## 4 Proposed Design and Method  
### Proposed Method and Design for Casually Loading  
In this study, we adopted the loco-manipulation approach presented in our previous work [23] for the casualty extraction method. This method was evaluated in the study presented in [19; 23]; it has shown potential for the safe loading of casualties and satisfies several safety measures [43; 58]. One of the objectives of this study is to propose a robot design to safely load an average-size person's entire body onto the robot's stretcher bed and secure it safely. In order to achieve this objective, the size of the robot's stretcher bed and conveyor must be increased. This increase in length would lead to an increase in the overall size of the robot. Figure 4a,b illustrates the different robot sizes. The size of the stretcher bed can be increased without a significant change to the robot's design. There are at least two major problems with this design: (1) The robot's overall length increases by 1.5 times the length of the original ResQbot 1.0. This will cause the robot to struggle while manoeuvring in typical indoor environments, and (2) the more extended stretcher bed module (potentially loaded with a casualty) towed behind the differential-drive mobile base would make it difficult to manoeuvre the robot and keep the stretcher bed stable, since the mobile base would require much more effort to turn with an asymmetrical load towed behind the mobile base. Moreover, slight turns by the mobile base would cause much more movement on the stretcher bed, making it challenging to keep the stretcher bed stable during transportation. Figure 4c illustrates the ideal position of the stretcher bed on the mobile base. In this position, the load would be uniformly distributed to the robot's mobile base. In comparison with the original ResQbot 1.0 configuration (Figure 4a), upgrading the robot's stretcher bed size would result in a similar overall length when configured as shown in Figure 4c. Moreover, since the robot's configuration in Figure 4c is symmetrical, the mobile base's manoeuvrability will be improved seeing as it is a mobile base with a differential-drive wheel mechanism with the driving wheel placed in the middle. Consequently, the stretcher bed would be more stable while manoeuvring the robot during transportation--even when loaded with a casualty. Figure 4: Illustration showing the ResQbot 1.0 stretcher-bed conveyor in comparison to the longer stretcher-bed conveyor designs that enable safe loading of the casualty’s entire body onto the stretcher bed. (**a**) ResQbot 1.0 original size. (**b**) ResQbot 1.0 with an expanded stretcher bed. (**c**) The ideal position of the stretcher bed on the differential-drive mobile base (i.e., proposed design). To accommodate the configuration shown in Figure 4c and retain the robot's locational capability to load the casualty, we propose adding tilting and sliding mechanisms to the stretcher module on the mobile base platform. Figure 5 illustrates the stretcher bed sliding and tilting mechanisms proposed for ResQbot 2.0. With these additional mechanisms, ResQbot 2.0 could perform casualty extraction in a similar manner to ResQbot 1.0, but with a slightly modified procedure. Figure 6 illustrates the proposed new casualty extraction procedure using ResQbot 2.0. Figure 5: Illustration of proposed tilting mechanism and sliding mechanism adapted in the ResQbot 2.0 proposed design. These mechanisms were adapted in order to accommodate the upgraded size of the stretcher bed—capable of loading the entire body of an average-size casualty—while maintaining the overall compact design of the robot. Figure 6: Illustration of the proposed casualty extraction procedure using ResQbot 2.0 comprising of seven main sequential phases: (**1**) Aligning the robot’s pose with respect to the casualty’s orientation. (**2**) Approaching the casualty in the desired target position in readiness to load the casualty.