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SCARA Development, Servo Controller for a Dynamic Arm Robot


Sven Zwicker

Semester/Bachelor Thesis, WS 04/05

SCARA robots are normally used for pick-and-place operations which require high-speed reproducible movements. The Automatic Control Laboratory has an old IBM 7575 model. A SCARA has four joints and therefore four degrees of freedom powered by four dc motors. The outdated control environment and servo drivers were to be replaced with a more modern Rapid Application and Development (RAD) package based around real-time operating systems. xPC Target was selected as the real-time operating system for this work. This rapid prototyping package allows dierent types of control systems to be developed under Matlab Simulink, downloaded to the xPC Target and run in real-time.
The first step was to investigate replacing the existing servo drivers with small compact circuits which can accept analog input voltages and provide voltage scaled outputs at high currents. The H-Bridge motor driver A3959 from Allegro Microsystems, Inc. was chosen to fulfill this task. No manuals nor circuit diagrams were available for the IBM 7575 manufacturing system, so that everything had to be identified by first principles. Very helpful preparatory work was done by Marc Lawrence from the institute who was able to obtain some circuit diagrams and who had already started identifying pins. With the interfaces and pin assignments identified other needed components such as voltage regulators, optocouplers to electrically isolate all signals, and differential line receivers to convert differential encoder signals into single-ended signals were selected. A circuitry for the new servo driver unit was designed and a one-axis prototype was built on a breadboard. Furthermore a dc power supply with 48V and 10.4A output ratings was ordered to provide enough power to drive the robot's servo motors.
A printed circuit board (PCB) was developed using state-of-the-art CAE/CAD techniques. The schematic entry and the physical layout was done using Protel - a board-level CAE/CAD software. All components and connectors were placed on a four-layer printed circuit board with the size of 100 183mm. Design rules were set up, components were routed and manufacturer's data was created. Once the the board was built by the manufacturer and delivered, components were soldered and some basic testing could be done.

Supervisors: U. Maeder, Dr. F.J. Kraus, Prof. M. Morari


Type of Publication:

(13)Semester/Bachelor Thesis

F. Kraus

No Files for download available.
% Autogenerated BibTeX entry
@PhdThesis { Xxx:2005:IFA_2789
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