Optimum Design and FEA of a Hybrid Parallel-deployable

Structure-based 3-DOF Multi-gripper Translational Robot for Field

Pot Seedlings Transplanting

Samy F. M. Assal

1,2 a

and Isaac Ndawula

Department of Mechatronics and Robotics Engineering,

Egypt – Japan University of Science and Technology (EJUST), Egypt

On leave: Department of Production Engineering and Mechanical Design,

Faculty of Engineering, Tanta University, Egypt

Keywords: Transplanting Robot, Multi-gripper, Optimum Design, Pot Seedlings Transplanting, Hybrid

Parallel-Deployable Structure.

Abstract: Pot seedlings transplanting is an activity in the agricultural production industry. In its manual level, it is a

time consuming, labour intensive, costly activity with low transplanting rate, uneven plant distribution and

low degree of accuracy. So, in this paper, a novel partially decoupled 3-DOF multi-gripper pot seedlings

transplanting robot is proposed to be used in the open agricultural field to increase the transplanting rate.

The proposed robot is composed of two identical 2-DOF Diamond Delta robots, 1-DOF scissor mechanism

and belt conveyor. Delta robot is a high speed parallel robot that is used to control the grippers in the X-Z

plane while the scissor mechanism is a deployable structure that is worked in the multi-gripper and used to

control the grippers in Y direction. Different kinematic and design aspects are considered; namely, the

kinematic analysis and the optimum design as well as the finite element analysis in the most critical loading

configuration are carried out. A unified frame work for the optimum dimensional synthesis for a prescribed

workspace with force transmission and singularity avoidance constraints is developed for the optimal

dimensions of the design parameters. The proposed robot is shown to have high transplanting rate and is

safe in terms of stress and deformation.

https://orcid.org/0000-0002-7997-4363

1 INTRODUCTION

Transplanting is a crucial agricultural activity which

involves the transfer of seedlings from their raising

medium to the growing medium which is either in an

open field or prepared beds under a greenhouse. It is

carried out from the high dense trays to low dense

ones in green house or to low dense distribution in

the open agriculture field. The seedlings are

classified as bare-root, plug and pot seedlings.

Vegetable seedling transplanting, the pot seedling

one, is one of major activities in vegetable

production. It is still in the manual level featured as

a time consuming, labour intensive, costly and

inefficient task. Robotic transplanting as a special

transplanting mechanization method is a remedy for

such problems. Four types of robotic and automated

transplanters have been developed for such

agriculture activity in literature; namely, robotic arm

type, door frame type, automated transplanters for

greenhouse and automated transplanters for open

field in which walk behind type transplanter

undergoes. Since the former type has been

developed mostly in green house, it leaves the open

field robotic transplanting problems unsolved.

Different robotic arm type transplanters have

been developed for greenhouse. For instance, a 5-

DOF robotic manipulator for transplanting pot

pepper seedlings was developed in greenhouse

(Hwang et al, 1986). It consisted of a gripper, pot-

type mechanical planter and 8-bit microcomputer. It

picks the seedling, transfers it and drops it in a

guided hole of the mechanical planter. One seedling

is fetched per transplanting cycle and a transplanting

rate of 6 plants/min was recorded. A feasibility study

Assal, S. and Ndawula, I.

Optimum Design and FEA of a Hybrid Parallel-deployable Structure-based 3-DOF Multi-gripper Translational Robot for Field Pot Seedlings Transplanting.

DOI: 10.5220/0007833500680077

In Proceedings of the 16th International Conference on Informatics in Control, Automation and Robotics (ICINCO 2019), pages 68-77

ISBN: 978-989-758-380-3

and a simulation of using Puma 560 robot to

transplant bedding plants were performed (Kutz et

al, 1987). The robot was used to validate the model

and a transplanting productivity of 11 plants/min

was achieved with a performance of 96%. Another

feasibility study for the application of SCARA robot

in seedlings transplanting was carried out (Tmg et al,

1990). The robot was equipped with sliding needle

sensor at its gripper to ensure that each cell in the

growing tray is filled. The cyclic time of seedling

transplanting was from 2.60 to 3.25 sec and a

transplanting of 18 to 23 seedlings/min was

achieved. The performance of those serial type

manipulators is not satisfactory due to the redundant

DOF they have and their low transplanting rates. On

the other hand, the dimensional synthesis and

kinematic simulation of a 2-DOF parallel

mechanism with a pneumatic gripper for greenhouse

transplanting was studied (Hu, 2014). The

transplanting capacity was 58 seedlings/min.

Door frame type robotic transplanters for

greenhouse have been also developed. For instance,

a robotic transplanter prototype that consists of

automatic seedling feeding mechanism, a rank of

pistons, a transverse conveyor and a rotating insert

cup has been developed (Sakaue, 1996). This

transplanter can operate in both greenhouse and

open agricultural field with a productivity of 35

plants/min. A bedding plants’ robotic transplanter

that composed of a robotic manipulator with two

electrical linear motors, end-effector, a conveyor and

a vision system was developed (Ryu, 2001). The

manipulator was used to move the end-effector to

the desired working position while the vision system

was used to identify empty cells and to reduce

transplanting time with a success rate of 98%. A

vegetable transplanting robot that consists of pot

moving conveyor, planting pot conveyor, cell tray

moving conveyor, transplanting device and fingers

was developed in (Kang, 2012). The transplanting

capacity of the developed robot was 2800 pots per

hour and the rate of success was 99%. The main

demerits of door frame structure robotic

transplanters are the very huge size machine, work

only in greenhouse and low transplanting rate.

Moreover, automated transplanters for

greenhouse have been developed. For example,

automatic transplanter for plug seedling that

includes manipulator (a gantry-gate type arm),

conveyor system for plug tray, flowerpots and four

end-effectors was developed (Tian et al, 2010). The

cycle time for successful transplanting is from 1.5 to

2 sec/seedling, and the transplanting productivity is

from 1800 to 2400 seedlings/hr. A fully automated

greenhouse mechanical transplanter for potted

tomato seedlings was presented (Jin et al, 2019). It is

composed of a seedling supply mechanism, a

picking mechanism composed with a gear-rod

component and an eccentric-disk parallelogram

planting part. The transplanting speed was between

60 and 90 seedlings/ min. A vegetable seedlings

automatic conveying system was design for

greenhouse application (Jin et al, 2018). It consisted

of a tank wheel, storage seedlings mechanism,

seedlings tray and hanging cup. The results showed

success rate of 97.91% for taking an individual

seedling.

Furthermore, rather than developing automated

transplanters for greenhouse, a swing seedling pick

up device for automatic precise field transplanter

was designed and tested in field (Han et al, 1015). It

consisted of an oscillating guide linkage mechanism

and globoidal cam mechanism and two grippers. The

transplanting productivity was 70 seedlings/min. An

intelligent transplanting system for pot seedlings in

field was design and implemented (Xin et al, 2018).

It consisted of fixed-axis gear train and five bar as

picking mechanism, conveying system, eccentric

disc as planting mechanism, electric sensor for

detection and identification of missing and

unhealthy seedlings, the position sensor, the control

system and stepper motors. The system was tested

and the productivity was found to be 90 plants/min.

Also, automated walk behind type transplanters have

been developed for open field. Three models of

riding type automated vegetable transplanters were

developed (Tsuga, 2000). These prototypes consisted

of 2 rows transplanting mechanism working

simultaneously at productive frequency of 60

plants/row/min. A fully automated walk behind type

hand tractor powered vegetable transplanter for

paper pot seedlings was developed (Kumar and

Raheman, 2011). It consisted of two sets of feeding

conveyor, metering conveyor, seedling drop tube,

furrower opener, soil covering device, an automatic

feeding mechanism, a depth adjustment wheel and

hitching arrangement. The transplanting rate was 32

seedlings/min with an efficiency of 85%. A two-row

vegetable automated transplanter for transplanting

pot seedlings in the field was developed (Dihingia et

al, 2018). The transplanter was hitched to the walk-

behind hand controlled tractor as the main source of

power. The transplanting productivity of this

transplanter was evaluated in the field and found to

be 31 seedlings/min.

Form the aforementioned literature; it is

considerably to highlight that, the introduced

transplanters have low transplanting rate due to large

Optimum Design and FEA of a Hybrid Parallel-deployable Structure-based 3-DOF Multi-gripper Translational Robot for Field Pot

Seedlings Transplanting

cyclic time of the transplanting as well as the plant-

by-plant manner of carrying out the transplanting

task; specifically, the transplanting of one seedling

at a time. So, in this paper, as an extension of our

work (Ndawula et al, 2018), a row-by-row pot

seedling transplanter robot with low cyclic time is

proposed to achieve high transplanting rate. It has

multi grippers with 3-DOF translational motion. Its

structure permits seedlings transplanting from high

dense seedlings in a tray to low dense, equally

spaced seedlings in the open agriculture field.

The rest of the paper is organized as follows. The

description of the components of the proposed

transplanter robot and its working principle are

presented in Section 2. The kinematics, differential

kinematics, singularity and workspace analyses are

discussed in Section 3. The optimal dimensional

synthesis is developed in Section 4. The finite

element analysis (FEA) of the robot in the most

critical loading condition is carried out in Section 5.

Simulation results are presented in Section 6.

Finally, conclusion is drawn in Section 7

2 DEVICE STRUCTURE AND

WORKING PRINCIPLE

2.1 Device Structure

The proposed 3-DOF translational robot for row-by-

row pot seedlings transplanting in the open

agriculture field consists of three main parts as

shown in Fig. 1. Two of which are two identical 2-

DOF Diamond Delta robots positioned in two apart

X-Z planes with respect to a fixed frame. Basically,

the Diamond Delta is a 2-DOF translational planar

parallel robot with fixed and moving platforms

connected by two limbs. Each limb is composed of

active and passive links. The moving platform of

Delta robot is called end-effector. The two fixed

platforms of those two Delta robots are assembled in

the fixed frame of the proposed device such that they

can counter translate in Y-direction using two guide

way shafts that are used to ensure the smooth

translational motion. A half-length right and half-

length left hand ball screw (bidirectional ball screw),

those two symmetrically placed Delta robots in Y

direction to come close or apart from each other

depending on the desired motion. This ball screw is

meshed with two nuts fixed to the two translating

platforms of those Delta robots. The active links that

are actively connected to the translating platforms of

Fixed frame

Two Delta robots

Two servomotors to

drive Delta robots

End-effectors

of Delta robots

Two sets of

multi-scissor

Multi-bracket

frames

Multi-gripper

to be fixed

Belt

conveyer

Servomotor to Drive

the ball screw

(a) Main components of the proposed transplanter.

Spline shafts

Guide way shafts

ball Screw

Fixed Frame

Diamond Delta robot

Translating base of

Delta robot

(b) Top right magnified portion.

Figure 1: The proposed 3-DOF translational robotic

transplanter.

those Delta robots are connected by two spline

shafts which are coupled to two servo motors

mounted at the top of the fixed frame as illustrated

in Fig. 1. Those two spline shafts are used to

mechanically synchronize the motions of the two

end-effectors of the two Delta robots.

The third part of the proposed device consists of

1-DOF double planar foldable scissor mechanisms,

which works in the multi-gripper, positioned in two

apart Y-Z planes shown in Fig. 2. Basically, the

scissor mechanism is a deployable structure with 1

DOF. The ends of the scissor mechanisms are fixed

to the moving end-effectors of the two identical

planar Delta robots to work as multi grippers. Those

double planar foldable scissor mechanisms are

connected together by multi-rectangular frames with

ICINCO 2019 - 16th International Conference on Informatics in Control, Automation and Robotics

revolute joints and sliding grooves as shown by the

3D SolidWorks model in Fig. 2. The rectangular

frames are used to keep fixed orientation of the

grippers and thus restrict any orientation of the

seedling grippers in any direction. This scissor

mechanism keeps equal spacing between the

grippers from unfolded configuration to the folded

one. Thus, it allows suitable spacing in the picking

up and transplanting of the seedlings. Therefore, this

scissor mechanism allows row-by-row pot seedlings

transplanting as many as grippers. For instance, for

the standard 6×12 tray, the proposed robot can

equipped with 6 grippers Therefore, the grippers

have decoupled 3-DOF translational motion;

namely, 2-DOF translational motion in X-Z plane

accomplished by the parallel robots (Diamond Delta

robots) and 1-DOF translational motion in Y-

direction achieved by the scissor mechanism, the

deployable one.

Two sets of

multi-scissor

Multi-bracket

frames

Grippers

to be fixed

Figure 2: Two identical sets of foldable multi-scissor with

multi-bracket frame.

A pot seedlings belt conveyor is another part of

the device as illustrated in Fig. 1. This belt conveyor

is used to carry pot seedlings tray to the appropriate

position for picking up. The multi-gripper end-

effector picks up pot seedlings from growing tray,

holds, transfers and releases them at the time of

transplanting. The proposed robot that is carried

over a wheeled frame is hitched to a tractor as a

source of power and its speed is synchronized with

transplanting frequency of the robot.

2.2 Working Principle

The pot seedlings transplanting cycle in the field by

the proposed robot occurs in three stages namely;

fetching, transplanting and returning phases. The

robot starts from its initial position P

, then follows

the path P

-P

in X-Z plane while closing

gripper's spacing in Y-direction to suite the seedlings

spacing on the nursery tray during seedlings

fetching, as depicted in Fig. 3. At P

, it picks 6

seedlings in a row of the tray at once by the 6

grippers and holds them. In the transplanting phase,

the robot follows the path P

-P

while opening

the scissor mechanism in Y-direction to suite the

planting space in the open agriculture field. At P

, it

releases the seedlings and drops them by gravity in

the vertical orientation that is achieved by the multi-

bracket frames. Then, in the returning phase, it

returns to its original position P

following the path

-P

. This cyclic process is repeated over and over

again until the operation is done. The belt conveyor

ensures the steady supply of pot seedlings at the

appropriate picking up position and the tractor

controls column spacing of the seedlings through

synchronization of motion between the tractor and

proposed robot. Note that, six furrows can be opened

in the agriculture field by 6 teeth shovel type furrow

opener while covering the seedlings with sufficient

soil and pressing the soil around the seedlings can be

done by six pairs of press wheels tilted outside at the

top, which is out of scope. The furrow opening as

well as covering and pressing the soil around the

seedlings should be synchronized with transplanting

process.

, W

Seedlings

Belt conveyer

Wheeled carrier

frame

Agriculture

field ground

Hitched

tractor

Figure 3: Seedlings transplanting cycle.

3 KINEMATIC ANALYSES

The main components of the proposed robotic

transplanter to be kinematically analysed are the two

2-DOF planar Diamond Delta robots. Delta robot is

a well-known positioning planar parallel

manipulator that consists of a base frame and a

moving frame (end-effector) as shown in Fig. 4.

Those two frames are connected together by two

mirror symmetrical kinematic chains. Each

kinematic chain consists of two parallelograms

which represent the proximal and distal links that are

connected by revolute joints. The proximal link is

activated by servo motor that is fixed to the fixed

frame of the device through the spline shaft, while

Optimum Design and FEA of a Hybrid Parallel-deployable Structure-based 3-DOF Multi-gripper Translational Robot for Field Pot

Seedlings Transplanting

the distal link is passive. Due to the equivalence of

length of the inner and outer links of each

parallelogram, Delta robot can be simplified as a 5-

bar mechanism as illustrated in Fig. 4(b). The

inverse kinematic of this Delta robot is of interest

since it is required for the positioning control and the

trajectory planning.

3.1 Inverse Kinematics

The inverse kinematics of Delta robot is to obtain

the joint angle variables



for i=1, 2 for the given

end-effector position P(x, z). For this sake, the loop

closure equation of the two closed loop kinematic

chains depicted in Fig. 4(b) are given as follows:

iii

lle wuep



for i=1, 2 (1)

where

 

zxp

is the position vector of the

end-effector; e

is a unit vector directed from O to O

while 2e is the centre distance between the two

spline shafts that connected the active links to the

two servo motors; l

is the proximal (active) link

length while u

is a unit vector directed from O

to A

given as

 

sincos

iii



u

, l

is the distal

(passive) link length, while w

is a unit vector

directed from A

to P given as

 

sincos

iii



w

. From (1), the active joint

angle variables can be obtained in terms of the end-

effector position as follows (Huang et al, 2004).

iiii

MNLiL







222

)sgn(

arctan2



for i=1, 2 (2)

where

zlL

2

 

eixlM

)sgn(2 

and

xeillezxN

)sgn(2

222



, in

which sgn(i)=1 for i=1, otherwise sgn(i)=-1

3.2 Differential Kinematics

Differentiating the loop closure equation (1) with

respect to time yields velocity relation as the

following

iiii

QlQl wuv





2211



for i=1, 2 (3)

Inner proximal

link

Outer proximal

link

Inner distal

link

Outer distal

link

Distal

link l

Proximal

link l

Moving Frame

(end-effector)

Translating

base frame

Guide way shafts

to be fixed

Spline shafts

to be fixed

Ball screw

nut

(a) SolidWork model

P (x,z)

(b) 5-bar simplified model of Delta robot

Figure 4: The 2-DOF planar Diamond Delta robot in X-Z

plane.

where

















zxv

is the Delta robot end-effector

linear velocity vector in the X-Z Cartesian space,

















is a skew symmetric matrix. Pre-

multiplying (3) by

, the passive joint angles

velocities





for i=1, 2 can be eliminated and the

result can be written in a matrix form as follows





1112



JlJ v

(4)

ICINCO 2019 - 16th International Conference on Informatics in Control, Automation and Robotics

where J

and J

are the direct and inverse Jacobian

matrices, respectively given as follows:















(5)

 

212

wwJ

(6)

On the other side, the linear velocities of the

grippers in the Y direction are related to the angular

velocity of the ball screw. For instance, the linear

velocities of gripper G

and G

shown in Fig. 2 are

given as follows:









(7)

where L

and





are the lead of the ball screw and

its angular velocity. Also, the linear velocities in Y

direction of the other grippers based on the time

derivatives of the point displacements on the

deployable scissor mechanism can be obtained as

G1GG

vvv 

and

G1GG

vvv 

3.3 Singularity Analysis and

Transmission Angle

The singularity analysis is a critical issue in parallel

robots since the robot loses its controllability in

singular configurations. To carry out such analysis,

the singularity of Jacobian matrices must be studied.

The direct kinematic singularity (second type)

occurs whenever

while inverse kinematic

singularity (first type) occurs whenever

The third type of singularity which is the combined

singularity occurs whenever

and

Examining those Jacobian matrices reveals that

when

is along or coincident with

for i=1, 2,

direct kinematic singularities take place, while when

coincides with

, inverse kinematic

singularities occur.

It is considerably to note that, for Delta robot,

the direct kinematic singularity is related to the

transmission angle



for i=1, 2 shown in Fig. 4(b).

Namely, four singular configurations occur for



equals to zero or π for i=1, 2. From the geometry of

Fig. 4(b), the force transmission angle



can be

obtained as follows

 















)sgn(

arccos zxeill



for i=1, 2 (8)

In order to have high force transmission, the

transmission angle







min

where



35





and

),min(

min2min1min





(Huang et al, 2004).

3.4 Workspace Analysis

Two different types of workspaces are considered

here, the achievable workspace and the objective

one. The achievable workspace is based on the Delta

robot construction while the objective workspace is

based on the required transplanting task.

3.4.1 Achievable Workspace

The achievable workspace of the translational Delta

robot in the X-Z plane is defined as the region in this

space that can be reached by its end-effector. Carful

inspection of the inverse kinematic solution (2)

reveals that, the condition

0

for i=1, 2, should

be hold in order to have real solution, where

  

4 llZlZF

iiii



for i=1, 2 (9)

in which

 

xeillezxZ

)sgn(2

222



(10)

It can be proven that, (9) represents the equation of

two concentric circles in X-Z plane, which

represents the boundary of the achievable workspace

as shown in Fig. 5.

3.4.2 Objective Workspace

Based on the transplanting cycle discussed above,

the end-effector path during this cycle can be

described as P

-P

from which the

regular objective workspace can be considered as a

rectangle with vertices of

),(W

iii

for i=1,..,4 as

shown in Fig. 3. From the ergonomics point of view,

the vertices W

(-40,-60), W

(-40,-115), W

(50, -

115) and W

(50, -60) in cm shown in Fig. 3 are

Optimum Design and FEA of a Hybrid Parallel-deployable Structure-based 3-DOF Multi-gripper Translational Robot for Field Pot

Seedlings Transplanting

considered. Figure 5 illustrates the overlapped of the

objective workspace and the achievable workspace.

Achievable

workspace

Objective

workspace

Agriculture

field ground

Figure 5: The achievable and the objective workspaces.

4 OPTIMAL DIMENSIONAL

SYNTHESIS

The optimal dimensional synthesis is applied here

for the Delta robot to obtain the optimal dimensions

of its design parameters. Different objective

functions either local or global for parallel

manipulators are proposed in literature (Huang, T.,

et al 2004; Assal, S. F. M., 2017). Here, since the

objective workspace of the proposed device is a

specific workspace of a rectangle with known

vertices, then the optimal dimensional synthesis is

carried out here based on satisfying a prescribed

workspace.

The objective function is a function that

describes the achievable workspace that includes the

objective workspace. Since the achievable

workspace is given in (10) as

0

for i=1, 2,

while the objective workspace is given by vertices

points

),(W

jjj

for j=1,…,4, then the objective

function based on the power of point method [Laribi,

M.A., et al 2007] is given as follows

 

 



 

j i

jif

PWFO

(11)

in which

 

ellP ,,



is the design parameters

space.

Additionally, some kinematic constraints should

be achieved; namely, high force transmission and

avoiding forward kinematic singularities should be

satisfied. In order to have high force transmission,

then







min

where

),min(

min2min1min





From (8) this condition is equivalent to

0 cos2C



 2

K- llll



(12)

On the other hand, the forward kinematic

singularities avoidance that is related to the force

transmission angle can be achieved as





max

where

),max(

max2max1max





. Carful inspection

of (8) reveals that this condition is equivalent to the

following condition

   

 

cos2C



e-hK- llll



(13)

Furthermore, in order to have enough space for

mounting the two servo motors, the following

constraint should be hold

0cm10

 eC

(14)

In summary, the optimal dimensional synthesis is

optimize the function O

(P) subjected to the

constraints (12-14) to obtain the optimal

 



 ellP ,,

. The genetic algorithm (GA)

toolbox of MATLAB is used to solve such

optimization problem.

5 FINITE ELEMENT ANALYSIS

The finite element analysis (FEA) is used to carry

out structural analysis. Structural analysis is the

measure of how physical structure of a device and its

components resist the deformation under certain

loading conditions. The FEA of the proposed robot

is carried out using ANSYS 17.2 version to

investigate the effect of applied loads on the

proposed robot at its worst case loading

configuration. The configuration at which the

proposed robot inserts its grippers into the growing

tray to pick up the seedlings is the worst load

configuration. This configuration takes place during

the fetching phase and exactly at point P

. At this

configuration, the inserting force per each gripper is

14 N, while the picking up force is 1 N per seedling

(Kang et al, 2012). The obtained results from this

analysis are then assessed to verify the suitability

and the safety of the proposed robotic structure for

the application. The steps for performing structural

ICINCO 2019 - 16th International Conference on Informatics in Control, Automation and Robotics

analysis using ANSYS for the proposed robot are

described as follows.

First, the Solid Works model of the proposed

transplanter is exported into ANSYS Workbench.

After having the proposed transplanter geometry

defined, the Aluminium alloy material is selected

and assigned to all parts of the multi-gripper scissor

mechanism and the links of the two Diamond Delta

robots, while Steel material is assigned to the rest of

the components as illustrated in Table 1. The contact

joints are assigned as well at this stage.

The adaptive meshing of the virtual prototype is

then carried out. So, several trials are performed to

improve the accuracy of the final results. After

several trials, a mesh size of 10 mm is chosen and

used. This meshing size gives better meshed

structure with less computational time and cost than

those of the values greater than or below 10 mm.

The number of nodes and elements generated in this

case are 643830 and 356630, respectively.

After the adaptive meshing, the boundary

conditions are then applied. Namely, the

bidirectional ball screw and sliders are fixed at both

ends. Furthermore, a constant insertion force of 14 N

in positive Z-direction is assigned to each of the 6

grippers that fixed at the scissor mechanism for the

worst case loading configuration.

After applying the boundary conditions and

loads, the deformations in X, Y, and Z- directions,

total deformation and Von Mises Stress analyses are

carried out.

Table 1: Material properties.

Material

Young’s

Modulus

Poisson’s

ratio

Density

Steel

200 GPa

0.3

7850kg/m3

Aluminium

71 GPa

0.33

2700kg/m3

6 RESULTS AND DISCUSSION

The optimal dimensional synthesis stage is carried

out using the GA toolbox of MATLAB and yields

= 400 mm, l

= 921 mm and e= 120 mm. Based on

those link dimensions, the 3D model of the proposed

robot is developed using Solid Works to be imported

in ANSYS software for structure analysis as

described in Section 5.

The FEA of the proposed transplanter is carried

out using ANSYS at the worst case loading

configuration and the results are presented here. The

meshing of the constrained virtual prototype of the

proposed transplanter is illustrated in Fig. 6. The

deformations in X, Y and Z directions are depicted

in Figs 7, 8 and 9. It can be noted that, the maximum

deformations in X, Y and Z directions are 0.044

mm, 0.0139 mm and 0.1482 mm, respectively.

Additionally, the maximum total deformation of

0.1866 mm occurs in the middle of the scissor

mechanism as illustrated in Fig. 10, which is quite

acceptable.

Furthermore, the Von Mises stress is carried out

to check whether the proposed transplanter is safe

under the worst case loading condition. The results

of Von Mises stress is shown in Fig.11. It can be

pointed out that, the maximum Von Mises stress

occurs at the ends of bidirectional ball screw and

sliders. The maximum Von Mises stress is recorded

as 43.186 MPa. Since the maximum allowable

strength of the Aluminium alloy and the Steel

materials considered for the transplanter parts are

280 MPa and 460 MPa, respectively, then the

transplanter is shown to be safe with high factor of

safety.

Figure 6: ANSYS meshing of the proposed transplanter.

Figure 7: Deformation in X-direction.

Optimum Design and FEA of a Hybrid Parallel-deployable Structure-based 3-DOF Multi-gripper Translational Robot for Field Pot

Seedlings Transplanting

Figure 8: Deformation in Y-direction.

Figure 9: Deformation in Z-direction.

Figure 10: Total deformation.

Figure 11: Von Mises stresses.

7 CONCLUSIONS

A novel multi-gripper 3-DOF translational robot for

row-by-row pot seedlings transplanting in the open

agriculture field is introduced. It is based on hybrid

parallel-deployable structure that enables seedlings

transplanting from high dense distribution in a tray

to low dense distribution in the open agriculture

field in a row-by-row manner to increase the

transplanting rate. The optimum design as well as

the finite element analysis in the most critical

loading configuration of the proposed transplanter is

carried out. The FEA results prove that the proposed

robot is safe in terms of stresses and deformations.

Dynamic analysis and controller design as well as

prototype fabrication are the future extension of this

work.

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