At Rensselaer


Controlling Unstable Systems

Paul Castle

Tubes of water are a key component in the hydraulically balanced beam system designed and built by mechatronics students.

When a system is inherently unstable, it takes a creative control system to maintain balance. A group of Rensselaer seniors and first-year graduate students demonstrated this spring that they are mechanical engineers with sufficient understanding of computer controls to create such systems.
  Students in the second course of a two-course sequence in mechatronics presented four projects they had designed, analyzed, modeled, and built during spring semester: a hydraulically balanced beam system, a ball-on-beam balancing system, a ball-on-plate balancing system, and a device that encompassed two inverted pendulum systems, rotary and arm-driven.
  Mechatronics integrates mechanical engineering, control engineering, electronics, and computer science into the design process, according to Kevin Craig, associate professor of mechanical engineering and originator of the course. Mechatronics engineers are needed because electronics and computer controls have became so common that mechanical engineers must consider them from the earliest stage of design.
  In the hydraulically balanced beam system, for example, a horizontal bar rotated about a pivot point, much like a seesaw. Two cylinders of water were installed atop the bar and a pumping system could move water back and forth between them. The students demonstrated that when they gave the device a shove and started it rocking up and down, the computer control system operating the pumps shifted sufficient water from one cylinder to another to bring the bar back into horizontal balance.
  Visitors from industry and from local schools viewed the presentations, which were held in the School of Engineering's newest studio classroom, a large amphitheater in which those seated around the room could get a close-up look on flat-panel displays located on their desks.


All rights reserved
© 1999 Rensselaer Polytechnic Institute
Send comments, opinions, or questions to