Event Details

Design, Fabrication and Control of a Microrobotic System Using Magnetic Levitation

Presenter: Dr. Behrad Khamesee - University of Calgary
Supervisor:

Date: Tue, August 12, 2003
Time: 14:00:00 - 15:00:00
Place: EOW 430

ABSTRACT

This research presents a prototype microrobotic system based on magnetic principles. The goal is to build a system in which miniature items can be transported and assembled within hazardous environments. A microrobot can be remotely operated with three degrees of freedom (DOF) in an enclosed environment by transferring magnetic energy and optical signals from outside. A magnetic drive unit generates magnetic energy for the microrobot's manipulation. The drive unit consists of eight electromagnets (four pairs), two permanent magnets, a return yoke made from a soft magnetic iron, and a special pole-piece. The microrobot is manipulated in a workspace under the pole-piece by regulating magnetic field. It consists of three main components; magnetic head, body consisting of electronic circuit and batteries, and fingers made from two thin ribbons of a copper alloy. A shape memory alloy (SMA) actuator activates the fingers to grasp or release an object by illuminating/extinguishing several LEDs facing the microrobot.

PID controls are applied for positioning of the microrobot in the three axes. As the microrobot deals with various payloads, a PID control may not be sufficient to maintain the microrobot on high performance in the vertical axis. To improve the performance, an adaptive control law is also examined for the positioning in the vertical axis so that the controller parameters become adjustable in real-time to cope with uncertainties and variations in payloads. A model-reference adaptive system (MRAS) based on the augmented error is designed, and simulations and experiments are conducted to verify the effectiveness of the control. The microrobot has a net mass of 8.1 g, and it can elevate and manipulate objects with masses of up to 1.5 g within a volume of approximately 30-mm cube with a precision of 0.05 mm.

Prototyping a Novel Instrument Combining Fluorescent Microscopy and Surface Measurement Tools

The objective of this project is to develop a Visualized Captive Bubble (VCB) from ideas and concepts, to design, to development, and on to implementation. The Visualized Captive Bubble VCB enables studies of surface active agents from macroscopic and microscopic points of view using image processing and fluorescence microscopy. Of particular application is simulation of alveoli to test and develop new drug treatments for respiratory diseases such as Respiratory Stress Syndrome. An alveolus is molded and simulated by an air-bubble. Development of the VCB is divided into four major tasks:

  1. Image acquisition software,
  2. Automation control software,
  3. Hardware design and fabrication, and
  4. Image processing software.
The VCB consists of a self-contained fluid chamber. An air-bubble is injected into the chamber which floats under a vertically movable stem. Two microscopes are focused on the bubble in order to study the surface active agents (e.g. lung surfactants). Using a computer-controlled dispenser, the size of the bubble is varied by adjusting the volume of the injected air (e.g., to simulate breathing). By varying the size of the bubble, a mechanism is needed to maintain the apex of the bubble in the focus of the fluorescence microscope. To do this, a servomotor moves the stem up or down to keep a constant distance between the bubble apex and the objective of the fluorescence microscope. The servomotor operates in a closed loop with a fuzzy PID control algorithm and a feedforward compensator.