Journal of Robotics, Networking and Artificial Life
Vol. 8(2); September (2021), pp. 73–77
DOI: https://doi.org/10.2991/jrnal.k.210713.001; ISSN 2405-9021; eISSN 2352-6386
https://www.atlantis-press.com/journals/jrnal

Research Article

System Integration and Application of a Networking
Production Line for Aerospace Precision Manufacturing
Chau-Chung Song1,2,*, Chun-Chi Wang3, Geng-Yi Lin1, Chung-Wen Hung4
Department of Aeronautical Engineering, National Formosa University, Huwei, Yulin, Taiwan
Smart Machine and Intelligent Manufacturing Research Center, Nation Formosa University, Huwei, Yunlin, Taiwan
3
Graduate Institute of Aeronautical and Electronic Technology, National Formosa University, Taiwan, R.O.C.
4
Department of Electrical Engineering, National Yunlin University of Science &Technology, Taiwan, R.O.C.
1
2

ARTICLE INFOABSTRACT

Article History

In this paper, the networking integration application of an intelligent production line is studied and developed for aerospace precision
manufacturing. The technical development of the performance equalization and control for EDM machine is also introduced with therelated technologies of the machine network and Ethernet for Control Automation Technology (EtherCAT) network. In addition, thedevelopment of intelligent production lines is integrated to improve the system stability and production efficiency of production line
systems for aerospace component manufacturing. The key technologies of Cyber-Physical System (CPS) and intelligent networking
are also integrated to construct the real-time intelligent system monitoring system [Supervisory Control and Data Acquisition(SCADA)] for data record and management. The key technologies of the drilling process are developed for intelligent diagnosis anddrilling holes inspection of related production processes. The integrated robot arm is responsible for the loading and unloading of
the material, and the entire production line is connected by the EtherCAT network. The automatic optical inspection is introduced
at the rear end of the production line to realize the quality judgment of the finished product. Furthermore, the virtual cloud networkand the intelligent factory are achieved with the information collection and intelligent monitoring system.

Received 13 November 2020
Accepted 23 March 2021
Keywords
Aerospace precision manufacturing
EtherCAT
SCADA
intelligent production line

© 2021 The Authors. Published by Atlantis Press International B.V.
This is an open access article distributed under the CC BY-NC 4.0 license (http://creativecommons.org/licenses/by-nc/4.0/).

1. INTRODUCTION
In recent years, as the tendency of the popularity in the global aerospace industry, the number of airline passengers has grown yearby-year. Therefore, there is a strong demand for new civil aircraft
development. However, the machine object equipment mostly
relied on aerospace manufacturing overseas. Because of the weak
confidence level, the domestic aerospace manufacturing industry
goes into a declining phase. Therefore, in 2014, the Executive Yuan
hopes to introduce the manufacturing line to carry out the aerospace components and then promote the domestic tool machineindustry to enter the aerospace processing field. The final goal isto promote domestic machine tools to enter the international aerospace supply chain. In this paper, the intelligent networking system
is integrated and developed for production line applications basedon the EtherCAT network, including control of the robotic arm.

2. MATERIALS AND METHODS
2.1. EtherCAT
Ethernet for Control Automation Technology (EtherCAT) is an
Ethernet-based Fieldbus system, invented by Beckhoff Automation.
This technology breaks through the system limitations of other
Ethernet solutions in the past and has the characteristics of highCorresponding author. Email: ccsong@nfu.edu.tw*

availability requirements, flexible topology, high-performance,
Distributed Clocks for High-Precision Synchronization, and lowcost [1–3]. The EtherCAT master uses a standard Ethernet port andnetwork configuration information stored in the EtherCAT Network
Information (ENI) file. The ENI is created based on EtherCAT slave
information files which are provided by the vendors for each device.
Slaves are connected via Ethernet, any topology type is possible for
EtherCAT networks [4]. EtherCAT architecture is shown in Figure 1.

2.2. CANopen over EtherCAT
Using the CANopen over EtherCAT (CoE) application layer protocol, EtherCAT communication has the same standard protocol
as CANopen, Including the same Object Dictionary (OD), Service
Data Object (SDO) settings, Process Data Object (PDO) datatransmission, and the objects refer to Controller Area Network(CAN) in Automation (CiA) 402 for motion control. These objects
can define the state control of the motor, basic motor parametersettings, and data feedback objects, etc., providing objects that canbe used for basic motor control operations [5].

2.3. Control of Robotic Arm
For the robotic arm control, it will bypass its upper controller for
PC control. Here, a Six-Axis articulated robot will be used as an
example. To control the Six-Axis articulated robot, regard it as six

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Figure 2 | Link coordinate system D–H parameters.

Figure 1 | EtherCAT network architecture [4].

motion control cards for communication connection and control,and use EtherCAT as the communication method of the motion
control cards network communication. In the part of physical control, the robot kinematics must be rediscussed, and it is mainly
divided into two parts, forward kinematics, and inverse kinematics. Forward kinematics is to substitute the known rotation
angle qi of each axis arm into the homogeneous transformation
matrix, and then obtain the position of the end controller relative
to Cartesian coordinates (xi, yi, zi). On the contrary, inverse kinematics is to know the posture and position (xi, yi, zi) of the arm
relative to Cartesian coordinates, and in turn, obtain the required
rotation angle qi for each axis joint of the arm and used in the derivation and verification of robot arm control. To get the relative
relationship between forward and inverse Kinematic equations, therotation and translation position relationship between each axis of
the Six-Axis articulated robot is expressed by Denavit–Hartenberg
parameters, to obtain the simplified four main parameters, as
shown in Figure 2 [6–8].
 i , in X
 i −1 direction
 i −1 and Z
a : Angle between Z

Figure 3 | Six-Axis articulated robots and the axis length diagram
between each axis [9].
Table 1 | Denavit–Hartenberg parameters
Joint

pi

di (m)ai (m)`i (°)

1
2
3
4
5
6

q1
q2
q3
q4
q5
q6

0
0
0
0.438
0
0.08650.03
0.4398
0.04
0
0
0

90
0
90
−90
90
0

i−1

 i −1 and Z
 i , in X
 i −1 direction (a > 0)ai−1: Distance between Zi
 i −1 and X
 i , in Z
 i direction
q : Angle between Xi i −1 and X
 i , in Z
 i direction
di: Distance between X
After defining the parameters required for the relative transformation of each axis coordinate system, the relationship between
translation and rotation can be obtained through Figure 3, thenobtained the DH parameter table, see Table 1. The four parameters
defined in the DH parameter table are briefly described below, andtheir geometric meanings are as follows:
qi: The angle of joint rotation.
di: The translation distance of the joint between the rotation
coordinates.
ai: The length of the mechanical link between the two joints.

3 × 1 matrix in the upper right corner of the translation matrix. By
finding the conversion relationship between the space points of thetwo coordinate systems, the transformation matrix between eachjoint can be calculated. Put it into Equation (2) to find the transformation matrix between the endpoint and the origin.
 R11
R
R
T


i −1
=  21
iT = 

0 0 0 1  R31
 0

R21
R22
R32
0

R13
R23
R33
0

0
0 1 2 3 4 5
		 BaseEndT = 6T = 1T 2T 3T 4T 5T 6T 

Px 
Pz 

Pz  
1 

(1)

(2)

At this point, the position of the end controller in the forward
kinematics Cartesian coordinates (xi, yi, zi) obtained by this transformation matrix can be used as a verification of the position of
the control calculation [6–8].

ai: The rotation angle of the output shaft of the two joints.
The position of the robotic arm endpoint in the coordinate system
is derived from the homogeneous transformation matrix. Since
the coordinate conversion between the axis of the robotic arm isrotational and translational, by substituting the listed D–H tableparameters into Equation (1), the homogeneous transformation
matrix between each axis can be established. In Equation (1), the3 × 3 matrix in the upper left corner is the rotation matrix, the3. SYSTEM DESIGN AND ARCHITECTURE
For the development of an intelligent production line application,
the Electric Discharge Machine (EDM) is the core machine and­integrates the robotic arm by the EtherCAT network. The Supervisory
Control and Data Acquisition (SCADA) system is to connect the
EDM, the robotic arm, and the Automated Optical Inspection system

C.-C. Song et al. / Journal of Robotics, Networking and Artificial Life 8(2) 73–77(AOI system) through the communication network to establish anaerospace precision manufacturing, as shown in Figure 4.

4. SYSTEM INTEGRATION AND TESTING
The experimental method of Intelligent Production Line
Application is to run the overall electric discharge machining production line after the EtherCAT local area network and the SCADA
system have been constructed and connected to monitor. Review
the results of drilling at special angles of the workpiece to verify theeffectiveness of the EDM production line automation. To add theSix-Axis articulated robot to the overall machining production line
network for control, it will bypass its upper controller of the initial factory and connects to the six motion control cards, which are
regarded as nodes. To control the Six-Axis articulated robot, use thekinematic calculation method above to calculate the corresponding
value of pulse to the rotation angle of each axis required to reach thetarget position. Then use the CiA402 moving object of the motion
control cards itself for EtherCAT transmission, the control object
is shown in Figure 5. Then use the value of pulse which is obtained
from the feedback object to infer the current angle position information. There are several modes for motion control of the roboticarm, here use interpolated position mode. Also, the control of theelectric gripper matched with the robotic arm uses its USB port tocommunicate and control with the computer via UART.
Before the SCADA system starts to connect and control, it is necessary to use TwinCAT to create related corresponding objects andsettings through the description of each slave device XML file toconstruct an EtherCAT network. After the completion of network
construction, set the initial parameters of SDO, and set through theobjects in the object dictionary, then set the PDO Output object thatwill be added during subsequent operations. Real-Time numericalcontrol can execute after it into the operational state. Then, SCADA
software can be used to connect to the network for reading object
information and issue control commands. The SCADA system is
to monitors the EtherCAT network status of the entire production

Figure 4 | Aerospace precision manufacturing.

Figure 5 | Control object of the robotic arm.

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line, it is mainly connected to the master station TwinCAT via API.
SCADA system can be used to instantly grasp the actions and statusof each machine and equipment, and establish a user interface
for users to monitor and manage the production line status andto provide the inspection results of the finished workpiece. The
SCADA system is shown in Figure 6.
According to the function, C# based SCADA system can be divided
into four parts, device connection, Six-Axis articulated robot, AOI
system, and electric discharge machine. The functions of each partwill be introduced below.

4.1. Device Connection
The main function of the device connection is to connect with
the EtherCAT Master TwinCAT on the production line and communicate and control transmission with each node through thisnetwork. In addition to the EtherCAT network connection, thisSCADA system also integrates other hardware connections, suchas the USB connection of the AOI automatic positioning system,and the connection control of the electric gripper of the roboticarm. On the network connection, the customized RJ45 interface
100BASE-TX is used as the network physical layer, which is connected to the main station by serial connection with each station, and a personal computer is used as the main station. Other
devices are connected to a personal computer using USB Port andthen controlled by the SCADA system. The interface of TwinCAT
master is shown in Figure 7.

4.2. Six-Axis Articulated Robot
After connecting its motion control cards via the network andcompleting the network communication, the robotic arm can be

Figure 6 | The SCADA system.

Figure 7 | The interface of TwinCAT master.

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controlled. It operates on the Cartesian coordinate system andcoordinated with single-axis angle numerical control of the rear
three axes to adjust the detection angle, and calculated by feedback object to know the current position information and feedback
information of each axis. Also, a single-axis control is added for theuser to find the grasping point to ease the scheduling design.

4.3. AOI System
This AOI system consists of two parts, the automatic positioning
system, and the AOI optical inspection. Connect the MCU and AOI
system to obtain the current positioning information and display the
result of the finished workpiece inspection on the interface. The AOI
system of this EDM production line is composed of an industrial
camera, a telecentric lens, a ring light source, and an inspection platform. The inspection platform is used as the starting station for the
feed of the production line and the placement station for the processing completion, when the processing flow starts, the workpiece to beprocessed is placed on this platform, after the processing finished, sendit back to the platform for the final AOI optical inspection, and perform drilling holes information inspection, acquisition, and analysis
on the processed product for quality inspection. The pictures and analysis information are sent to the production line monitoring system forusers to use and judge. The analysis information is shown in Figure 8.

4.4. Electric Discharge Machine
Given the issues related to industrial safety, the EDM manufacturer(Ching Hung Machinery & Electric Industrial Co., Ltd.) does notprovide control methods related to EDM computer host and external connection, like an independent working machine. However, toachieve the goal of automation of the production line, an EtherCAT
network node must be constructed separately. Through the external relay circuit with the EtherCAT communication control boardthat transmits the signal to the internal relay of the EDM, thenthe existing programs in the EDM computer will be activated, theprogram including executing, signals of fixed-point feedback, andemergency stop. The control interface is as shown in Figure 6, thered light is matched with the feedback signal. While the electric
discharge machine is stably ready, the green light will be on, andthe processing program can be started with Start at this time. The
workpiece being drilled by EDM is as shown in Figure 9.
As aerospace consumables workpieces are not available, it can only
be machining through similar workpieces, such as galvanized ironblocks, stainless steel plates, aluminum plates, and radiator statorscrap for machining and measurement. During the trial run of the

Figure 9 | The workpiece being drilled by EDM.

Figure 10 | Workpieces after machining.

Figure 11 | Electric discharge machining production line.

overall electric discharge machining production line, the network
controller issues work instructions, the robotic arm carries out thereclaiming operation, and the electric discharge machine is processed. After the machining is completed, the robotic arm sends itto the AOI system for quality inspection. The entire automated production line operates smoothly. The workpieces after machin­ing areshown in Figures 10 and 11 depict the integral EDM production line.

5. CONCLUSION

Figure 8 | Images inspected by AOI system.

In this paper, the networking system integration and development
is focused on EtherCAT protocol for an intelligent production line
application, use the EtherCAT network to integrate the ­Six-Axis­articulated robot and EDM, and design a SCADA system to connect the EDM, Six-Axis articulated robot, and AOI system via
the communication network to build an automated network control station. During the trial run of the overall electric dischargemachining production line, the network controller issues work

C.-C. Song et al. / Journal of Robotics, Networking and Artificial Life 8(2) 73–77

instructions, the robotic arm carries out the reclaiming operation,and the EDM is processed. After the machining is completed, therobotic arm sends it to the AOI system for quality inspection. The
entire automated production line operates smoothly. On the network control station, the SCADA system can be used to grasp theactions and status of each machine tool and equipment of the production line in real-time, and establish a user interface for users
to monitor and manage the production line status, and to provide
the inspection results of the finished workpiece. This Networking
System Integration and Development of an Intelligent Production
Line Application has been completed, which can implement intelligent communication between machine tools and equipment, andachieve the goal of intelligent control of machining equipment,
improve machining quality and productivity.

CONFLICTS OF INTEREST
The authors declare they have no conflicts of interest.

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ACKNOWLEDGMENTS[8]This research was supported by the Ministry of Science andTechnology, Taiwan, R.O.C. under Grant: MOST 107-2218-E-150007 and 108-2218-E-150-004.

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AUTHORS INTRODUCTION
Chau-Chung Song

Geng-Yi Lin

He is with the Department of AeronauticalEngineering, National Formosa University,
Taiwan. He received the PhD degree inElectrical and Control Engineering from
National Chiao Tung University in 2001 at
Taiwan. He is currently a Professor in Instituteof Aeronautical and Electronic Technology,
and Department of Aeronautical Engineering, National Formosa
University since 2006. His research interests include the analysis
and control of nonlinear systems, the integration application of
networking information system, the UAV technology and applications, and the cloud network and Cyber-Physical system (CPS).

He received his Bachelor’s degree from the
Department of Aeronautical Engineering,
National Formosa University, Taiwan in
2021. He is currently a Master’s course
student in National Formosa University,
Taiwan.

Chun-Chi Wang

Chung-Wen HungHe received his Bachelor’s degree fromthe Department of Materials and Energy
Engineering, MingDao University in 2018. Hereceived the M.S. degree in Graduate Instituteof Aeronautical and Electronic Technology
from National Formosa University in 2021 at
Taiwan. He is currently a PhD course student
in National Yunlin University of Science and Technology, Taiwan.

He received the PhD degrees in ElectricalEngineering from National Taiwan University
in 2006. Currently, he is an Associate Professor
in National Yunlin University of Science &Technology. His research interests include
IoT, IIoT, Power Electronics, Motor Control,and AI Application.