How
mechanized layout works.

Prepared geometry reaches the site

The robot receives a task: place specified lines, points or symbols in defined locations. Digital data must first be prepared, tied to the site coordinate system and passed to the control system.

For example, the site needs two faces of a partition, a door opening and a room number. In the source model these may be solid objects with many properties. The layout task retains the specific geometry and text that help the installer carry out the work.

The task starts with a drawing

The source may be a BIM model or a prepared CAD drawing. Having a 3D model does not by itself make the file ready for the robot. Elements are selected for the relevant floor and construction stage, coordinates are checked, and readable layout information is prepared.

• Geometry: axes, wall faces, openings, fixing points or other elements of the agreed task.
• Presentation: layers, labels, symbols and the purpose of each line.
• Coordinates: units, floor level and the relationship between the drawing and site coordinates.
• Revision: the agreed design version actually approved for transfer to the site.

Input requirements differ between systems. HP, for example, describes preparing a 2D DXF file containing printable elements, known obstacles and control points. BIMPRINTER describes tasks prepared from DWG drawings. These are examples of particular workflows, rather than a universal format for every robot. [1] [4]

Survey control connects the design, robot and building

A floor plan can be freely moved and rotated on a computer. On site, its position must be unambiguous: each design line must reach its intended location in the building.

This requires a geodetic construction control network (GRO): a network of physically marked survey points with known coordinates and elevations. It provides the basis for the building’s internal setting-out network, including control points on individual floors. These points connect the digital design, measuring equipment and physical site. [5]

Once registered, the robot executes the task in the common site coordinate system. The design positions of columns, partitions, openings and service fixings are coordinated through the same control framework. A proposed partition line, for example, can be checked against a building design axis by survey measurements. Coordinate consistency also matters when the robot moves to another work area.

Registration includes verifying that the same coordinate system is being used and that any coordinate transformation applies the correct parameters. A few lines visually matching existing structures is not sufficient evidence of correct design positioning.

In a robotic total station system, the instrument is set up and oriented using control points. Robot position measurements can then be related to design coordinates. HP describes this sequence, for example. [1]

How the system determines robot position

During motion, the system needs information about the robot’s position and orientation. How that information is acquired and combined depends on the design. Localization must support operation in coordinates aligned with the project.

One approach uses an external measuring instrument to track a reflector mounted on the robot. HP SitePrint uses a robotic total station, while Dusty describes a Leica laser tracker. Calling both instruments simply total stations would be inaccurate. [1] [2]

Other approaches also exist. Rugged Robotics describes onboard localization and site reference targets. Losing external instrument visibility, re-registration methods and equipment placement requirements therefore affect different systems in different ways. [3]

Obstacle detection is a separate task. Detecting an object in front of the wheels helps manage movement, but does not by itself establish the printing tool’s positioning accuracy in building coordinates.

Coordinates must be translated into tool placement

Suppose the system knows the coordinates of a reflector on the robot. The line is printed by a different assembly some distance away. To place a mark correctly, the relative positions of these assemblies and the platform’s orientation must be taken into account.

The situation changes continuously during motion. The robot travels and turns, the tool activates at the right moment, and the controller adjusts task execution. Coordination between measurement, motion and marking is as important as the accuracy of an individual sensor.

The marking method itself also varies: a printhead, paint spray or another technical solution. It affects line width and readability, text capabilities, operation near obstacles and surface requirements.

On the floor, the result is clear without opening a model: where a partition runs, where an opening belongs and what a marked point represents. The meaning of symbols and task boundaries still need to be agreed with the people who will use the layout.

The result depends on the complete chain

The question about robot accuracy needs clarification: does it refer to reflector position, platform motion, tool position, or the completed line relative to survey control? These characteristics describe different parts of the process.

These factors cannot automatically be reduced to a single advertising figure. Evaluation requires stated conditions, a verification method and a clear understanding of the quantity the specification describes.

Site verification must establish the position of the finished layout relative to the building’s GRO. Ideally, the checks should detect an error in the initial registration: repeating the same incorrect transformation in the task and report will not reveal that error.

What remains the surveyor’s responsibility

Automation transfers some actions to the machine, while people remain responsible for organizing and evaluating the result. Roles depend on the contractor and equipment, but three groups of tasks remain part of the workflow.

The practical purpose of robotics is to free time from repetitive operations for preparation, verification and complex situations. It requires an understanding of the complete process: where the coordinates came from and why a particular floor line can be trusted.

What can prevent successful operation

• Obstacles and occupied areas. Materials and operating equipment change access to a work area. Obstacle sensors do not mean that the robot can mark a point covered by an object.
• Blocked sight lines. Systems with external tracking depend on visibility of the robot. HP explicitly requires a clear line of sight between the instrument and reflector. [1]
• Surface condition. Dust, water, unevenness and substrate properties can affect motion, marking quality and durability. Permitted conditions depend on the system and marking material.
• Differences between design and site. If an existing structure is not where expected, an engineering decision is required. Automatically continuing layout does not resolve the discrepancy.
• Uncoordinated work. It must be clear which area is being laid out, which design revision applies, who accepts the result and how inaccessible locations will be handled.

Productivity should therefore be assessed through a completed and verified task. Travel speed across an unobstructed area does not establish the time needed for preparation, equipment moves, obstacle handling and checks across a whole floor.

fieldBIM explores this technology and is developing its own prototype. The principles described apply to the field as a whole and are not claims about the current capabilities of our robot.