optimization of structural base frame for robot mounting using fea analysis · 2019-05-07 ·...

Optimization of Structural Base Frame for Robot

Mounting Using FEA Analysis Kaushalkumar Pansuriya

#1, Jatinkumar Patel

*2, Vipulkumar Rokad

*3

#PG student Mechanical Department, Kalol Institute of Technology and Research Centre *Professor Mechanical Department,Kalol Institute of Technology and Research Centre

Kalol, Gujarat, India

[email protected]

[email protected]

[email protected]

Abstract— This articledeals with modifications in thedesign and analysis of the structural base frame for mounting of articulated

robot using Finite Element Analysis (FEA) method.The base frame is important for mounting of the articulated robot to perform its

required tasks effectively under certain loading conditions within certain period of time.If the structural base frame is overdesigned

or under designed then many types of problem can take place like, vibrations, fatigue failures, high instability, more material

consumption, higher fabrication cost.The 3D model is prepared using SOLIDWORKS software and the static, dynamic and modal

analysisis done using simulation software ANSYS. The design verification is done using analytical method.The optimization is done

with the help of specified method of structural optimization in terms of material utilization and strength.This process helps in finding

and validating the optimized design of the structural base frame for articulated robot mounting.

Keywords—CAD, Modification, Articulated Robot, Structural base frame, Structural Optimization, FEA.

I. INTRODUCTION

Now a days, Automation is vastly growing field in the industry. Automation is a combination of technologies that results in

operation of systems and machines without significant human involvement and achieves performance superior than manual

operation. In most of the industrial automation projects robots are used as to come up with to solutions like, machining, pick

&place, etc. Robots require specialized supporting structure to accurately work during the operations. The main supportive

member for the robot is the base of the robot on which it is mounted for functioning. It gives support as well as stabilization to

the robot. Robot mounting structural base frame and robot platformsmade with precision are standard capital equipment and are

required in today’s high technology manufacturing companies.

Most of the robots are designed for specific functions within a custom environment for performing elevated tasks. Each robot

usually requires its own custom manufactured robot structural base frame, which is custom built to size and strength in order to

ensure immobility while firmly supporting the robot.The robot base is the substructure of any robot, which, under each kind of

loads of the robot, should keep motion of robot stabilized.

Because of the importance of the structural base frame, design of structural base frame must be optimized in terms of

stability, strength, weight andmaterial utilization using structural optimization method.Therefore, it is must to enhance the

stability and reliability of the Structural base frame.

II. PROBLEM IDENTIFICATION

In the existing design, the structural base frame is used for mounting KUKA robot KR-8 R2010, which is assigned for the

application of pick & place. Now, the design validation is necessary for the effective working of the robot. So, when the

analytical design validation is done, it is found out that the existing structural base frame is actually having more than enough

strength and excessive material utilization is done. That directly affects the cost of material, cost of fabrication and weight

adaption along with lead time.Due to excessive material usage the structural base frame weight is 225.5kg.

JASC: Journal of Applied Science and Computations

Volume VI, Issue V, May/2019

ISSN NO: 1076-5131

Page No:501

Fig. 1CAD Model of Existing Structural Base Frame

TABLE I

MATERIAL PROPERTIES

When the robot is mounted on the structural base frame and it is in steady condition at that time the total deformation is

0.026mm and the value of the equivalent stress is 8.70Mpa. So, the total deformation is here is very negligible. Even the stress

value is also very low, evenif we consider factor of safety 2, as compare to allowable stress limit. So, itneeds to be optimized.

So, main objective of this analysis is to redesign the model by using proper optimization method to have enough strength

and reduced material usage.

III. DESIGN AND SETUP DETAILS

The existing structural base frame design is overdesigned and it is need to be validated using analytical method. Then the

optimization is need to be done using structural optimization method. Then for the static analysis of the final optimized

structural base frame, the total weight (Dead weight) of the robot is required.The details for the total weight of the robot is

extracted from the officially KUKA robot technical data sheet. The dynamic analysis requires maximum vertical load and

maximum circular moment, those are also extracted from the technical data sheet of robot.The natural frequency of the final

optimized base frame is found out using simulation software ANSYS and 3D model is prepared using Solidworks software.

A. Design Calculations:

The structural base frame is having number of members including vertical and horizontal members. There are some forces

acting on all the members connected through the joints. It is required to solve for these forces acting on the members of the

structural base frame. Here, the structural base frame is considered as the 3D truss and the METHOD OF JOINTS is used to

find out the forces acting in the base frame. The initial loading conditions like total weight of robot including maximum payload,

maximum vertically acting load and the maximum moment are show in below table,

TABLE II

TYPES OF LOAD ACTING ON THE BASE FRAME

Now, consider the structural base frame as the 3D truss and using the Method of Joints for solvefor the forces acting on

joints of the members of the base frame. The total force acting on the base frame is,

𝐹𝑡𝑜𝑡𝑎𝑙 = 𝐹𝑚𝑎𝑥. + 𝐹𝑏𝑎𝑠𝑒 𝑝𝑙𝑎𝑡𝑒

∴ 𝐹𝑡𝑜𝑡𝑎𝑙 = 4434 + 1138.

Material Structural Steel (S235)

Modulus of Elasticity 210GPs

Yield Strength 235 MPa

Poisson’s Ratio 0.30

Density 7850 kg/m3

Frame Weight 225.5kg

Total Weight of Robot 255 kg

Maximum Vertical Load 4434 N

Maximum Moment 2361 Nm



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∴ 𝐹𝑡𝑜𝑡𝑎𝑙 = 5572 Now, considering factor of safety = 2,

∴ 𝐹𝑡𝑜𝑡𝑎𝑙 = 5572 × 2

∴ 𝐹𝑡𝑜𝑡𝑎𝑙 = 11144 𝑁

So, the 𝐹𝑡𝑜𝑡𝑎𝑙is divided into 4 equal parts. Then the value of 𝐹𝑡𝑜𝑡𝑎𝑙 is 2786 𝑁.

Now, for solving the forces, the FBD (Free Body Diagram) of the base frame is need to be drawn as below.

Fig. 2 Free Body Diagram (FBD) of Structural Base Frame

Using the force equilibrium equations of three directions in every joint, the forces are calculated.

Force equilibrium equations as shown below,

Σ𝐹𝑋 = 0,

Σ𝐹𝑦 = 0,

Σ𝐹𝑧 = 0.

After solving for all the forces acting, using the Method of Joints for Truss, the normal stress acting on the vertical members

is found out using,

𝜎𝑛 = 𝐹𝑣𝐴

∴ 𝜎𝑛 = 27861900 ∴ 𝜎𝑛 = 1.47 𝑁𝑚𝑚2

∴ 𝜎𝑛 = 1.47 𝑀𝑃𝑎

Finding Critical load using Euler’s Column Formula, 𝑃𝑐 = 𝑛 × 𝜋2 × 𝐸 × 𝐼𝐿2

∴ 𝑃𝑐 = 0.25 × 𝜋2 × 210 × 103 × 2865833.33(650)2

∴ 𝑃𝑐 = 3514.66 𝐾𝑁



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Here, the value of the critical load is very much higher. This much of load is never going to act on frame.

Finding Bending stress value considering moments,

𝜎𝑏 = 𝑀𝑍

For the square hollow section, the value of Z is given by,

𝑍 = 𝑏4 − 𝑑46𝑏

∴ 𝜎𝑏 = 4177 × 10357316.67

∴ 𝜎𝑏 = 72.88 𝑁𝑚𝑚2

Now, for the shear stress acting on the base plate,

𝜏 = 𝐹𝑏 × 𝑡

Here, 𝜏 = 𝑎𝑙𝑙𝑜𝑤𝑎𝑏𝑙𝑒 𝑠𝑡𝑟𝑒𝑠𝑠2 ∴ 𝜏 = 8868700 × 30

∴ 𝜏 = 78.12 𝑁𝑚𝑚2

So, here it is concluded that the existing structural base frame is overdesigned in terms of excessive strength and material

utilization. So, the further optimization of the existing base frame is required,which is beneficial in terms of reduction in

material utilization and as well as cost reduction.

B. Design Optimization Method for CAD Model of Structural Base Frame:

In general, optimization is the process of getting optimal or best results from the existing one by maximizing or minimizing

the objective functions considering the constraints and design variables. Optimization of the existing structural base frame

design is need to be done using Structural Optimization Method. By using these types of optimization methods, the weight of

the of the structure can be reduced, change the shape and the size of the structure or structural members.In structural

optimization, the method of sizing optimization is very simple form of method. In this method, the objective is to optimize the

structure by adjusting the sizes of the components in the structure. The design variables are the sizes of the structural elements.

Here, for optimizing the structural base frame, Sizing method of optimization can be used.

Using this method, the cross sections areas of three different sizes in the square hollow sections are taken into account for the

optimization of the structural base frame considering the constraints and design variables like weight reduction and the strength.

All three optimized CAD models are shown below with details of their sizes of cross sections used for it.

TABLE III

OPTIMIZED FRAMES HAVING DIFFERENT CROSS SECTION

SIZES

Here, From the sizing method, the most optimized frame size is the frame having the cross-section size 60x60x5mm. It is

having lowest weight and the lowest material utilized.

Frame Cross Section Size (mm) Weight (kg)

Optimized Frame-1 80x80x5 207.2

Optimized Frame-2 72x72x6 211.2

Optimized Frame-3 60x60x5 189



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C. Static and Dynamic Analysis of Structural Base Frame:

Simulation is a reliable tool for the design and development of the structural base frame. Simulation of the structural base

frame is dividedin to two patterns:

(1) Static and Dynamic Analysis

(2) Model Analysis

For the static analysis, The Details of mesh strategy are defined in the below table,

TABLE IV

DETAILS OF MESH STRATEGY

Fig. 3Meshing in Modified Structural Base Frame

TABLE V

DETAILS OF BOUNDARY CONDITIONS

Fig. 4Boundary Condition in Modified Structural Base Frame

Element Size Default

Relevance Center Coarse

Nodes 59182

Elements 18759

Solid Element Nodes Program Controlled

State Fully Defined

Scoping Method Geometry Selection

Geometry 1 Face

Type Fixed Support

Suppress No



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Static Analysis Results –

Fig. 5Total Deformation of Modified Structural Base Frame (Static)

Fig. 6Maximum Principal Stress of Modified Structural Base Frame (Static)

Dynamic Analysis Results –

Fig. 7Total Deformation of Modified Structural Base Frame (Dynamic)

Fig. 8Maximum Principal Stress of Modified Structural Base Frame (Dynamic)



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D. Modal Analysis of Structural Base Frame:

In the modal analysis, the natural frequency of structural base frame is found out. Consider a 5 Mode shape for Frequency

for Modalanalysis.

Step-1: Engineering data Assign

Step-2: Geometry Import (STP, IGES, Parasolid)

Step-3: Input Constraint

Fig. 9Condition applied for Structural Base Frame

Fig. 10Mode Shape-1

Fig. 11Mode Shape-2



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Fig. 12Mode Shape-3

Fig. 13Mode Shape-4

Fig. 14Mode Shape-5

New optimized design of the Structural base Frame,

Fig. 15New Optimized Design of Structural base Frame



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IV. RESULT

After performing different analysis following observations are noted –

A. Decrease the weight of the Structural base frame:

The optimized structural base frame weight is reduced about 16% compare to existing structural base fame. The New

optimized structural base frame weight is about 189-190kg where, the existing structural base frame weight is 225.5kg.

TABLEVI

DYNAMIC ANALYSIS RESULTS OF OPTIMIZED

STRUCTURAL BASE FRAME

In the Modal Analysis, Frequency generated at different 5 mode of the optimized model of frame. In the optimized structural

base frame frequency is varying in between 150-377Hz. All generated natural frequencies are given in below table.

TABLE VII

MODAL ANALYSIS RESULTS FOR OPTIMIZED STRUCTURAL

FRAME

B. Reduced Material Utilization and Overall Cost:

The optimized structural base frame having the cross-section size of 100x100x5mm where, the optimized structural base

frame having the cross-section size of 60x60x5mm. Due to this reason the optimized structural base frame is lighter than the

existing one.So, the optimized structural base frame is having reduced material utilization in the fabrication. So, it also gives the

cost cutting in the overall cost of the structural base frame.

V. CONCLUSION

An effort is taken for the Design and Analysis of the Structural base frame for robot mounting. Initially Design of structural

base frame is optimized by using sizing method of structural optimization method. New optimized structural base frame CAD

model is developed in Solidworks software. Static and dynamic analysis results are carried out by Ansys Software and

developed optimized design of structural base frame for robot mounting. In new optimized design of structural base frame,

cross section size is changed from 100x100x5mm to 60x60x5mm and Overall gearbox casing weight is reduced up to 15-16%

as compared to existing structural base frame. The material utilization is also reduced as a result of that overall cost of the frame

is also reduced. So, it is concluded that new optimized structural base frame is technically justified and proven its effectiveness

over an existing structural base frame.

ACKNOWLEDGMENT

Research reported in this article has been developed at Modtech Machines PVT. LTD., Changodar, Gujarat.Authors would

like to thanks Mr. Apoorva Oza and Mr. Tushar Patel and Mr. Maunil Sheth for his support in this ongoing work in organization.

REFERENCES

[1] Xiaoping Liao, Changliang Gong, Yizhong Lin, Weidong Wang (2010).“The Finite Element Modal Analysis of the Base of Welding Robot”. 3rd

International Conference on Advanced Computer Theory and Engineering (ICACTE)

[2] Ashwini R. Hagawane, Vijay L. Kadlag(2016). “Analysis and Optimization of Robot Pedestal Design using FEA”. 2nd International Conference on

Advances in Mechanical Engineering (ICAME-2016)

[3] Gwang-Jo Chung, Doo-Hyung Kim. “Structural Analysis of 600Kgf Heavy Duty Handling Robot”. Principal Research engineer in Robotics Lab.

KoreaInstitute of Machinery & Materials Daejon, Korea.

[4] G.A.Yadav, A.M.Pirjade, M.M.Jadhav,Vinaay Patil (2016). “Design Analysis & Optimization of Robot Paedestal”. International Journal of Engineering

and Technical Research (IJETR).

[5] Mr.Ankit.J.Gitay, Mr.Pramod.S.Sarode, Mr. Akshay. T.Misal, Mr. Mayur.J.Gitay’(2017). “Design and Analysis of the Robot Pedestal”. International

Research Journal of Engineering and Technology (IRJET).

[6] Mohd Azizi Muhammad Nor, Helmi Rashid, Wan Mohd Faizul Wan Mahyuddin, Mohd Azuan Mohd Azlan, Jamaluddin Mahmud. “Stress Analysis of a

Low Loader Chassis”. International Symposium on Robotics and Intelligent Sensors 2012 (IRIS 2012).

Material Structural Steel (S235)

Total Deformation 0.029mm

Maximum Principal Stress 10.92 MPa

Equivalent Stress 12.89 MPa

Mode Natural Frequency (Hz)

Mode Shape-1 151.34

Mode Shape-2 181.43

Mode Shape-3 265.37

Mode Shape-4 278.19

Mode Shape-5 376.21



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[7] Mohd RafiqMahbob, JamaluddinMahmud, MohdAzuanMohdAzlan, AidahJumahat. “Finite Element Analysis of Telecommunication Mini Mast

Structure”. The Malaysian International Tribology Conference 2013, MITC2013.

[8] Lluis Gil, Antoni Andreu. “Shape and cross-section optimisation of a truss structure.”Computers and Structures 79 (2001) 681±689 (Pergamon) (2000).

[9] Haichao An and Hai Huang. “Topology and Sizing Optimization for Frame Structureswith a Two-Level Approximation Method.”, AIAA

JOURNAL(2017).

[10] Mr. Muralimanoj Varadharajan. “Optimization of Structures: Shape and weight optimization of structural members”, Hochschule Ostwestfalen Lippe

University, Germany.

[11] Paolo Cicconi, Michele Germani, Sergio Bondi, Alessandro Zuliani, Emanuele Cagnacci. “A Design methodology to support the optimization of steel

structures.” Procedia CIRP.

[12] Prashant Kumar Srivastava1, Simant, Sanjay Shukla. “Structural Optimization Methods: A GeneralReview”, International Journal of Innovative

Researchin Science,Engineering and Technology (2017).



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optimization of structural base frame for robot mounting using fea analysis · 2019-05-07 ·...

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