Robotization of Agricultural Vehicles - Various Operation with Tilling Robot-

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ROBOTIZATION OF AGRICULTURAL VEHICLES - VARIOUS OPERATION WITH TILLING ROBOT -

*tSatoshi Yamamoto, *lOsamu Yukumoto, *IYosuke Matsuo

*I Fundamental Technology Department, Institute ofAgricultural Machinery (/AM-BRAIN) Nisshin 1-40-2, Saitama, 331-8537, Japan *2Department ofFarm Mechanization, National Agricultural Research Center Kannondai 3-1-1, Tsukuba, 305-8666, Japan

Abstract: Tilling robot was developed to be able to recognize its own position and heading in the field, while performing an unmanned tilling as well as a manual operation.

To improve

the ability of the tilling robot, some operation softwares have been studied and developed for executing various agricultural works such as seeding and soil paddling. It was confirmed that unmanned operations with these softwares and the tilling robot could be performed at almost the same accuracy and efficiency as manual operations. Keywords: Mobile robots, Autonomous vehicles, Teaching, Path Planning, Navigation

operations,

1. INTRODUCTION

2) High-precision work superior to human work, Currently, agricultural industry in Japan is facing to

and

a critical phase due to the difficulty in finding

3)

successors and the rapidly expanding market of

eliminating the intervention of an operator.

imported agricultural products.

Improvement

of safety

and

amenity

by

Efforts are being

made to promote the industry through labor-saving,

Subsequently, new working methods will be created

As one

in response to the robotization of agricultural

of these efforts, studies on the robotization of

vehicles and the following additional benefits are

agricultural vehicles

expected:

lower cost, and enhanced product quality.

have been conducted in

recent years to achieve the following objectives:

1) An operator can manage and operate several

I) Labor-saving through completely unmanned

vehicles simultaneously,

203

2) Through continuous day and night work, a small machine can perform the operation of a large area and solve the problems such as soil compaction, and 3) The ability to detect vehicle position will enable to obtain information on yield and soil conditions of each part of the field in respect to performing precision farming tasks. Men

The IAM-BRArN has accumulated technologies for

SSModem

Controll..

SS Modem

robotization of agricultural vehicles through several trials since 1988.

The Ministry of Agriculture,

Forestry and Fisheries launched an agricultural machine development project in the fiscal year of 1993 .

The five-year is development of a tilling

robot was implemented under this project.

This

development

with

was

KUBOTA

Co.,

Industries,

Ltd.,

performed Japan

together

Aviation

Hokkaido

Fig. I . The XNAV system configuration position and heading of the vehicle in the field .

Electronics

University

Considering the variation of the field in which the

and

lAM-BRAIN . After the development of the tilling

robot operates, three types of navigation system

robot, some operation softwares have been studied

were developed. As the result of development, each

and developed to improve its applicability to various

navigation system was able to satisfY the aimed

agricultural works such as seeding and soil paddling.

performance, i.e. less than 5 cm position error and 2

This paper describes the construction of the tilling

system, mainly applied to the improving study from

robot,

1998, is outlined below.

Hz of data acquisition. The XNAV navigation some softwares

developed

for

various

agricultural operations and the results of working The components ofXNAV system are shown in Fig.

performance tests with the tilling robot and these

I. The optical surveying device tracks and ranges a

softwares.

target prism on the vehicle automatically by a single and modulated laser beam. It calculates the position of the target according to the principle of traverse

2. CONSTRUCTIONS OF TILLING ROBOT

surveying. For the surveying device, a commercial The development of the tilling robot was aimed at

product (AP-L I, TOPCON Co.) was used . On the

making a working vehicle that can recognize its own

other hand, the heading of the vehicle is detected by

position and heading, while performing unmanned

a terrestrial magnetic sensor (TMS ). Because the

tilling, including headland treatment, at the same

target prism position detected by AP-L I is different

work rate as a manual operation. Fields are limited

from the vehicle position on the ground when the

to an almost flat and rectangular shape that covers a

vehicle is tilted, a clinometer is mounted to correct

paddy field and an upland field. As a basic principle

the difference. It is also used to correct the heading

of our study, the robot works within sight of the

data from TMS. Furthermore, there are radio

operator, which enables the operator to stop the

modems to communicate between the base station

robot by remote control in case of emergency.

and the mobile station. As a result of the field tests, the XNAV system fully reached the target accuracy and tracks a moving

2.1 Navigation System

object in a very stable manner.

It performs

automatic tracking, position measurement, and data The most important element to execute unmanned

communication at a distance up to 500 m in an area

operations is the navigation system to detect the

with a good perspective.

204

~ :

Operation Path Moving Path Entrance of the Field

o

Field

/~ . 1222

'.

0(

32 ---_~

---+.. 3~: 121 11

::!I.

11(.. I 2 ... -__

::1

:

13

23

33

Fig. 2. ROBOTRA

!"

Area

·:l·t.

., ....

2.2 Vehicles (ROBOTRA)

The ROBOTRA (Fig. 2) was developed using a

Returning Operation

.:

D-I

(

-

I'31 1 1

~ ~

---4. + ..... • 34--~'" -t:I!. -===:;:~·=3~.n

24 Headland Proce~s Operation Area

Fig. 3.

~

The

example

' 14 --::._

of path

planning

for

tilling or cultivating

commercial tractor as the base vehicle for its versatility as well as the low development costs . Since this base vehicle has the latest functions such

for the main controller with various 110 boards for

as a shuttle gear, a bi-speed turning system and

the input and output of signals .

automatic depth and level control functions for rotary tiller, it was possible to simplify the control parts of the vehicle .

3. OPERATION SOFTWARE

Control of each part of the vehicle is achieved

3.1 Elements ofsoftware

through an exclusive vehicle controller. For steering control, the steering angle is detected by the

The operation software is composed of two parts,

potentiometer and fed back to the servomotor so that

i task planning part! and i vehicle control part! .

the specified steering angle can be obtained. To The task planning part consists of a i teaching

simplify the system, a shift position is manually set prior to the operation so that the velocity is

module! and a i path planning module! . In case the

controlled in two stages by switching between a

ti lIing robot is applied in a field first, the teaching

previously set throttle position and full throttle. To

module is used to recognize the shape, size and

ensure safety, the ROBOTRA has an emergency

direction of the field . In this module, the robot logs

stopping mechanism that is activated by anyone of

various data (teaching data) that are necessary for

a bumper switch, an emergency switch or through a

the

radio control.

operation along the field border. The path planning

un manned

module

operation

generates the

during

optimal

the

manual

operation

path

automatically according to the teaching data. An 2.3 Main COl1lrol/er

example of the path planning is shown in Fig. 3. This is mainly for tilling or cultivating, which

The

main

information

controller and

the

inputs internal

the

navigation

information

includes the moving path, the returning operation

of

path and the path for headland process.

ROBOTRA, detennines the control value for each

The vehicle control part consists of a i moving

part of the vehicle according to the path planning,

module!, a i returning operation module! and a

and outputs them to the vehicle controller. A factory

i headland process operation module! . Each module

computer which allows easy modification and

consists of various routines, such as a i straight

replacement of software programs is presently used

operation routine!, a i 180 degrees turning routine!,

205

Table I Various operation software

Ope. B "

-..

----------------------Boundary of the field

B

Operauon Area

Objects

Features

Basic operation

Tilling, Cultivating

Almost the same way as manual operation

Diagonal operation

Flaning the ridge, Tilling, Cultivating

Set the angle of diagonal operation

Round from center

Tilling, Cultivating

Continuous round operation from the center of the field

Round from outside

Harvesting

Continuous round operation from the outside of the field

Seeding

Seeding of wheat, soybean, etc

Unrnanned operation and stop for supplying

Soil Paddling

Paddy field

One path slap returning operation

abnormality according to the display.

I

j:

Process for Returning

-----

:

Software

--------' ' - - Process for Headland

Fig, 4. The flow of soil paddling software

3.2 Variation a/the Unmanned Operation

a i 90 degrees turning routinei, and a i sideways

Besides the basic operation software for tilling or

movement routinei , While the robot executes these

cultivating described above, some softwares can be

routines, the cycle time to get the position data and

used

to control the steering is approximately 0,5 s. In

developed . These are summarized in Table I . Only a

addition, the positioning accuracy was improved by

seeding software and a soil paddling software are

complementing position information at intervals of

illustrated below.

for various agricultural operations were

0.1 s, using the dead reckoning based on the vehicle velocity and heading, The tilling robot can be

The seeding software was based on the returning

applied under the operation velocity from 0.2 m I s

operation module of the basic operation software. In

to 1.2 m Is.

the seeding operation, the robot makes the returning operation,

and

stops

every

several

returning

a

operations for materials supplying. It is possible to

abnormality

set the number of continuous returning operation

alarming software were developed. These softwares

according to the capacity of the hopper on a seeding

In

addition

to

self-diagnosing

the

operation

software

and

software,

an

deal with the various situations or unexpected

implement and the field length . The operator only

accidents in the field, and perform more reliable

needs to supply materials, the restart of operation

is

after the supplying is made by an input from

unmanned

operation.

executed automatically

The

self-diagnosing

before each

unmanned

keyboard.

operation. In the concrete, it checks the initial setting of shift gear, implement position, and PTO. It also

The soil paddling software was coded by modifYing

confirms each actuator, XNAV system and the radio

the returning operation module in skipping adjacent

modem, and the remaining fuel. On the other hand,

paths to keep the surface of the paddy field from

the abnormality alarming is for detecting the

being in rough when turning.

abnormalities of the navigation data, operation

operation with skipping paths is executed from one

velocity, work load, and so on . In case abnormality,

side of the field to the other side, and the returning

The returning

it indicates the alarm to the operator with a horn and

operation, after tuming back at the other side, is

a flashing light, and the robot stops until the

executed

abnormal state is eliminated. The operator can

(untreated area) on the former operation. These go

restart the unmanned operation after recovering the

(Ope . G) and back (Ope . B) operations make one

206

with

processing

the

skipped

path

Table 2 The results of the unmanned operation

Tilling

Un manned

Manual

165 x 30

165 x 30

1276

1155

Field area (m) Work time (min)

Untreated area Cm:)

0.0

40

475

49.3

286 x 66

286 x 20

086

1.17

Wheel tracks on the treated area (rn)

Seeding

Field area (m)

A vcrage operation velocity (mts) Sideway deflection of the

47

straight operation (cm)

Soil paddling

Fig. 5. The result of the seeding operation

60 x 50

Field area (rn)

Untreated area

428

(ml)

Standard deviation of the measured height of the field surface (cm)

series of returning operations for soil paddling. In

-, field for manual operation I

the execution of the software, according to the field condition, it is possible to select the repeat number of the soil paddling from one to four. The flow of

2.7

77

100

X

50.

90 I

1

60 x SO·:

54 I I8

*2 . field for manual operation :!

4.2 Seeding Operation

this software is shown in Fig. 4. When the repeat number is selected one (# I), the robot executes one

The seeding operation test was carried out with a wheat seeder (9 rows, width 2.7 m) attached to the

series of returning operations, and executes 3 round operations to treat the headland of the field. In case

ROBOTRA. The picture taken one month after the seeding is shown in Fig. 5. Although the average velocity of the unmanned operation was slow, the operator only needed to supply materials once in a

of the repeat number is selected two or more, after 2 round operations, the robot executes the next series toward the perpendicular direction of the former series, and continues until the repeat counts becomes

while in the un manned returning operation. After all,

equal to the selected number.

an operator does not need to take a recess and consequently obtains better work efficiency. In respect to the work accuracy, the sideway deflection of the straight operation was superior to the manual operation.

4. EVALUATION OF UNMANNED OPERATION The performance of the above mentioned software was evaluated by comparing the unmanned operation by the ROBOTRA with the conventional

4.3 Soil Paddling Operation

manual operation. The main results concerned to the efficiency and accuracy are shown in Table 2.

The soil paddling operation test was carried out with a drive harrow for soil paddling (width 2.3 m) attached to the ROBOTRA. Three fields were provided for the test, one for the unmanned operation, one for the manual operation based on the returning operation (manual operation I), and one

4.1 Tilling Operation

The unmanned operation test was carried out in the

for another manual operation based on the racetrack

fields after wheat harvest. The work accuracy of the un manned operation was superior, and the work

operation (manual operation 2). Each soil paddling operation by manual was aimed at twice, the repeat number ofthe unmanned operation was selected two

efficiency was almost equal to the manual operation. Consequently, it is considered that almost two fold work efficiency can be expected if an operator performs a manual operation while supervising an

(#2). The percentage of overlapping area in the tests

unmanned operation at the same time.

shown in Fig. 6. As a result, the unmanned operation obtains better uniformity and work efficiency

and the work trace of the unmanned operation are

compared to the manual operations.

207

~80

5. CONCLUSIONS AND FUTURE PROSPECTS

.~ 02: ..

~--~==~~~~~~~

...oo

1-----------

Currently, the tilling robot can execute various

~~ r---------------------------~

~ 40

agricultural operations in the field . However, the tilling robot must attain higher reliability and safety to be on the market. At the same time, it is needed to continue researches of the following subjects:

<.>

~20 C

1) Establishment of the cooperation method with the

u

~

"

c.. 0

tilling robot and the manual operation,

l...ICI_"--'-......__-'--

unterated

area

2

0

3

2) Development of the software that can operate

4

other works such as rice planting and chemical or

The overlap count of each mesh

fertilizer application, 50m

3) Application of the navigation system to be used for tasks in precision farming.

REFERENCES Matsuo, Y. et at. (1998). Navigation System and Work Performance of Tilling Robot, ASAE Annual Meeting Paper, No. 983192, 1-11. Matsuo, Y. et at. (2001). Navigation System and Work Performance of Tilling Robot (Part 2), Journal of the Japanese Society of Agricultural Machinery, 63(3): 122-129. Yukumoto, O. et at. (1998). Development of Tilling Robot (Part 2), Journal of the Japanese Society

ofAgricultural Machinery, 60(4): 29-36. Yukumoto, O. et at. (1998). Development of Tilling

The overlap count of each mesh

Fig. 6. The percentage of overlap area and the work

Robot (Part 3), Journal of the Japanese Society

trace of the unmanned operation

ofAgricultural Machinery, 60(5): 53-61. Yukumoto, 0 (1999). Text for GPS Symposium 1999, Japan Institute of Navigation,

The height of each field surface was also investigated to evaluate the leveling performance of each operation. In the manual operation 2, the field

pp.153-163 . Yukumoto, O . et at. Agricultural Agricultural 107-114.

was well treated because the operator adj usted the height of the implement (drive harrow) and changed the velocity ofthe vehicle carefully. To execute soil paddling operation more efficiently and accurately, it is necessary to research the optimum path planning for the unmanned operation, and to develop the hardware system that can control the harrowing level according to the surface of the field.

208

(2000). Robotization of

Vehicles Research

(Part 2), Quarterly,

Japan 34(2):