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Trades Embrace Robotics on Construction Sites

POSTED 04/29/2019  | By: Tanya M. Anandan, Contributing Editor

Welcome to boomtown. Where the hum of heavy equipment permeates the air. Cranes tower above skyscrapers. Scaffolding wraps buildings and bridges. Where suburbia gives rise to new neighborhoods and strip malls at every turn. Orange cones and barricades line our routes to work and play. Sound familiar?

Construction is booming from one U.S. coast to another and in metropolitan cities around the globe. But the construction industry has a big problem. There’s more demand than supply.

Workers are in short supply. The cost of building is rising as materials and labor become scarce. The need for infrastructure repairs and reconstruction is omnipresent. Technology is lagging behind other industries. The construction industry is lacking the sea change it needs, the disruptive innovation it requires to do more with less. But not for long.

The global construction market for robotics is expected to more than double to $166 million by 2023, according to a report by Markets and Markets. Innovations in semi- and fully autonomous equipment will help the construction industry build more with fewer resources. Robotic devices will help laborers work safer and more efficiently, for longer. Technology that empowers workers will help attract a new generation of construction industry workers eager to master these new, groundbreaking tools of the trade.

Continuous Track to Autonomy
When Benjamin Holt first attached wooden planks around the wheels of his steam-powered tractor to create a “continuous track” to prevent the half-ton machine from sinking in the soft earth of the early 1900s farmland, he could not have envisioned the variety of earthmoving equipment that would one day be the flagship of the Caterpillar lineup. Neither could C. L. Best, whose tractor company would merge with Holt Caterpillar to form the Caterpillar Tractor Company in 1925. Peoria, Illinois, would serve as the company’s home base for over 90 years.

Line-of-sight remote control technology for automated dozing helps keep machine operators safer in potentially hazardous environments. (Courtesy of Caterpillar Inc.)Today, Caterpillar Inc. is headquartered in Deerfield, Illinois, and is a world-leading manufacturer of construction and mining equipment, diesel and natural gas engines, industrial turbines and diesel-electric locomotives. With its trademark “Caterpillar Yellow” equipment, this Fortune 500’s machines are recognized the world over, with 59 percent of its $54.7 billion sales coming from outside the United States. Behind the iron are more than 100,000 employees at about 150 primary facilities around the world that support a global dealer network over 160 strong.

Both Holt and Best would be astounded by Caterpillar’s progress in autonomous vehicle solutions, a feat that would have been considered “magic” in the pre-Depression era. Now the unimaginable is here. A $2 million prize helped sweeten the pot.

From Mining to Construction
Mining is one of the leading industries for adoption of autonomous machines. Ten years ago, mining companies operating in remote areas, especially Australia, experienced a significant shortage of machine operators. Around the same time, the DARPA Grand Challenges demonstrated that autonomous vehicles were becoming a reality. Watch how the DARPA races propelled the self-driving vehicle industry. (Caterpillar was a major sponsor of the $2 million-winning team in the 2007 DARPA Urban Challenge.)

As a result, Caterpillar began working with mining companies to develop its Cat® Command portfolio of autonomous trucks, drills and track-type tractors, and its underground Load-Haul-Dump (LHD) loaders. Watch them on the job. The productivity improvements range from 20 to 30 percent or more, while creating significant enhancements in mine site safety, according to Caterpillar. Autonomy allows miners to reduce process variability in their operations as they journey towards a fully autonomous mine.

Many of the challenges faced by the mining industry over the past 10 years are now impacting the construction industry. Site safety, talent pipeline, efficiency improvements, linking silos of information together, and digital construction site evolutions are all current construction industry priorities. But that’s where the similarities end. Variability is a major factor on construction sites.

On-Site Variability and Mixed Autonomy
Compared to the mining world, construction sites are less structured and less controlled environments with far more variability in day-to-day operations. People and machines work in close proximity on varying construction tasks. Caterpillar believes this variability will influence the level of autonomy we can expect to see on construction sites.

While mining tends to be a repeatable process, construction contractors rarely have two jobsites that look the same. Autonomous technology solutions must be more modular and flexible to accommodate variability from jobsite to jobsite.

Whereas mines have long horizons of operation, some spanning decades, and can support autonomous fleets with economies of scale, construction site machinery typically comprises owned, rented and subcontracted machines. Users are unlikely to re-fleet for a single job. Autonomous vehicles are introduced over time. For a while, both autonomous and manned machinery are expected to coexist on construction sites.

Because a mine remains stationary over time, it’s possible to invest in infrastructure such as Wi-Fi to support autonomy. But construction jobsites can span as little as a few hours. Autonomous solutions need to minimize their dependence on fixed infrastructure. Caterpillar is developing solutions that leverage new technologies, such as 5G private networks and perception systems, to allow machines to communicate and locate themselves.

Perception a Key Enabler
Much of Caterpillar’s early work in autonomous mining technology originated with a long-standing collaboration with Carnegie Mellon University (CMU) and its National Robotics Engineering Center (NREC) in Pittsburgh, Pennsylvania. The Steel City turned Roboburgh is a great pipeline for top talent and CMU’s Robotics Institute is one of the Dream Labs of Future Robotics we covered last fall.

Located in the heart of the Pittsburgh robotics community, Caterpillar’s Pittsburgh Automation Center (PAC) partnered with NREC to develop Autonomous Haulage Systems for large mining trucks. They also tapped into the world-class talent pipeline, hiring CMU’s graduates in computer science, robotics and computer vision.

“A key enabling technology for autonomy and automation products is the ability for a machine to ‘see’ the environment around it by using electronic components and software,” says Narayana Nadukuru, Electronic Engineering Manager at the Pittsburgh Automation Center. “This technology is often referred to as ‘perception’ and much of our perception development is done at the PAC.”

The engineering team at PAC delivers software algorithms for data processing from components such as cameras and LIDAR sensors, then creates useful information about the surrounding environment for higher-level applications such as autonomy, safety and operator-assist features. Features that are a part of Command, one of six Cat Connect Technologies and Services that can be mixed and matched to suit the unique needs of Caterpillar’s customers.

An equipment operator uses an over-the-shoulder remote console for line-of-sight control of an autonomous bulldozer up to a quarter mile away. (Courtesy of Caterpillar Inc.)Jobsite Safety and Productivity
Cat Command for Dozing increases operator safety and productivity when maneuvering steep slopes or unstable surfaces, handling hazardous materials, or experiencing prolonged exposure to noise, dust and vibration. Remote operation is achieved either with the over-the-shoulder operator console for line-of-sight remote control operation from up to a quarter mile away, or via a remote operator station that offers both line-of-sight and non-line-of-sight remote control operation.

Watch this video to see automated dozing at work. At 48 seconds into the footage, check out the non-line-of-sight Remote Control Station in action. Located in a remote center potentially many miles away, this technology allows operators to work for long periods of time while seated in a safe, comfortable “virtual cab.”

Already proven in mining applications, Command technology includes remote control systems available on Cat dozers, wheel loaders and skid steer loaders used on construction sites. Remote control is just the first step in automated construction equipment. Cat Command is paving the way for tomorrow’s semi- and fully autonomous equipment systems for the construction industry.

Disrupting the Construction Ecosystem
According to Caterpillar, autonomy could have profound ramifications for the construction ecosystem. The adoption of autonomy on a jobsite could provide a quantum leap in differentiation for Caterpillar customers. Early adopters have the opportunity to disrupt the industry by delivering a step change in efficiency, quality and safety. Everything – from the size of the equipment deployed, to the role of dealers and OEMs, to the definition of laborer versus that of subcontractor – may be disrupted.

Caterpillar provides an example. Today’s traditional fleet of 50 machines requires a contractor to have about 10 mechanics and 50 operators, all of whom require either a travel allowance or room and board. On an autonomous jobsite, a fleet of 50 machines might be operated by 15 local mechanics to maintain and stage the machines, and 10 more remote operators to provide oversight of the autonomous operations and remote control when needed. They liken this to the operation of military drones, where local mechanics tend to the drone’s mechanical needs and prepare them for takeoff, but the missions are conducted by remote pilots in containers halfway around the world.

“This may sound far-fetched, but it’s already a reality for our customers who are using the Cat Non-Line-of-Sight Remote Stations for Dozing,” says Fred Rio, Product Manager, Construction Digital & Technology at Caterpillar. “A single operator can run up to five machines simultaneously!”

Caterpillar’s remote control technology also enables new or less-skilled operators to be more productive using autonomy and operator-assist features. These features also improve consistency of machine productivity and tracking.

(Special thanks to Narayana Nadukuru, Fred Rio and the entire Caterpillar team for their article contributions.)

Rather than try to break into a market already dominated by world-renowned players, Built Robotics Inc. offers retrofit kits that turn existing construction equipment into self-driving vehicles. The company integrates off-the-shelf sensors and writes software to enable a machine, such as a dozer, excavator or skid steer, to autonomously map and navigate its surroundings. Watch the technology in action.

While innovators work to bring more autonomy to construction sites, other semi-automated equipment continues to clear the way for progress.

Remote-controlled demolition robot works in confined spaces while enhancing efficiency and jobsite safety. (Credit: Brokk)Demolition Robots
The first remote-controlled demolition robot was conceived in the mid-1970s and has been commercially available since the ‘80s. Demolition robots promote jobsite safety by keeping workers a safe distance away from falling debris, dust and other hazards. These robots tend to pack a lot of power in a compact package, allowing for more precise work in tight spaces.

Demolition robots are used in the construction of buildings, bridges, roads and tunnels, among other hazardous applications in metal processing, nuclear, mining, and defense and rescue missions. Watch a pair of demolition robots tear in to this shopping mall renovation.

Demolition robots may break it down. Bricklaying robots transform construction sites one brick at a time. This robotic bricklayer from Australia builds on a grand scale. No mortar, just a specialty adhesive and a really long arm. Check out HadrianX.

Robotic Bricklaying
Any mason will tell you that bricklaying and masonry is an art, a carefully honed craft requiring years of experience. But the actual brick-and-mortar application for your typical stretch of wall is a grueling job. Repetitive arm and shoulder movements, the backbreaking task of lifting and positioning brick after brick, eventually takes its toll on the body. And that’s if you can find bodies.

Bricklayers are in short supply around the country and more experienced masons are aging out of the industry. Even though wages are rising, younger generations are looking for work that is less labor-intensive.

One company is looking to lend a helping hand to masons. Located in Victor, New York, just south of Rochester, Construction Robotics designs and builds a bricklaying robot called SAM, for Semi-Automated Mason. Cofounders Nathan Podkaminer and Scott Peters established the company in 2007 and received a boost in their R&D efforts with grants funded by the National Science Foundation Small Business Innovation Research (SBIR) program.

Robotic bricklaying system applies mortar and precisely positions bricks on the wall according to a digital blueprint. (Courtesy of Construction Robotics)“We looked at all different aspects of bringing robotics to the construction industry and after an in-depth effort and analysis, we settled on the bricklaying trade and masonry because of the challenges from a labor standpoint,” says Peters. “It is a very physically demanding trade. It’s very repetitive. You have motion injuries, you’re carrying a lot of weight, so it’s a good opportunity to incorporate robotics and automation.”

Podkaminer is a registered architect and construction industry veteran with 50-plus years in institutional, industrial and residential building. Peters comes from the manufacturing world. With a bachelor’s and master’s in chemical engineering, he worked as a process engineer for Intel and General Motors, and most recently, as a manufacturing engineer for A3 member Progressive Machine & Design (PMD).

Lighten Your Load, Boost Productivity
With help from the SBIR program, Construction Robotics built its first prototype in 2013 and PMD was the first commercial test site.

“PMD’s new building in Victor was probably the first building in the world to have a robot lay bricks on site,” says Peters. “It was one of our early prototypes that was run by a bunch of engineers. We ran the machine for a few weeks and learned a lot. We proved we were able to apply mortar to the bricks and it would stick and that our technology was good. We also proved that we could get the bricks where they needed to go using our sensor system and dynamic robot stabilization. Those were two huge milestones for us.”

They also learned that in order for the technology to be useful and effective on a construction site, the system would need to be easy to set up, use and operate by a mason. So the team went back to the shop, and in late 2014, they were on their first commercial jobsite with a totally redesigned, new version of SAM.

“We were down in Virginia on a job and ran SAM with significantly improved speeds, quality and productivity. Yet we still learned a lot about what it takes to bring robots to the jobsite. We spent a couple more years just running demos of the machine in various jobs throughout the country. In 2017, we launched SAM commercially with a rental program and started bringing on distributors. We’ve continued to grow and add more units to the fleet over the last couple of years.”

The robot installed bricks on the University of Nevada Reno Arts Building, the Poff Federal Building in Roanoke, Virginia, and the University of Michigan Brighton Center for Specialty Care, among other masonry projects around the country. 

SAM is capable of laying 350-380 bricks an hour on average, according to Peters. The system combines a Stäubli Robotics arm with machine vision, along with feeding systems for bricks and mortar, a propane generator for power, and a sophisticated sensor package for safety and dynamic stabilization.

Here’s a brief introduction. Watch SAM work.

Peters says they chose this particular robot for its load-to-weight ratio and software integration. “We wanted a high payload but didn’t want to deal with a heavy robot and controller package. We also wanted to have a robot that was sealed from dust and weather. This robotic package also had software capabilities that allowed us to have deeper control for speed and motion.

“Not every robot package allowed for real-time adjustments as you were moving to place the brick,” he continues. “You can imagine being up on that scaffold and it’s moving around with the wind. You have general movement and then you have guys moving quickly on the scaffold or jumping down from above. All that creates very quick, dynamic movement. Stäubli’s package allowed for a deeper integration from a software standpoint and then we were able to build in all of our software customization around the sensing system.”

The robot itself has six axes, but the system has seven. The carriage that holds the robot, feeding system, propane generator and tanks, plus all of the controls and user interface is the seventh axis. It autonomously moves along the wall as bricks are laid.

“In reality, there’s an eighth axis that we don’t control at all, which is the manually controlled scaffolding system,” says Peters. “After the robot builds within its (vertical) workspace of roughly three feet, it runs out of reach, so then you have to raise the scaffolding.”

Adjusting On the Fly and Sticking It
Extensive development went into Construction Robotics’ real-time operating system to manage the overall safety aspects of SAM, as well as the material feed and human interface. They leveraged off-the-shelf components wherever possible, but when there was no existing solution that fit, they built their own.

“If it was a straightforward solution, we would have gone to an integrator and said hey, build me a robot that lays bricks,” says Peters. “But when we really peeled back the onion and analyzed the challenges, there are really three simple technology challenges that are incredibly complex.”

1. How do you lay all your bricks on the wall and deal with on-site variations?

Construction Robotics developed a system that adjusts for variations on the fly. “As we set up our mapping system in our software, there’s a step in the process where you set your story poles, then you take measurements just by walking through a measurement process, and then the system automatically adjusts the spacing of all the bricks. Now you know the real location of where the bricks are supposed to go relative to the actual dimensions of the wall, and of the windows, the doors and the corners of the building. So you have that automatic correction. That was one huge problem we had to solve.”

2. How do you put the brick right where it’s supposed to go in space, especially in a dynamic environment?

Peters likens it to being on a boat that is constantly moving and trying to adjust for those movements in real time. They developed custom software that when integrated with the Stäubli robot’s control software accounts for dynamic stabilization.

3. How do you get mortar to stick to the brick?

When masons lay bricks, they typically spread the mortar on the brick wall before placing the next brick. Rather than have multiple robot arms doing different tasks, Construction Robotics simplified the process by applying the mortar to the brick.

“We ended up having to develop our own mortaring system,” says Peters. “Commercially available systems either didn’t provide the right pressures, or if they did, they would get clogged easily and were too hard to clean. Ours is very easy to clean, easy to manage and maintain. We’re able to apply the right amount of pressure with the right amount of control, which allows us to manage a very wide range of mortars, apply that to the brick and get it to stick.”

The proper volume of mortar to apply to different sizes of brick and what parts of the brick to mortar are built into the control system.

“The spec is not that tight on a brick,” explains Peters. “You’re basically dealing with dirt that is compressed and heated. There’s a level of deviation that we need to account for in our ability to grip the brick, measure it, and then use those measurements to change how we mortar the brick so that it doesn’t crash into the nozzle and so we get good adhesion.”

The entire system is patented, with additional patents on aspects of the laser sensing and mortaring systems, both built from scratch. The laser system is mounted on the story poles.

“Masons typically use two story poles and pull a string between the poles to define the course of brick they are going to lay. Because that was a very familiar process to the mason, we basically mimicked that, in a sense, by allowing them to hang a pole on the building and set their coursing (vertical course adjustment of the brick). The robot goes to the wall, and using its camera, it looks at that string line and then we correct for multiple degrees of freedom (by communicating with the laser system) and place the brick right where it’s supposed to go.”

Lift More, Sweat Less
SAM handles bricks ranging in size from 4 inch cut brick up to 12 inch brick. For laying large blocks, SAM has a sidekick.

Construction Robotics offers a lift-assist device called the MULE, for Material Unit Lift Enhancer. It reduces some of the strain on bricklayers working with 50 pound blocks. Whether this device falls under the category of robotics, however, depends on your definition of a robot. What constitutes a robot in the manufacturing world is often different for professional service robots like SAM and many other semi-autonomous machines in the construction industry.

“We typically do not call the MULE a robot. It’s a smart lift-assist device,” says Peters. “There is definitely some automated motion in it. We have some control algorithms, sophisticated software and sensing. It has a single axis of motion that is controlled.”

Decide for yourself whether MULE is a robot. Watch it work.

Now take a newcomer to the construction industry offering exoskeletons to the trades. These are non-powered mechanical devices, but often considered robotic. The upper-body bionic skeletons reduce workers’ strain and fatigue during long periods of overhead work.

“For a lot of what we’ve learned and what we do in the construction industry, it’s about helping and enabling workers to be more efficient,” says Peters. “Because it’s such an uncontrolled and dynamic environment, the worker is unbelievably critical.”

Human-Robot Collaboration
Human-robot collaboration is a critical component of many of the robots and robotic devices in the construction space. When asked why SAM is called a “semi-automated” mason, Peters echoes other’s comments.

Robotic bricklaying system includes brick manipulation and feeding, mortar system, controls, power and safety all self-contained for easy portability on site. (Courtesy of Construction Robotics)“The worker is very much in the loop. They have to set up SAM. They have to do the mapping, the layout, and then during its operation they are not only feeding the machine, but they also have to strike the joints (remove excess mortar), put the wall ties in, the installation in – a lot of the process still needs to be managed and operated by the workers.”

Typically you have a three-person crew including two masons and a laborer working with SAM. The masons handle the setup and are striking joints and managing wall quality. The laborer keeps SAM fed with bricks and mortar throughout the process, similar to the tasks of a traditional bricklaying tender.

“SAM is just another tool of the trade. It’s a way to get your job done. It’s there to work alongside the worker and assist them. We’ve never seen SAM replace a worker, per se, but it allows contractors to do more with their crew.”

Do More With Your Crew
In addition to increased productivity, less heavy lifting and enhanced ergonomics, robotic bricklaying has other benefits. It allows for parallel processing of tasks. While the robot is laying bricks, a mason can be simultaneously striking joints on another part of the wall where the bricks are already installed. A mason can also be examining blueprints, installing installation or wall ties, working on a corner, or doing some other aspect of the job.

SAM can also do complex patterns with different brick colors, sizes and configurations. To the robot, bricks are just pixels on a screen. It’s all digital, the machine’s language.

“That aspect of SAM is really enabling future architects to think about building their buildings differently,” says Peters. “It can do in and outs (offset brick placement for 3D design effects). It can do soldier courses, where the brick is set on end. It can do logos and intricate designs with different colored bricks. We did a sample wall in our shop that was designed by an architect, where every brick was on a different plane at very fine increments so the entire wall created a wave pattern. That’s one of the things robotics brings to the table.”

Robotic bricklaying is helping drive digital design, and drive more brick jobs and opportunities in the construction industry. Another benefit is the digital data collected by the robot as it’s working.

“SAM pushes real-time data to the cloud and you get updates on how your SAM(s) are doing throughout the day. All of that information is available to you in real time, so as a foreman or as an owner of a mason company, you can make better, educated decisions about your jobsite productivity.”

Just like real-time data from robots and automation is helping manufacturers improve how they monitor and maintain their factory equipment and make operational decisions, automated masonry can have the same effect for the construction industry. Digital fabrication is the future.

Robotic Digital Fabrication
While digital fabrication on construction sites is an emerging technology still in its infancy, few are denying its potential. Digital fab uses computer-controlled technologies to create structures and buildings in nontraditional configurations that typically streamline the design and utility of the structures, while inspiring new forms of architectural expression. With digital fabrication, building design and construction is more precise and efficient. It also makes better use of building materials, requires fewer labor-intensive processes, and boosts overall productivity and sustainability.

Today’s construction sites still pose challenging working conditions with ergonomic, safety and job-satisfaction issues that make them less than compelling to new generations of workers. This could be overcome with digital fabrication and open the construction industry to a whole new talent pool, one that uses its brain more than its brawn.

Researchers in Switzerland are leading the charge for digital fabrication on construction sites, with the first-ever habitable building designed, planned and built using predominantly digital construction technologies, namely industrial robots and 3D printers.

The three-story DFAB HOUSE was erected atop the NEST research building of Empa and Eawag in Dübendorf. It officially opened its doors in February. Watch the DFAB HOUSE’s digital rise.

On-site construction began with robotic fabrication of a mesh mould wall using the in situ Fabricator (IF), an autonomous mobile manipulator developed to work in dynamic on-site construction environments. The steel-wire mesh mould wall serves as both formwork and reinforcement for concrete. Watch the IF robot on the job at the DFAB build site, as it bends, cuts and spot welds the steel wire, fabricating the mesh mould wall one vertical section at a time until complete.

Mobile construction robot used in digital fabrication on a construction site autonomously builds a steel-wire mesh mould in an intricate wave pattern for a concrete wall. (Credit: Roman Keller/NCCR Digital Fabrication)The result is a graceful double-curved, load-bearing concrete wall that characterizes the modern architecture of the living room. A unique concrete ceiling reminiscent of a set from the movie “Alien” was cast in 3D-printed formwork and the massive panels were assembled on site. The two upper-level residential floors have exposed wooden frames in complex geometries, which were prefabricated off-site by two inverted gantry-mounted robots using a new method for digital timber construction called Spatial Timber Assemblies.

For the first time, several digital fabrication technologies emerged from the lab to transform a blank slate into a one-of-a-kind smart home. But development was not a walk in the park.

Unique Vision, Multidisciplinary Collaboration
The in situ Fabricator robot has come a long way from its first iteration. The unfortunately named “dimRob” required far more human intervention. The DFAB HOUSE project would need more robotic autonomy and a multidisciplinary approach. That spawned a collaboration between several professorships and their labs at ETH Zurich, the nearly 165-year-old Swiss university of science and technology, the alma mater of Albert Einstein and many other Nobel Prize winners.

Gramazio Kohler Research, the Chair of Architecture and Digital Fabrication at ETH and former professor Jonas Buchli’s now defunct Agile & Dexterous Robotics Lab (ADRL) joined with other research labs and industry partners to bring architecture, robotics, control systems engineering, materials science, computer science, and structural design together in an ambitious partnership to establish digital technology as an essential part of future building processes. Initiated in 2014, the multidisciplinary consortium became the National Centre of Competence in Research (NCCR) Digital Fabrication funded by the Swiss National Science Foundation.

“Our primary goal is to develop tools that allow us to build things we couldn’t build before,” says Timothy Sandy, a post-doc researcher and NCCR member at ETH Zurich’s Institute for Robotics and Intelligent Systems. Sandy worked closely with Dr. Buchli (now with DeepMind Technologies) on robotic fabrication of complex structures on construction sites.

“It’s a very different motivation than a commercial view where you’re trying to automate current processes,” continues Sandy. “We want to look to the next step in development and have these smart machines on the construction site build what we can’t even imagine now. Not just interesting architecture, but also more functional buildings, where you integrate the different functions of a room into a single unit, so that buildings are simpler and more materially efficient.”

Mobility, Accuracy and Autonomy
The primary challenges of robotic manipulation for on-site building are mobility, accuracy and autonomy, the subject of Sandy’s 2018 doctoral thesis. The ADRL team developed localization, sensor fusion and motion control strategies that enabled mobile manipulation systems to achieve high-accuracy end effector positioning throughout large workspaces and over long periods of time. The in situ Fabricator integrates a standard industrial robot arm made by ABB Robotics mounted on a base equipped with hydraulically driven tracks.

Because construction sites have a high level of variability and an uncontrolled environment, the IF robot was designed to be a completely self-contained machine with fully integrated, onboard control, sensing and power systems. The research team also wanted to avoid dependence on external reference systems, so extensive setup and tedious calibration routines would not be required. But robotic digital fabrication on a construction site is very different from in the lab.

A mobile construction robot equipped with sophisticated end-of-arm tooling autonomously bends, cuts and spot welds a steel-wire concrete mould. (Credit: Roman Keller/NCCR Digital Fabrication)“Once we took the robot out of the lab and to the construction site of the DFAB HOUSE, and began building the mesh mould wall, we were surprised at how much more challenging it was than we expected,” says Sandy. “For example, the ground in the lab is always flat and level. The ground at the house where we had to build was angled one to two degrees for drainage reasons. That completely changes your dynamics and the way the robot moves as you maneuver the arm,” which he acknowledges required some on-site software tweaks to compensate.

While autonomy may be the Holy Grail, the researchers learned that you have to choose the level of autonomy in an efficient way, both for development and execution. As the team experimented with more realistic environments and building tasks, they realized that it wasn’t efficiently feasible for the robot to be completely autonomous, especially when humans were already a necessary part of the building process.

In the mesh mould build, the robot was repositioned about a dozen times. Repositioning was done manually, which involved driving the robot with a joystick console. The team choose to focus the autonomy on the robot building the mesh mould and making sure it can do that process on its own.

“The robot has to regulate the feeding of the wire and monitor how accurate it’s building,” says Sandy. “It would be nearly impossible for a person to build the structure with comparable accuracy to the robotic system.”

The IF robot localizes itself by detecting the markers on the wall foundation. Before the build, a faceplate was installed. Then the markers were installed arbitrarily on the plate. The robot takes one measurement with a drive along the length of the wall to build a map of those markers’ locations, which it can always reference to know where it is in the space. The robot builds a section, then you drive it manually to the next area. It goes through a quick localization routine, and then continues building that section.

One of the benefits of the robot building on site is that you have this continuous loop from the robot building a portion of the structure, then comparing where it’s supposed to be positioned to where it actually is, and then adapting the build. As it’s building the wire mesh, the robot is doing that comparison and adjusting as it goes, a process not possible with prefab.

A Smarter, Lighter, More Accurate Future
With the DFAB HOUSE complete and the first residents about to move in, and the ADRL lab shut down, Sandy is now leading a small group of ETH researchers still focused on robotic construction, but within the Robotic Systems Lab (RSL) headed by Prof. Marco Hutter. RSL might sound familiar. You may have seen the ANYmal on the prowl, a quadrupedal robot co-developed with spinoff ANYbotics.

RSL is also working on an autonomous excavator robot. Meet HEAP.

With these types of influences, it’s no surprise that the next-generation construction robot will look a bit different. Sandy’s research group is trying to make the robot smarter, more accurate and lighter.

“One of the limiting characteristics is that it’s so heavy that it is difficult to transport and needs to operate very slowly to be safe,” says Sandy, noting that the IF robot is 1-1/2 metric tons. “It gets to the point where some buildings can’t support it. There needs to be a step change in the actuation technology to allow such robots to be twice as light, but just as strong.”

Sandy says the new generation of collaborative robots are moving in the direction they need for building construction. They just need them three times bigger. His group is now working with a smaller prototype robot using a Kinova collaborative robot arm. He says they are also working toward autonomous navigation and obstacle avoidance for a construction robot that can safely but still efficiently work among its human coworkers.