Computational Methods for Coordinating Multiple Construction Cranes Shih-Chung Kang 1 and Eduardo Miranda 2 Abstract: The incremental coordination method a computational method for preplanning and coordinating the use of multiple tower cranes in relatively narrow construction sites is presented. The incremental coordination method considers the kinematics and the geometrical constraints of cranes to plan the motion of two or more cranes, which are being operated in collaboration. By following such planned motions, erection tasks are completed safely, even when the cranes are operated in close proximity of each other. This method allows the use of computers to plan and coordinate the crane activities from start to end of an erection process. This paper also explains the computational methods required by the incremental coordinate method including path-finding and collision detecting methods. An example case shows two construction cranes, each of three degrees-of-freedom, operating together on a building project where the working areas of the cranes intersect, hence possibility colliding with each other. A numerical test was conducted to verify the efficiency and effectiveness of applying the incremental coordination method in planning and synchronizing all motions of the two cranes to avoid any collision between the cranes themselves and collision with obstacles on the construction site. DOI: 10.1061/ASCE0887-3801200822:4252 CE Database subject headings: Cranes; Construction equipment; Construction sites; Construction management; Graphic methods. Introduction An increasing trend toward the simultaneous use of multiple cranes multicrane at a site has recently been observed. This is particularly evident in high-rise construction in which the use of multiple cranes can translate into significantly faster construction. However, computational motion planning when two or more cranes are working simultaneously and share a portion of their workspace is significantly more complex than the motion plan- ning for a single crane project. There are two main aspects that contribute to the complexity of dealing with multiple cranes: 1 in addition to new obstacles being added by the crane for each element that is erected, the collision detection and motion plan- ning algorithms must also consider new obstacles that are placed by other cranes on the site; and 2 motion planning must consider multiple moving objects, whereas in the case of a single crane, the only moving object is the one being moved by the crane. To deal with multicrane related problems, Zhang et al. 1999 developed a computerized model to optimize the placement of a group of tower cranes. Sivakumar et al. 2003 employed a heu- ristic search and Ali et al. 2005 applied a genetic algorithm to search the erection paths for two cooperative cranes. Al-Hussein et al. 2005 developed an optimization algorithm for determining the location of mobile cranes. Other related work such as crane simulation, visualization, and onsite monitoring has been pub- lished by many researchers worldwide, such as Bennett and Ditlinger 1994, Liu 1995, Lin and Haas 1996, Bernold et al. 1997, Stone et al. 1999, Lipman and Reed 2000, Navon and Goldschmidt 2003, and Sacks et al. 2005. The aforementioned research, however, does not deal with methods for efficiently planning the simultaneous motions of multiple cranes. The major challenge in developing these methods is that in planning the cranes motions we have to consider the motion of each part of each crane. This is to avoid the possible collision of crane parts with stationary objects at the project site, as well as possible collision between the cranes and the elements being transported. This research aims at solving this problem and developing a computational method for this purpose. This paper explains a computer algorithm for planning the simultaneous motions of multiple cranes. Since coordinating the activities of two or more moving cranes generally requires a very large number of calls to collision-checking functions, a particu- larly efficient computational method for detecting intercrane col- lisions is detailed. This paper also presents an example case in which two cranes are coordinated by using the computational methods developed in this research. Existing Methods for Coordination of Multiple Robots The problem of motion coordination has been researched for years in the field of robotics. Many methods have been developed for coordinating the motions of multiple robots working together in close proximity. For example, in the automobile industry it is very common that multiple robots are simultaneously used for 1 Assistant Professor, Dept. of Civil Engineering, Civil Engineering Building, National Taiwan Univ., No. 1, Sec. 4, Roosevelt Rd., Taipei 10617, Taiwan corresponding author. E-mail: sckang@ntu.edu.tw 2 Associate Professor, Dept. of Civil and Environmental Engineering, Terman Engineering Center, Standford Univ., Standford, CA 94305. E-mail: emiranda@standford.edu. Note. Discussion open until December 1, 2008. Separate discussions must be submitted for individual papers. To extend the closing date by one month, a written request must be filed with the ASCE Managing Editor. The manuscript for this paper was submitted for review and pos- sible publication on March 28, 2007; approved on September 18, 2007. This paper is part of the Journal of Computing in Civil Engineering, Vol. 22, No. 4, July 1, 2008. ©ASCE, ISSN 0887-3801/2008/4-252–263/ $25.00. 252 / JOURNAL OF COMPUTING IN CIVIL ENGINEERING © ASCE / JULY/AUGUST 2008 J. Comput. Civ. Eng. 2008.22:252-263. Downloaded from ascelibrary.org by National Taiwan University on 08/29/14. Copyright ASCE. For personal use only; all rights reserved.