Development of a Mechanism for transplanting rice seedling

1. Development of a mechanism for
transplanting rice seedling
Edathiparambil Vareed Thomas
Presented by:
Priyabrata Pradhan(10AG61R08)

2. 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.

3. 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.

4. Rough sketch
1. transmission case
2. engine
3. ground wheel shaft
4. side clutch
5. planter crank shaft
6. handle
7. finger assembly
8. crank
9. couple link
10.tray
11.seedling pusher
12.ground wheel
13.fuel tank
14.float.
Sketch of self-propelled rice transplanter incorporating the new mechanism

5.  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.

6. 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

7. 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.

8. 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.

9. Contd…
1. Determination of movability of the linkage
Grashof 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; and
q= length of other remaining link.

10. Contd…
2. Calculation of coupler angle Φ
Summing 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.

11. 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
   
                 
          
 
   
( ) ( ) f    
        
 
( ) ( ) f    
        
 
……….(6)
f f
1 1
k 
1 k
1 2 1 1 1
k 
1 k
2 2 2 2 2
1 2
f
f f f
f f
1 k 1 k 1 k 1 k
1 1 2 2 1
1 2
f f
2 k 1 k 2 k 1 k
1 1 2 2 2
1 2
1
2 1
1
f
L sin

  

1
3 2
2
f
L sin

  

2
2 1
1
f
L cos

 

2
3 1
2
f
L cos

 


12. Contd…
Substituting these partial derivatives in Eqn (5), we get
………………(7)
  
1
      
2
……………………..……(8)
…………(9)

13. 3. Calculation of coordinates of F in space
…………(10)
Where
xF =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.

14. 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 completed
9. 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.

15. 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

16. 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

17. 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

18. 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.

19. 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 between
The 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.

20. 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.

21. Contd…
 Path of motion of the finger relative
to the ground

22. 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.

25. 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.

26. Thank you