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Experiment of a Practical Automatic Snowplow
IFAC
Copyright 't" IF AC Intelligent Autonomous Vehicles. Sapporo. Japan . 2001
C:UC> Publications www.eIsevier.comlIocate/ifac
Experiment of a practical automatic snowplow
Soichiro Suzuki, Hiroshi Kumagami, Hideyuki Tsunemoto, Hiroyuki Haniu
Kitami Institute ofTechnology 165 koen-cho, Kitami, Hokkaido, 090-8507, Japan
Abstract: In this study, two kinds of automatic snowplow are experimentally investigated. One is a remote-controlled snowplow that works aroWld residence. Another is an autonomous snowplow that works in wide and simple space such as a car parlcing lot for a large-scale retail store. The original merchandized snowplow was improved for remote-control that utilizes communication line of PRS. (personal Handy-phone System). The autonomous controller utilizes a vision sensor that is composed of CCD video camera and a computer for image processing. In addition, design of practical landmark is examined. Copyright © 200J IFAC
Key Words: Automatic Snowplow, Rernote-control, Autonomous control, PRS., VISion Sensor, Experiment
1. Introduction
operation of a remote-controlled snowplow which is modified fiom commercially sold snowplow after successive trial of improvements. And also results on an autonomous test model equipped with vision sensor for recognition of landmark are presented
Since the Dlunber of elderly household is remarkably growing in local community, accidents in snow removing work by elderly people are increasing in cold region. The operation of the multifimctional snowplow that ha<; many control levers is very difficult for elderly people because the control of the levers require skills and power. However, few studies on automatic snowplow were reported up to date. The purpose of this study is mainly to develop ~ kinds of automatic snowplow which anyone can handle ~y and safely. One is a remote-controlled automatic snowplow that works around residence. This snowplow is remote-controlled by using P.H.S . (Personal Handy-phone System) while the operator supervises it on a video monitor placed in a room. Another is an autonomous snowplow that works in wide and simple space such as a car parlcing lot of a large-scale retail store. This paper presents experimental results on the
2. Composition of systems
2. J Remote-controlled snowplow Control levers originally provided for the snowplow is shown in Fig. 1. The number of control levers would increase drastically as the number of functions increased. In a society with many elderly people, presence of a high-performance snowplow with easy handling is demanded. Therefore, a simple controller shown in Fig.2 is provided for the control of the snowplow. Fig.3 shows the developed snowplow that can be controlled fiom indoor. The communication
221
Limit switch
D.C. motor
Rack and pinion
Fig.! Control-levers of snowplow
Fig.4 D.e. motor tmit
Fig2 Remote-controller
(personal Handy-phone System). The on board computer feeds voltage signal to a motor tmit shown in Fig.4 as a command from the operator is given. Thus the levers were enable to be manipulated by D.e. motors. The motor offers linear motion by rack and pinion to move the links of accelerators, clutch or brake. 10 addition, the posture of the auger and the shooter is controlled by a contactless relay-circuit By adopting this remote control system, the snow removing work can be instructed the snowplow beforehand. Consequently, the operator's control is needed only for the compensation of error in work.
2.2 Autonomous snowplow At the first step, the driving tmit of a snowrnobile
model is modified for autonomous locomotion, and
Fig.3 Remote-controlled snowplow between the computer in operator side and that on board the snowplow is established by using P.H.S.
Fig.5 Experimental model of autonomous snowmobile
222
C!nera adaptor
•
Color
decoder
CaIoosite
Fig.6 Outline of signal path
Fig.8 Remote-controlled snow removing work
Servo-motor2
Left
~~~~~~~~==~F=~====~~br~e
various speed of locomotion according to instruction of landmarks.
Pulse
r.:l:==~ v==~~==~~m
contro 11 er
t::1!=== rh>2
3. Experimental results
brake
+7. 2[V]
CH> Rotary speed
Right
D .. r IVlng [V] IIIltor
Fig.7 Outline of control writ a vision sensor as shown in Fig.5 is attached. Fig.6 shows the signal path of this system. Distinction of each predetennined action is given by the color of landmarl<, and the distance between the snowmobile and the landmark is obtained from coordinates of the center position in the image of the landmarlc. As shown in Fig.7, two pulse signals of voltage determined by the commands of action and the distance are sent from computer to two servo-rnotors through DJA converter in order to control the rotational velocity of the driving motor and change the course respectively. These servo-rnotors are positioned by changing width of the pulse signal. The position of servo-motorl detennines rotational angle of a rotary speed controller that controls the rotational direction and velocity of the driving motor. Servo-motor2 changes the brake system for turning. Consequently, two servo-motors can respectively control forward and backward motion and right and left turning of the autonomous snowmobile model in
3.1 Remote-control and programmed control Since P.H.S. was utilized for the wireless commwrication, control of the automatic snowplow was stable without interference in the outdoor operation as shown in Fig.8. However, it was difficult for the operator to confirm the working situation in detail by using only an image of a monitor. 10 addition, it is necessary to control the revolution of engine and posture of the auger to adjust to the condition of snow and rough ground geometry. On one hand, programmed control means the operator must instruct the working plan to the snowplow in advance. Therefore, the snowplow can repeat the same wotX anytime. 10 the experiment of the programmed controL the snowplow deviated from the target path when the slip occurred. Therefore, it is effective to combine the remote-control and the programmed control for the accurate snow-removing wotX by the automatic snowplow.
3.2 Autonomous control Color of landmark is sorted according to trichromatic ROB so that each color means a different corrunand
22 3
200 -0
GOAl
0
EJ
_
~
Cl)
Q) ~
150
~
.....
~
Target path
0
Q)
100
::I
-0-
8III~_• • IGreenl-o--
START
co >
Progranaed control
a
Autonomous
x
~
control
50
Red mark Green mark - M - Blue mark
135 ttnDer of light
(a) FI at course
Fig. I 0 Change of value of threshold about luminance
IBlue I
3.3 Design oflandmark
_
Target path
-0-
Prograaned control
a-"~~""I Greenl-o-- Autonanous START control (l)stac
(b) Uneven course
Fig.9 Experimental results oflocomotive path such as backward movement, right and left twning. Fig. 9 shows the experimental results of comparison of locomotive path between two types of control technique. One is programmed control that operates the switches of driving motors and brakes according to the instructed timetable in advance. Another is autonomous control that operates the switches according to the preset landmarks. In the case of (a) where the course is flat, the difference of the experiment results ~ not recognized between the two control techniques. In the case of (b), since the course for the experiment ~ artificially set slippay and uneven. the model of automatic snowplow controlled by progrannned controller deviated from the target path at the corner. On the other hand, the model of the autonomous snowplow with a vision sensor could move along the target path almost correctly.
In the above-mentioned experiment for autonomous locomotion, the necessity of remote-control was eliminated by recognition of color of landmark. However, it is expected that this technique is not fit for ussge in outdoor, because many color tones exist in such enviromnent, and the brightness always changes. Then, the maximum value of threshold of the luminance that makes 70 percent of pixels can recognize in the three- colored landmark ~ measured. As shown in Fig. 10, the threshold greatly changes according to the change of the number of the light in all colors. This result shows the necessity of automatic regulation of threshold according to the envirorunent Since this automatic regulation is very difficult, the technique to recognize the instruction from the shape of the mark is tested For experiment, 8 kinds of landmark that have 4 kinds of shape of the mark colored in white or black with black or white ground respectively. Fig. I I shows the binary image of the landmarks in various photographing distance. In addition, ratio of pixel number that is recognized as the mark is shown in Fig.12 as area ratio. As the result, longer the photographing distance is, smaller the black mark is recognized, and larger the white mark is. Therefore, when the instruction is judged according to the shape of the mark, white mark with black. ground is suitable for landmarlc. Considering the practical use, the landmark that is composed of intemallight source and diffuser is suitable for the correct recognition even in night and in
224
snowfall as shown in Fig.13.
4. Conclusion
Distance of photographing (m) Fig.11 Binary image oflandmark
In the experiment of remote-controlled snowplow, the locomotion and automatic snow removing work are stable without interference. The model of autonomous snowplow was able to move along the target path by using a vision sensor and landmarks even if the course was set slippery and lUleven. In the future research, time of the image processing for the vision sensor will be shorten by optimizing the design of the landmark and by combining the control techniques. As a result, actual autonomous snowplow will be developed.
200 Acknowledgements
,......
cf. 150
'--"
The financial support by ministry of education and science of Japan (subject no. 12650241) is gratefully acknowledged.
0 -+-J
ro
100
L.
ro
Q) L.
50 References
0
1
2
3
Photographing distance (m) Fig.12 Change of area ratio of landmark in various photograplllng distance
Tada., T., H. Takahashi, S. Fukuzawa and K. Isoda (1999). Development of an autonomous snowremoving machine Partl . Proceedings of '99 Cold Region Technology Conforence, 15,607-609. Ogawa, K., R Itoh, S. Suzuki, K. Miyakoshi, H. Ishitani, H. Haniu and H. Tsunemoto (1999). Development of radio-controlled automatic snowplow. Proceedings of '99 Cold Region Technology Conference, 15, 598-602.
Internal light Diffuser
Fig.! 3 Practical design oflandmark.
225
Copyright 't" IF AC Intelligent Autonomous Vehicles. Sapporo. Japan . 2001
C:UC> Publications www.eIsevier.comlIocate/ifac
Experiment of a practical automatic snowplow
Soichiro Suzuki, Hiroshi Kumagami, Hideyuki Tsunemoto, Hiroyuki Haniu
Kitami Institute ofTechnology 165 koen-cho, Kitami, Hokkaido, 090-8507, Japan
Abstract: In this study, two kinds of automatic snowplow are experimentally investigated. One is a remote-controlled snowplow that works aroWld residence. Another is an autonomous snowplow that works in wide and simple space such as a car parlcing lot for a large-scale retail store. The original merchandized snowplow was improved for remote-control that utilizes communication line of PRS. (personal Handy-phone System). The autonomous controller utilizes a vision sensor that is composed of CCD video camera and a computer for image processing. In addition, design of practical landmark is examined. Copyright © 200J IFAC
Key Words: Automatic Snowplow, Rernote-control, Autonomous control, PRS., VISion Sensor, Experiment
1. Introduction
operation of a remote-controlled snowplow which is modified fiom commercially sold snowplow after successive trial of improvements. And also results on an autonomous test model equipped with vision sensor for recognition of landmark are presented
Since the Dlunber of elderly household is remarkably growing in local community, accidents in snow removing work by elderly people are increasing in cold region. The operation of the multifimctional snowplow that ha<; many control levers is very difficult for elderly people because the control of the levers require skills and power. However, few studies on automatic snowplow were reported up to date. The purpose of this study is mainly to develop ~ kinds of automatic snowplow which anyone can handle ~y and safely. One is a remote-controlled automatic snowplow that works around residence. This snowplow is remote-controlled by using P.H.S . (Personal Handy-phone System) while the operator supervises it on a video monitor placed in a room. Another is an autonomous snowplow that works in wide and simple space such as a car parlcing lot of a large-scale retail store. This paper presents experimental results on the
2. Composition of systems
2. J Remote-controlled snowplow Control levers originally provided for the snowplow is shown in Fig. 1. The number of control levers would increase drastically as the number of functions increased. In a society with many elderly people, presence of a high-performance snowplow with easy handling is demanded. Therefore, a simple controller shown in Fig.2 is provided for the control of the snowplow. Fig.3 shows the developed snowplow that can be controlled fiom indoor. The communication
221
Limit switch
D.C. motor
Rack and pinion
Fig.! Control-levers of snowplow
Fig.4 D.e. motor tmit
Fig2 Remote-controller
(personal Handy-phone System). The on board computer feeds voltage signal to a motor tmit shown in Fig.4 as a command from the operator is given. Thus the levers were enable to be manipulated by D.e. motors. The motor offers linear motion by rack and pinion to move the links of accelerators, clutch or brake. 10 addition, the posture of the auger and the shooter is controlled by a contactless relay-circuit By adopting this remote control system, the snow removing work can be instructed the snowplow beforehand. Consequently, the operator's control is needed only for the compensation of error in work.
2.2 Autonomous snowplow At the first step, the driving tmit of a snowrnobile
model is modified for autonomous locomotion, and
Fig.3 Remote-controlled snowplow between the computer in operator side and that on board the snowplow is established by using P.H.S.
Fig.5 Experimental model of autonomous snowmobile
222
C!nera adaptor
•
Color
decoder
CaIoosite
Fig.6 Outline of signal path
Fig.8 Remote-controlled snow removing work
Servo-motor2
Left
~~~~~~~~==~F=~====~~br~e
various speed of locomotion according to instruction of landmarks.
Pulse
r.:l:==~ v==~~==~~m
contro 11 er
t::1!=== rh>2
3. Experimental results
brake
+7. 2[V]
CH> Rotary speed
Right
D .. r IVlng [V] IIIltor
Fig.7 Outline of control writ a vision sensor as shown in Fig.5 is attached. Fig.6 shows the signal path of this system. Distinction of each predetennined action is given by the color of landmarl<, and the distance between the snowmobile and the landmark is obtained from coordinates of the center position in the image of the landmarlc. As shown in Fig.7, two pulse signals of voltage determined by the commands of action and the distance are sent from computer to two servo-rnotors through DJA converter in order to control the rotational velocity of the driving motor and change the course respectively. These servo-rnotors are positioned by changing width of the pulse signal. The position of servo-motorl detennines rotational angle of a rotary speed controller that controls the rotational direction and velocity of the driving motor. Servo-motor2 changes the brake system for turning. Consequently, two servo-motors can respectively control forward and backward motion and right and left turning of the autonomous snowmobile model in
3.1 Remote-control and programmed control Since P.H.S. was utilized for the wireless commwrication, control of the automatic snowplow was stable without interference in the outdoor operation as shown in Fig.8. However, it was difficult for the operator to confirm the working situation in detail by using only an image of a monitor. 10 addition, it is necessary to control the revolution of engine and posture of the auger to adjust to the condition of snow and rough ground geometry. On one hand, programmed control means the operator must instruct the working plan to the snowplow in advance. Therefore, the snowplow can repeat the same wotX anytime. 10 the experiment of the programmed controL the snowplow deviated from the target path when the slip occurred. Therefore, it is effective to combine the remote-control and the programmed control for the accurate snow-removing wotX by the automatic snowplow.
3.2 Autonomous control Color of landmark is sorted according to trichromatic ROB so that each color means a different corrunand
22 3
200 -0
GOAl
0
EJ
_
~
Cl)
Q) ~
150
~
.....
~
Target path
0
Q)
100
::I
-0-
8III~_• • IGreenl-o--
START
co >
Progranaed control
a
Autonomous
x
~
control
50
Red mark Green mark - M - Blue mark
135 ttnDer of light
(a) FI at course
Fig. I 0 Change of value of threshold about luminance
IBlue I
3.3 Design oflandmark
_
Target path
-0-
Prograaned control
a-"~~""I Greenl-o-- Autonanous START control (l)stac
(b) Uneven course
Fig.9 Experimental results oflocomotive path such as backward movement, right and left twning. Fig. 9 shows the experimental results of comparison of locomotive path between two types of control technique. One is programmed control that operates the switches of driving motors and brakes according to the instructed timetable in advance. Another is autonomous control that operates the switches according to the preset landmarks. In the case of (a) where the course is flat, the difference of the experiment results ~ not recognized between the two control techniques. In the case of (b), since the course for the experiment ~ artificially set slippay and uneven. the model of automatic snowplow controlled by progrannned controller deviated from the target path at the corner. On the other hand, the model of the autonomous snowplow with a vision sensor could move along the target path almost correctly.
In the above-mentioned experiment for autonomous locomotion, the necessity of remote-control was eliminated by recognition of color of landmark. However, it is expected that this technique is not fit for ussge in outdoor, because many color tones exist in such enviromnent, and the brightness always changes. Then, the maximum value of threshold of the luminance that makes 70 percent of pixels can recognize in the three- colored landmark ~ measured. As shown in Fig. 10, the threshold greatly changes according to the change of the number of the light in all colors. This result shows the necessity of automatic regulation of threshold according to the envirorunent Since this automatic regulation is very difficult, the technique to recognize the instruction from the shape of the mark is tested For experiment, 8 kinds of landmark that have 4 kinds of shape of the mark colored in white or black with black or white ground respectively. Fig. I I shows the binary image of the landmarks in various photographing distance. In addition, ratio of pixel number that is recognized as the mark is shown in Fig.12 as area ratio. As the result, longer the photographing distance is, smaller the black mark is recognized, and larger the white mark is. Therefore, when the instruction is judged according to the shape of the mark, white mark with black. ground is suitable for landmarlc. Considering the practical use, the landmark that is composed of intemallight source and diffuser is suitable for the correct recognition even in night and in
224
snowfall as shown in Fig.13.
4. Conclusion
Distance of photographing (m) Fig.11 Binary image oflandmark
In the experiment of remote-controlled snowplow, the locomotion and automatic snow removing work are stable without interference. The model of autonomous snowplow was able to move along the target path by using a vision sensor and landmarks even if the course was set slippery and lUleven. In the future research, time of the image processing for the vision sensor will be shorten by optimizing the design of the landmark and by combining the control techniques. As a result, actual autonomous snowplow will be developed.
200 Acknowledgements
,......
cf. 150
'--"
The financial support by ministry of education and science of Japan (subject no. 12650241) is gratefully acknowledged.
0 -+-J
ro
100
L.
ro
Q) L.
50 References
0
1
2
3
Photographing distance (m) Fig.12 Change of area ratio of landmark in various photograplllng distance
Tada., T., H. Takahashi, S. Fukuzawa and K. Isoda (1999). Development of an autonomous snowremoving machine Partl . Proceedings of '99 Cold Region Technology Conforence, 15,607-609. Ogawa, K., R Itoh, S. Suzuki, K. Miyakoshi, H. Ishitani, H. Haniu and H. Tsunemoto (1999). Development of radio-controlled automatic snowplow. Proceedings of '99 Cold Region Technology Conference, 15, 598-602.
Internal light Diffuser
Fig.! 3 Practical design oflandmark.
225