Lasers: The Stepping Stone Toward Machine Automation
by Harry O. Ward PE
January 1, 2005
Grading with the Topcon RL-H1Sa slope laser offers mid- to long-range single slope capabilities and self-leveling, allowing for superior accuracy over the entire grade range.
Contractors and manufacturers agree that lasers are essential on many sites offer upgradeable benefits.
Traditionally, laser-based machine control has been one of the strongest methods for achieving vertical accuracies. And although GPS control is making great strides on construction jobs, it can be more costly.
“By using lasers on constant or planar grade projects we consistently achieve tighter tolerances and greater accuracy vertically than GPS can provide,” says Bill Woodside, vice president of operations for the Damon Pursell Construction Co. in Liberty, Missouri, a site prep contractor that has been using laser technology since the 1960s. In addition to several display and indicator systems, Damon Pursell utilizes Leica Geosystems (www.leica-geosystems.com) Laser Alignment LB4 laser transmitters and has the Leica Sonicmaster 2000 Ultrasonic Laser Control systems with 360-degree laser receivers installed on its motor graders, which include a Komatsu (www.komatsu.com) GD650, five Caterpillar (www.cat.com) 140Gs, one 16G and one 140H. Damon Pursell’s work comprises floor grades, pavement, landfills and levee construction. The contractor has also had success with lasers on 10- to 50-acre warehouse sites and in the construction of railroad yards where huge amounts of sub-ballast are installed in fairly flat expanses of areas.
While not a new technology (they have been around for some 30 years), lasers are an effective and low-cost technology worthy of consideration for construction surveying and site preparation. For the contractor interested in moving toward 3D machine automation, lasers are an excellent technology transition due to their cost-effectiveness and upgradeability.
“Newcomers to the machine control market can start with laser control as their introduction to machine automation,” advises Phil Metts Jr., general superintendent for Richardson Construction, a site grading contractor specializing in earthmoving serving North Carolina, South Carolina and Georgia. Richardson also provides services to handle asphalt, curb and gutter, and utilities. Metts offers further advice for contractors starting out with laser technology. “Have definite goals to achieve in machine automation. Once you have solidly achieved each goal, then make additional investments to increase automation in areas that will help your business most.” He continues, “And above all, be patient. There is a learning curve. But the results are well worth it.” At Richardson, Metts and his crews use precison laser receivers and sonic sensor systems to complement several GPS-guided systems. Even when satellites are blocked or diluted and GPS units aren’t effective, lasers provide a working technology. Richardson uses Topcon (www.topcon.com) HiPer+ integrated GPS receivers, Topcon RL-Ha flat plane lasers and several RL-H3C rotating lasers for grade control. The laser control provides a strong advantage for the company’s flatwork, which currently consists of 1,000,000-square-foot pad sites and 2,000,000 square feet of paving.
The initial cost to invest in laser technology is reportedly recouped quickly, and the continued expenses for laser use are manageable, according to numerous contractors. Todd Tutterow, owner of West End Grading in Yadkinville, North Carolina, is another contractor benefiting from laser technology for site preparation. Tutterow uses a Trimble (www.trimble.com) GCS400 Grade Control System on a Caterpillar D5G track-type tractor, applying the complete system to build pad grades for commercial and residential projects. He has also accomplished a number of street grading jobs that include final grade crowns and shoulders using the complete system.
“I am looking at acquiring another one [GCS400 system] as soon as possible. I can achieve a one-year return on investment in the equipment,” Tutterow estimates.
A number of manufacturers offer scalable technology for laser systems, further supporting the decision of many contractors to adopt laser technology. Scalable technology is the concept of building systems (hardware, software, firmware) that allow users to add features and grow new capabilities in the future without sacrificing the initial investment. The computer industry has used this business model for years. Scalable servers, for example, allow additional and larger hard drives to be installed or offer the ability to increase memory. In construction, scalability might include the option to add on GPS equipment. High-end 3D systems now feature the capability to add lasers for fine grading operations like those for airport runways and roadway projects. Further, both GPS and laser technology machine automation use the same 3D design files for mass excavation, rough grading and final grading activities.
Lasers offer the advantages of automation, accuracy, resilience and scalability, but how do contractors know if lasers are right for them?
Applications for Laser Control
The Spectra Precision CR600 laser by Trimble can be used as a handheld or rod-mounted receiver for a wide range of applications including machine control, and is an ideal low-cost entry to machine control productivity.
A simple example of laser use in machine control applications is the grading of a building pad. The setup and use of a self-leveling laser is relatively easy and inexpensive. A motor grader equipped with a dual-mast laser control system can grade an area with no need for stakes, hubs or stringlines. As the machine moves, the control system is able to determine the elevation of each side of the blade through laser detectors mounted on the masts so that it can automatically make adjustments, thereby maintaining the required grade.
Laser receivers can also be mounted on track-type tractors (dozers) and scrapers for mass excavation projects. For a fairly low initial investment, this machine control implementation can bring a jobsite to a required elevation tolerance in advance of fine grading activity. The equipment consists of a rotating laser receiver mounted on a mast attached to the blade of a dozer or the bowl of a scraper. The operator in the cab observes visual grade indicators on the laser receiver or on a panel in the cab. The operator then manually moves the blade to the desired elevation as needed. Numerous contractors report that the technology’s simple concepts make it easy to install and doesn’t require a lot of operator training.
“The system is easy to use,” West End’s Tutterow says. “The training I received provided me with all the basics and [information on] what the equipment is capable of. I immediately found myself in production.”
In addition to laser use on dozers and motor graders, lasers can be applied to many other earthmoving vehicles including tiling machines for trenching and setting drain tiles, skid-steers (with additional attachments) for digging, concrete screeds for finishing jobs, box blades for leveling uneven ground, and various scrapers. What’s more, lasers can diversify the capabilities of particular equipment in a company’s current arsenal, according to Tutterow.
“Due to laser technology I have increased the functionality of my dozer. [With laser control] I get extremely fine control of the blade; I can use it as a motor grader for grading parking lots and related projects,” he explains.
Contractors have experienced a routine increase in productivity using laser technology, with estimates ranging from 30 to 50 percent reduction in grading time and 25 to 70 percent1 improvement in vertical accuracies achieved. Damon Pursell’s Woodside estimates that “you can expect 33 percent productivity improvements on projects [with lasers], and depending on the size and type of project, you may see as high as 100 to 150 percent improvements.” Woodside attributes this improvement to “a combination of cost savings and production gains since you are achieving better accuracies while eliminating a grade checker.”
The increased accuracy provided by lasers minimizes the number of passes an earthmover must make and ensures that dirt is not placed in the wrong place. This in turn helps to decrease material overruns, reduce labor costs and minimize potential rework since it is performed correctly the first time. In addition, fewer (or sometimes no) grade checkers are required, which means lower cost and fewer communication errors.
How Do Lasers Work?
Using two separate ultrasonic sensors and advanced computer technology, the Leica Geosystems Sonicmaster 2000 can automatically side-shift the blade of a motor grader to keep the grader blade online and the sensor positioned over the reference string or curb.
The second use for lasers builds on the first and adds laser-based grade control. By adding proportional valve controls to the machine’s hydraulics and a correspondingly more complex display, the laser-based display system is upgraded to an automatic system. If an electric mast is used, the laser receiver can be raised or lowered from within the operator’s compartment. The signals from the laser receiver activate a proportional hydraulic valve controlling the blade.
The third use for lasers is 3D grade control augmented by laser technology. A self-leveling laser is set up on a tripod and emits a beam along a fixed plane. The laser can be tilted to a specified grade within limitations. The emitted laser plane is 7-8 mm wide; some lasers have the ability to emit dual-slope beams with different slopes simultaneously. The receiving side of the system consists of a digital linear laser receiver with a photocell that has millimeter resolution and is capable of 360-degree operation. It can usually be installed on a manual or electric mast on the machine. The electric mast allows the operator to control the height of the mast’s receiver from inside the cab. The sensor reads the beam emitted and the signals from the laser receiver are used to control a proportional hydraulic valve for blade correction.
A laser system can be used as a stand-alone machine guidance display or as a component of a complete automatic grade control system. When a laser beam strikes the receiver, the operator then puts the machine in automatic mode to conduct machine control. If the contractor uses the system for visual guidance, then the operator would compensate with manual adjustments called for by the system. Laser systems can control as many pieces of equipment as needed, provided there is line of sight to the laser and the same grade or elevation is required.
The range of the laser depends on the laser used in a particular application. Some lasers work over short ranges (300 to 500 ft) and are ideal for small jobs such as foundation work, while others are capable of operating over ranges up to 3,000 ft.
Once the background of laser technology is understood, contractors can examine the laser equipment options available today. What specific laser-guided machine control products are available on the market and what are industry manufacturers’ observations for this construction technology?
Discussions with Manufacturers
Topcon's Dozer System Five includes a rotating laser set up as a grade reference and the LS-B2 laser receiver, which automatically guides the machine to grade according to information previously set into the control box.
Fred Rogers, Leica Geosystems’ director of 3D machine automation, says that Leica provides a variety of solutions for the use of lasers in construction, ranging from simple indicators to machine control. According to Rogers, lasers work well for fixed plane jobsites such as 2 percent cross slopes for a road in a tangent section or for parking lots, but are not the correct technology for roadway curves that are superelevated, transitioning or have rolling surfaces. Rogers says that good uses for lasers include setting drain tile; performing agricultural land leveling, especially cotton and rice fields2; and constructing dams. Lasers are also good on various aspects of levees and for concrete pours on large building sites. Rogers also notes that lasers are beneficial where users can’t obtain satellite coverage for GPS guidance. Ultrasonic devices augment lasers where the grade is referenced from stringlines. With ultrasonics, a sound wave pings the string and returns to a sonic receiver; calculations are made based on the time of travel. Ultrasonics are a proven, traditional approach, and along with laser technology, are a sound stepping stone for those considering investing fully in 3D machine control.
“A customer could begin with a laser indicator system for approximately $1,700 and move up to fine grade control by adding a control panel and valve system to control blade lift,” Rogers says. The cost to upgrade from indicator/display mode to grade control ranges between $5,000 and $15,000, depending on the options chosen. To upgrade from grade control to laser-guided machine control systems, a customer can expect to pay between $15,000 and $20,000. Customers can add another receiver or tilt sensor to control blade slope, making the system scalable to 3D machine control, for approximately $95,000. In this case, the laser technology is supplemented with GPS so the upgrade can often be incremental and vary according to customer needs.
Topcon
Jamie Williamson, vice president of sales for Topcon, agrees with Richardson’s Phil Metts that lasers provide an excellent introduction to machine control and automation. He also suggests some specialty applications for laser control: irrigation and drainage channel sidewalls (as long as they have consistent grades) and laying base material for large (6', 8' and 10') box storm drainage sections. Laser applications include digging foundations, footings and house pads, and earthmoving for sites such as tennis courts and ballfields. The contractor’s benefits for using lasers can include the ability to move on and off the job on his own time, without waiting on staking and control tasks.
Williamson says that Topcon has been selling laser technology for 30 years, going back to land leveling applications in the agricultural field in the mid-’70s. He recalled that Topcon introduced the first dual, steep slope laser--a rotating total station with a removable remote control. Today, Topcon has a family of six laser receivers, the RT-10S, the RT-5Sb, the RT-5Sa, the RL-H2Sa, the RL-H1Sa and the RL-H3CS, that offer various beneficial features depending on a contractor’s needs. The instruments range from approximately $1,195 to $8,395. A laser and receiver can be purchased for less than $2,500 and can turn the traditional level and rod from a two-person job into a one-person job. The laser doesn’t require an operator after setup and the only person needed is one to operate the detector at the “business end.”
Trimble
Mark Forrest, division vice president for construction at Trimble, believes that using laser-based grade display systems to guide the cutting edge of a blade to grade is an affordable system that is easier to use and set up than the more expensive 3D systems. “The future for lasers is that they will continue to be used to meet the tight tolerances required on vertical applications such as highways [and] airport runways,” Forrest says. “They are already being incorporated into 3D systems because of the vertical accuracies.”
As with other manufacturers, the costs for Trimble systems range depending on customer needs. Display systems, which range from $1,000 to $5,000, can be moved from machine to machine, making them a viable choice for contractors who use rental fleets. These systems are, however, manually operated and designed for single plane grade work with each setup. Grade control systems, which range from $5,000 to $15,000, have automated controls. These systems offer higher accuracies since operator error is reduced. Again, only single plane grade work can be done with each setup. These installations are semi-dedicated to the machine and are not readily movable between machines. Laser-guided machine control systems, which range from $15,000 to $20,000, offer a higher degree of flexibility over display and grade control systems since they can be expanded. Trimble’s BladePro system, for example, can be expanded to 3D capability, uses alternate sensors for specific application needs and is not tied to operating on a single plane. By adding ultrasonics, the machine operator can use the system to follow a reference line for grading tasks.
Lasers: A Viable Starting Point
Laser machine control offers many attractive features: it is relatively inexpensive; at the lower end of the spectrum, it is relatively portable from machine to machine; implementation issues such as administrative overhead, operator training and maintenance only marginally increase the level of complexity; and laser technology is familiar to management, supervisors and line personnel alike. Lasers can also be frequently used, even when the supporting infrastructure of 3D data among project principals is not available. For contractors who are thinking about taking advantage of the productivity and profitability benefits of machine control, laser machine control offers a great transition technology. By implementing lasers, important lessons can be learned before moving on to more complex machine control systems. For contractors who concentrate on building mostly flat surfaces, whether they are horizontal or tilted, laser machine control may be as far as they will want to take the machine automation process. Regardless, the benefits of lasers are undoubtedly real.
Sidebar: Costs & Savings
In today’s market, some components for laser machine automation such as laser indicators start at $995; receivers can cost as little as $1,700. A contractor can achieve entry-level machine automation using laser technology for approximately $4,500. Additional features can be added for approximately $20,000. These features include multiple receivers to obtain 360-degree laser coverage;additional lasers to increase horizontal and vertical range and laser upgrades to allow for longer range and higher accuracies; control boxes; proportional hydraulic valves for blade corrections; and dual-grade control dozer systems, which allow for simultaneous and automated control of a dozer’s lift and tilt functions.
Glossary of Terms
Ultrasonics use a stringline that is placed at the grade desired. An ultrasonic device sends out sound signals that reflect off the string and are obtained by a receiver to determine the distance to the string, thereby telling the machine control where the blade should be.
A stringline is a line of string placed on stakes at the desired grade for the tasks at hand.
An (electric) mast allows the operator to control the height of the laser receiver mounted on the mast from inside the cab, rather than changing it manually from outside.
Indicators are visual displays (lights, CRTs, LCD panels) that are mounted on the construction machine. They indicate to the operator where the blade is relative to the ground it is digging or the surface that is being built.
Laser-based Grade Display Systems are modular systems that are configurable to the machine or project requirements and used for machine guidance. Some contractors use laser receivers mounted on the front of the machine on top of an electric mast. Using a number of receivers provides 360-degree operation. This range yields information that allows the operator to make manual adjustments to the cutting edge, which speeds up grading operations by eliminating the need for the operator to reference the surface that is being built to grade stakes.
Laser-based Grade Control Systems add proportional valve controls to the machine’s hydraulics and a correspondingly more complex display to upgrade a grading operation to automatic. If an electric mast is used, the laser receiver can be raised or lowered from within the operator’s compartment. The signals from the laser receiver activate a proportional hydraulic valve controlling the blade.
Laser Augmentation for 3D Grade Control Systems include high-end 3D systems that now feature options to add lasers for fine grading operations like runways or roading. The same 3D files used for mass excavation, rough grading and final grading combine GPS with lasers. Another more traditional example is that by adding ultrasonics instead of GPS, the machine operator can use the system to follow a reference line that can change grade as it moves.
A control box is used to enter the criteria desired for grading. The operator enters the elevations and grades for which the blade can move the dirt. When the machine begins grading, real-time information from each of the sensors is sent to the control box where it is compared to the grade and elevations entered by the operator. If necessary, the control box sends out corrections to the hydraulic valves to move the blade to the grades and elevations set by the operator.
Harry O. Ward PE
Harry
O. Ward, PE, is president of Harken-Reidar Inc. He has been a member of the
engineering faculty at George
Mason University
since 1997 and was named “Outstanding Adjunct Professor” for GMU in 2010. He
can be reached at hward@harken-reidar.com or hward@gmu.edu.
References
1.
This range is vast because lasers have been proven to offer huge improvements to those contactors performing jobs manually and have been proven to offer incremental improvements to those who are using lower levels of laser control, such as laser displays.
2.
Early laser machine control was used for agricultural purposes, and still is today.
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