Greater accuracy can be achieved by the machine operator.
  4. Automatic control of the machine.
  5. Communication between machine operator and ground crew is reduced.
  6. Greater construction efficiency.
  7. No need for profile boards or batter rails.

The Cons of Machine Control.

  1. A digital design is needed on the machine control system.
  2. Difficulty for site staff to see the proposed works.
  3. For the best accuracy a base station is required.
  4. The machine control systems can be expensive.
  5. Site Staff not trusting machine control systems.
  6. The need for several survey software systems.
  7. When the machine control system breaks down.

Let’s dive into some more detail about the Pros and Cons of machine control. Starting with the Pros first and then look at the Cons. I have listed 7 of each. There will be more, and these will change depending on the type of machine control being used.

Machine Control Pros.

Less people needed to work around the machine.

So often on construction sites we are told that Safety is the number one priority. And rightly so. We all want to be able to go home at the end of the day.

One of the major risks on construction sites is the people plant interface. A lot of effort has gone into eliminating the people plant interface risk over the years. And we are still striving to reduce this risk.

And this is one area that machine control can help.

With machine control systems being employed on construction sites, we can virtually eliminate the need to have operatives working near the machines giving guidance to the driver.

Preventing people from being within the working area of any large construction machinery is by far the major pro of machine control systems.

Easier for the machine operator to see what they need to achieve.

Years ago, I remember an excavator driver struggling to trim type 1 on a road junction. He was a good driver, but he could not see what levels he needed to achieve. This was in the days before machine control was commonplace. The instructions from the operatives on the ground were also confusing him. It was only when we built up two small areas to the right level and said fill between those, that he could see what we needed to achieve level wise.

If he had a machine control system, the driver would be able to see what level he needed just by looking at the screen in the excavator. He would have been able to see the fall across the road and the levels needed along the road too.

Having a display showing the either the bucket or blade relative to the surface that needs to be achieved is a great help to any excavator or dozer driver. It helps them achieve the desired results quicker which drives productivity higher.

Greater accuracy can be achieved by the machine operator.

I think that there are two parts to this. Greater accuracy because the machine operator has a screen that shows the required surface in real time and because the surface is complete.

Being able to see the surface to be graded on a screen in the machine is a great aid to increasing accuracy for a machine driver. Being able to zoom in on the screen and see fine details for grading helps achieve the desired surface within tolerance much quicker. This enables the driver to grade to the correct level in one go, rather than grading to a level, checking with the ground operatives, then regrading to a level and repeating this process until the correct surface is achieved.

The part of the greater accuracy that I think is often overlooked is that the surface is complete. By this I mean that there are often gaps in batter rails, profile boards and other work guidance methods that will be overlooked by the site team.

The easiest example I can give would be profiles set at 10m intervals along a proposed road. Here it is easy to see that there is a 10m gap along the road between profiles. This gap can be tricky to see between and the surface levels may vary from desired. But with a DTM model on machine control these gaps are eliminated.

Automatic control of the machine.

Once the machine manufacturers started to incorporate machine control systems within their new machines, it became possible to control the machine within set limits. The driver is still in ultimate control, but the fine grading done with the bucket or blade can be controlled by the machine control system.

This has major impact on the speed and productivity for the construction site. With the blade or the bucket being controlled by the machine control system, adjustments needed to keep the blade or bucket at the correct level can be done more quickly than the operator can.

The skill of the machine operator is still vitally important even with automatic control of the machine. The machine driver needs to get the surface within a certain level to enable the automatic control to function properly.

Too little material in front of the machine and the blade or bucket will float above the surface. Too much and the machine will labour and potentially damage the surface already laid.

Communication between machine operator and ground crew is reduced.

Communication between the operatives on the ground and the machine driver can be difficult at the best of times. Constructions sites are noisy environments at the best of times. And often the only way to communicate will be by signs or signals.

The sign language used on site is very different from the sign language that deaf (or hard of hearing) people would use. The sign language used on site is clear but limited in its range of communication.

Reducing the communication between the operatives on the ground and the machine drivers helps productivity. If there is no need for the guys on the ground to give instructions to the driver there is obviously a reduction in time note working productively.

Greater construction efficiency.

Greater construction project efficiency is achieved not only by all the good points mentioned above, but also by reducing the errors or mistakes that made on site.

Having to do work twice on a construction project is not only costly in the materials that may need to be bought again, but also in the time taken to do the works correctly.

No need for profile boards or batter rails.

Removing the need for setting out to be done before any works can commence can also increase project efficiency. Often the surveyors or site engineers are under great pressure at the start of a project to get the required profiles and batter rails out so that works can start. With machine control systems the whole project can be loaded on to the machines in a matter of minutes.

There is also no longer the requirement to constantly maintain profiles or batter rails throughout the construction project life. Often when profiles or batter rails get damaged, the site team will put them back in and not say anything. This can lead to costly mistakes if they are not set correctly. It is the bane of every surveyor or site engineer’s life having to re-establish profile boards or batter rails.

Machine Control Cons.

Having established what I think are the 7 major pro points of machine control, it is now time to have a look at the cons. These are the major con points about machine control systems and their use on construction projects.

A digital design is needed on the machine control system.

For the machine operators to be able to use machine control systems they need to have a digital design loaded on to the machine. Depending on the machine control system being employed, the proposed design data will need to be processed into a format that is suitable.

Construction site designs can be complex and data rich. My thoughts are that the machine control models need to be as data light as possible. By this I mean that only the necessary points and lines are included in the model and that the triangles (of the digital terrain map) are as big as possible. Bear in mind that machine buckets and dozer blades can be big and that the triangles of the DTM should be bigger than the bucket or blade. This will make the machine operators working life easier.

Creating the machine control models can be a specialist operation that requires dedicated software to create, deploy and maintain the operations. This is sometimes beyond the capabilities of the site team and will require the services of a specialist surveying firm.

Model of Cat Dozer with Machine Control Fitted

Difficulty for site staff to see the proposed works.

This is one of the major hurdles for the site team. Especially with members of the site team who do not look at site drawings as a matter of course.

If you have an empty field with no marks on the ground or pegs showing the way it can be almost impossible for anyone to envisage where a building might be or where the road will go. Let alone at what level the new building or road may be at. It is almost like the construction site team is working blind apart from the machine operator.

This can lead to logistical problems on site. Construction materials can be stored in the wrong location, plant parked in the way along with a whole host of other issues that come from not being able to visualise the site layout.

One way to combat this issue I find is to produce files that can be viewed on either mobile phones or tablets with local position provided on google maps. Alternatively, produce a drawing with the current ariel view as a backdrop on a CAD drawing.

For the best accuracy a base station is required.

There are two options for getting corrections for GPS surveying equipment on construction sites. My preferred option would be a local GPS Base Station. And second choice would be a VRS network solution.

With machine control systems being an additional cost to most construction projects and margins are always thin there can be a temptation to skip the purchase or hire of a GPS Base Station.

I think this would be a mistake. A GPS base station for any site will have a benefit in the accuracy that can be achieved. This is based on my experience of using both GPS Base Station solutions and VRS Network corrections.

I have found that there is significant variation in 3D position when using VRS Network solutions. I have not found the same variation when using GPS Base Stations, especially when they are fixed for months on end. Read about the test that I performed on VRS Network Solutions to find out how accurate they are.

For Greater Accuracy Always Use a GPS Base Station

The machine control systems can be expensive.

Machine control systems can be expensive. And this can be off putting for some firms. Especially when retro fitting machines.

Then there is the cost of either survey equipment or GPS base station required to provide positioning accuracy.

And don’t forget about a support system for when things go wrong. Not to mention the site team that may need training and specialist software.

All these additional requirements are often not thought about when first considering fitting and using machine control systems.

Site Staff not trusting machine control systems.

It can take some time for the site team to trust machine control systems. By this I mean that they are not sure that they have done it to the right line or level. The problem that they have is that there is nothing for them to check against. No profiles or batter rails to guide them on their construction progress.

With machine control systems the only people that can see where the construction works should be, are the people with the machine control screens or the survey equipment. The survey equipment is usually always with the surveyors or site engineers.

Part of this mistrust of machine control systems is linked with the difficulty for the site staff to see the proposed works. It often requires a section of the works to be completed before the site staff can see and trust the machine control systems.

The need for several survey software systems.

With several different manufacturers devising machine control systems, they have been somewhat protective over their systems. This means that quite often different machine control systems are employed over the same site. And with this comes the need for the specialist software from each manufacturer.

In my experience it is Trimble that is the worst offender. Pretty much the only software that will produce machine control models for their systems is either Trimble Terramodel or Trimble Business Centre. Which means no matter what, if you have a Trimble equipped machine on site, you need Trimble software.

I find that the Leica and Topcon systems are the most user friendly in respect of what model software you can use and the file formats that these systems can take.

When the machine control system breaks down.

There is no doubt that machine control systems are used in harsh environments. And breakdowns can happen from time to time. The problem is that once the machine control breaks down then the work can’t continue. This is the same as if the machine itself breaks down.

The potentially bigger problem would be if the base station was to break down. If this happens all the plant on site that receive corrections from the GPS base station would not be able to work accurately. The most common reason for base stations to stop working is a loss of power. A supplementary battery supply usually sorts out this problem.

This is where a good machine control support system comes in. This can not be underestimated. The better the support you have the quicker you can get back to work.

Conclusion of the Pros and Cons of Machine Control.

The aforementioned Pros and Cons of machine control should give you enough information to consider whether machine control systems are for you and your site. The above is not an exhaustive list but should be the main points that you need.

For more information on machine control you should look at the article about the history of machine control and the basics of machine control. Both these articles are on this site.


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A Brief History of Machine Control

The Basics of Machine Control

How to Calculate Road Offset Profiles

The Real World Accuracy of GPS Network Rovers

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