# Conceptual Design of the Combinable Legged Robot Bio-Inspired by Ants' Structure
## 1 Introduction  
In the last decade, there have been many research efforts in robot design that have promised more efficient and more reliable mechanisms than before [1; 2; 3; 4]. However, it is not feasible for them to perform all the tasks required. Most of the robot designs are mainly focused on the application requirements. More research is needed in exploring innovative mechanisms to solve the limited physical capability of conventional robots.  
In recent years, a variety of designs have been evolving in the field of biomimetic robots, which applies the characteristic of bio-systems to robotic systems [5]. This biomimetic design usually shows outstanding outcomes in innovating the physical capability of the robot. [PERSON] et al. proposed a climbing robot, \"Rat-Nic\", that was inspired by the adaptability of rats on a slope [6]. [PERSON] et al. developed a bouncing robot \"Grillo\", the ingenuity of which was based on the jumping of leafhoppers [7]. [PERSON] et al. created a hybrid leg structure for a quadrupped robot that improved the load capacity of conventional multi-legged robots [8]. [PERSON] et al. introduced a fire rescue snake-like robot, \"Anna-Konda\" [9]. [PERSON] et al. demonstrated a new six-legged robot inspired by ant locomotion [10].  
However, there is little research on robot design that is bio-inspired by the hybrid behaviors of animals like the multi-functional mode of ants. Ants are eusocial insects that favor a temporary mechanical combination for movement to improve the physical performance as a group in a given situation [11; 12]. As shown in Figure 1, ants are not only able to behave like a modular multi-legged robot with an identical body structure, they are also capable of combining with each other using their claws. Therefore, the realization of the ants' structure could possibly expand the robot's capability.  
Up to now, the previous research has generally focused on mimicking the walking motion of ants with a variety of walking gaits on uncertain terrain [1; 13]. Although there are many types of research to implement the collaborative behavior of ants [5; 14; 15], robot structures that enable implementing physical capabilities like ant locomotion have not been realized yet. This is due to the difficulty in realizing a structure for a multi-legrobot that consists of the coupling mechanisms at the same time. This study focuses on the investigation into the physical combinable behavior of legged robots inspired by ants' structure. For the realization of the multi-leg robot with the coupling mechanism, the structure of the proposed robot is simplified.  
The objective of this research is to present the design and performance of the combinable multi-leg modular robot bio-inspired by ants' leg locomotion and their claws. The details of the robot design are presented in Section 2. The control system of the proposed robot is described in Section 3. Basic locomotion in the experiment is explained in Section 4: the robot walking alone and in combined status. The results of the experimental data are tabulated and presented in Section 5. The results are discussed in Section 6.