Auton Robot (2006) 20:251–260 DOI 10.1007/s10514-006-7099-7 Olfactory coordinated area coverage Svetlana Larionova · Nuno Almeida · Lino Marques · A. T. de Almeida Published online: 8 June 2006 C  Springer Science + Business Media, LLC 2006 Abstract This paper proposes an olfaction based method- ology to automatically cover an unknown area enabling the decoupled cooperation of a group of floor cleaning mobile robots. This method is based on the utilisation of low cost chemical sensors in cleaning mobile robots, in order to dif- ferentiate clean from dirty areas. The experimental results show that the use of olfactory capabilities allows to effi- ciently cover and clean a certain area, and demonstrate the possibility of coordinating several mobile robots without the need of expensive sensing capabilities, map building or com- plex algorithms for task scheduling. Keywords Complete coverage . Robot olfaction . Cleaning robots . Robot cooperation 1. Introduction Covering large areas is a task that is obviously useful in a large number of applications such as cleaning large surfaces (e.g. supermarkets, airports, shopping centres, etc.), deter- mining the spatial distribution of a parameter such as metal concentration in the ground or explosive vapours concen- S. Larionova () · N. Almeida · L. Marques · A. T. de Almeida Institute of Systems and Robotics, Department of Electrical and Computers Engineering, University of Coimbra, Portugal e-mail: sveta@isr.uc.pt N. Almeida e-mail: nuno@isr.uc.pt L. Marques e-mail: lino@isr.uc.pt A. T. de Almeida e-mail: adealmeida@isr.uc.pt tration at a near ground level in demining applications, or simply for mapping purposes (Choset, 2001). The efficiency of these tasks can be largely increased if they are performed by multiple robots instead of a single one. Enabling cooper- ation through the use of chemical information is a common procedure in several animal societies such as ants or bees. In this paper it is proposed an algorithm to enable decoupled co- operative coverage of a certain area by multiple robots based on the use of chemical information, keeping in mind that for both cleaning and demining it is essential to guarantee total coverage of the area of interest. Employing more than one robot decreases the coverage time, although this option increases the complexity of the overall control. Using chemical information will enable the implementation of a decoupled cooperation technique which will allow scalability without increasing the complexity of the system. If each robot can leave a chemical mark along its path and all robots are able to sense it, there is no need for map building or to implement a global control layer to coordinate the robots. This principle is easily implementable on floor cleaning robots using the fact that after cleaning, water and cleaning chemicals are released on the floor and might be used as a mark that can be detected by chemical sensors. 1.1. Covering algorithms Several approaches are possible for covering an unknown en- vironment with mobile robots. The most common solution is to implement cellular decomposition of the target area. In approximate cellular decomposition, the working area is divided into cells of equal size. Gabriely and Rimon (2002) proposed the following approach for online covering of an unknown environment: the working area is incrementally Springer