E-LABORATORY PRACTICAL TEACHING FORAPPLIED ENGINEERING SCIENCES

OPEN DAYUniversity of Oradea

12 March 2012

Project HURO/0901/028Acronym: EPRAS

Pavel Alina, University of Oradea, Romania

The content of this presentation does not necessarily represent the official position of the European Union.

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Control of a Stepper Motor Using Data Acquisition Systems and LABVIEW

Purpose

This presentation illustrates the physical structure of an application and how to use a LabVIEW virtual instrument remotely from a web browser, Internet Explorer. The central piece of the application is a stepper motor, and its stepping modes and several practical aspect of command are being studied.

Obtaining the control of the application remotely

The LabVIEW application VI must be loaded on the server computer in order to obtain remote control through Internet Explorer.

Once this application VI is published for web, there is only one person who can control

the application at a time, because we choused the VI not to be reentrant, for stepper motor safety reasons.

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Clients navigate to the Web Server by entering the Web address of the Web Server in the address or URL field at the top of the Web browser window. The plug-in displays the front panel in the Web browser window and communicates with the Web Server so the client can interact with the remote front panel. Clients request control by selecting Request Control of VI at the bottom of the remote front panel window in their Web browser or by right-clicking anywhere on the front panel and selecting Request Control of VI from the shortcut menu.

If no other client is currently in control and if no other browser window on the same connection is currently in control, you have control of the front panel. If another client is currently controlling the VI, the server queues other clients requests until the client in control relinquishes control or until the control time limit times out. In the mean time a message is prompted to the new client. After opening front panel of the VI in the Internet Explorer, the client obtains control of the VI if no one else is working.

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There are several messages that can be seen on the front panel in Internet Explorer when working.

When the client gains control, the message is “Control granted”.

After that, you will follow the indications for register, and do the application.In the meantime, others could see the front panel of the same application, but with limitation. Only a controller can remotely view the front panel of a VI dynamically opened and run using the VI Server or the front panel of a subVI configured to display the front panel when called. Clients not controlling the VI cannot view the front panel. As you see in the next figure, there could be many clients requesting control at the same time.

If the server requested the control of the VI, the client will see:

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When you are done with the application, release it.

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III. Application structure

- Step motor control board, with Applied Motion Products 5023-196D stepper motor- Personal Computer, “Epras1”- National Instruments LabVIEW 2011, fall edition- NI USB 6216 DAQ device- NI USB 6361 DAQ device- Manufactured board for acquiring stepper motor currents - MATRIX power source- A4Tech USB camera- Application programs

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IV. Work to do

After obtaining the control of the VI, the user must use the password obtained from the test. The front panel of registration window is the following:

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After you launch the VI, appears the user dialog, as in Fig a.: If you passed the test and obtained the password to run the application, type in your name and password, click OK button and the message indicated in Fig b. will pop up:

User registration window Message on successful registration

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After another click on OK the block diagram the main acquisition program will launch.

If you do not have a password or you have typed the wrong password the following message will be displayed to you:

www.huro-cbc.euThree aspect are important to our VI:

1. Controlling the stepper motor; as an example, is Digital commands for full stepping.vi:

www.huro-cbc.eu2. Representing the phases currents, with contcurrentmeasurement_epras.vi

3. Using a web camera in order the remote clients to see the actual motor.

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CONCLUSIONS

Because the stepper motor is not working in these pictures, the current is nearly to zero. When working, you will obtain pulses, and you have to analyze them to see how close to the square form they are.

Because the stepper motor has 4 phases, at running time you should observe the effect of selected o number of steps that is a multiple of 4, multiple of 4+1, multiple of 4+2, and multiple of 4+3. You can observe if the number of steps to execute is the same as the number of steps executed, as acquired.

For the same problem you will observe on the camera the rotating direction for the first step executed in all b. situations.

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Thank you for your attention!