inventions Article
Development of a Bridge Inspection Robot Capable of Traveling on Splicing Parts Yogo Takada *
ID
, Satoshi Ito and Naoto Imajo
Department of Mechanical and Physical Engineering, Osaka City University, Osaka 558-8585, Japan;
[email protected] (S.I.);
[email protected] (N.I.) * Correspondence:
[email protected]; Tel.: +81-6-6605-2970; Fax: +81-6-6605-2769 Received: 21 July 2017; Accepted: 23 August 2017; Published: 26 August 2017
Abstract: Several infrastructures, such as bridges and tunnels, require periodic inspection and repair to prevent collapse. There is a strong demand for practical bridge inspection robots to reduce the cost and time associated with the inspection of bridges by an inspector. Bridge inspection robots are expected to pass through obstacles such as bolted splice part and right-angled routes. The aim of this study involved developing a bridge inspection robot that can travel on a right-angle path as well as splicing parts. A two-wheel-drive robot was developed and equipped with two rimless wheels as driving wheels. A neodymium magnet was provided at the tip of each spoke. Non-driving wheels were attached at the rear as a rotatable caster. The robot can turn on the spot to avoid the bolt on the splicing part. Experiments were conducted to check the performance of the robot. The results confirmed that the robot passed through the internal right-angle paths in a laboratory and in an actual environment that corresponds to a box girder of a bridge. It is extremely difficult to manually control a robot on the splicing part. Therefore, a camera and an LED (light emitting diode) were attached to autonomously control the robot. The results indicate that the newly developed robot could run through the splicing part without hitting the nuts. Keywords: moving robot; bridge inspection; steel bridge; magnet; bolt; splicing part; two-wheel-driven robot; right-angle path; rimless wheel
1. Introduction Social infrastructures, such as bridges and tunnels, that have been constructed in various places are vital to the daily lives of people. However, there is a decrease in their functionality over time. Bridges are designed to withstand the load of running vehicles for over 50 years after their construction. However, an increase in the number of bridges over 50 years old is expected in the near future. The measures for old bridges constitute a significant challenge. It is not easy to renew the large infrastructures given the time and financial resources required to do so. Thus, performing periodic inspections, determining damaged areas early, and repairing any such areas to maintain the infrastructures to the maximum possible extent constitute a realistic option. Thus, lifecycle management to maintain bridge structures is important [1]. For example, the number of aging infrastructures is increasing in Japan. Japanese bridges and tunnels were constructed during a period of high economic growth. Currently, a first inspection of bridges is required within two years of use, and a periodic bridge inspection is then performed once every five years from the second time onward [2]. The inspectors must investigate damage conditions including corrosion, cracks, bolt loosening, falling bolts, and breakages for all members in all spans. After this, it is necessary to perform four levels of judgment with respect to the soundness of each member. Periodic inspections are based on visual observation by inspectors that use scaffolding or a special-purpose vehicle. Therefore, each local government is burdened with the tremendous costs associated with performing such inspections. Inventions 2017, 2, 22; doi:10.3390/inventions2030022
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Recently, various robots have been developed for bridge inspection to reduce the burden of periodic inspection. Since 2015, a multi-rotor helicopter has become an attractive and suitable option for bridge inspections, and has been examined by several studies [3–5]. In the case of steel bridges, as magnet adhere to the structure, a robot equipped with magnets is more suitable for inspecting the lower side of the bridge in detail. However, difficulties exist with respect to the detailed inspection of several members located under the steel bridge structure. Therefore, there is a demand for a robot that moves to a target location and delivers photographs of each part of the bridge. Since the inspection of a steel bridge is mainly based on the visual inspection, it is required that the robot does reduce the ability to move in all directions, even if the camera is fixed on a mount. Many robots can move along the flat parts of a ceiling surface or can climb up and down a wall to avoid falling due to gravity [6–9]. For example, a flexure-based mobile sensing node (FMSN) developed by Zhu et al. is able to climb a wall and then continue to run on the surface of a floor [8]. However, it is difficult to change the travel course in the left and right directions in the FMSN because the magnets used in this robot include a large ground contact area. Robots named “BIREM” were also developed to move in complex environments under steel bridges to inspect cracks and corrosion areas. BIREM moves while adsorbing to the steel wall using a rimless wheel with attached magnets [10,11]. Additionally, BIREM has a high success rate while traveling between a ceiling and a vertical wall. Furthermore, it is possible to change the course in the left and right directions with the steering mechanism on the front and rear wheels attached to second generation BIREM (BIREM 2nd) because of the small ground contact area of the magnets. Steel bridges are constructed by joining several steel plates with bolts. However, the splicing parts with many bolts hinder the path of robots. It is not possible for BIREM 2nd to run on this route. Moreover, to the best of the authors’ knowledge, extant studies have not examined whether it is possible for a robot to run on routes that include splicing parts. Therefore, in this study, the latest generation BIREM (BIREM 3rd) is developed with the aim to run it on a right-angle course as well as to run it on the splicing parts of a bridge. 2. Required Bridge Inspection Robots 2.1. Performance Requirements for Robots Currently, bridge inspection is conducted by inspectors. A few items are required so that a robot can perform this work. In this study, points (1) to (4), which are discussed below, are considered, although the specific aim of the development of the robot corresponds to (1). (1) Ensuring a moving ability that can overcome any obstacles in the inspection environment. (2) Ensuring a climbing ability even if the robot is equipped with a sensor to detect cracks and corrosion. (3) Ensuring an ability to inspect for a long time. (4) Ensuring an ability to withstand disturbances such as the vibration of a bridge by automobiles or a strong wind at a high altitude. 2.2. Splicing Parts in a Box Girder One of the main purposes of the study is to develop a robot that runs through the splicing parts of a bridge. Figure 1 shows the splicing parts with several bolts on the ceiling inside a box girder of a bridge. Bridge inspection robots are required to run along a path, including splicing parts, to inspect a bridge. The bolts of the splicing parts completely block the traveling path of the robot. Therefore, it is not possible for a robot to run through the traveling path in the absence of measures for the splicing parts. For example, it is not possible for previously developed robots [8,9] or old-type BIREM [10] introduced in Section 1 to run through the splicing parts because there are no measures set in place to overcome this obstacle.
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Figure 1. The bolted splicing part in the box girder of a bridge. Figure 1. The bolted splicing part in the box girder of a bridge.
3. 3. Structure Structure of of the the BIREM BIREM 3rd 3rd Robot Robot 3. Structure of the BIREM 3rd Robot 3.1. How to Run through the Splicing Part 3.1. How to Run through the Splicing Part Figure 22shows showsthe thephysical physical relationship between the wheel of aprototype new prototype robot relationship between the wheel tracktrack of a new robot named Figure 2 shows the physical relationship between the wheel track of a new prototype robot named on the splicing parts. size of bolts steel bridges Japan BIREM BIREM 3rd and3rd theand boltsthe onbolts the splicing parts. The sizeThe of bolts used inused steel in bridges in Japaninmostly named BIREM 3rd and the bolts on the splicing parts. The size of bolts used in steel bridges in Japan mostly corresponds M24. The interval of theon bolts the splicing parts was examined corresponds to M22 to or M22 M24.orThe interval of the bolts the on splicing parts was examined [12]. In[12]. the mostly corresponds to M22 or M24. The interval of the bolts on the splicing parts was examined [12]. In the specifications for highway the minimum bolt intervals for M22 M24 correspond specifications for highway bridges,bridges, the minimum bolt intervals for M22 and M24 and correspond to 75 and In the specifications for highway bridges, the minimum bolt intervals for M22 and M24 correspond to andrespectively. 85 mm, respectively. if it is unavoidable withtorespect to theofdesign of thethe bridge, 85 75 mm, However,However, if it is unavoidable with respect the design the bridge, bolt to 75 and 85 mm, respectively. However, if it is unavoidable with respect to the design of the bridge, the bolt for intervals for M24 M22can and M24 cantocorrespond to 66 and 72 mm, respectively. While intervals M22 and correspond 66 and 72 mm, respectively. While manufacturing a the bolt intervals for M22 and M24 can correspond to 66 and 72 mm, respectively. While manufacturing robot, it isand easier to design and manufacture a wide wheel track. However, wheel robot, it is easiera to design manufacture a wide wheel track. However, the wheel track the is fixed at manufacturing a robot, it is easier to design and manufacture a wide wheel track. However, the wheel track is such fixedthat at 74the mm suchcan that thethrough robot can through part ininterval which the bolt interval 74 mm robot run therun splicing partthe in splicing which the bolt corresponds to track is fixed at 74 mm such that the robot can run through the splicing part in which the bolt interval corresponds to 66 mm.asAdditionally, as BIREM 3rd runs through the splicing part, eachpasses bolt relatively 66 mm. Additionally, BIREM 3rd runs through the splicing part, each bolt relatively through corresponds to 66 mm. Additionally, as BIREM 3rd runs through the splicing part, each bolt relatively passes through part of the robot’s main bodymanner. in a successive manner. the space underthe thespace lowerunder part ofthe thelower robot’s main body in a successive passes through the space under the lower part of the robot’s main body in a successive manner.
Figure 2. Bolt pitch of splice part. The length d is the wheel track of the robot and the length p is the Figure pitch of of splice splice part. part. The The length lengthddisisthe thewheel wheeltrack trackof ofthe therobot robotand andthe thelength lengthppisisthe the Figure 2. 2. Bolt Bolt pitch interval of the the bolts. bolts. interval of interval of the bolts.
Furthermore, it is also necessary to consider the height direction of the bolts and nuts to avoid Furthermore, it is also necessary to consider the height direction of the bolts and nuts to avoid collision with bolts or nuts. The splicing part connects the plates with bolts, nuts, and washers. nuts. The collision with bolts or nuts. The splicing splicing part part connects connects the the plates plates with with bolts, nuts, nuts, and and washers. washers. Therefore, especially on the nut side, it is necessary to prevent the height of the nut as well as the Therefore, especially on the nut side, it is necessary to prevent the height of the nut as well as the threaded portion of the bolt from the nut center from hitting the main body of the robot. For this the nut nut center center from from hitting hitting the main main body body of of the the robot. robot. threaded portion of the bolt from the this reason, the vehicle height is designed such that it is sufficiently the high to pass over the nuts, at For 70 mm. height is designed designed such such that that it it is is sufficiently sufficiently high high to to pass pass over over the the nuts, nuts, at at 70 70 mm. mm. reason, the vehicle height 3.2. Configuration of BIREM 3rd 3.2. Configuration of BIREM 3rd Figure 3 shows the appearance of the bridge inspection robot BIREM 3rd that is manufactured Figure 3 shows the appearance of the bridge inspection robot BIREM 3rd that that is is manufactured manufactured based on the concept discussed in Section 3.1, and Figure 4 shows the configuration. The main body based on the concept discussed in Section 3.1, and Figure 4 shows the configuration. The main body of the robot consists of CFRP (Carbon Fiber-Reinforced Plastic) and acrylic material to ensure that it of the robot consists of CFRP (Carbon Fiber-Reinforced Plastic) and acrylic material to ensure that it is light. Table 1 shows the specifications of BIREM 3rd. The total length corresponds to 245 mm, the is light. Table 1 shows the specifications of BIREM 3rd. The total length corresponds to 245 mm, the
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of the robot consists of CFRP (Carbon Fiber-Reinforced Plastic) and acrylic material to ensure that width corresponds 80 to mm, 80 mm, the total height corresponds to 133 mm, and weight corresponds to width thespecifications total height corresponds to 133 mm, and thethe weight corresponds it iscorresponds light. Table to 1 shows the of BIREM 3rd. The total length corresponds to 245 to mm, 411 gf. The wheel track is set as small as possible at 74 mm, based on the M22 or M24 bolts on the 411the gf.width The wheel track istoset small possible 74 mm, based onmm, the M22 or M24 bolts on the corresponds 80as mm, theas total heightatcorresponds to 133 and the weight corresponds splicing parts. Subsequently, the vehicle height is set high such that the main body does not hit a bolt splicing parts. Subsequently, the vehicle height is set high such that the main body does not hit a bolt to 411 gf. The wheel track is set as small as possible at 74 mm, based on the M22 or M24 bolts on the a nut. A robot with a small wheel track and a high vehicle height possesses poor running ability or aor nut. A robot with a small wheel track and a high vehicle height possesses poor running ability splicing parts. Subsequently, the vehicle height is set high such that the main body does not hit a bolt poor turning ability when compared with a robot with a large wheel track andlow a low vehicle andand turning ability with a robot a large wheel track and vehicle orpoor a nut. A robot with when a smallcompared wheel track and a highwith vehicle height possesses poora running ability height. However, running through splicing parts constitutes a top priority to practically height. However, running thethe splicing parts constitutes top priority to practically useuse thethe and poor turning abilitythrough when compared with a robot with aa large wheel track and a low vehicle bridge inspection robot. The main controller, FPGA (Field-programmable gate array), Xilinx bridge inspection Thethrough main controller, (Field-programmable array), Xilinx height. However,robot. running the splicingFPGA parts constitutes a top prioritygate to practically use the XC6SLX45 CSG324, the receiver (Futaba R2106GF) installed, thus making it possible XC6SLX45 CSG324, andand the (Futaba R2106GF) areare installed, thus it possible to to bridge inspection robot. Thereceiver main controller, FPGA (Field-programmable gatemaking array), Xilinx XC6SLX45 remotely control the robot with an external transmitter, namely, Futaba T6J. The power source remotely control the robot with an external transmitter, namely, Futaba T6J. The power source CSG324, and the receiver (Futaba R2106GF) are installed, thus making it possible to remotely control corresponds a lithium polymer battery with two cells rated 7.4 at 7.4 V, mAh. Additionally, corresponds to atoan lithium polymer battery with two cells rated 800800 mAh. Additionally, a a the robot with external transmitter, namely, Futaba T6J. The at powerV, source corresponds to a lithium camera LED (Light emitting diode) are attached for autonomous driving. details camera andand an an LED (Light diode) autonomous TheThe details areare polymer battery with twoemitting cells rated at 7.4are V, attached 800 mAh.for Additionally, a driving. camera and an LED (Light described in Section 4. described in Section 4. emitting diode) are attached for autonomous driving. The details are described in Section 4.
Figure 3. Bridge Bridge inspection robot (BIREM 3rd). Figure 3. inspection robot (BIREM 3rd). Figure 3. Bridge inspection robot (BIREM 3rd).
(a) (a)
(b) (b)
Figure 4. Mechanism of BIREM (a) Side view; view. Figure 4. Mechanism of BIREM 3rd.3rd. (a) Side view; (b) (b) toptop view. Figure 4. Mechanism of BIREM 3rd. (a) Side view; (b) top view. Table 1. Specifications of BIREM FPGA, field-programmable array. Table 1. Specifications of BIREM 3rd.3rd. FPGA, field-programmable gategate array. Table 1. Specifications of BIREM 3rd. FPGA, field-programmable gate array.
Property Specifications Property Specifications Property Specifications Length 245 Length 245 mmmm Length 245mm mm Width 80 Width 80 mm Width 80 mm Total height Total height 133133 mmmm Total height 133 mm Vehicle height 70 mm Vehicle height 70 mm Vehicle height 70 mm Wheel track 74 mm Wheel 74 mm Wheeltrack track 74 mm Weight Weight 411gf gf Weight 411411 gf Controller FPGA (Spartan-6) Controller FPGA (Spartan-6) Controller FPGA (Spartan-6) This robot runs using large wheels at the right connected to the direct current motors This robot runs using thethe large wheels at the leftleft andand right connected to the direct current motors gears. A neodymium magnet is wheels attached at of right each spoke. A rubber coating exists on This runs using the large thethe lefttip connected to the direct current viavia gears. A robot neodymium magnet is attached atatthe tip ofand each spoke. A rubber coating exists onmotors thethe magnet surface at which amagnet magnet isattached in contact with wall, orAceiling. This robot can climb via gears. A neodymium at the tipthe of floor, each spoke. rubber coating exists on the magnet surface at which a magnet isisin contact with the floor, wall, or ceiling. This robot can climb wall because permanent magnet is chosen so that frictional force between rubber magnet surface at the which a magnet is in contact with floor, wall, or ceiling. This robotthe canthe climb the thethe wall because the permanent magnet is chosen sothe that thethe frictional force between rubber coated on the magnet and the steel wall is larger than the robot weight. Additionally, rimless wheels wallon because the permanent magnet so that frictional between the rubber coated coated the magnet and the steel wall is chosen larger than the the robot weight.force Additionally, rimless wheels manufactured molding ultraviolet curable resin, surface is reinforced with CFRP areare manufactured by by molding an an ultraviolet curable resin, andand thethe surface is reinforced with CFRP (Carbon fiber reinforced plastic) plates with a thickness of 0.2 mm. (Carbon fiber reinforced plastic) plates with a thickness of 0.2 mm.
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on the magnet and the steel wall is larger than the robot weight. Additionally, rimless wheels are manufactured by molding an ultraviolet curable resin, and the surface is reinforced with CFRP (Carbon Inventions 2017, 2, 22plastic) plates with a thickness of 0.2 mm. 5 of 13 fiber reinforced On the rear part of the robot, seven non-driving wheels that correpsond to cylindrical neodymium On are the attached rear partto of seven non-driving wheels that correpsond to cylindrical magnets thethe left robot, and right. Specifically, the front most wheel rotates freely in the left neodymium magnets are attached to the left and right. Specifically, the front most wheel rotates freely and right directions. The 14 non-driving wheels are described in Section 3.3. in the left and right directions. The 14 non-driving wheels are described in Section 3.3. 3.3. Enhancing Running Ability and Turning Ability 3.3. Enhancing Running Ability and Turning Ability The wheel track is small and the vehicle height is high; thus, ingenuity is necessary to enhance Theability wheeland track is small and the thus, to enhance running turning ability. Thevehicle runningheight abilityisishigh; defined as ingenuity the ability is to necessary run the robot without running ability turning it dropping fromand a ceiling or aability. wall. The running ability is defined as the ability to run the robot without dropping a ceiling orrunning a wall. on a bolt on the splicing parts unless the turning ability It isitdifficult for from a robot to avoid It is In difficult for asimilar robot totoavoid runningcar, on aa bolt on the splicing unless ability is high. a manner a passenger four-wheeled robotparts cannot turnthe onturning the spot, and is high. In a manner similar to aturning passenger car,Therefore, a four-wheeled robot cannot turn on thethat spot,it and thus, it does not possess sharp ability. BIREM 3rd is developed such can thus, does notwheels possess sharp turning ability. BIREM 3rd to is the developed such two-wheel that it can travelitwith two and can turn on the spot. Therefore, However, with respect left and right travel wheels and can turn on the the spot. However, with respect to the due left and right tworobots,with rear two wheels are required to support main body to prevent rotation to the reaction wheel robots, rear wheels are required to support the main body to prevent rotation due to the torque generated when the main wheels are rotated. Figure 5 shows the postures when a two-wheel reaction torque generated when the maindown wheels rotated. 5 shows theorpostures a robot, such as BIREM 3rd, moves up and theare wall. When Figure the robot ascends descendswhen on the two-wheel suchexperiences as BIREM a3rd, moves and wall.centered When the robot ascends or wall surface,robot, the robot moment of up force duedown to thethe gravity on the rotating point descends the wall thewhen robot the experiences a moment of force due to the centered on as shown on in Figure 5. surface, In the case robot ascends the wall, the moment of gravity force due to gravity the rotating point shown in Figure the case the moment of is supported by theasnon-driving wheels5.atInthe rear as when shownthe in robot Figureascends 5a, and the thus,wall, the robot can move force dueHowever, to gravityinisthe supported by the therobot non-driving wheels at the as shown in Figure and upward. case when descends the wall, therear moment of force due to 5a, gravity thus, can if move upward. the case thesurface, robot descends the robot wall, falls the cannotthe be robot supported the rear wheelsHowever, are not in in contact withwhen the wall and thus, the moment of force dueas to shown gravityin cannot be5b. supported if thethe rear wheels are notrobot in contact with the walla down from the wall Figure Specifically, structure of the is designed with surface, and thus, robot falls down the wall as shown Figure 5b. Specifically, high vehicle heightthe such that it can runfrom through the bolts on theinsplicing parts, and thus,the thestructure moment of force the robot is gravity designed a high vehicle height such thatstrong it canpermanent run through the bolts on the due to is with significantly high. Therefore, a very magnet is adopted splicing parts, and thus, thetomoment force due to gravitythe is significantly high.makes Therefore, a very for the non-driving wheels preventof falling. Additionally, adsorption force the turning strong permanent magnet is adopted for the non-driving wheels to prevent falling. Additionally, movement of the robot difficult, and thus, a caster structure is adopted, which rotates and changes the adsorption makes the wheel turningatmovement direction of force the non-driving the rear. of the robot difficult, and thus, a caster structure is adopted, which rotates and changes the direction of the non-driving wheel at the rear.
(a)
(b)
Figure Figure 5. 5. Attitude Attitude of of the the two-wheel-drive two-wheel-drive robot robot on on the the vertical vertical wall. wall. (a) (a) Robot Robot climbing climbing wall; wall; (b) (b) robot robot moving down. moving down.
Additionally, bridge inspection robots are required to run through the splicing parts as well as Additionally, bridge inspection robots are required to run through the splicing parts as well as on on a right-angle path. If a rear wheel is attached to the main body, then the rear wheel moves with a right-angle path. If a rear wheel is attached to the main body, then the rear wheel moves with the the trajectory shown in Figure 6a around the center of the drive wheel as the rotation center. trajectory shown in Figure 6a around the center of the drive wheel as the rotation center. The rear magnet wheel touches the ceiling surface until it passes immediately above the center of the front wheel. However, the rear magnet wheel is subsequently released from the ceiling surface because the rear magnet wheel moves along the trajectory shown in Figure 6b. This posture is similar to the situation shown in Figure 5b, and thus, the moment of force due to gravity decreases with respect to the wall. To prevent this fall, it is necessary for the rear wheel to touch the ceiling surface or wall surface, even when the robot runs on the right-angle path.
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(a)
(b)
Figure 6. 6. Robot Robot falling falling from from the the right-angled right-angled route. route. (a) touching ceiling; rear wheel wheel Figure (a) Rear Rear wheel wheel touching ceiling; (b) (b) rear releasing ceiling. ceiling. releasing
To prevent the robot from falling when it runs on the right-angle path, an original rear wheel The rear magnet wheel touches the ceiling surface until it passes immediately above the center of system with multiple cylindrical magnet wheels arranged in an arc shape is adopted, as shown in the front wheel. However, the rear magnet wheel is subsequently released from the ceiling surface Figure 7. The front wheel corresponds to a rotating caster, and the robot has a structure that makes it because the rear magnet wheel moves along the trajectory shown in Figure 6b. This posture is similar (a) (b) easy to turn. to the situation shown in Figure 5b, and thus, the moment of force due to gravity decreases with Figure 6. Robot falling from this the right-angled route. (a) touching ceiling; rear wheel respect to the wall. To prevent fall, it is necessary forRear the wheel rear wheel to touch the(b) ceiling surface or releasing ceiling. wall surface, even when the robot runs on the right-angle path. To prevent the robot from falling when it runs on the right-angle path, an original rear wheel To prevent the robot from falling when it runs on the right-angle path,isan originalasrear wheel system with multiple cylindrical magnet wheels arranged in an arc shape adopted, shown in system with multiple cylindrical magnet wheels arranged in an arc shape is adopted, as shown in Figure 7. The front wheel corresponds to a rotating caster, and the robot has a structure that makes it Figure The front wheel corresponds to a rotating caster, and the robot has a structure that makes it easy to7.turn. easy to turn.
Figure 7. Magnetic rear wheels with a caster.
Figure 8 shows the manner in which the robot moves from the ceiling surface to the vertical wall surface using the rear wheel system. Figure 8a shows the state when the robot moves horizontally on the ceiling and the front wheel touches the vertical wall surface. Following this, the front rimless wheel descends the wall, and the rear wheel “B1” comes in contact with the ceiling surface, as shown in Figure 8b. At this time, the rear wheel “B2” does not yet touch the ceiling surface. After the rear wheel “A” leaves the ceiling, the rear7.7.wheel “B2rear ”rear soon touches ceiling surface, as shown in Figure Figure Magnetic wheels withthe caster. Figure Magnetic wheels with aacaster. 8c. When the front wheel advances, the magnet wheels are repeatedly attached and detached from the rear wheel “B2”the to manner the rear in wheel “Bthe 5”. robot Finally, the rear “C” surface comes withwall the Figure 88 shows which from the to the Figure shows the manner in which the robotmoves moves fromwheel theceiling ceiling surfacein tocontact thevertical vertical wall ceiling surface, as shown in Figure 8d. Subsequently, as shown in Figure 8e, the rear wheel “B 5” is surface using the rear wheel system. Figure 8a shows the state when the robot moves horizontally surface using the rear wheel system. Figure 8a shows the state when the robot moves horizontallyon on released from the ceiling surface, and the rear wheel “A” gradually approaches the vertical wall the and the thefront frontwheel wheel touches vertical surface. Following the rimless front rimless the ceiling and touches thethe vertical wallwall surface. Following this, this, the front wheel surface. wheel descends the wall, andrear the wheel rear wheel 1” comes in contact with ceiling surface, shown descends the wall, and the “B1 ”“B comes in contact with thethe ceiling surface, as as shown in Following this, the rear wheel “A” touches the wall surface, as shown in Figure 8f. Finally, as in Figure time, wheel 2” does nottouch yet touch the ceiling surface. thewheel rear Figure 8b.8b. At At thisthis time, the the rearrear wheel “B2 ”“B does not yet the ceiling surface. After After the rear shown in Figure 8g, rearrear wheel “C” moves away from the ceiling surface, and the transition from wheel “A” leaves thethe ceiling, thewheel rear wheel “B 2 ” soon touches the ceiling surface, as shown in Figure “A” leaves the ceiling, the “B ” soon touches the ceiling surface, as shown in Figure 8c. 2 the ceiling to the wall is completed. This original rear wheel system is used, and it is possible for the 8c. When the front wheel advances, the magnet wheels are repeatedly attached and detached from When the front wheel advances, the magnet wheels are repeatedly attached and detached from the robot BIREM perform running the splicing parts, sharp turning, and running through the rear wheel 2”the to rear the rear wheel 5”. Finally, the wheel rear wheel “C” comes in contact with the rear wheel “B3rd toto wheel “B5through ”.“B Finally, the rear “C” comes in contact with the ceiling 2 ”“B the right-angle path. ceiling surface, as shown in 8d. Figure 8d. Subsequently, as in shown in8e, Figure 8e, the rear “B5” is surface, as shown in Figure Subsequently, as shown Figure the rear wheel “Bwheel ” is released 5
released the ceilingand surface, and the rear “A”approaches gradually the approaches the vertical from the from ceiling surface, the rear wheel “A” wheel gradually vertical wall surface. wall surface. Following this, the rear wheel “A” touches the wall surface, as shown in Figure 8f. Finally, Following this, 8g, the the rearrear wheel “A”“C” touches theaway wallfrom surface, shown in Figure as as shown in Figure wheel moves the as ceiling surface, and 8f. theFinally, transition shown in ceiling Figure 8g, thewall rear is wheel “C” moves fromrear thewheel ceilingsystem surface, theand transition from from the to the completed. Thisaway original isand used, it is possible the ceiling to the wall is completed. This original rear wheel system is used, and it is possible for the robot BIREM 3rd to perform running through the splicing parts, sharp turning, and running through the right-angle path.
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Figure 8. Robot running along the right-angled route. (a) Front wheel touches the vertical wall after
Figure 8. Robot running along the right-angled route. (a) Front wheel touches the vertical wall after the robot moving horizontally; (b) rear wheel B1 touches the ceiling as well as the rear wheel A; (c) the robot moving horizontally; (b) rear wheel B1 touches the ceiling as well as the rear wheel A; (c) after after rear wheel A released, rear wheel B2 touches the ceiling promptly; (d) after rear wheel B4 rear Figure wheel 8. A Robot released, rear wheel B2 touches the ceiling promptly; (d) after rearthe wheel B released, running along the right-angled route. (a) Front wheel touches vertical wall after rear released, rear wheel C touches the ceiling promptly; (e) rear wheel B5 is released from the4 ceiling; (f) wheel touches the ceiling promptly; (e)wheel rear wheel B5 isthe released theasceiling; whileA;the theCrobot moving horizontally; (b) rear B1 touches ceilingfrom as well the rear(f)wheel (c)rear while the rear wheel C is in contact with the ceiling, the rear wheel A contacts the vertical wall; (g) thecontacts ceiling the promptly; (d)wall; after(g) rear wheel B4 C is after rear wheel Awith released, rear wheel B2 touches wheel C is in contact the ceiling, the rear wheel A vertical rear wheel rear wheel C is released from the ceiling and the robot descends. released, C and touches ceiling promptly; (e) rear wheel B5 is released from the ceiling; (f) released fromrear thewheel ceiling the the robot descends. while and the rear wheel C isfor in Experiments contact with the ceiling, the rear 4. Results Discussion with BIREM 3rdwheel A contacts the vertical wall; (g)
rear wheel C is released from the ceiling and the robot descends. 4. Results and Discussion for Experiments with BIREM 3rd
4.1. Experimental Results of Running on a Right-Angle Path in a Bridge Box Girder 4. Results andResults Discussion for Experiments with BIREM 3rd 4.1. Experimental of Running on a Right-Angle Path in a Bridge Box Girder Experiments were performed to ascertain as to whether BIREM 3rd can travel on a right-angle path under actual circumstances. The experimental environment using thecan bridge box girder, shown 4.1. Experimental Results of Running a Right-Angle ininvolved a Bridge Box 3rd Girder Experiments were performed toonascertain as toPath whether BIREM travel on a right-angle in Figure 9a, installed in the Earthquake museum of Hanshin Expressway Co., Ltd (Osaka, Japan). The path under actual circumstances. The environment usingonthe bridge box girder, Experiments were performed to experimental ascertain as to whether BIREMinvolved 3rd can travel a right-angle path right-angle paths where the robot travels in the experiment correspond to 1 and 2, as shown in Figure 9b. shown in Figure 9a, installed in the Earthquake museum of Hanshin Expressway Co., Ltd (Osaka, under actual circumstances. The experimental environment involved using the bridge box girder, shown Japan). The right-angle the robot travels in the experiment correspond to 1 and 2, asThe shown in Figure 9a, installedpaths in thewhere Earthquake museum of Hanshin Expressway Co., Ltd (Osaka, Japan). in Figure 9b. paths where the robot travels in the experiment correspond to 1 and 2, as shown in Figure 9b. right-angle
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Figure 9. Box girder of the bridge. (a) External view; (b) enlarged view. (a)
(b)
Prior to performing the experiment in the field, the experiment was performed on the same Figure 9. Box girder of the bridge. External view; (b) enlarged view. at the start time routes in the laboratory, experiments were(a) performed However, Figure 9. and Box 10 girder of the bridge. (a) External successfully. view; (b) enlarged view. of the field experiment, the magnets on the rimless wheel slipped, and the robot was unable to even Prior to performing the experiment in the field, the experiment was performed on the same routes in the laboratory, and 10 experiments were performed successfully. However, at the start time of the field experiment, the magnets on the rimless wheel slipped, and the robot was unable to even
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Prior to performing the experiment in the field, the experiment was performed on the same routes Inventions 2017, 2, 22 and 10 experiments were performed successfully. However, at the start time 8 of of 13 in the laboratory, the field experiment, the magnets on the rimless wheel slipped, and the robot was unable to even climb the the wall. wall. The steel materials climb The box box girders girders used used for for bridges bridges are are paint-treated paint-treated on on weather weather resistant resistant steel materials to prevent a magnetic force reduction approximately ranging fromfrom 25% 25% to 40% to prevent corrosion. corrosion.InInthis thiscase, case, a magnetic force reduction approximately ranging to exists. For example, in the laboratory steel box, the magnetic force between the bottom surface “A” 40% exists. For example, in the laboratory steel box, the magnetic force between the bottom surface of Figure 10 and to 1960togf1960 when magnet diameter corresponds to 10 mm. “A” of Figure 10 steel and wall steel corresponds wall corresponds gf the when the magnet diameter corresponds to Conversely, in the case of the box girder in the actual environment, the magnetic force only 10 mm. Conversely, in the case of the box girder in the actual environment, the magnetic force only corresponds to magnetic force with respect to corresponds to 1180 1180 gf gf given giventhe thesame sameconditions. conditions.Table Table2 2shows showseach each magnetic force with respect thethe steel wall surface. When the the rubber coating is applied to the and the is tilted with to steel wall surface. When rubber coating is applied to magnet the magnet andmagnet the magnet is tilted respect to the wall surface, the minimum magnetic force decreases to approximately 900 gf. Then, the with respect to the wall surface, the minimum magnetic force decreases to approximately 900 gf. Then, friction coefficient between the rubber and the painted general steel measured around 0.35 in our the friction coefficient between the rubber and the painted general steel measured around 0.35 in our experiment. In force ofof both thethe leftleft andand right wheels is approximately 630 experiment. Inother otherwords, words,the thefrictional frictional force both right wheels is approximately gf, which is larger than the weight of the robot (411 gf), so the magnets on each wheel do not slip. 630 gf, which is larger than the weight of the robot (411 gf), so the magnets on each wheel do not slip. Besides, the the wall if the total weight of Besides, the motors motors mounted mountedon onthe therobot robotwould wouldallow allowthe therobot robotclimb climb the wall if the total weight thethe robot body andand thethe load such as aashigh-resolution camera is under 545545 gf. gf. However, when the of robot body load such a high-resolution camera is under However, when magnetic force reduces from 1960 to 1180 gf, the frictional force of both the left and right wheels the magnetic force reduces from 1960 to 1180 gf, the frictional force of both the left and right wheels becomes 380 380gf. gf.Therefore, Therefore,despite despitethe thesufficient sufficient motor torque, robot to climb the becomes motor torque, thethe robot waswas not not ableable to climb the wall wall of the box girders. of the box girders.
Figure 10. Neodymium magnet. Table 2. Table 2. Magnetic force to steel steel surface. surface.
Size of the Magnet Size of the Magnet Contact surface Contact surface Surface of the steel box in the laboratory Surface of the steel box in thebridge laboratory Surface of the box girder Surface ofof the box girder bridge Size the Magnet
10-mm Diameter Magnet 10-mm Diameter Magnet Surface A Surface B Surface A Surface B 1960 gf 535 gf 1960gf gf 535 1180 405 gfgf 1180 gfDiameter Magnet 405 gf 12-mm
Contact surface Size of the Magnet Surface of theContact steel boxsurface in the laboratory
Surface A Diameter Surface B 12-mm Magnet 2900 gf A 820 gf B Surface Surface 1850 gf 620 gf 2900 gf 820 gf
Surface of the box girder bridge Surface of the steel box in the laboratory Surface of the box girder bridge
1850 gf
620 gf
Thus, it is necessary to use stronger magnets. As shown in Table 2, the magnetic force for a diameter of 12 mm corresponds to 1850 gf at the bottom surface “A” and 620 gf at the side surface Thus, is necessary usebridge stronger Asisshown in the Table 2, the magnetic for “B” for theitwall surface oftothe box magnets. girder. This close to magnetic force for aforce 10-mm adiameter diametermagnet of 12 mm corresponds to 1850 gf at the bottom surface “A” and 620 gf at the side surface “B” for the wall surface in the laboratory. Therefore, an attempt was made to allow the for thetowall surface of the bridge boxthe girder. Thiswith is close to the magnetic force for robot climb the wall by replacing magnets 12-mm diameter magnets. Asaa10-mm result, diameter the robot magnet wall the laboratory. Therefore, an attempt was made to allow the robot to was ablefor to the climb thesurface wall inin the real environment. climbFigures the wall11byand replacing thethe magnets 12-mmBIREM diameter As a route. result, Itthe robottravels was able 12 show mannerwith in which 3rdmagnets. runs on each easily on to climb the wall environment. a right-angle pathinifthe thereal magnetic force is adjusted appropriately. Figures 11 and 12 show the manner in which BIREM 3rd runs on each route. It easily travels on a right-angle path if the magnetic force is adjusted appropriately.
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Figure 11. BIREM 3rd moving along route 1. 1. (a) s; (b) s; (c) (c) 10 10 s; s; (d) 15 15 s. Figure 11. 11. BIREM 3rd 3rd moving moving along along route route (a) 000 s; s; (b) (b) 555 s; s; Figure BIREM 1. (a) (c) 10 s; (d) (d) 15 s. s.
(a) (a)
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Figure 12. BIREM 3rd moving along route 2. (a) 0 s; (b) 3.3 s; (c) 6.7 s; (d) 10 s. Figure 2. (a) 10 s. s. Figure 12. 12. BIREM BIREM 3rd 3rd moving moving along along route route 2. (a) 00 s; s; (b) (b) 3.3 3.3 s; s; (c) (c) 6.7 6.7 s; s; (d) (d) 10
4.2. Experimental Results of Running on the Splicing Part 4.2. Part 4.2. Experimental Experimental Results Results of of Running Running on on the the Splicing Splicing Part The splicing part includes several bolts and nuts. Figure 13 shows a model of a splicing part used The splicing part includes includes several bolts bolts and and nuts. nuts. Figure 13 shows a model of splicing part used splicing part Figurefifteen 13 shows model of aaplaced splicing used in theThe experiment performed inseveral the laboratory. Specifically, M22a nuts were inpart the same in the experiment performed in the laboratory. Specifically, fifteen M22 nuts were placed in the same in the experiment performed in the laboratory. Specifically, fifteen M22 nuts were placed in the same location as the splicing part in a bridge. The experiments were performed to run BIREM 3rd on the location as splicing part bridge. The on the the location as the the splicing part in in aa bridge. The experiments experiments were were performed performed to to run run BIREM BIREM 3rd 3rd on splicing part. splicing part. splicing part. There is enough space for a nut to pass under the robot, and thus, it is necessary for the operator There is enough space for a nut to pass under the robot, and thus, it is necessary for the operator There is enough spacethe fornut. a nut pass under to themaneuver robot, andthe thus, it is for wheels the operator to move the robot toward It istonot difficult robot bynecessary keeping the from to move the robot toward the nut. It is not difficult to maneuver the robot by keeping the wheels from to move the robot thethe nut.operator It is not is difficult to robot. maneuver the robot keeping difficult the wheels from lifting above each toward nut when near the However, it isby extremely to keep lifting above each nut when the operator is near the robot. However, it is extremely difficult to keep lifting above each nut when the operator is near the robot. However, it is extremely difficult to keep the wheels from lifting on the nuts when the operator maneuvers the robot from a distance or when the wheels from lifting on the nuts when the operator maneuvers the robot from a distance or when the operator wheels from lifting on the nuts when the operator maneuvers the robot from a distance or when maneuvers the robot while watching the image from camera installed on the robot. the operator maneuvers the robot while watching the image from the camera installed on the robot. the operator maneuvers the robot while watching the image from the camera installed on the robot.
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Figure 13. Model of the splicing part with 15 nuts for the experiment. Figure Figure13. 13.Model Modelofofthe thesplicing splicingpart partwith with1515nuts nutsfor forthe theexperiment. experiment.
This robot includes a structure to run through the splicing parts and possesses excellent turning This robotincludes includes structure runthrough through thesplicing splicingparts parts andpossesses possesses excellent turning This robot aastructure totorun and excellent turning ability. However, it is difficult to manually adjust the the traveling direction. Therefore, the robot is ability.However, However, itisruns isdifficult difficult manuallyadjust adjust traveling direction. Therefore, therobot robot ability. totomanually traveling direction. Therefore, the controlled such thatitit semi-autonomously. First,the athe small camera and an LED are attached to theisis controlled such thatititruns runs semi-autonomously. First, small camera and an LED areattached attached the controlled such that First, a asmall camera and an LED are totothe robot. Second, a program forsemi-autonomously. hardware description language was created. In this program, the FPGA robot. Second, program forhardware hardware description language was created. this program, theFPGA FPGA robot. aaprogram for description language was InInthis program, the sends aSecond, command to the motor based on the image acquired bycreated. the camera, and the robot itself sends a command to the motor based on the image acquired by the camera, and the robot sends a the command to the motor onrobot the image the camera, the robot itself controls robot direction such based that the faces aacquired nut. Thebycontrol methodand corresponds toitself a controls the robot direction such that the robot faces a nut. The control method corresponds to controls the robot direction such that the robot faces a nut. The control method corresponds to a simple simple proportional control, and the feedback control is performed such that the illuminated nut is a simple proportional control, and the feedback control is performed such the illuminated proportional control, and the feedback control is performed such that the that illuminated nut is atnut theis at the middle of the camera image. at the middle of the camera image. middle the camera image. Theof inside of the box girder is dark. Therefore, it is considered that the following method, using The inside of the box girderin dark.Therefore, Therefore, considered that thefollowing method, using The inside of the box girder isisestimating dark. ititisisconsidered that the using the reflection of light, is effective the position of a bolt or a nut infollowing front ofmethod, the robot. thereflection reflection oflight, light, effectivein inestimating estimating position boltoror nutininfront frontofofthe therobot. robot. the isiseffective position a abolt a anut (1) White of light is illuminated with an LED the inthe the robot’sofof traveling direction. (1) White light is illuminated with an LED in the robot’s traveling direction. (1) The White light illuminated with an LED in the robot’sreflects traveling direction. (2) bolt or isnut in the illuminated range strongly light, and the part is brightly (2) The bolt or nut in the illuminated range strongly reflects light, andisthe part displayed is brightly (2) The bolt or nut in the illuminated range strongly reflects light, and the part brightly displayed even in the camera image. displayed even in the camera image. even(3) inThe the camera positionimage. of the bolt or nut is estimated based on the information in the bright part in the (3) The position thebolt boltorornut nutisisestimated estimatedbased basedon onthe theinformation informationininthe thebright brightpart partininthe the (3) The position ofofthe camera image. camera image. rate of the autonomous control varies based on how the camera and LED are camera Theimage. success The success rate of the control based the and camera LED are The As success rate the autonomous control varies based on how thehow camera LED are installed. installed. shown inofFigure 14,autonomous the distance from thevaries floor and theon attachment angle areand important. installed. As shown in Figure 14, the distance from the floor and the attachment angle are important. shown 14, the distance from the is floor and the attachment aretravels important. the place IfAsthe placeintoFigure be illuminated with the LED inappropriate, then theangle robot to theIfopposite If the place to be illuminated with the LED is inappropriate, then the robot travels to the to be illuminated with thecorresponds LED is inappropriate, for the direction for the nut that to a target.then the robot travels to the opposite directionopposite direction for the nut that corresponds to a target. nut that corresponds to a target.
Figure 14. Position relationship between the camera and the LED attached to the robot. Figure 14. Position relationship between the camera and the LED attached to the robot. Figure 14. Position relationship between the camera and the LED attached to the robot.
Figure15 15shows showsthe theilluminated illuminatedranges rangesof of“A”, “A”,“B”, “B”,and and“C”. “C”.In Inthe therange range“A” “A”the therobot robotturns turns Figure Figure 15 shows the illuminated ranges of “A”, “B”, and “C”. In the range “A” the robot turns appropriatelyto tothe theleft leftbecause becausethe theilluminated illuminatednut nutisison onthe theleft leftside sideininthe thecamera cameraimage. image.However, However, appropriately appropriately to the left because the illuminated nut is on the left side in the camera image. However, inrange range“B”, “B”,the thelit litnuts nutsare areon onboth bothsides sidesof ofthe thecamera cameraimage, image,and andthus, thus,ititisisnot notpossible possiblefor forthe the in in range “B”, the lit nuts are on both sides of the camera image, and thus, it is not possible for the robot to determine the direction of the turn. Additionally, in range “C”, the robot moves in the wrong robot to determine the direction of the turn. Additionally, in range “C”, the robot moves in the wrong robot to determine the direction of the turn. Additionally, in range “C”, the robot moves in the wrong directionsince sincethe thelit litnut nutisison onthe theright rightside. side. direction direction since the lit nut is on the right side.
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Figure 15. Position of each nut shown in the camera that changes based on the irradiation position of Figure15. 15.Position Positionof ofeach eachnut nutshown shownin inthe thecamera camerathat thatchanges changesbased basedon onthe theirradiation irradiationposition positionof of Figure the LED (from A to C). theLED LED(from (fromAAto toC). C). the
withthe theLED LEDlight. light.Therefore, Hence,ititisispreferable preferableto toilluminate illuminatethe thenut nutclose closeto tothe therobot robotwith Therefore,the the Hence, ◦ , θ = 55◦ , H = parameters in Figure 14 are defined as follows: θ = 12 = 91 mm. installation parameters in Figure 14 are defined as follows: θ c = 12°, θ L = 55°, H c 85 mm, H L = 91 mm. c c L L installation parameters in Figure 14 are defined as follows: θc = 12°, θL = 55°, Hc = 85 mm, HL = 91 mm. Runningexperiments experimentswere wereconducted conductedwith withthe the model the splicing parts. Gears were used Running experiments were conducted with the model ofof the splicing parts. Gears were used to Running model of the splicing parts. Gears were used to to transmit torque to the driving wheels of BIREM 3rd. positional relationship of either transmit torque tothe the driving wheels ofBIREM BIREM 3rd. TheThe positional relationship ofeither either thethe leftleft or transmit torque to driving wheels of 3rd. The positional relationship of the left or or right gear adjusted to reduce the transmission efficiency of the torque, and thus, the robot right gear waswas adjusted toreduce reduce thetransmission transmission efficiency ofthe thetorque, torque, andthus, thus, the robot cannot right gear was adjusted to the efficiency of and the robot cannot cannot run straight. Figures 16 and 17 are images of the camera attached to the front of BIREM. This run straight. straight. Figures Figures 16 16 and and 17 17 are are images images of of the the camera camera attached attached to to the the front front of of BIREM. BIREM. This run nutuses usesthe thecamera cameraand andFPGA FPGAattached attachedto tothe therobot. robot. autonomouscontrol controlto torun runwithout withoutriding ridingon onaaanut nut uses the camera and FPGA attached to the robot. autonomous However, we were not able to determine how controller performed based on the image. Therefore, the However, we were not able to determine how controller performed based on the image. Therefore, However, we were not able to determine how controller performed based on the image. Therefore, camera images have been encoded, transferred, decoded, andand projected on the external TFTTFT (thin-film the camera images have been encoded, transferred, decoded, and projected onthe theexternal external TFT (thinthe camera images have been encoded, transferred, decoded, projected on (thintransistor liquid-crystal display) to confirm the status of the autonomous control in real time. However, film transistor liquid-crystal display) to confirm the status of the autonomous control in real time. film transistor liquid-crystal display) to confirm the status of the autonomous control in real time. like in Figure 17, sometimes projecting on the TFT fails when transferring images taken in the dark. However,like likein inFigure Figure17, 17,sometimes sometimesprojecting projectingon onthe theTFT TFTfails failswhen whentransferring transferringimages imagestaken taken in However, in Thedark. imageThe transfer failed on the grayon rectangular parts in Figure 17.in Figure 1617. shows the16 experimental the dark. The image transfer failed on the gray gray rectangular rectangular parts in Figure 17. Figure 16 shows the the the image transfer failed the parts Figure Figure shows result when the robot thatthe cannot run straight and does not possess a steering control systemcontrol is used. experimental result when the robot that cannot run straight anddoes does notpossess possess steering control experimental result when robot that cannot run straight and not aasteering This figure shows the camera image taken by the robot every 1 s when running on the splicing systemisisused. used. This This figure figureshows shows the thecamera cameraimage image taken taken by by the the robot robot every every 11ss when when running runningpart on system on model. After 2 s, the robot turned away to the right, theright, wheel ran on a nutran at on 4ons. the splicing part model. Aftergradually therobot robot gradually turned awayand tothe the right, and the wheel ran the splicing part model. After 22s,s,the gradually turned away to and the wheel the images every 2 s when the22steering control system is used. Theisis images nutat at17 s.Figure Figure 17camera showsthe thecamera camera images every whenthe the steering control system used. aaFigure nut 44s.shows 17 shows images every sswhen steering control system used. indicate that the robot can on the splicing part. In the experiment, the operator The images indicate that thetravel robotsuccessfully cantravel travelsuccessfully successfully onthe the splicing part. Inthe theexperiment, experiment, the The images indicate that the robot can on splicing part. In the provides only the forward direction speed command from the transmitter, and the rotation direction operator provides only the forward direction speed command from the transmitter, and the rotation operator provides only the forward direction speed command from the transmitter, and the rotationis autonomously controlled. controlled. direction autonomously controlled. direction isisautonomously
(a) (a)
(b) (b)
(c) (c)
(d) (d)
(e) (e)
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Figure 16. Images of camera attached to the front of BIREM without the control. (a) (b) (c) Figure Figure16. 16.Images Imagesof ofcamera cameraattached attachedto tothe thefront frontof ofBIREM BIREMwithout withoutthe thecontrol. control.(a) (a)000s;s; s;(b) (b)111s;s; s;(c) (c)222s;s; s; (d) 3 s; (e) 4 s; (f) 5 s. (d) (d)33s;s;(e) (e)44s;s;(f) (f)55s.s.
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Figure toto thethe front of of BIREM with thethe control. (a) 0(a) s; 0(b) s; (c) s; (d) Figure17. 17.Images Imagesofofcamera cameraattached attached front BIREM with control. s; 2(b) 2 s;4(c) 4 s; 6(d) s; (e) 8 s; (f) 10 s. 6 s; (e) 8 s; (f) 10 s.
5.5.Conclusions Conclusions The Theaim aimof of this this study studywas wasto to develop developaa robot robot for for bridge bridge inspection inspectionby bycreating creatingaaright rightand andleft left two-wheel-drive robot called BIREM 3rd that runs through a right-angle path as well as a splicing two-wheel-drive robot called BIREM 3rd that runs through a right-angle path as well as a splicing part. part. The following results obtained respect to BIREM The following results werewere obtained with with respect to BIREM 3rd. 3rd. (1) The results confirmed that it was possible to run the robot oninner the inner right-angle path, (1) The results confirmed that it was possible to run the robot on the right-angle path, where where theisrobot is expected toinspect run to the inspect the damaged parts the box girder. However, the robot expected to run to damaged parts in the boxingirder. However, in contrastin to contrast to the ordinary steel plates used in the laboratory, the magnetic force decreased to the ordinary steel plates used in the laboratory, the magnetic force decreased from 25% tofrom 40%25% for the 40% the steel and necessary thus, it was replacein allthe magnets in the robot steelfor members formembers bridges, for andbridges, thus, it was to necessary replace allto magnets robot with stronger with stronger magnets for actual field applications. magnets for actual field applications. (2) (2)The Thewheel wheeltrack trackof ofBIREM BIREM3rd 3rdisis small small(74 (74mm), mm),and andthus, thus,the therobot robotcould couldrun runthrough throughthe the splicing part with bolts located at an interval of 75 mm by keeping the wheel from riding on the bolt splicing part with bolts located at an interval of 75 mm by keeping the wheel from riding on the bolt or or nut splicing parts. However, rotatable-caster-type rear wheels indispensable. thethe nut onon thethe splicing parts. However, rotatable-caster-type rear wheels areare indispensable. (3) It is very difficult for an operator to manually maneuver the robot to avoidonbolts on the (3) It is very difficult for an operator to manually maneuver the robot to avoid bolts the splicing splicing part. However, the appropriate attachment ofand a camera the robot enabled part. However, the appropriate attachment of a camera an LEDand on an theLED roboton enabled autonomous autonomous control, and thus, it was easy to maneuver the robot such that it could run through the control, and thus, it was easy to maneuver the robot such that it could run through the splicing part. splicing part. Acknowledgments: The authors would like to express their gratitude to Kenichi Sugii and Tetsuya Unotsu, Acknowledgments: The authors would like to express their gratitude to Kenichi Sugii and Tetsuya Unotsu, Hanshin Expressway Engineering Co. Ltd. (Osaka, Japan), for the research funds and for providing the Hanshin Expressway Engineering Co. Ltd. (Osaka, Japan), for the research funds and for providing the experimental environments. experimental environments. Author Contributions: Naoto Imajo and Satoshi Ito manufactured the BIREM 3rd and performed running experiments; Satoshi Ito Naoto performed theand experiment autonomousthe control of the robot; Takadarunning came up Author Contributions: Imajo Satoshi for Ito the manufactured BIREM 3rd and Yogo performed with the ideaSatoshi for the Ito mechanism and visual control for of BIREM 3rd and wrote theofpaper. experiments; performed the experiment the autonomous control the robot; Yogo Takada came up with the for the mechanism and visual controlofofinterest. BIREM 3rd and wrote the paper. Conflicts ofidea Interest: The authors declare no conflict
Conflicts of Interest: The authors declare no conflict of interest.
References
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