**2. Essential mechanisms for in-pipe inspection robots**

For each of the in-pipe robots described above, the body structure consists of three essential components: (1) a propulsive mechanism for moving forward and backward, (2) a steering mechanism for turning at bent and branch sections, and (3) an extending mechanism for avoiding slipping and falling at vertical sections. The propulsive and steering mechanisms are very common in the mobile robot field, whereas the extending mechanism is specific to in-pipe mobile robotic applications. A general in-pipe mobile mechanism is shown in **Figure 1**.

We believe that a key point in designing a small and highly adaptable in-pipe robot is its functional complex. If three components (propulsive, steering, and extending) are installed separately, then an increase in size is inevitable. In a sense, the legged-type, peristaltic-type, and serpentine-type locomotion can be regarded as the common principle because the propulsive mechanism works simultaneously as an extension and as a steering component. Moreover, the radial size of the snake and peristaltic robots may be reduced because the robot body itself generates a propulsive force by shifting its body shape, which suggests the nonnecessity of additional motion mechanisms. As mentioned above, animallike locomotion in pipes is slower than wheel-driven locomotion. Therefore, it is important to develop a scheme that combines the advantage of the wheeled mechanism (faster movement) and the snake and peristaltic mechanism (small size).

**3**

**Figure 2.**

*Robotic Search and Rescue through In-Pipe Movement DOI: http://dx.doi.org/10.5772/intechopen.88414*

articulated wheeled robot.

*General in-pipe mobile mechanism.*

**Figure 1.**

Structures with several components generally conflict with downsizing. Nonetheless, this issue is solved to some extent by combining multiple functions in one part of the robot (a functional complex). In this study, we tackle two approaches for the functional complex, namely, a differential mechanism and arranging multiple degrees of freedom (DoFs) on a common axis. Conceptually, the differential mechanism approach is applied to a steering mechanism of a screw-drive robot [11] and a step adaptation mechanism of a three-modular robot, whereas the idea of arranging multiple DoFs on a common axis is applied to an

An overview of the screw-drive-type in-pipe robot that we first introduced [12] is illustrated in **Figure 2**. This in-pipe robot consists of a front rotator that generates thrust and a rear stator that supports the reaction of the rotator. The rotator has several tilted passive wheels arranged on its circumference and can move forward

By arranging a motor and a gear reduction along the pipe axis, the output drive axis can be connected directly to the rotator without changing the direction of rotation through a transmission mechanism, such as a miter. This implies that the screw-drive type can be miniaturized easily, although it would face difficulty passing through T-branches with only a drive mechanism. To solve this challenge, an

**3. Functional complex by a differential mechanism**

and backward while tracing a spiral curve.

*Screw-drive in-pipe mobile robot for 5-in pipelines [12].*

*Robotic Search and Rescue through In-Pipe Movement DOI: http://dx.doi.org/10.5772/intechopen.88414*

**Figure 1.** *General in-pipe mobile mechanism.*

*Unmanned Robotic Systems and Applications*

So far, a number of methods called smart pipe inspection gage (PIG) have been reported to utilize fluid force in the pipe to push out and move the camera or inspection device. Owing to this passive movement, a route cannot be selected at the branch sections and cannot propel unless the internal pressure of the pipeline is sufficient. In the pipeline business, PIG is not suited to "unpiggable pipelines." Instead, industrial endoscopes with a camera attached to the tip are widely employed. Nevertheless, as the endoscopes require being pressed in with hands,

To solve this problem, companies, universities, and research institutions have been working on a large number of self-mobile in-pipe inspection robots. The robot's movement can be roughly classified into legged type [1], peristaltic type [2], serpentine type [3], and infinite rotation type [4–10]. The legged-type robot walks in pipes while extending its legs against the inner wall. However, multiple degrees of freedom cause complicated control systems and an increase in the entire robot size. The peristaltic-type robot produces propagating contractive waves found in earthworms and leeches to move as it pushes out its multiple segments in order. Any of the segments always comes in contact with the inner wall of the pipe to support the body; thus, it can move upward at vertical sections. The serpentine type moves in pipes by sending a waveform to an elongated structure consisting of multiple segments as seen in snakes. Unlike conventional planar snake-like robots with passive rollers at their bottom, the directions of the wave and the travel are the same. Those types are very interesting and important in the sense of scientific investigation on how animal locomotion adapts to tubelike narrow environments. However, the infinite rotation type, such as in drive wheels and crawler mechanisms (belt-driven), was the one substantially studied as it provides a significantly faster and more efficient motion than the abovementioned animal locomotion schemes despite its simple structure and low cost. Thus, this is expected to contribute in checking buildings or infrastructures before and after disasters, especially in enter-

ing into a collapsed building through pipes to search for human casualties.

For each of the in-pipe robots described above, the body structure consists of three essential components: (1) a propulsive mechanism for moving forward and backward, (2) a steering mechanism for turning at bent and branch sections, and (3) an extending mechanism for avoiding slipping and falling at vertical sections. The propulsive and steering mechanisms are very common in the mobile robot field, whereas the extending mechanism is specific to in-pipe mobile robotic appli-

We believe that a key point in designing a small and highly adaptable in-pipe robot is its functional complex. If three components (propulsive, steering, and extending) are installed separately, then an increase in size is inevitable. In a sense, the legged-type, peristaltic-type, and serpentine-type locomotion can be regarded as the common principle because the propulsive mechanism works simultaneously as an extension and as a steering component. Moreover, the radial size of the snake and peristaltic robots may be reduced because the robot body itself generates a propulsive force by shifting its body shape, which suggests the nonnecessity of additional motion mechanisms. As mentioned above, animallike locomotion in pipes is slower than wheel-driven locomotion. Therefore, it is important to develop a scheme that combines the advantage of the wheeled mechanism (faster move-

**2. Essential mechanisms for in-pipe inspection robots**

cations. A general in-pipe mobile mechanism is shown in **Figure 1**.

ment) and the snake and peristaltic mechanism (small size).

they are not suitable for inspection in long winding pipelines.

**2**

Structures with several components generally conflict with downsizing. Nonetheless, this issue is solved to some extent by combining multiple functions in one part of the robot (a functional complex). In this study, we tackle two approaches for the functional complex, namely, a differential mechanism and arranging multiple degrees of freedom (DoFs) on a common axis. Conceptually, the differential mechanism approach is applied to a steering mechanism of a screw-drive robot [11] and a step adaptation mechanism of a three-modular robot, whereas the idea of arranging multiple DoFs on a common axis is applied to an articulated wheeled robot.
