Automation and Control for Offline Impedance Matching using PLC

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Automation and Control for Offline Impedance Matching using PLC and

LABVIEW for ICRH Transmission line in SST-1

Aniruddh Mali1, Ramesh Joshi2, H.M.Jadav2, Krupa Mehta3 and S.V. Kulkarni2

1B.E Student L.D College of Engineering, Ahmedabad-380015

2Institute for Plasma Research, Bhat village, Gandhinagar – 382428

3PG Student U V Patel College of Engineering, Kherva, Gujarat-384012

1Email: [email protected]

Abstract

Ion Cyclotron Resonance Heating (ICRH) system has two impedance matching networks, one for

offline matching which has been employed before experimental shot. Another is online impedance

matching which has been employed during experimental shot. Offline matching network consists of

two static stubs, coarse tuner and coarse phase shifter identical in both transmission lines. Both stubs

are being used to vary transmission line length. Phase shifter is used for phase shifting. PLC

(Programmable Logic Controller) based automation and control technique has been used for the

system as it works below 1 kHz frequency operation of stepper motors. There are motorized

arrangements installed in each stub and phase shifter. PLC based system is developed for automation

and control. LabVIEW software is used as SCADA/ HMI i.e. front end GUI. User interface has been

designed using LabVIEW which communicates with OPC (Open Process Control) server. Further,

OPC communicates with PLC for control of motorized arrangement. This paper describes technical

approach, system feasibility and optimized solutions for the same.

1. Introduction

Ion Cyclotron Resonance Heating (ICRH) requires impedance matching of antenna to the generator

impedance for maximum delivery of power during tokamak plasma experiments. It has significant

role in ICRH plasma heating during tokamak plasma experiments. ICRH has two impedance

matching networks i.e. online and offline to be used for impedance matching during tokamak plasma

experiments and before plasma experiments respectively. It consists of following sub systems

identical for both ICRH transmission lines:

1. Static Stub

2. Coarse Stub

3. Phase Shifter

To control each transmission line stub movement for requisite matching, a stepper motor based

control facility is used which has been programmed using Delta PLC. Each stepper motor has its

motor driver for sufficient driven voltage and current for movement of the load i.e. stub. PLC is used

to control and monitor the complete system. PLC program developed using ladder logic programming

in WPLsoft 2.33. SCADA – Supervisory Control and Data Acquisition is used to develop HMI –

Human Machine Interface for industrial PLCs which is provided by vendor. LabVIEW communicates

with PLC modbus data register using OPC (OLE for Process Control) interface provided by

LabVIEW which provide modbus communication libraries.



2. System Overview

OPC is used to communicate with industrial PLCs which is provided by proprietary PLC

manufacturers. It is implemented in server/client pair. The OPC client software is a program that

needs to connect to the hardware. The OPC client uses the OPC server to get data from or send

commands to the hardware. Traditional OPC software is identical for particular PLC. OPC Server

which can communicate to any PLC using modbus communication. It can communicate with the

hardware using different types of interfaces i.e. ASCII serial, RTU and Ethernet. In our case OPC has

been used to communicate with Delta PLC using MODBUS ASCII serial interface in this system.

This paper describes utilization of proprietary OPC to control industrial PLC. Further, it will explain

application of LabVIEW as user interface for PLC instead of traditional SCADA/ HMI. It also

compensates the cost of development of user interface than traditional development cycle.

2.1. Schematic Diagram

Figure 1: Schematic of offline impedance matching system

It is used for offline impedance matching. Delta PLC DVP28SV has been procured for it which

communicates with OPC using serial interface in which MODBUS ASCII Serial is used as

communicating protocols. PLC provides each I/O on24V. Stepper motor and its driver need 5V pulse

to be operated so it needs to be converting 24V into 5V and 5V into 24V vice versa. An electronic

circuit is developed for it which is as shown in figure 1. Hence stubs have to be operated from a

remote location i.e. shield room of SST-1, Fibre optic based transmitter (Tx) and receiver (Rx) circuits

are used to send generated pulse to load i.e. stub. Transmitter card converts generated pulse into

optical signal and receiver card converts optical signal into electrical pulses which fed into motor

driver which drives the stepper motor. Plastic fibres are used as communication media between

transmitter and receiver. Static stub of 500mm length, coarse stub 1500mm length, phase shifter

3000mm lengths are used for impedance matching in SST-1 tokamak. Each stub movement can be

performed in both clock wise (CW) and counter-clockwise (CCW) direction using stepper motor

facility as per experimental requirement.



2.2. Data flow

Figure 2 shows data flow of offline impedance matching system based on PLC and LabVIEW

GUI. OPC client has corresponding tags of each physical I/O of PLC. These tags can be created in

OPC server using I/O address. LabVIEW uses shared variable engine to deploy all bound

variables on to communicate with OPC client. These bound variables are indentified as ‘shared

variables’. An I/O server has to be created in LabVIEW which enable utilization of OPC client

tags as shared variables. Figure 3 shows OPC server consisting all created tags for proprietary

PLC. Tag properties can be seen in the figure. Specific tag can be created as per requirement. Tag

Figure 2: Data flow

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properties dialog box shows name of the tag, its address, description, data type, access mode and

scan rate, etc. These values are user settab

of each tag can be monitored.

2.3. LabVIEW User Interface

Figure 5.1 shows user interface for offline impedance matching

LabVIEW. It consist user interface for Transmission Line 1 coarse machine and static stub 1 and stub

2 as well Transmission Line 2 coarse machine and static stub 1 and stub 2. Requisite stub movement

can be set using numeric control ‘Coarse stub movement’ in millimetre (mm). Generated square pulse

is indicated using ‘Motor Pulse’. UP button is used for Clockwise (CW) movement and DOWN

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These values are user settable. Figure 4 shows OPC quick client using which status

Figure 3: OPC tag properties

Figure 4: OPC Quick client

Figure 5.1 shows user interface for offline impedance matching which has been developed in



ntrol ‘Coarse stub movement’ in millimetre (mm). Generated square pulse


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Figure 4 shows OPC quick client using which status

which has been developed in



ntrol ‘Coarse stub movement’ in millimetre (mm). Generated square pulse




button is used for counter clockwise (CCW) movement. Frequency range can be selected from ‘Pulse

Time’ for square pulse generation which drives motor speed. ‘Stub’ and ‘Pulse’ are used for stub

movement progress as well generated pulse execution respectively. Upper and lower limit of the stub

movement progress as well generated pulse execution respectively. Upper and lower limit of the stub

is indicated by Boolean button. When stub reach its maximum limit, it will be red else it will be green.

10 mm is set in ‘Coarse Stub movement’ as shown in figure 5.1. Generated pulses are indicated by

using ‘Motor Pulse’ which is 5000 in this example. Selected frequency is 333 Hz as indicated in

‘Pulse Time’.

3. Test Setup

Figure 5.2 and 5.3 shows test setup using which developed LabVIEW user interface has been tested

successfully. Test Setup consists of PLC, transmitter and receiver circuit, 24 V to 5V circuit, motor

driver module and load i.e. stepper motor. User interface communicate with PLC over serial interface

in this system. Generated square pulses have been monitored on oscilloscope as shown in figure 5.2.

Motor pulses generated using PLC modules are fed to transmitter circuit which transmitted using

optical fibres. Receiver circuit receive these pulses and then it is fed to motor driver module which

drives the stepper motor. Motor can be operated at different frequencies ranges from 333 Hz to 1 KHz

according which motor speed can be controlled to drive the stub movement. It provides fast response

without any interruption and working properly.

Figure 5.1: Developed LabVIEW User Interface

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Figure 5.2: Developed LabVIEW user interface with PLC

Figure 5.3: Stepper Motor with electronic interface

3. Conclusion

Automation and control for offline impedance matching usi

tested using test set up as shown in figure

movement can be done in both directions as per experimental requirement. LabVIEW GUI provides

interactive user interface to control the complete system efficiently.

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Figure 5.2: Developed LabVIEW user interface with PLC

Figure 5.3: Stepper Motor with electronic interface

Automation and control for offline impedance matching using PLC and LabVIEW GUI has been

tested using test set up as shown in figure 5.1 successfully. It is working properly and stepper motor


interactive user interface to control the complete system efficiently.

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ng PLC and LabVIEW GUI has been

successfully. It is working properly and stepper motor




4. References

1. R. Joshi et all, Testing and Optimization of the Matching Response Time for the Real Time

Controlled ICRH Automatic Matching Network (AMN) System of SST-1 with Hybrid

Coupler and Complete Transmission Line, IPR-Technical Report, IPR/TR-149/2008,

December 2008.

2. Alan M. Barker et all, A Case Study of modern PLC and LabVIEW controls: Power Supply

Control for the ORNL ITER ECH test stand, ," Future of Instrumentation International

Workshop (FIIW), 2011 , vol., no., pp.1,4, 7-8 Nov. 2011 doi: 10.1109/FIIW.2011.6476800

3. Anjali S. Ashtekar et all, Application of MODBUS to Communicate the PLC and Lab VIEW

for Real Time Process Control, International Journal of Emerging Science and Engineering

(IJESE) ISSN: 2319–6378, Volume-1, Issue-11, September 2013

4. http://www.ni.com/white-paper/7450/en/

5. http://www.ni.com/white-paper/3742/en/

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Automation and Control for Offline Impedance Matching using PLC