Development of a mechanism for transplanting rice seedling

Edathiparambil Vareed Thomas

Presented by:Priyabrata Pradhan(10AG61R08)

Introduction

India is predominantly an agricultural country with rice as one of its main food crop.

Its produces about 80 million tons rice annually, which is about 22% of the world rice production.

Culturally, transplanting of young seedlings is preferred over direct seeding for better yield and better crop management practices.

But this operation requires large amount of manpower (about 400 man-hour/ha) and task is very laborious involving working in a stooping posture and moving in muddy field.

Hence, this is considered as an activity that needs mechanisation.

Objectives

To develop a mechanism for transplanting rice seedlings using the method of analytical synthesis.

To develop a four row self-propelled transplanter and an optimized-planting finger using the above mechanism.

Rough sketch

1.transmission case2.engine3.ground wheel shaft4.side clutch5.planter crank shaft6.handle7.finger assembly8.crank9.couple link10.tray11.seedling pusher12.ground wheel13.fuel tank14.float.

Sketch of self-propelled rice transplanter incorporating the new mechanism

The seedlings are stacked in a tray. A mechanical finger operated by a suitable mechanism pick up seedlings

from the tray. Seedling are carried to the soil and placed at proper depth in a nearly

upright posture. The mechanical finger comes back to its original position so that it can

repeat the process. The machine moves forward to the next location for planting.

Methodology 1. Output motion requirements of the proposed planting mechanism

The seedlings are to be picked up from a tray which is provided with slots to facilitate an uninterrupted movement of the fingers.

During the downward travel, the fingers pick up the seedlings, carry these to the soil and plant at a desired depth at a nearly upright position.

During the return motion the fingers are required to move without interfering with the seedlings that are planted as well as arranged in the tray. Thus, the path of forward travel and the path of return travel shall be different.

The finger must not interfere with other members of the machine during its motion.

Panting cycle are continuous as the machine moves with a constant forward speed of travel

2. Linkage parameters for design

Length of crank, L1.

Length of coupler, L2.

Length of follower, L3.

Length of fixed link, L4.

Length of coupler extension, LF. Angle of coupler extension, True size of the linkage. Angle of fixed link with the horizontal, Speed of travel.

3. Analysis of the Linkage

The analysis involves

Determination of movability of the linkage

Calculation of coupler angle Calculation of coordinates of F in space.

Contd…

1. Determination of movability of the linkageGrashof condition is used to determine the movability of the four-bar loop ABCD. Crank AB is able to make full rotation if the Grashof condition is satisfied.

s+l ≤ p+q ……………….(1)Where

s= length of shortest link;l= length of longest link;p= length of one remaining link; andq= length of other remaining link.

Contd…

2. Calculation of coupler angle ΦSumming x and y components of link vectors, …………(2)Let f1 and f2 are functions defined as

………(3)

This is a set of non-linear equations with two unknowns, Φ1 andΦ2.

This can be solved iteratively using the Newton’s method.Φk+1=Φk-J-1(Φk).f(Φk) ……………..(4)

where k=Order of iteration k=0,1,2,….. J-1 =Inverse of the Jacobian matrix J.

Contd….

Or Φk+1-Φk =-J-1(Φk).f(Φk)Or J(Φk)(Φk+1-Φk ) =-f(Φk)Or J(Φk)(Φk+1-Φk ) =-f(Φk) ……………(5)

Or

Or

……….(6)

1 1

k 1 k1 2 1 1 1

k 1 k2 2 2 2 2

1 2

f f

f

f f f

k 1 k k 1 k1 11 1 2 2 1

1 2

f f( ) ( ) f

k 1 k k 1 k2 21 1 2 2 2

1 2

f f( ) ( ) f

12 1

1

fL sin

13 2

2

fL sin

22 1

1

fL cos

23 1

2

fL cos

Contd…

Substituting these partial derivatives in Eqn (5), we get

………………(7)

1

2

…………(9)

……………………..……(8)

3. Calculation of coordinates of F in space

…………(10)

WherexF =x-coordinate of coupler point F;

yF =y-coordinate of coupler point F;

LF = length of coupler extension; and

ψ = included angle between coupler and coupler extension.

Computational procedure for calculation and display of the path of motion of the finger

1. The link dimensions L1,L2,L3,L4,LF and ψ are read.2. The movability of the linkage is checked using Eqn(1).3. For a triangular configuration of linkage, values of θ and δ are calculated

using Eqn(9).4. Value of Φ1 and Φ2 for the above value of θ are calculated using Eqn(8).5. Value of θ is incremented by a small value, say 1°.6. Starting values of Φ1 and Φ2 at the above value of θ are estimated

approximately.7. Accurate values of Φ1 and Φ2 are calculated using the iterative Eqn (7). The

set of values θ,Φ1 and Φ2 are stored.8. Step 5-7 are reapted until full rotation of the crank is completed9. Using Eqn (10) the coordinates(xF, yF ) of finger are calculated for all the

stored values of θ andΦ1. 10. The values (xF, yF ) are plotted on an XY space on computer screen. The

points (xF, yF ) corresponding to adjacent values of θ are joined by lines. This gives the path of motion of the finger.

4. Choice of link dimensions in stage 1

In this stage the linkage is synthesized using relative link length. The forward speed of travel and the inclination of fixed link with

the horizontal is neglected. The link dimensions are varied in a wide range and then the

ranges are narrowed down as the synthesis proceed. Several rounds are required to finally arrive at the best

combination of link dimensions

Contd…

A point of planting can be located at L where, the finger goes up to a desired depth in the soil and retraces at about 180° sharply.

Seedling could be picked up for transplanting at K where, the finger movement is downward.

There is a separate path of return motion of the finger from the point of planting to the point of picking up.

The vertical distance between K and L represents the clearance available for the standing seedlings

Second and third stages

In this stage, the forward speed of travel of the machine is incorporated.

An angle of inclination to the fixed link is also decided.

Effect of speed of travel of the machine on the path of motion of the finger

Effect of link dimensions in bringing a change in path

With a small change in link dimensions a sharp point can be obtained again at L.

A small change in coupler extension angle ψ will be sufficient to give a sharp point at L again.

At larger values of ψ a rounded path is obtained. At smaller values additional loop is formed at L.

Effect of angle of inclination of the fixed link ß

The crank pin passes through a lowermost point E during its rotation.

We have to arrange the mechanism Such that the vertical distance betweenThe lowermost point of crank pin and the point of planting will be sufficient.

In order to select a suitable value of ß at actual forward speed of travel, three values of ß, namely -

20.0,-24.5 and -29.0° are chosen for study in this stage.

Contd…

Path of motion of the finger during planting by the mechanism with different angle of orientation of the fixed link and at different angles of the coupler link extension and with optimized forward speed of travel.

Contd…

Path of motion of the finger relative to the ground

Conclusions

The CAD for the synthesis of a linkage mechanism is an elaborate but effective process to attain a near perfect simulation of manual transplanting system.

The fixed fork type fingers traversed the path in the form of a loop as per theoretical design and these are simple in construction and easy to operate.

Fuel consumption is less because of a smaller engine. It can be further reduced by reducing the weight of the machine, using lighter materials in frame, transmission system and float.

The output of the machine can be further improved by increasing the number of rows.

The standing posture involved in machine transplanting is more comfortable compared to the stooping posture of manual system.

References

Thomas E V. Development of a mechanism for transplanting rice seedlings. Mechanism and machine Theory 37(2002) 395-410

Kepner R. A.; Bainer Roy; Barger E.L. Principles of farm machinery; crop planting 233-234.

J.E. Shigley, Kinematic Analysis of Mechanisms, second edition, McGraw-Hill, 1969.

L. Zimmerman, Mechanization of Motion, Wiley, New York, 1961.

Thank you