Texas A & M University : Virtual Electrical Drives Enhance Engineering Learning

A major challenge of electrical engineering professors is to provide a laboratory environment in which their students can reinforce their understanding of complex engineering concepts in a way that is pedagogically valid, cost-effective and - above all - safe. This is particularly true when trying to understand the effects of the various parametersin an electrical drive system.

By their nature, these systems are costly to acquire and maintain, require high voltages and currents to drive them and, hence, need very close supervision. In fact, in order to minimize potential danger and damage, the range of experiments that can be carried out are so proscribed, the level of experience students gain is very limited. Also, because of the cost of such systems, most universities can't afford enough systems to provide any depth of experience for all their engineering students.

One solution to this problem is being used by a team of electrical engineering teachers at Texas A & M University. Prof. Mehrdad Ehsani and his assistant, Mr. Neeraj Shidore, have developed an electrical drive simulator that behaves exactly like a real drive, but without the inherent dangers. Using this system, students can work on experiments and other coursework completely unsupervised - changing parameters and observing the effects on the drive without fear of causing damage if they make a mistake.

"In fact, entering erroneous parameter values is encouraged", said Mr. Shidore, "in this way, they can build an intuitive feel for the envelope of operation, beyond which the system goes unstable, and understand why things go wrong."

Beyond the safety aspects, students are able to modify parameters that would be difficult, or even impossible, in a real system. Changes to rotor mass, winding configurations, and physical dimensions can be easily accommodated in the system in order to optimize a design for given duties. "There's no way you can do that on a physical drive system", Mr. Shidore told us, "We can even offer the student a range of completely different types of drive to work with on the same workstation"

Based on the RT-LAB real-time simulation platform from Opal-RT Technologies, and using drive models developed in-house on Mathworks' Simulink, the electrical drive simulators provide a high-fidelity, flexible environment for the student, in order to give them an experience that is as close to reality as possible.

"We believe that it is essential that the system runs in hard-real-time at high update rates because we don't want students to get fixated on the fact that it is a simulation," Mr. Shidore explained, "Other so-called real-time environments introduce computational errors through jitter into the simulation that effected the behavior of the system, so you had to warn the students that certain results could be due to the simulation, not the physical behavior of the drive. With RT-LAB, this is no longer an issue."

The students use a specially developed user interface, created with National Instruments' LabVIEW, to change parameters by simply turning knobs or sliders on the computer screen and observing the results in on-screen "scopes". The entire system is supplemented with a comprehensive set of experiment notes that keys into the "chalk and talk" elements of the course.

So, does this spell the end for physical electrical drive systems in the teaching lab?

"Absolutely not," Prof Ehsani told us, "We view the virtual electrical drive system as an excellent complement to the physical system - nothing will replace getting your hands on the real thing. I see our tool as a way for universities to eliminate the limitations of physical systems in the learning process, allowing the student to gain a deeper understanding through exploration beyond the proscribed experiments. This gives the students an opportunity to be more creative and self reliant in their learning and practice of engineering. In this way, when they do work on the real system, they have a much greater appreciation of what they are working with, reducing the risk of damage to the system, or injury to themselves."

Click here for more information about the Virtual-Actual Laboratory for Power Electronics and Motor Drives.