The Computer Control System of a Wall-Climbing Inspection Robot*

Copyright © IFAC Low Cost Automation, Shenyang, P.R. China, 1998

THE COMPUTER CONTROL SYSTEM OF A WALL-CLIMBING INSPECTION ROBOT'

Feng Yong, Li Tao, Xu Dianguo, and Wang Yan

Department of Electrical Engineering, Harbin institute of Technology Harbin 150001 , P.R. China, E-Mail: yfeng@!Zope. hit. edu.cn

Abstract: This paper describes a master-slave computer control system of the wall-climbing inspection robot. The optical fibers are used in the system to realize the long-distance communication between the master computer and the slave computer. the data signal. audio signal and video signal are mixed together to be transmitted. The communication protocol between the master computer and the slave computer is designed to transmit the data synchronously and correct any communication error automatically. Copyright © 1998 1FAC Keywords: Computer control: Control system: Manipulators; Robot control: Robots.

l. INTRODUCTION

canisters in oil and chemistry field .

Wall-climbing inspection robots are mainly used in

The diagram of the wall-climbing inspection robot

inspecting outlook of walls of the wasted liquid

system is shown in Fig.I . The system consists of

canister in radioactive wasted liquid workshop. The

some subsystems, such as a wall-climbing robot, a

robots can find the hidden troubles caused by

carrying cart, a manipulator, a humper, a remote

corroding revelation of radioactive wasted liquid,

control station, and a diagnose equipment. The

assuring the safety of the circumstance. This kind of

movement of the wall-climbing robot can be

robots can also be widely used in cleaning of

controlled by operators with camera 1. The diagnose

skyscrapers. inspection, rust elimination. painting of

equipment placed in the wall-climbing robot adopts

. This work is supported by 863 high tecnology project of China

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Video Video

STD Bus Computer

I---+---i PC Bus 1--+---iC omputer

Contol Pannel

Fig. 1 The diagram of the wall-climbing inspection robot system ultrasonic to detect flaws and thickness of the wasted

date and state information. The baud rate of the selial

liquid canister. The carrying cart is used to carry the

communication is 9600DB, the transmitting distance

wall-climbing robot from remote place to the vicinity

is more than 100 meters.

of the wall to be inspected with the camera 2 and 3. The manipulator is used to carry the wall-climbing

(5)The system has the function of self diagnose and

robot from the carrying cart to the wall or take off the

fault alarm.

robot from the wall with the camera 2 and 3. The humper is used to avoid the wall-climbing robot

(6)The pull-down menu in the master computer is

dropping from the wall accidentally. Operators can

realized in Chinese.

control every subsystem in the remote control station with the video system (the camera 1,2, and 3).

(7)There are six operating modes: send robot, fetch robot, manual check, automatic check, alone operate, self diagnose.

2. MAIN SPECIFIC AnONS OF TIlE COMPUTER CONTROL SYSTEM

(8)The logical protection is adopted in the operating buttons

The main specifications of the computer control system of the robot can be described as follow 3. HARDWARE OF TIlE COMPUTER CONTROL (1 )The control of the robot is line-remote.

SYSTEM

(2)The structure of the computer control system is

The computer control system is essential in the wall-

two lever. the master computer is placed in the

climbing inspection robot system, its function is to

remote control station and the slave computer is

coordinate and control all subsystems for inspecting

placed in the carrying cart.

the outlook of the wasted liquid canister walls . At the same time , the computer control system can also

(3 )The master computer can coordinate and manage

monitor and display all the states of the system in the

the whole system.

remote control station for operators.

(4 )The master computer of the system can make

The structure of the computer control system is two-

communication with the slave computer through

leveL the master computer is placed in the remote

serial ports and optical fibers, to transmit commands,

control station, and the slave computer is placed on

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the carrying cart. The master computer monitors and

commands to the slave computer and receives the

controls the wall-climbing robot, the carrying cart,

system state information from the slave computer.

the manipulator, the humper, and the diagnose equipment through sending a serial of commands to

Three video signals, one audio signal, and two data

the slave computer and receiving all the system state

signals in the system must be transmitted using the

information from the slave computer. Meanwhile,

optical fibers simultaneously. The communication

the slave computer controls and monitors all the

between two computers is realized through RS232C

systems directly according to the commands from the

serial port. There are six optical fibers in the optical

master computer.

line, every optical fiber can transmit two channel different signals. Fig.3 shows the transmission of one

The computer control system of the wall-climbing

channel of video signal and one channel of audio

robot is shown in Fig.2. The two-level computer

signal using one fiber; Fig.4 shows the transmission

structure is adopted in the system. The master

of one channel of video signal and one channel of

computer is a PC bus computer. the slave computer is

data signal using one fiber: and Fig.S shows the

a STD

bus computer. The master computer

transmission of one channel of audio signal and one

communicates with the slave computer through the

channel of data signal using one fiber: the other two

optical fibers.

optical fibers are reserved for future .

The master computer transmits

;Master Comouter Control System: I

~--+I

Wall-climbing robot

Optic al T emUnal

\

;/

Manuplator Vision System

Carrying Cart I

I

I

'~'~Fi/ ~.

- - - - - - - - - - - - - - - - - - - -'

RS232C

Fig.2 The computer system ofthe wall-climbing robot

Fig.3 The transmission of the audio and video signals

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Hump er

Diagnose Equipment

Fig.4

The transmission of the video and data signal

Fig.5 The transmission of the audio and data signal 4 THE COMMUNICATION BETWEEN MASTER

the data communication between the two computers,

CONWUTERANDSLAVECONWUTER

the master computer and the slave computer can correct them automatically.

In order to realize the long-distance communication between the master computer and the slave computer

The idea of designing communication between the

of the wall-climbing robot control system, the optical

master computer and the slave computer is that the

fibers can be used to link the master computer and

communication is controlled by the master computer.

the slave computer. The master computer and the

The slave computer makes communication according

slave computer communicate each other through the

to the command from the master computer. The

RS-232C serial port, the speed of signal transmission

master computer receives the state information of the

is the baud rate 9600DB.

wall-climbing robot system from the slave computer. The message exchange between the master computer

The communication between the master computer

and the slave computer in the two directions is

and the slave computer is very important to the

processed as the following protocol:

climbing robot control system. There must be two

problems to be considered in the design of the

(1)

computer control system. Since the control of the wall-climbing robot system is real-time, the first

where ACK=60h describes the transmission of the

problem is speed of signal transmission between the

old message has ended and the transmission of new

two computers: the second is reliability of the system,

message has started: LN(l byte) shows the length of

the commands from the master computer and the

the

state information from the slave computer are

commands from the master or the response from the

required absolute exactness. if some errors occur in

slave computer: LRC( I byte )is used to certify the

86

useful

message: :MESSAGE indicates the

message transmitted, the algorithm of LRC can be

computer and the slave computer can correct the

described as follow

error automatically, so that the slave computer can avoid operating the wrong commands from the

LRC=ACKEElLNEEl(1v1ESSAGE I

master computer and the master computer can avoid

EElMESSAGE 2••••••EEl MESSAGE IN)

(2)

getting the wrong state information from the slave computer.

where the symbol EEl indicates XOR logic operation; MESSAGE i indicates the ith byte of the message. The computer sending message must compute LRC

5 SOFTWARE DESIGN

as Eq.(2). then send them to another computer according to Eq.(l) through the RS232C serial port.

The master computer control system software is

Each of the two computers receiving the message

programmed using C++ program language, the

which is formed as Eq.(l) will compute LRC

software consists of six function modules: send robot,

according to Eq.(2), then compares the computed

fetch robot, manual check, automatic check, alone

LRC with the received LRC. If the two LRC are same,

operate, diagnose. The block diagram of the software

the logical certification is successful. But if the two

in the master computer is shown in Fig.6. The

LRC are different the certification is faiL which

program diagram shown in Fig.6 only lists the two-

shows the serial message received can not be used.

level menu of the sole operate function, the other five

The computer receiving the message must send back

function modules in the software are omitted in the

an empty message to another computer. If the

paper.

computer receiving message does not receive the additional message LRC, it will also send back the

According to the requirements of the robot system,

same empty message to another computer. The empty

the Chinese pull-down menu is adopted in the

message (NACK) to be transmitted is formed as

software. The system adopts the Chinese menu in

follow

English DOS. In order to save time for real-time control. the paper builds a Chinese character font

base in the hard disk. When the control system

(3)

begins to run, the font base is read into RAM, the If the computer receiving message finds any error in

Chinese font module can be achieved only by access

communication, the computer can repeat sending an

to RAM, and the different type Chinese characters

unsuccessful message (3), but the computer must set

can be displayed together. Graphics and window

the limitation of sending times to avoid circulating.

techniques are adopted in the system software to

the computer can also send another different message

make the screen simply and clear.

to the computer sending message under the same condition above. Accordingly, if the computer

The keyboard interrupt and timing interrupt are

sending

message

adopted in the system software to manage all tasks of

(NACK). the computer will repeat the previous

the control system conveniently. The timing interrupt

message.

control uses the 8th interrupt in the master computer.

message

receives

an

empty

the sample time is set to be 50 ms. The keyboard After design of the communication protocol between

interrupt control uses the 9th interrupt in the master

the master computer and the slave computer

computer. The main and the subroutine programs

according to the above idea, the specification of the

setting and using these two interrupts in the master

wall-climbing inspection robot system can be

computer are shown as follow

satisfied, the data communication synchronism of the two computers can be realized automatically. If any

void interrupt timerO:

error occurs in the communication. the master

void interrupt keyO:

87

Function Select

•

Send Robot

+

f-+

Fetch Robot

+ H

Manual Check

.

+

+

.....

Automatic Check

Alone Operate

r+

.. -i

..

Self Diagnose

Function Select

+ Manuplator

--i

Vision System

l-i

1

...

+

~

Diagnose ~

Hump er

+

-.

Robot

+ H

Others

Fig.6 The block diagram of the software in the master computer CONCLUSION

mainO union bw{int i;

The paper describes the wall-climbing inspection

unsigned char ch[1);}tbw

robot computer control system. The system adopts two-level computer structure. The optical fiber is

outportb(Ox43 ;Ox36);

used in the system to realize the long-distance

tbw.i=59625:

communication between the master computer and the

outportb(Ox40. twb.ch[O) );

slave computer, the data signal, audio signal and

outportb(Ox41 , twb.ch[1) );

video signal are mixed together to be transmitted, so

setvector(8, timer);

two different signal can be transmitted on one optical

setvector(9, key);

fiber. The design of communication protocol between

outportb(0x21 ,Oxfc);

the master computer and slave computer can make the communication synchronous, and can correct any

}

error automatically.

void interrupt timerO {

REFERENCE

enableO;

Adasa, H. and Slotine J-J-E.(l986). Robot analysis

outportb(0x20, 0x20);

. and control. John Wiley and Sons, Inc.

}

Reinhold C. M.,William R. H.,and Charles R. W. (1988). The development of an intelligent

void interrupt keyO

nuclear maintenance robot IEEE Inter. Con! on

Robotics and Automation, Vo1.2 ., pp621-623 Kweon I. S., Kuno Y. , et a1.(1992) . Behavior-based enableO;

intelligent robot in dynamic indoor environment.

outportb(0x20, 0x20);

Proc. of IEEEIRSJ, Inter. Con! on Intelligent,

}

Robots and Systems. pp. 1339-1346.

88