Citation: Song, W.; Wang, Z.;
Wang, T.; Ji, D.; Zhu, S. A Path
Tracking Method of a Wall-Climbing
Robot towards Autonomous
Inspection of Steel Box Girder.
Machines 2022, 10, 256. https://
doi.org/10.3390/machines10040256
Academic Editor: Giovanni
Boschetti
Received: 22 February 2022
Accepted: 30 March 2022
Published: 2 April 2022
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Article
A Path Tracking Method of a Wall-Climbing Robot towards
Autonomous Inspection of Steel Box Girder
Wei Song
1,2,3
, Zhijian Wang
1
, Tong Wang
1
, Daxiong Ji
1,
* and Shiqiang Zhu
1,2
1
Ocean College, Zhejiang University, Zhoushan 316000, China; weisong@zju.edu.cn (W.S.);
21834119@zju.edu.cn (Z.W.); 3160100561@zju.edu.cn (T.W.); sqzhu@sfp.zju.edu.cn (S.Z.)
2
Zhejiang Lab, Hangzhou 311100, China
3
Technology and Equipment of Rail Transit Operation and Maintenance Key Laboratory of Sichuan Province,
Southwest Jiaotong University, Chengdu 610031, China
* Correspondence: jidaxiong@zju.edu.cn; Tel.: +86-18334324673
Abstract:
This paper proposes an autonomous inspection method for steel box girders that uses a
wall-climbing robot instead of human workers. According to the 3D operating environment inside
the steel box girder, the method proposes a 3D path for the robot to traverse positions to be inspected.
The path comprises two alternate sections of the lane’s centerline and U-shaped steering. To realize
the robot’s tracking of the desired path, kinematics analysis based on different poses during the
inspection was carried out. Corresponding path tracking algorithms were adopted to ensure that
the robot moves accurately and efficiently. In addition, for the smooth transition of the two path
sections, this method adopts an algorithm of cooperatively controlling the lifting mechanism and
the wheel speeds to achieve stable crossing of a 90
◦
concave corner. Finally, experiment results show
that the robot can steadily cross 90
◦
concave corner and can steer to the adjacent lane and complete
lane inspection along the desired path. The method can realize autonomous inspection for steel box
girders using the wall-climbing robot.
Keywords: steel box girder; wall-climbing robot; inspection path; path tracking
1. Introduction
Steel box girder (SBG) is an important structural unit of long-span bridges, and its
condition inspection is an important means to ensure safe use. SBG is an approximately
closed structure, and its inspection is usually aimed at the internal structure. As shown
in Figure 1, the current detection methods are mainly manual [
1
,
2
]. Workers use ladders
to reach the target wall and then use naked eyes or flaw detection equipment to perform
an inspection. This method has limitations such as low detection efficiency, high labor
intensity, and a certain degree of danger. However, the wall-climbing robot, as a mobile
platform that can be attached to the wall, can replace workers to complete labor-intensive
and high-risk tasks.
To overcome the shortcomings of manual inspection, researchers have developed
many wall-climbing robots that can be used in bridge maintenance and inspection [
3
–
11
].
For example, the biomimetic inchworm robot in reference [
3
] can transition between two
walls with an angle of 0–360
◦
, and can pass through the manhole of the bridge partition;
the tracked wall-climbing robot in reference [
10
] adapts to the cylindrical wall surface of
the bridge by using a reciprocating mechanism. These robots operate on multiple planes or
curved surfaces, which means relatively complex work paths and difficult path tracking.
To conduct a comprehensive and reliable inspection, the primary goal of this task is to
ensure that the wall-climbing robot accurately tracks the inspection path. Therefore, it is
essential to perform effective path tracking for the robot.
Nowadays, path tracking algorithms are mainly based on geometric models [
12
–
14
],
kinematic models [
15
,
16
], and dynamic models [
17
–
20
]. In our study, the robot moves
Machines 2022, 10, 256. https://doi.org/10.3390/machines10040256 https://www.mdpi.com/journal/machines
