Simulation of automated construction using wire robots

Despite a high potential to improve the productivity, quality and safety and also to reduce costs, automated technologies are not widely spread in the construction sector. This paper presents a simulation-based approach to analyze the technical and economic feasibility of wire robots for automated construction in future investigations. Masonry buildings are considered as an appropriate application case due to repetitive construction procedures and high demands concerning accuracy of construction. A simulation model representing the fundamental mechanics of a wire robot is created. Special focus lies on creating collision-free motion profiles which can be exported to the robot control system. BIM models can be used to set-up the simulation model and to prepare the required input data. Following a modular structure, the model can be applied with different purposes in the exploration of the approach. The construction of a one-story masonry building serves as case study proving the concept’s functionality.

In mechanical engineering branches like automobile and consumer goods fabrication, the automation of processes has reached a high level. Development and production processes have been established towards standards, tools and interfaces that allow for the application of robots and automated production lines. Nowadays, even individualized products are aspired in the upcoming Industry 4.0 approach. While automated techniques are widely spread in the manufacturing industry, construction work is mainly conducted in a conventional manner. In general, construction projects are characterized by a high number of individual boundary conditions. Except for the prefabrication of building components, automated construction techniques are rarely applied. With regard to the typical processes of construction projects, the size of a building lot makes the application of robots extremely demanding. Thus, the integration of robots in the construction of buildings has always been challenging.

Due to the potential to save working time while increasing work quality, automated construction by using robots is worth being investigated. Still, many past initiatives did not succeed, most because of two major conditions (Cousineau and Miura 1998):

  • As a masonry building is a large product, no conventional robot technology is known to cover it entirely. Accordingly, the robot base needs to move, which is usually avoided for industrial robots due to cost and robustness reasons.
  • Masonry buildings are usually unique projects. In conventional planning, this is associated with drawings that are not prepared for automated processing and production planning.

The latter has dramatically changed with the emergence of Building Information Modeling (BIM) in the last decades. A detailed overview on BIM and its benefits for the construction industry can be found in Borrmann et al. (2015). Automatization techniques may now benefit from detailed and precise information provided in BIM models. Thus, the ongoing development of BIM can be regarded as key motivation for examining the application of robots for automated construction. In this regard, repetitive work patterns are particularly suitable for automatization. Considering the construction of domestic buildings, the creation of masonry buildings represents a practicable example. The lack of large-scale robots has also recently been resolved by the demonstration of huge wire robots. This novel robot concept created by a set of computerized winches that are connected with the payload allows building robots that can easily cover the base area of a masonry building.

However, challenges evolving with the application of robots need to be investigated. These can be divided into technical and economic challenges: For example, in the path planning, collisions between robot parts and other elements need to be avoided. Furthermore, the robot workspace needs to be adjusted to the dimensions of the created building. Stiffness and load calculations are necessary to compute and optimize accuracy, while the installed actuator power determines the required time for the single robot operations. Finally, the economic efficiency of the concept needs to be proven based upon these findings. An evaluation of the developed concept can be achieved by the help of process simulation. Following this approach, conducting time-consuming and cost-intensive practical tests at early project stages can be avoided. In this paper a concept for the simulation-based validation of wired robots for automated construction is presented.

The paper is structured as follows: Section 2 gives a brief overview concerning the background of the general idea. Special focus lies on recent developments concerning robot application for construction — especially wire robots, process simulation for construction as well as processing information from BIM models. Section 3 contains basic information concerning wire robot modeling. In section 4, the developed framework is presented in more detail. A case study conducted with the discrete event simulation can be found in the last section.

Discrete Simulation

Discrete-event simulation concept

Figure 1: Discrete-event simulation concept.

Analyzing the feasibly of wire robot use for automated construction represents the main objective of this work. Special focus lies on calculating collision-free moving paths of the robot. To achieve reliable simulation results, both the robot geometry and the operation method need to be represented correctly. The BIM model of the project provides information concerning building geometry and material and thus, decisively influences the robot operation. With regard to reutilization, the simulation model can be used for different building projects provided that the BIM model is available. Robot and site layout (e.g., the position of the brick storage) are regarded as significant input parameters. Due to a modular, component-based structure the model can be easily adapted to different working conditions. Figure 1 shows the general structure of the simulation model.

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