Supervising Professor: Panayiotis S. Shiakolas
Title: A Magnetic Levitation Device an Engineering Education Testbed.
Abstract
This report discusses the use of a magnetic levitation device as an aid in engineering education. There are several classes at UTA that can benefit from the use of such a device. A specific analysis, design, build, and operation of the device as well recommendations for future work on this particular device are discussed.
Introduction
A magnetic levitation device is ideal for classroom demonstration and laboratory work. If the electromagnet is inverted and used to pull an object up into the air then the system is inherently unstable. Also, the magnetic force is a highly non-linear function of air gap and coil current. These two characteristics alone can be used to demonstrate several concepts conveyed throughout the semester in courses involved with system modeling and analysis, automatic control, control systems components, measurements and instrumentation, statics, and rigid body dynamics.
The device is made up of 3 basic components: the electromagnet, a sensor to detect the object’s position, and the control electronics. In our particular case the object is a steel ball and the position sensor is a IR emitter/phototransistor. The electromagnet is 3600 turns of 22 AWG enamel coated wire wrapped around a steel core. The control electronics use 2 dual operational amplifiers for compensation, sensor offset/gain, coil current bias and power amplifier gain. The power to the coil is supplied through a bipolar junction transistor. The figure 1 shows the mechanical configuration of the device. The IR emitter/phototransistor are mounted inside the tube on either side of the ball. The delivery mechanism is marked in 22.5 degree increments to provide for the ease of sensor gain determination. The entire delivery mechanism is adjustable between the vertical supports to allow for changing of the air gap while maintaining the ball/sensor relationship so that once the ball has been positioned in the sensor zero position it never needs to be adjusted again. Jam nuts have been provided to lock down the position and provide for repeatable positioning.
The system governing equations, block diagrams, control design and analysis are shown in the following sections. A discussion of recommendations and a summary is included.