In-pipe running robot and method of running the robot

An in-pipe running robot includes a vehicle body movable inside piping along a piping axis, and a pair of running devices disposed in front and rear positions of the vehicle body. Each of the running devices has a pair of wheels secured to opposite ends of an axle. The wheels are steerable as a unit about a vertical axis of the vehicle body, and have a center of steering thereof extending linearly in a fore and aft direction of the vehicle body. When the robot is caused to run in a circumferential direction inside the piping, the vehicle body is set to a posture having the fore and aft direction inclined with respect to the piping axis, with the running devices set to a posture for running in the circumferential direction. Then, the running devices are driven to cause the vehicle body to run stably in the circumferential direction of the piping.

BACKGROUND OF THE INVENTION 
1. FIELD OF THE INVENTION 
This invention relates to in-pipe running robots, and more particularly to 
an in-pipe running robot for use in various operations inside piping such 
as inspection of interior conditions or repair of inner walls of piping. 
The invention relates also to a method of running such a robot. 
2. DESCRIPTION OF THE RELATED ART 
In order to inspect and repair piping interiors, such an in-pipe running 
robot is required to run straight along a piping axis, and to run round 
circumferentially in the piping while adhering to an inner wall and 
maintaining a fixed position axially of the piping. 
The robot runs straight along the piping axis, for example, to arrive at an 
intended location quickly or to inspect piping bottoms successively which, 
generally, are the most susceptible part of the piping. Where the piping 
includes a welded joint formed circumferentially thereof, for example, the 
robot is required to run circumferentially in the piping to inspect or 
repair the joint as necessary. 
This type of in-pipe running robot has adherent wheels to be able to run 
while adhering to running surfaces in vertically extending piping as well, 
for example. 
FIG. 6 (a) shows a running state of a conventional in-pipe running robot. 
This in-pipe running robot includes a vehicle body movable inside piping 
along a piping axis, and a pair of front and rear running devices attached 
to the vehicle body. Each running device includes a pair of wheels mounted 
on opposite end regions of an axle, and is steerable about a vertical axis 
of the vehicle body. The center of steering extends linearly in a fore and 
aft direction of the vehicle body. The robot further includes drive 
control devices for individually driving the pair of running devices, and 
steering control devices for individually steering the running devices. 
When the robot is required to run straight along the piping axis, the 
vehicle body and running devices are placed in the posture shown in FIG. 3 
(a) (with the fore and aft direction of the vehicle body extending 
parallel to the piping axis, and the axles of the running devices 
extending at right angles to the piping axis). When the robot is required 
to run round the piping axis, the vehicle body and running devices are 
placed in the posture shown in FIGS. 3 (b) and 6 (a) (with the fore and 
aft direction of the vehicle body extending parallel to the piping axis, 
and the axles of the running devices aligned to each other and extending 
parallel to the piping axis). 
Conventionally, the in-pipe running robot is intended to maintain a fixed 
position axially of the piping in running round circumferentially in the 
piping. However, as shown in FIG. 6 (a), the robot would turn over by 
gravity when the robot becomes tilted to a certain degree. 
It is therefore necessary with the robot having the above construction to 
rely on the adhering ability of the running devices for an appropriate 
selection of the center of gravity of the robot, or to limit a load 
capacity of the robot. This presents restrictive conditions in designing 
of the robot, which are undesirable. 
SUMMARY OF THE INVENTION 
An object of the present invention, therefore, is to provide an in-pipe 
running robot which does not easily turn over even when running round 
circumferentially inside piping, and a method of running the robot which 
allows the robot to run stably circumferentially inside piping. The above 
object is fulfilled, according to the present invention, by an in-pipe 
running robot comprising: 
a vehicle body movable inside piping along a piping axis; 
a pair of running devices disposed in front and rear positions of the 
vehicle body, each of the running devices including a pair of wheels 
secured to opposite ends of an axle, the running devices being steerable 
as a unit about a vertical axis of the vehicle body and having a center of 
steering thereof extending linearly in a fore and aft direction of the 
vehicle body; 
drive control means for individually driving the pair of running devices; 
steering control means for individually steering the pair of running 
devices with respect to the fore and aft direction of the vehicle body; 
first detecting means for detecting angular displacement of the fore and 
aft direction of the vehicle body with respect to the piping axis; 
second detecting means for detecting steering amounts of each of the 
running devices with respect to the fore and aft direction of the vehicle 
body; and 
running posture control means for controlling the drive control means and 
the steering control means in response to results of detection by the 
first detecting means and the second detecting means, to place the vehicle 
body in a position for running in a circumferential direction of the 
piping, with the fore and aft direction of the vehicle body inclined with 
respect to the piping axis, and the running devices set to run in the 
circumferential direction. 
In a further aspect of the invention, a method of running an in-pipe 
running robot through piping is provided, the robot having a vehicle body 
movable inside piping along a piping axis, and a pair of running devices 
disposed in front and rear positions of the vehicle body, each of the 
running devices including a pair of wheels secured to opposite ends of an 
axle, the wheels being steerable as a unit about a vertical axis of the 
vehicle body and having a center of steering thereof extending linearly in 
a fore and aft direction of the vehicle body, the method comprising the 
steps of: 
setting the vehicle body to a posture having the fore and aft direction 
inclined with respect to the piping axis; 
setting the running devices to a posture for running in a circumferential 
direction of the piping; and 
driving the running devices to cause the vehicle body to run in the 
circumferential direction of the piping. 
The present invention provides the following functions and effects. 
The in-pipe running robot has a pair of running devices disposed in front 
and rear positions of the vehicle body, and the running devices are driven 
and steered individually under control of the drive control means and 
steering control means. The first detecting means detects a posture of the 
vehicle body with respect to the piping axis, while the second detecting 
means detects a steering amount of each running device. When changing the 
robot from a straight running posture for running along the piping axis to 
a circular running posture for running circumferentially of the piping, 
the running posture control means causes the drive control means and 
steering control means to place the vehicle body having the fore and aft 
direction thereof inclined with respect to the piping axis, with the 
running devices set to run in the circumferential direction of the piping 
(the posture shown in FIGS. 3 (d) and 4). In this state, the robot runs 
circumferentially of the piping. In this posture, as also shown in FIG. 6 
(b), a direction (referenced B in FIG. 4) extending through centers of 
steering of the two running devices is displaced from the direction of the 
axles of the running devices. Consequently, the running devices are 
arranged to have a transverse width when seen from the front of the robot, 
whereby the robot runs in the circumferential direction of the piping 
without overturning. 
In the method of running the in-pipe running robot according to the present 
invention, the robot stably runs in the above-noted posture 
circumferentially of the piping. 
Thus, the present invention provides an in-pipe running robot having a 
unique construction and a method of running the robot, which assure stable 
running along the piping axis and in the circumferential direction of the 
piping. 
When the vehicle body is in a straight running posture for running along 
the piping axis, the fore and aft direction of the vehicle body extends 
along the piping axis, and the turning devices are directed to run along 
the piping axis. The running posture control means is operable for 
switching the vehicle body from the straight running posture to a circular 
running posture to run in the circumferential direction through the steps 
set out hereunder. The robot having arrived at a predetermined location 
axially of the piping is allowed to run circumferentially of the piping 
while substantially maintaining the location axially of the piping. 
Step 1 
Operate the steering control means to turn the axles of the running devices 
to extend along the piping axis while maintaining the fore and aft 
direction of the vehicle body parallel to the piping axis; 
Step 2 
operate the drive control means to drive the running devices in opposite 
directions to displace the vehicle body to an inclined posture relative to 
the piping axis; and 
Step 3 
operate the steering control means to turn the axles of the running devices 
to extend along the piping axis. 
Alternatively, the running posture control means may switch the vehicle 
body from the straight running posture to a circular running posture to 
run in the circumferential direction through the following steps, thereby 
to effect posture switching relatively quickly: 
Step 1 
operate the steering control means and the drive control means at the same 
time to incline the fore and aft direction of the vehicle body with 
respect to the piping axis; and 
Step 2 
operate the steering control means to turn the axles of the running devices 
to extend along the piping axis. 
Further, the pair of wheels of each running device may have different 
polarities, so that each running device adheres to the piping walls 
through a magnetic field formed between the wheels. Then, the in-pipe 
running robot can stably run straight or circumferentially, with the 
running devices adhering to piping walls through a strong magnetic 
attraction. 
The foregoing and other objects, features and advantages of the invention 
will be apparent from the following more particular description of 
preferred embodiments of the invention, as illustrated in the accompanying 
drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
An in-pipe running robot according to the present invention will be 
described in detail with reference to the drawings. 
FIG. 1 shows a side view of a robot 1 running inside piping 11. FIG. 2 
shows a front view of the robot 1 running through a valve section 2. 
As shown in FIG. 1, the in-pipe running robot 1 is operable under control 
of and upon command information received from a system 3 disposed outside 
the piping 11. This system 3 includes a command unit 3a for giving running 
instructions, operating instructions and the like, a display unit 3b for 
displaying image information received from an image pickup 4 mounted on 
the robot 1, and a data processing unit 3c. 
The robot 1 has a main body 5 of rectangular shape, in plan view, elongated 
axially of the piping 11 as shown in FIG. 3, part (a). The main body 5 
includes a vehicle body 50 having a characteristic configuration in side 
view as shown in FIG. 1, and a pair of running devices 60 arranged under 
the vehicle body 50. The vehicle body 50 includes a body frame 51a 
supported on the running devices 60 and having a plate-like upper surface, 
and a plastic cover 5lb enclosing various devices mounted on the body 
frame 51a as described later. 
The body frame 51a includes an upward recess 52 formed in a middle position 
longitudinally thereof between the pair of running devices 60. The recess 
52 is formed to avoid interference with an inner wall 7a of an elbow 
section 7 when the in-pipe running robot passes therethrough as shown in 
solid lines in FIG. 5 (a). Further, the vehicle body 50 includes upper end 
regions 53 defining a curved (arcuate) front surface 53a and a curved 
(arcuate) rear surface 53b, respectively, in the fore and aft direction of 
the robot 1. The curved upper end regions 53 are shaped to avoid 
interference with opposite inner walls 7b across the elbow section 7 when 
the robot 1 is in the elbow section 7 as shown in the solid lines in FIG. 
5 (a). 
The vehicle body 50 further includes stepped front and rear regions 55a and 
55b continuous with the curved front surface 53a and curved rear surface 
53b, respectively, and at a lower level than top portion 54 of the robot 
1. These stepped regions are included to minimize the cross sectional area 
perpendicular to the long axis of the body 50 in the regions above the 
wheels 60. Minimizing cross sectional area while retaining a usable volume 
in the robot is important for applications in high flow pipes such as 
natural gas pipes. 
The body frame 51a includes stepped lower front and rear end regions 56a 
and 56b which are closer than a standard level L of the body frame 51a to 
a running plane 9. These lower regions 56a and 56b provide increased 
accommodating space in the robot 1. 
FIG. 5 (a) shows, in dot-and-dash lines, a positional relationship between 
the main body 5 and the piping resulting from a further advance of the 
robot 1. 
The body frame 51a includes rollers 57 mounted on front and rear and right 
and left corners thereof (see FIG. 4) to contact inner walls 10 of the 
piping and guide the vehicle body 50 when the robot 1 takes a posture for 
running circumferentially in the piping. 
This vehicle body 50 has a trapezoidal shape in front view as seen from 
FIG. 2, to facilitate passage through a valve section 2 or the like. 
The various devices mounted on the vehicle body 50 will be described next. 
The image pickup 4 mentioned hereinbefore is mounted in the stepped lower 
front region 56a on the body frame 51a. The image pickup 4 comprises a 
laser scanner used in observation and inspection of the piping interior 
ahead of the robot 1. The vehicle body 50 includes drive control devices 
61 for individually driving the running devices 60, and steering control 
devices 62 for individually steering the running devices 60 with respect 
to the fore and aft direction of the vehicle body 50. The vehicle body 50 
further includes a first detecting device 63 for detecting displacement of 
the vehicle body 50 from a position parallel to an axial direction D of 
the piping through which the robot 1 is running. The first detecting 
device 63 may comprise proximity sensors or range finders, such as eddy 
current proximity sensors or ultrasonic range finders, for determining the 
distance from both sides of the body 50 to the piping 11. By knowing the 
distance to the piping 11 on both sides of the body 50, angle of the body 
relative to the pipe axis can be determined. Alternately, image pickup 4 
can be used to visually estimate the body angle relative to the pipe. In 
this embodiment first detecting device 63 and image pickup 4 are the same 
device. The estimation can be done by a human operator from the visual 
image or by an automatic machine vision program. The vehicle body 50 also 
includes second detecting devices 64 for detecting steering amounts of the 
running devices 60 with respect to the fore and aft direction of the 
vehicle body 50. The second detecting devices 64 can be optical encoders 
or one of the other rotation detecting devices known in the prior an of 
rotation sensing. 
Thus, the running devices 60 may be driven and steered individually. A 
running posture control device 65 is provided to operate the drive control 
devices 61 and steering control devices 62 in response to results of 
detection by the first and second detecting devices 63 and 64. Based on 
the results of detection by the first and second detecting devices 63 and 
64, the running posture control device 65 controls steering and running 
amounts of the respective running devices 60 through the drive control 
devices 61 and steering control devices 62, to place the robot 1 (vehicle 
body 50) in a position for running in a circumferential direction E of the 
piping. In this position, the fore and aft direction of the vehicle body 
50 is inclined with respect to the piping axis D, and the respective 
running devices 60 are set to run in the circumferential direction E. 
This control usually is started when the robot 1 (vehicle body 50) is in a 
straight running posture for running along the piping axis D, with the 
fore and aft direction of the vehicle body 50 extending along the piping 
axis D, and the running devices 60 directed to run along the piping axis 
D. 
The control for switching from the straight running posture to the 
circumferential or circular running posture is effected through the 
following steps (see FIGS. 3, parts (a)-(d)): 
First Step 
Operate the steering control devices 62 to turn axles 66 of the respective 
running devices 60 to extend along the piping axis D while maintaining the 
fore and aft direction of the vehicle body 50 parallel to the piping axis 
D; 
Second Step 
Operate the drive control devices 61 to drive the running devices 60 in 
opposite directions to displace the vehicle body 50 to an inclined posture 
relative to the piping axis D; and 
Third Step 
Operate the steering control devices 62 to turn the axles 66 of the 
respective running devices 60 to extend along the piping axis D. 
The above steps are executed in the reversed order when switching from the 
circular running posture to the straight running posture. 
The construction of the running devices 60 employed in the in-pipe running 
robot 1 will be described next with reference to FIG. 2. 
As noted hereinbefore, these running devices 60 are provided in a pair 
arranged in the fore and aft direction of the vehicle body 50. Each 
running device 60 includes a pair of wheels 67 secured to opposite ends of 
the axle 66, and is steerable as an integral unit about a vertical axis of 
the vehicle body 50. The centers of steering are parallel arranged in the 
fore and aft direction of the vehicle body 50. 
As shown in FIG. 2, each running device 60 further includes a magnet 68 
mounted in the axle 66. The pair of wheels 67 disposed at the opposite 
ends of the axle 66 are different in polarity. This produces a magnetic 
field in a piping wall 10 between the wheels 67 to secure a strong 
magnetic attraction. As a result, the robot 1 runs while adhering to the 
piping wall 10. 
Devices used in data communication between the in-pipe running robot 1 and 
the system 3 disposed outside the piping will be described next. As shown 
in FIG. 1, the vehicle body 50 includes a reel 21 mounted on an upper rear 
position thereof to hold a predetermined amount of information 
transmitting optical fiber 20. This reel 21 unwinds the optical fiber 20 
as the robot 1 runs forward along the piping axis D, and takes up the 
optical fiber 20 as the, robot 1 runs backward. Thus, running of the robot 
1 through the piping does not apply any significant tension to or drag the 
optical fiber 20. 
The foregoing is the construction of the in-pipe running robot 1 according 
to the present invention. 
The straight running and circular running of the robot 1 will be described 
hereinafter with reference to FIG. 3. 
When the robot 1 (vehicle body 50) runs straight through the piping, the 
fore and aft direction of the vehicle body 50 is set parallel to the 
piping axis D, with the respective running devices 60 running along the 
piping axis D (FIG. 3, part (a)). In this state, the in-pipe running robot 
1 (vehicle body 50) is in the straight running posture. Since the running 
devices 60 are steerable, the robot 1 may be placed in selected postures 
in the piping 11. 
In a state for circumferential running, the fore and aft direction of the 
vehicle body 50 is inclined with respect to the piping axis D, and the 
respective running devices 60 are set to run in the circumferential 
direction (FIG. 3, part (d)). In this state, the robot 1 is in the 
circular running posture. In this posture, the axles 66 of the running 
devices 60 arranged in front and rear positions of the robot 1 are out of 
alignment as distinct from the posture shown in FIG. 3, part (b), to avoid 
overturning of the robot 1 (see also FIG. 6 (b) showing a front view of 
this state). The vehicle body 50 in this posture is reliably guided by the 
guide rollers 57 contacting the pipe walls 10. 
The running posture control device 65 is operable to change the robot 1 
from the straight running posture to the circular running posture.(FIG. 3, 
parts (a) through (d) show a sequence of the steps taken for this change, 
as follows: 
First Step 
Operate the steering control devices 62 to turn axles 66 of the respective 
running devices 60 to extend along the piping axis D while maintaining the 
fore and aft direction of the vehicle body 50 parallel to the piping axis 
D (FIG. 3, part (b)); 
Second Step 
Operate the drive control devices 61 to drive the running devices 60 in 
opposite directions to displace the vehicle body 50 to an inclined posture 
relative to the piping axis D (FIG. 3, part (c)); and 
Third Step 
Operate the steering control devices 62 to turn the axles 66 of the 
respective running devices 60 to extend along the piping axis D (FIG. 3, 
part (d)). 
After these steps, the running devices 60 are driven to run the robot 1 
circumferentially of the piping 11. 
The above steps are executed in the reversed order when switching from the 
circular running posture to the straight running posture. 
In the circular running posture, as also shown in FIG. 4, two diagonally 
opposite corners of the vehicle body 50 may contact piping walls, 
depending on a pipe diameter. Consequently, the rollers 57 acting as guide 
members contact the pipe walls and positively guide the vehicle body 50. 
The rollers 57 may comprise a sphere captured within a socket of more than 
180.degree., similar to the rollers used in ball point pens and ball 
joints. 
Other embodiments of the invention will be described hereinafter. 
(a) In the foregoing embodiment, each running device includes a single 
magnet mounted in the axle, and a pair of wheels different in polarity, to 
have a magnetically attracting function. The running devices may have any 
construction as long as they are capable of running while adhering to 
piping walls. For example, where the piping contains a liquid having a 
relatively high viscosity, the vehicle body may adhere to piping walls by 
suction of the liquid. The vehicle body may adhere to running surfaces 
simply by friction. 
(b) The running posture control device may operate to switch the robot from 
the straight running posture to the circular running posture through the 
following steps: 
Step 1 
Operate the steering control devices and drive control devices at the same 
time to incline the fore and aft direction of the vehicle body with 
respect to the piping axis D (FIG. 3, part (e)); and 
Step 2 
Operate the steering control devices to turn the axles of the respective 
running devices to extend along the piping axis (FIG. 3, part (d)), 
(c) The foregoing embodiment has been described in which the in-pipe 
running robot is caused to run in the straight running posture axially of 
the piping, or in the circular running posture circumferentially of the 
piping. When running the robot helically along the piping, the fore and 
aft direction of the vehicle body may be set to an inclined posture with 
respect to the piping axis, with the axles of the running devices 
simultaneously set to a selected angle to the piping axis. Then, the robot 
may run helically with little possibility of overturning. 
(d) In the foregoing embodiment, the running posture control device is 
mounted on the main body of the robot. However, this control device may be 
incorporated into a command device disposed outside the piping. 
(e) In the foregoing embodiment, circular running of the robot has been 
described as making a complete circle on an inner wall of the piping. 
However, the robot may run describing part of a circle adjacent the piping 
bottom. In this case, the robot can secure a sliding contact state between 
the vehicle body and piping wall simply by friction. 
(f) In the described embodiment, the rollers have been exemplified as the 
guide members provided on the corners of the vehicle body. Instead, these 
corners may be made smoothly slidable such as by Teflon-processing.