Internet Laboratory Server in Engineering Systems Laboratory
Jim Henry, Ph.D., P.E.
Professor, Chemical and Environmental Engineering
College of Engineering and Computer Science
University of Tennessee at Chattanooga
Chattanooga, TN 37403, USA
The engineering systems laboratory at UTC has been made available for users via the World Wide Web. Users can conduct systems lab experiments from remote sites.
The hardware consists of distributed desktop computers connected to a variety of engineering laboratory equipment. The software is all implemented with LabVIEW. This paper describes the hardware and software that is used for this facility, describes the way the server & clients are managed and discusses strengths and "opportunities for improvement" that have been discovered. In other words, where the future lies in this project.
The web address (URL) for the lab is http://chem.engr.utc.edu
HARDWARE AND SOFTWARE
The systems laboratory at UTC for several years has been using desktop computers for data acquisition and control of engineering equipment. The students conduct experiments to accomplish system identification and to design feedback controllers for the systems. The data acquisition and control software is written with LabVIEW software. Controller design involves tuning two feedback controllers: a proportional controller and a proportional-integral controller.
The computers are all networked with ethernet and have internet (IP) addresses. A web-server program was developed which allowed users to conduct experiments using widely available web browsers. The users conduct the experiments either from computer labs on campus or from home computers via internet providers.
More details are given in Henry (1996).
Six different stations for systems experiments are available. They consist of
1. .. Pressure control by varying the speed of a blower
2. .. Level control in a water tank by varying the speed of a water pump
3. .. Flow control in a closed flow loop by varying the speed of a pump
4. .. Speed control of a motor-generator set by varying the signal to a motor power supply
5. .. Position control in a cart-on-a-rail by varying the torque in a motor
6. .. Temperature control in a heat exchanger by varying the flow rate of a hot water supply.
. .. (in development)
Each of these is a single-input, single output system. All are inherently stable systems when run in open-loop configuration. That is, if you specify a fixed input value, the system will reach a constant steady-state condition.
More complete descriptions of these have been given before (Henry, 1993, and Henry, 1995).
The systems are operated by student operators using the LabVIEW software on desktop computers at each station or by the Web user as described below. The software operates the equipment under the conditions of parameters as chosen by the student operators.
Seven different experiments can be run on each of the laboratory stations. The software runs an experiment, collects the data and writes the data on the Web server at the end of the experiment. The Web server computer draws a time response graph of the experimental data and returns the graph on a Web page. The file of results data is available to the Web user. The various experiments consist of the seven listed in the table below.
Experiments available. System identification (1-5) and controller design (6 & 7)
. .. Name. .. Application. .. Steady-state operation. ..
1. .. Constant input . .. Developing the steady-state operating curve for the system
-------------- System Dynamics -------------
2. .. Step input . .. Finding the first-order plus dead-time (FOPDT) parameters
3. .. Sine input. .. Finding the Bode plot
4. .. Pulse input. .. Refining the FOPDT parameters
5. .. Custom input. .. Design your own input function. Ramp, sawtooth, triangle, for examples.
------- Feedback Control ------------
6. .. Proportional feedback. .. Verifying controller design. Determining region of stability, quarter decay, offset, etc.
7. .. Proportional-integral feedback. .. Verifying controller design. Determining region of stability, quarter decay, offset, etc. Observing reset windup.
All stations are available for experimentation via the World Wide Web. Experiments run via the Web are run in "batch" mode. The steps for running an experiment via the Web are diagrammed in the figure below.
UTC is committed to continuing to develop and expand this Web-available laboratory. Extending the experiments to include thermodynamics, heat transfer and chemical engineering unit ops is in the plans.
UTC's Center of Excellence for Computer Applications has supported this effort with a generous grant. Other support has been received from the UTC College of Engineering and Computer Science, National Instruments, Plant Engineering Consultants, Apple Computer and Analog Devices. Partial support for this work in the lab is being provided by the National Science Foundation's Division of Undergraduate Education, Instructional Laboratory Improvement (ILI) grant DUE #97-51024 .
Henry, Jim, (1993), "Engineering Controls Systems with LabVIEW," Scientific and Engineering Applications for Macintosh, Woburn, MA, August, 1993. Available via Web at http://chem.engr.utc.edu/Henry-Pub
Henry, Jim, (1995), "LabVIEW Applications in Teaching Controls Systems Laboratories," ASEE Annual Meeting, Anaheim, CA, June, 1995. Available via Web at http://chem.engr.utc.edu/Henry-Pub
Henry, Jim, (1996) "Web-based Controls Laboratory Hardware and Software," available via Web at http://chem.engr.utc.edu/Henry-Pub