Researches on a Wall-Climbing

obot Based on Electromagnetic

Adsorption

Kai Huang

, Xiangdong Li

, Ye

Sun

2 b

, Yong Chen

2 a

, Miao Hao

and Yihui Zhang

Special Equipment Safety Supervision Inspection Institute of Jiangsu Province, Nanjing 210036, China

Nanjing Forestry University, Nanjing 210037, China

Keywords: Wall-climbing robot, electromagnetic absorption, embedded control.

Abstract: The technical bottleneck of the wall-climbing robots based on magnetic adsorption is that the magnetic

force is not only the adsorption force but also the moving resistance force. The bigger the adsorption force

is, the bigger the moving resistance force is. In order to solve this problem, a unique wall-climbing robot

based on electromagnetic adsorption is proposed. Electromagnets fixed in the synchronous belts get into or

out of work in turn to realize the unity of adsorption and mobility. An embedded Linux system is

constructed to transport videos from the robot to the handheld terminal in real time. A MCS-51 based

controller is designed to perform robot control. A prototype robot is manufactured and tested. Experiments

show the video delay is less 0.45s and the remote-control distance is beyond 80m.

1 INTRODUCTION

Wall-climbing robots have wide applications in

industry and other fields. According to serving

environment and working media, the adsorption

modes for wall-climbing robots are classified into

negative pressure adsorption[1-2], bionic dry

adhesive adsorption[3-4], magnetic adsorption and

etc. Negative pressure adsorption is not limited by

working media, but it will suffer from air leakage if

the surface is very rough. Bionic dry adhesive

adsorption is suitable for all kind of surfaces, and

magnetic adsorption only works for magnetic-

conductor. Magnetic adsorption includes

electromagnetic adsorption, permanent magnetic

adsorption and their combinations. As to magnetic

adsorption, many researches are focused on

permanent magnetic adsorption[5-8]. A few of

researches are based on electromagnetic

adsorption[9]. Extensive researches have been

carried on wall-climbing robots for many years, but

there is few prototype wall-climbing robot which is

suitable for actual uses until now. One of the

technical bottlenecks is the unity of adsorption and

mobility.

2 OVERALL DESIGN

In this paper, a unique structure is proposed to solve

the above problems. As shown in Figure 1, the

unique wall-climbing robot is composed of a main

frame, two synchronous belts with embedded

electromagnets, two conductive troughs, four

synchronous belt wheels, two step motors and its

controllers, and etc. The conductive plate provides

electric power for the electromagnet. 16

electromagnets are fixed in a synchronous belt

equispacedly. The U-shaped conductive trough is

arranged inside the synchronous belt. When the

synchronous belt wheels are driven to rotate, the

electromagnets will be brought into and out of

contact with the conductive trough one by one. That

is, only these electromagnets which contact with the

conductive trough can generate magnetic force. In

this way, when the wall-climbing robot moves

forward, the electromagnets will get into or out of

work in turn. As to our prototype, 6 electromagnets

always stick to the wall surface at the same time to

support the whole robot. According to this scheme,

the magnetic force is only the adsorption force

instead of the resistance force.

Figure 1: The plane assembly drawing of wall-climbing

robot

1-Conductive plate, 2-Timing belt pulley,3-Timing belt, 4-

Electromagnet, 5-Stepper motor

In addition, the main frame is made of

aluminium alloy in order to reduce the weight. The

robot outline is 335mm*295mm, and the wheel is

106mm in diameter. A camera on the robot is

employed to capture videos and the operator can

watch the pictures displayed on the screen of a

handheld terminal.

In this paper, comprehensive consideration of

different forms of controls, the control system of the

wall-climbing robot uses two distributed control

systems which are hand-hold terminal control and

vehicle on-board controller. Figure 2 shows the

overall block diagram of derusting wall-climbing

robot.

The main function of the wall-climbing robot’s

hand-hold terminal is to send the control signal to

the vehicle-mounted controller by wireless

transmission so as to realize the remote-controlled

movement of the wall-climbing robot.

The on-board controller is the execution layer of

the wall-climbing robot control system. It has two

main functions: one is to control the climbing robot's

forward, backward and steering on the wall, and the

other is to communicate with the handheld terminal

by wireless communication. The microcontroller

board of vehicle controller will immediately execute

the appropriate procedures to control the stepper

motor after receiving the command signal, and then

it can control the movement of the wall-climbing

robot.

Microcontroller

Left driver

Right driver

Left stepper motor Right stepper motor

Wireless

Router

Network video server

UVC camera

Video capture and

transmission

Vehicle On-Board

Controller

Wall-climbing robot

Video display Instruction transfer

Hand-held Terminal

Wireless communication

Figure 2: Block diagram of control system of derusting

wall-climbing robot

3 DESIGN OF THE CONTROL

SYSTEM

3.1 Hardware Design

The handheld terminal is based on a MCS-

51controller to realize remote-control and image

wireless transmission. The circuit of the vehicle

control system is composed of STC12C5A60S2

microcontroller, stepper motor drive circuit, wireless

receiving circuit, power conversion circuit and serial

port download circuit. The wireless receiving circuit

is responsible for constantly receiving the control

instructions issued by the handheld terminal. After

receiving the control signal, it is resolved by the

single chip microcomputer as the output of the pulse

command to the stepper motor driver.

3.2 Software Design

One can operate the robot movement through the

interface of the handheld terminal. The software of

the vehicle controller includes wireless transmission

and stepper motor driving. The wireless reception

subroutine is for receiving control instructions

issued by handheld terminal. Figure 3 shows the

flow chart of receiving and sending subroutines.

Initialize

NRF24L01

Set the sending/receiving mode to

send a reply signal

Start

Open the receive/send

interruption?

End

Yes

Configure to receive/send

mode

Answer completed?

Yes

Configure the module to

receive/send mode

Receive/send data packets

into the stack

Receive/send data

Aut o an swer

Figure 3: Subroutine for Wireless receiver/ transmission

4 WIRELESS IMAGE

TRANSMISSION

Images captured by a camera on the robot are

displayed on a screen mounted on the handheld

terminal. The hardware needed for wireless video

transmission is composed of an embedded

development board, a router and a camera. The

software development processes are shown in Figure

4 and Figure 5.

Cross compilation environment

construction

Transplantation of Bootloader

Transplantation of Linux kernel

The construction of the root file

system

Transplantation of wireless

network card driver

End

Start

Figure 4: The steps of building the software development

environment of Linux system

Transformation of wireless

router

Building of MJPG-streamer

video server

Installation of UVC camera

driver

Transmission of video data

End

Start

Figure 5: Building of video image acquisition end

5 RESULTS AND CONCLUSION

A prototype robot was designed and manufactured,

as show in Figure 6. Experiment results on video

transmission are shown in Table 1. The max video

delay is about 0.45s. Since the robot moves slowly

in routine inspection, the delay is acceptable in our

application.

Router

Camera

Wall-climbing Robot

Vehicle On-Board Controller

Stepper motor drive

Wireless communication

Hand-hold Terminal

Figure 6: Composition diagram of experimental system

Table 1: Main directory of root file system(unit:second)

Actual

stopwatch time

LCD display Delay

03:29.26 03:29.06 0.20

03:39.37 03:38.93 0.44

03:40.58 03:40.13 0.45

03:42.37 03:41.95 0.42

03:44.04 03:43.75 0.29

ACKNOWLEDGEMENTS

Thanks for the following supports for our

researches: General Administration of Quality

Supervision, Inspection and Quarantine of the

People's Republic of China (2017QK044), General

Administration of quality and Technology

Supervision of Jiangsu Province (KJ175915),

Special Equipment Safety Supervision Inspection

Institute of Jiangsu Province (KJ(Y)2016019).

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APPENDIX

Hong Xiaowei,the student of Nanjing Forestry

University, is the co-author of this article.