The described work was carried out as part of the TÁMOP 4.2.1.B 10/2/KONV 2010 0001 project in the framework of the New Hungarian Development Plan. The realization of this project is supported by the European Union, co-financed by the European Social Fund.

Internet-based Measurement Technology, Electrical Drives and Automation

A Sz. Váradi L. Szentirmai T. Szarka

Department of Electrical and Electronic Engineering

University of Miskolc, H-3515 Miskolc Hungary

Abstract –The rapid growth of fast and reliable

communication networks provides an easy exchange of information and commands between computers connected to sites of wide area networks such as the internet. Engineers from far away workstations can operate various remote equipment through the internet. Engineering is transformed into a constructive joint effort within the framework of simulation and exploration. Engineers share information at a rapid pace, with the collective aim of increasing the quality of product, process and service and reducing development time and costs. With the latter-day technology available, it reaches the same objectives as for a hands-on laboratory, and even more efficiently in most cases. The application properties now range right up to the internet-controlled visualization of processes far away from the platforms. University of Miskolc Department contributed to the solution of these challenges by an virtual laboratory serving the Ethernet network-based industrial measurement systems to all users through an “open for all” web site by Fieldpoint and General Purpose Interface Bus (GPIB) modules.

Index Terms—Computerized Instrumentation, Digital Circuits, World Wide Web.

I. INTRODUCTION The international electronic network having its acronym and

also popular term internet or world wide web, simply web is a new tool since measurement technology, electrical drives and automation are packed full of electronics for the exchange of data and information. The rapid growth of global internet connectivity, coupled with improved security norms and standards [1], provides a powerful tool to achieve these goals.

The internet forms one of the core foundations of a successful information technology- or knowledge-based society. The web is used not only to gain visibility, share information, sell products and conduct business, but also to improve the way we design engineering systems, manufacture them and test the final products. A balanced usage of internet facilities can reduce the length of design cycles and improve overall quality.

The implications of such a networking technology can be far reaching. For example, using network technologies in measurement technology, • the input to and output from a hardware platform located on a production floor or test rig can be governed, • deploy additional processing power for in-depth analysis in the control center via software support, • login and store post-analysis information on a corporate database, and • display key processed information to researchers, clients or consultants around the world via a standard web browser. Online feedback and corrective signals

can be received and executed when desired. A smart and dependable partnership between the hardware and controlling software, working in unison, is vital for success. The technology greatly widens the opportunities for collaborative research, development and experimentation, as it overcomes the need for the physical proximity of the experiment and the researcher [2].

Researchers and engineers from far away workstations can operate through the internet with various remote equipment,. Engineering is transformed into a constructive joint effort within the framework of simulation and exploration. With the latest technology available, it reaches the same objectives as for a hands-on research laboratory, and even more efficiently in most cases. The application properties now range right up to the internet-controlled visualization of processes far away from the platforms.

The Internet is thus an infrastructure on which to build an electrical machine or system, its attraction is three-fold: (i) Web browsers can provide a nice human interface for a machine or system because the browsers can display various media including animated cartoons, hypertext, motion pictures/images, sounds and three-dimensional (3D) graphics as well as handling interactive operations of the media; (ii) the hypertext transfer protocol (HTTP) or any other up-to-date protocol can be a standard communication protocol of an electrical system since machines connected to the internet can be accessed from any internet site via the protocol; (iii) It becomes possible to use various hardware and software distributed over the internet together to accomplish a single mission [3].

In the short history of internet-based laboratory, a number of experiments have been conducted. Section II presents the network technologies a few characteristic laboratories developed in different countries.

University of Miskolc Department contributed to the solution of these challenges by an internet-based laboratory serving the Ethernet network-based industrial measurement systems to all users through an “open for all” web site by Fieldpoint and General Purpose Interface Bus (GPIB) modules.

II. OVERVIEW OF INTERNET-BASED LABORATORIES

A. Network technologies

Studies on internet-based process control laboratory [4], [5] and [6] say that although realistic simulations can provide valuable experience, the importance of actual laboratory experiments cannot be understated. Real experiments bring with them valuable experiments on the effects of noise, control constraints, nonlinear effects, and time-varying parameters on

978-1-4673-1301-8/12/$31.00 ©2012 IEEE

2012International Symposium on Power Electronics,Electrical Drives, Automation and Motion

997

control or other system performance. However, visual feedback is also important.

There have been relatively few real-time laboratories, accessible over the public Internet, due to concerns about bandwidth requirements, quality of network service, robustness, safety, and security. Most research institutions today have reliable broadband connections so that real-time Internet-mediated control is feasible. Such a facility will also allow expensive physical hardware to be shared among different institutions and permit collaborative research. Multicast networks may be used to provide high quality audio and video transmission from the laboratory to the required place.

In the development of accessible remote experiments, six important issues have to be addressed include: (i) selecting a suitable communication protocol, (ii) restricting access to authorized users, (iii) handling multiple simultaneous users, (iv) maintaining a stable connection, (v) intrinsically fail-safe operation and (vi) effect of communication delays on operation.

B. Role of Internet-Based Laboratory

A typical process control internet-based laboratory (Fig.1) is divided into two parts: the server on the left-hand side and the user/client on the right. The two sides are connected via the Internet. The server side consists of a control server and a researcher or class management server. The DC server motor and the monitoring camera are connected to the control server.

Fig. 1. Schematic diagram of an internet-based process control

laboratory

The internet-based laboratory permits remote accessing and measurement for activities requiring collaboration on computer networks. More specifically, through these capabilities, one can:

• run experiments while interacting with instruments and remote devices;

• run experiment simulations while using numeric models;

• analyze numeric simulation results; • benefit from resource center capabilities and get

teaching or technical help over the computer network; • share data and applications with other participants

located in various geographical settings; • use the synchronous multipoint videoconference and

asynchronous conference.

Some authors use several software tools from different vendors, which led to a decrease in the development time, and

the maintenance cost. The platform Matlab/Simulink (with some additional toolboxes), has been chosen for the development of the application [7] for four reasons: ¯(i) Matlab, Simulink and the necessary tool-boxes constitute a reliable, well-known platform and with a lot of technical support, (ii) the time used to obtain the prototype and in the development is quite inferior to the time needed with other tools and platforms. (iii) The platform provides tools for remote performance of programs, and for real-time execution on a physical system, through a data system acquisition, using a specific control algorithm. (iv) The fourth reason, and not less important, is the great quantity of researchers that use this platform as development tool for simulations and real applications.

C. Mechatronics and Robotics

Mechatronics is an emerging technology area. Each mechatronic system contains at least one actuator (motor) supplied by a power converter and by a drive control. The control structure depends on the application field. In steel mill the stretcher, e.g. in the hot tandem mill line has an arm driven by a torque controlled DC drive system. Each block in the schematic block diagram appears after clicking in the relevant block by the mouse (Fig. 2). The mechanical performance is presented by the block f

M (�, �) . This

simplification provides deeper overview of the system performance than a sophisticated block diagram [8].

Fig.2. Schematic block diagram of drive system drawing out the

dc drive of a strip tension (Source [8])

Several publications deal also with robotics. An internet-enabled arm robot describes Internet transmission delay, Web user interface design and concurrent user access [3]. The experimental system shows the interaction between the system components. As an example, a remote operator uses a Web browser at the client PC to invoke the robot control applets from the Web server through the internet. The robot is controlled by the robot control programs. In order to provide a flexible, direct and easy-use interface for Web clients, a multimedia based dynamic simulator of the arm robot is embedded in the interface.

A client-server environment is generally designed and implemented also in robotics application. The architecture consists of a set of 30 or more Client measurement stations located in a computer laboratory, all networked to a Server station, which is located in the laboratory where the plant to be controlled is situated. The server acts as the data acquisition and control system. The acquired data are distributed through the network to the rest of the clients where the data are analyzed. In order to remotely control the plant from the computer laboratory, one of the computers, termed Remote

998

Controller is used to send information to the server station. This information is given in terms of the controller status, set-points and the parameters of the controller in the automatic operation mode, and the value of the manipulated variable in the manual operation mode. This feature allows the experimental system to be operated via any computer connected to the Internet. In particular, it allows the process control hardware to be operated from any place, thus allowing the system to be used for processing.

Three applications have been developed to enable the system to be operated that allow the user to access similar displays to those available on the control system: �• The Server application is constantly running in the computer server station. It contains the network related procedures on the server side. The server also contains the procedures related to instrument management. It has been designed to operate with serial ports and is used to manage acquisition boards, which are employed for control purposes.

�• The Client application contains the procedures that are related to the network of the client side as well as to the measurements processing. This application permits the data to be saved in order to be manipulated further with conventional spreadsheet programs.

• Remote Controller application contains the procedures that are related to the user interface of the parameters of the controller. This application has been developed in order to avoid researchers, engineers and students from different computers from sending contradictory orders to the controller at the same time.

The applications in some cases have been developed using the LabVIEW program from National Instruments. LabVIEW

is a graphical programming language for building data acquisition and instrumentation systems, and is ideally suited for the collection and distribution of data for basic process monitoring and control applications. It facilitates fast program development, provides many powerful built-in functions, and has universal acceptance in research and manufacturing settings; the authors also used LabVIEW.

D. Benefits of industry from internet access

Industry is a unique developer and an outstanding user of Internet . The application properties now range right up to the internet-controlled visualization of the processes far away from the platforms.

For Daniel-Control, M&M Software GmbH has developed terminal system DMS+, a browser-capable Web Front-End [9], which extends the operative range of the plant control and monitoring beyond the boundaries of a local Intranet. Complex plants like oil platforms can be visualized and monitored with this Web Front-End via Intranet and Internet connections. The solution has been implemented as an internet-capable Client- Server solution. This allows the use of process visualization also on offshore platforms, which provides a suitable Browser with Java support.

The integrated Environment for Functional Performance Engineering is implemented by Dassault Systèmes [10]. LMS Virtual.Lab offers an integrated software suitable to simulate the performance of mechanical systems in terms of structural integrity, noise and vibration, durability, system dynamics, ride and handling as well as other.

Fig.3. Block diagram of the new Internet-based laboratory

999

III. INTERNET-BASED LABORATORY FOR DC MOTOR MEASUREMENTS

A. General Description

The new internet-based laboratory [11] serves the Ethernet network-based industrial measurement systems to all users through an “open for all” web site. “In this laboratory” the users can also apply different sensors and analyze digital electronic circuits while they can gain experiences on the remote control (Fig. 3.).

The laboratory provides free access for all Internet users (Fig.4.). One of the most important requirements of the safe operation is the declared permissions given to the Internet users, the determination of those functions which can be used freely without putting any danger to the laboratory equipment, and provides information about the development of the most reliable protection methods of the system [12], [13] and [14].

When a usual Internet user is allowed to control real laboratory equipment a few problems must be solved. Most of the users will handle the system in such a way as: they will •enter the system, • use it by instructions and • close down it at the end of the switching off the equipment. But the system must be prepared also for those users, who make mistakes in use or at the appearance of unexpected system errors. For example (the list is not complete at all):

Fig. 4. Network structure of the new Internet-based Laboratory

- The user enters into the system, uses the resources but does not do anything – leaves the computer switched on and goes out for relaxation, smoking, etc. In this case nobody else can use the laboratory, but all equipment are staying switched on.

- The user does not close down the system as required and all the equipment are switched on.

- The user gives contradictory commands to the system e. g. the user sets the analog input module to the current measurement while the equipment is connected to measure voltage.

To balance the technical environment against such dangers the user software must be carefully designed and tested.

The virtual world meets the real world in this system and the interface between them is the control software. Software is developed in LabVIEW, which provides suitable visualization chances for user interface and also provides a simple way for network connections programming with its Web Publishing Tool package.

By the development of the internet-based laboratory a complete information technology system was created.

The laboratory incorporates the following subsystems:

• Linear distance sensor, power light emitting diode (LED) test and motor load-control measurement system with FieldPoint equipment

• Complex measurement system for analysis of electronic circuits using IEEE488 protocol (equipments using GPIB standard) and GPIB controlled instrumentation.

For both systems the following technological development steps had to be carried out:

• Development of the circuits to be controlled and measured,

• Development of measurement circuit along with network interface,

• Development of software for Internet use, and • Testing the safe and reliable operation of the system.

B. General Purpose Interface Bus (GPIB) Based System The first subsystem integrates GPIB instruments controlled

through the computer network (Internet). GPIB is a popular, worldwide standard for test and measurement system where the aim is to connect a computer and other systems. The built-in GPIB interface is needed in most units of the measurement systems (power supplies, function generators, oscilloscope). Various series of program and interface messages go through GPIB interface (for example status information, measurement results and control-configuration messages). GPIB instruments can implement an easy way to use instruments from the user side, because knowledge on instrument handling is necessary. The IEEE488 standard consists of hard limitations for the instrumentation arrangement, which reduces the range of applicability of the system.

The new generation of the GPIB controllers combines different instrument connectivity solutions with GPIB, keeping the advantages of the system and widening the instrumentation location possibilities. These combinations include serial buses, Ethernet, USB, IEEE 1394 (Firewire) and IEEE 1014 (VME bus). As one of the most widely used solutions, it was decided to use Ethernet for the development of GPIB system (Fig. 5.).

Fig.5. Block diagram of the GPIB system

• The new instrumentation system includes an oscilloscope, digital multimeter, function generator and triple power supply as follows:

• GPIB-ENET 100: this equipment is responsible for connecting GPIB devices and for connecting internet,

• TTi-PL-330P programmable power supply, • TEKTRONIX TDS 1002 oscilloscope (1 GSample / sec),

1000

• TTi TGA 1242 function generator: with the help of this device waveforms (sine, triangle, square) can be generated by setting frequency and amplitude,

• MULTIPLEXER / DEMULTIPLEXER module: this module is responsible for selection of the circuit with NI-PCI-6052E DAQ card (through digital outputs).

The system is connected to the traditional laboratory experiment, several amplifying electronic circuitries, like low-pass filter, unstable multivibrator, PI circuit, etc. When a user chooses between the circuits to be analyzed, function generator output is connected automatically to the circuit input, and the oscilloscope to the circuit input and output. At the same time GPIB controlled power supply is switching on and provides voltage supply to the circuit and to the instruments.

The concept is to gain experiences on the advantages of computer controlled measuring system on the one hand – and this is the main goal, – and just testing different electronic circuits on the other is entirely fulfilled.

Fig.6. Virtual interface of the GPIB instrumentation system

Software was developed in order to configure, control and measure the elements of virtual measurement system enabling to reach the remote measurement system with a simple web browser (Fig.6).

To run the software the following units are needed:

• The circuit has to be chosen through digital outputs of DAQ operational amplifier circuit are disposable (bypass, lowpass and bandpass filter),

• Signal has to be generated by function generator, and

• Measurement results might be analyzed by Digital Measurement Method (DMM) , the oscilloscope and FFT analyzer (Fig.6.).

C. Fieldpoint System The second subsystem includes modular instrumentation,

based on NI FieldPoint equipment. The National Instruments FieldPoint system is a flexible measurement and control system, built from modules. Modules are switched into cascade and connected to each other through the local bus connector. The 35 mm DN rail ensures fix positioning and safe connection of the modules.

The system must include an intelligent network controller, which is the central part of the system. This controller has its

own IP address and it is connected to the LAN on the RJ-45 Ethernet port. It also has a serial connector (RS232) to make direct connection to the PC if it is necessary.

Controller and measuring modules are connected to the main controller. The available modules of the system are :

• Analog input modules: they can be used for measurement of voltage and current signals of different ranges.

• Analog input/output modules: they serve as programmable input and output connections. The range of the signals can also be programmed.

• Analog output module: it integrates voltage or current generator with programmable ranges.

• Counter/timer module with count inputs, gates and outputs

• Digital input module

• Digital output module

• Digital Input/output module: programmable for receiving or sending digital signals

• QUAD module: quadratic controller for stepping motors

• Relay module can switch 24V or 230V

• Resistance Temperature Detection module can be used with different temperature sensors and for measurement of resistance changes (strain gauges, etc).

Fig.7. Motor and generator assembly with the speed sensor and the

controlling and measuring circuits

All the modules were developed for industrial applications with active noise reduction. The system supports real-time, embedded applications. The modules can run applications without input from the host computer.

D. User Interface for System Administrator The system administrator has permission to control all

functions of the connected modules, it has possibility to download control program to the Fieldpoint controller or to change IP address of the controller. Fig.8. shows the administrator’s user interface windows. The only administrator can change the module functions (for example switch over between the voltage or current measurement), change measurement range, or change relay module’s settings.

E. DC Motor Measurement by the Fieldpoint System The interface for the Internet users is developed with strict

safety limitations and with dynamic switching chances between the measurements. The software of FieldPoint contains three measurements: 1. Testing a linear position sensor; 2. Testing a small DC motor; 3 Testing power LEDs.

1001

All three tests include signals to be controlled by the Internet user through the analog output and relay modules of the FieldPoint and signals measured by different sensors on the analog inputs of the FieldPoint (Figs. 9.-10). Transducers based on Hall effect are used for current and voltage detection, a Pt100 resistance for temperature detection, and an encoder for revolution detection.

The DC motor is connected to a similar DC generator for providing controllable load to the motor.

Parameters to be controlled: voltage level of electricity supply and load.

Parameters to be measured: supply voltage, current of the motor, speed of rotation and Temperature of the motor.

Parameters to be computed: power and torque.

Fig. 8. User interface for system administrator for setting up controller

and modules. (Interfaces for FP-CTR-500 and FP-AO-2000)

Fig.9. Picture of the whole system . FieldPoint on the upper side; Linear

sensor test on the right side; Power LEDs test on the bottom side; Motor test on the left side; Web-camera in the middle

Fig.10. User interface of the FieldPoint system for DC motor test

REFERENCES [1] IEEE LTSC, Final 1484.12.1 LOM Draft Standard Document, IEEE

1484.12.1-2002. [2] SoundpraPandian, K.K., Manoj Rao and Sameer Khandekar: Remote-

access real-time laboratory: process monitoring and control through the internet protocol. International Journal of Mechanical Engineering Education, 6/26/2008, 2390 idd. p.1-14.

[3] Yang, S.H., Zuo, X. and Yang, L.: Controlling an internet-enabled arm robot in an open control laboratory. Emerald Group Publishing Ltd. Assembly Automation, Vol.24, No.3, p.280-288, 2004.

[4] Srinivasagupta, D. and Joseph, B.: An internet-mediated process control laboratory. IEEE Control Systems Magazine, 2003.

[5] Saad, M., Saliah-Hassane, H. Hassan, H., El-Guetioui, Z. and Cheriet M.: A synchronous remote accessing control laboratory on the internet. Proceedings of International Conference on Engineering Education, August 6-10, Oslo, Norway, 2001, p.8D1/30-8D1/33.

[6] Pérez-Herranz, V. et al.: An internet-based process control laboratory project. Proceedings of International Conference on Engineering Education, July 21-25 2003, Valencia, Spain, p.1-7

[7] Puerto, R. et al.: Remote control laboratory using Matlab and Simulink: application to a dc motor model. International Federation for Automation and Control (IFAC), 2004, p.1-6.

[8] Bauer, P. and Fedák, V. : Remote Controlled Experiments in ElectricalEngineering: a Survey. 8th Conference on Emerging eLearning Technologies and Applications. The High Tatras, October 28-29 2010 Slovakia p. 1-9

[9] M&M Software Northern Ireland Ltd: Monitoring offshore-platforms via internet. p.1-2. www.mm-software.de

[10] http://www.lmsintl.com/simulation/lmsvirtuallab [11] Szentirmai, L., Váradi, Sz. A. and Szarka, T. : Internet at the service of

electrical machinery and drives. Invited paper. Electronic Proceedings of Joint International Conference of Aegean Conference on Electrical Machines and Power Electronics (ACEMP) and periodical Electromotion, p.656-667. Istanbul, Turkey, 8-10 September 2011.

[12] Sz. A. Váradi: “Remote Control of Intelligent Virtual Instrumentation using the Internet.” OGÉT 2005. Szatmárnémeti, Romania, pp.156-159.

[13] FieldPoint User Manual (2002), National Instruments, USA. [14] Váradiné Sz.A.: „Monitoring System for Breakdown Identification of

Induction Motors.” NIWeek '95 Conference, Austin, USA, July 23-28, 1995. p.12/1-12/7.

1002