## 2 Background
### Robots in SAR  
Actions taken during the emergency response phase include saving lives and preventing further damage to people. Several steps are included in response phase operations, including 1. initial search and assessment, 2. targeted search, 3. localisation and identification, and 4. assistance. According to the type of emergency, environment, and available resources these stages might overlap and vary, as noted in the National SAR Manual [43]. The levels of automation for the robotic technology utilised in the response process can be categorised into **Level 1:** Teleoperation, **Level 2:** Semi-Autonomous, and **Level 3:** Fully-Autonomous. Different kinds of unmanned systems (heterogeneous) are utilised in SAR, giving it an edge by combining the best aspects of each type to provide compound capabilities. For instance, small UGVs might be deployed in a given area using UAVs to explore the environment. This approach is more flexible and effective in new situations. Interoperability makes it possible for heterogeneous teams to collaborate and share information and resources. Also, interoperability assigns specific responsibilities to specific robots at different operational levels. For example, scout robots (UAVs) are used to quickly assess unknown territory, and searcher & rescuer robots (UAVs and UGVs) are used to conduct victim searches and offer support for victims [11]. ICARUS developed a technology deployment framework in [38] which is used for mission planning and coordination between the systems during the operation. In general, robots are grouped according to their nature, autonomy, task, operational environment, and interaction [44]. The robots used for SAR can be categorised into UAVs,USV/AUV/ROV (unmanned surface vehicle/autonomous underwater vehicle/remotely operated vehicle), UGVs, UHV/UApV (unmanned hybrid vehicle/unmanned amphibious vehicle) shown in Figure 1. In SAR operations UGVs and UAVs have commonly been used systems [4, 41, 45, 46]. Several rescue robots currently in operation, including Emily, BEAR, SaffiR, Colossus, ANYmal, Centauro, etc. [47, 48, 49, 50, 51, 52]. These robots are limited to specific terrain and might have difficulties accessing constrained environments, especially during a collapsed environment. Especially in SAR, robots might encounter a variety of situations such as dirt, water, rain, confined spaces, uneven surfaces, and obstacles with unpredictable movement [53]. In these situations, a snake-like robot has the potential to be adopted due to its flexible body and multi-terrain locomotion capabilities. The benefit of utilising a snake-like robot extends beyond just entering confined spaces and field environments. In the past, the use of robots (UGVs) in SAR situations like the World Trade Center (WTC) tragedy brought up several significant design concerns [53]. By employing UGVs, it is stated that there is a high likelihood of failures in the effectors (driving systems) and control systems--roughly 50% and 54%, respectively. This indicates that features like field repairability are key for the robots to use in SAR. Additionally, to maintain the safety of the victims who are trapped, the robot should not alter the field environment. on other hand, UGVs experience difficulty to access the environment, and require assistance during gravity, stuck, track slippage, and occluded camera. This suggests that a snake robot would be a viable alternative to meet the many issues raised. For instance, unlike UGVs, the snake robot does not require any extra effectors (or driving systems), and the modular architecture has a benefit if the control system fails. And, the redundant design of the snake robot enables field repairability. It can grasp things with one end, lift the body, and achieve a smooth transition, even free falling may not be an issue for further locomotion. It does not require any aid (gravity, slippage) to reach the field environment.