The intrudoctory post

Hello,

let's get the introduction out of the way first - My name is Viktor Kajml and I study robotics at the Faculty of electrical engineering at the Czech technical university in Prague. During this summer I have been chosen for a temporary job at AA4CC - one of the faculty's research groups. More specifically I will be participating in the development of a project called MagMan, which is a device for planar manipulation of objects by the means of generating and shaping magnetic field.

The purpose of this blog is document the progress of my work on this project and, provided there will be no unexpected complications, it should be updated about once every week.


A full description of the MagMan device can be found in this article but I will provide a brief summary here as well. Basically, it consists of an array of electromagnets, which are individually controlled to generate the desired magnetic field and move the test object (currently a metal ball) around. The array is composed of a number modular units, each of which contains four electromagnets, mechanical and electrical connectors that plug into the rest of the array and a microcontroller, which I shall describe in more detail, because it will be the focus of my work.

The used micro controllers are LPC1313 with the ARM Cortex-M3 microprocessor. Their function is to measure the current running through the four electromagnets, regulate it by generating the correct PWM signals and to communicate with the master computer via RS485 bus.

My task will be to improve and finalise the microcontroller firmware. This will involve completing several different sub tasks:

First of these will be to implement a bootloader that will allow re-programming of the micro controllers over the RS485 bus. This feature is sorely needed, as manual re-programming of each individual module over it's dedicated programming pins is very cumbersome and will only get worse as the array grows in size.

Next task will be to make the communication over the RS485 as fast as possible. Again this is necessary, if we want to extend the array, in order to keep the delays in communication with the master computer sufficiently short and to allow for an effective control.

Lastly, it would be desirable to implement a feedback controller to handle the regulation of the currents flowing through the electromagnets. As of right now the regulation consists simply of setting the desired duty cycle of the controlling PWM signal and no feedback is utilized. As a result the rise time of the value of the current is sub-optimal, which affects the overall control of the magnetic field.

I think that this is quite enough of work for right now and I hope that next week I will be able to post some results.