Remote Manipulation with LabVIEW for Instruction

Author(s):
Denis Gillet - Swiss Federal Institue of Technology - Lausanne (EPFL)
Eduardo Gorrochategui - Swiss Federal Institue of Technology - Lausanne (EPFL)
Christophe Salzmann - Swiss Federal Institue of Technology - Lausanne (EPFL)

Industry:
University/Education

Products:
PXI/CompactPCI, LabVIEW

The Challenge:
Manipulating a physical setup located in a remote laboratory, so teachers can instruct from the classroom and students can learn from home. Providing distance access from campus, as well as worldwide.

The Solution:
Taking advantage of LabVIEW capabilities, such as distributed computing tools, to build a link via the Internet between client computers and the physical setup. Designing a user interface that reproduces the look and feel of the local environment on the client side by combining virtual representations and live video feedback of the distant setup.

Introduction
Instructors need to have a distance-learning opportunity readily available for classroom teaching. To avoid moving the experimental setup to the classroom or to overcome the difficulties of accessing laboratory facilities at any time, it is useful to provide interactive and remote access to such facilities. We designed a multiplatform client-server solution based on personal computers, which share information across the Internet, to serve this paradigm. LabVIEW is clearly the ideal candidate to provide the high level of interactivity and interoperability required for educational purposes.

View and Control through VI
One of the physical setups available for studying motion control at the EPFL consists of the real process - a servo drive - connected to a Power Macintosh via a data acquisition (DAQ) board, National Instruments PCI-1200. The control software locally piloting the real process is a program (VI) built using LabVIEW. An in-house real-time kernel extends LabVIEW capability and guarantees high speed and accurate pace.
The VI provides a complete interface between the user and the real process. With the VI, the user can generate excitation signals and observe corresponding responses. The main purpose of such an interface is to provide a general view of the real process evolutions and facilitate full control of the operations.

Communication Layer Provides Remote Control
Given its fully computer-based implementation, we can easily expand the laboratory environment for remote manipulation. To turn the locally controlled setup into a remotely controlled one requires moving the user interface away from the experiment. Two distinctive parts result - the remote client and the local server.

• The remote client is a computer equipped with the user interface functions. The client software, with which the users can observe and act on the remote experiment, is an executable application compiled for the target platforms using the Application Builder.
• The local server is the computer located in the laboratory, equipped with the hardware interface to the sensors and actuators. The server software receives the client commands and transmits them to the real process. It also returns the state of the real process to the client.
• A communication layer built on LabVIEW distributed computing tools links the client and server.
  
  

Distributed Computing Tools
National Instruments has introduced an approach to call a sub-VI in LabVIEW, referred to as a call-by-reference. This principle is similar to remote procedure call (RPC) under UNIX. Implementing an approach with LabVIEW means simplicity and ease of use. With this new mechanism, we can call a sub-VI on a local or remote machine transparently using TCP/IP. The only difference between these two types of calls is the need to define the IP address and IP port of the remote machine. The remote machine, acting as a server, needs correct configuration. Prior to calling the sub-VI, the user needs to establish a connection with the server. On termination, the user needs to close the connection.

On the server side, the user can specify access by allowing or denying given addresses or domains. The user can also restrict access to the VIs called. To implement the remote manipulation of the setup, we used four call-by-reference VIs. The first one transmits the controller parameters from the client to the server, the second sends the measured values from the server to the client, and the last two implement watchdogs to detect if the client or server is still available.

Applying the Remote Laboratory
We apply the remote, manipulation paradigm regularly in the basic automatic control course taught at the EPFL. Students from electrical engineering, mechatronics, mechanical engineering, and computer science attend this course simultaneously in a large auditorium. The teacher manipulates the client software installed on a portable computer equipped with a built-in Ethernet interface. The students can view a copy of the computer screen projected onto the wall.

We perform remote manipulation of the servo drive during the lecture to enhance the presentation of the subject matter. According to the topic studied, instructors can select different configurations - position or speed control, P, PI, or PID controllers with different sets of parameters. The user receives the transmitted image and sound of the physical setup via video-conferencing software. The audio/video server runs in parallel and independently of LabVIEW on the computer connected to the real process (server).

Easy Instruction and Experimentation
With the LabVIEW distributed computing tools, we can perform highly interactive remote manipulation inside an institution equipped with an intranet. This requires only minor changes when a local solution already exists. Therefore, the tools are well suited for live demonstrations conducted by the instructor in the classroom or for experimentation carried out by students from a computer laboratory.

For more information, contact:

Denis Gillet and Christophe Salzmann

Swiss Federal Institute of Technology - Lausanne, IA - DGM - Ecublens

CH - 1015 Lausanne, Switzerland

E-mail: denis.gillet@epfl.ch and christophe.salzmann@epfl.ch

Browse All Case Studies »

  Print