# Development of a Capsule-Type Inspection Robot Customized for Ondol Pipelines
## 4 Development of Prototype and Performance Experiment
### Performance Experiments  
To verify the performance of the developed prototype system, a laboratory with ondol piping was constructed, and performance verification experiments were conducted. The laboratory constructed for the performance experiments is shown in Figure 11. The experiment was conducted identically for three patterns, as shown in Figure 2. To ensure field applicability of the developed system, the following verification was required: first, verification of smooth movement through the straight and curved sections of the piping; second, verification that the video captured by the robot was well transmitted in real time to the monitoring system and that defects were clearly identified by the naked eye on the monitoring system; and lastly, verification of the wireless communication performance. The verification of the communication performance was excluded from this experiment because the movement of the robot could not be visually confirmed when the piping was embedded in the cement mortar. The wireless communication performance had already been verified through preliminary research. Therefore, the performance verification focused on the mobility of the robot and the quality test of the detection screen of the monitoring system. Figure 11: Laboratory constructed according to the installation patterns of ondol pipeline. Figure 10: Monitoring system application for pipeline inspection robot: (**a**) starting and connecting the application; (**b**) video captured inside the pipeline transmitted by the robot; (**c**) saving the video. Figure 12 shows the process of inserting the robot into the piping. Figure 12a shows the air compressor used to move the inspection robot inside the piping. The air compressor used in this experiment was an off-the-shelf product with specifications of 3.5 Hp and 40 L. Figure 12b shows the process of inserting the inspection robot into the piping and connecting the air compressor hose to the piping. Figure 12c shows the monitoring system confirming the video sent by the inspection robot. Figure 13 shows the movement of the inspection robot. The laboratory lights were turned off to confirm the moving position, and the LED on the robot was turned on. As shown in Figure 13a, the robot was brightly visible inside the pipe. Figure 13b,c show the curved and straight sections, respectively. The robot moved under the compressive force of the air introduced into the piping, and the moving speed was adjusted by the compressive force of the air compressor. In the experiment, the robot moved at an average speed of 350 mm/s with possible speed adjustments between 200 and 500 mm/s. Consequently, the robot was verified as moving smoothly in both straight and curved sections. Figure 14 shows representative images of the video sent by the inspection robot while moving. Various situations that could occur during the actual installation were set up in the piping to verify whether they could be identified through the images captured by the  
Figure 12: Starting the performance test: (**a**) air compressor used; (**b**) robot insertion; (**c**) monitoring system screen display. Figure 13: Movement of the robot inside the pipeline: (**a**) overall view of the pipeline; (**b**) curved section; and (**c**) straight section. robot. Figure 14a shows the normal interior of the piping. Figure 14b,c show the formation of wrinkles inside the piping due to bending beyond the elastic limit of the piping in the curved sections. The wrinkles occurred as a result of mistakes made by workers during the installation of the piping, which weakened the durability of the pipe wall, hindered the flow of hot water, and ultimately became a potential cause of leakage. Figure 14d shows pipe blockage. During the pipe installation, cement mortar and foreign substances could have entered, and the image showed such a situation.