Gelenkarm
Performers
Peter, Markus Groß; Paul Reiter; Stefan Miedler
Persons in charge
Dipl.-Ing. Andreas Schubert, Dipl.-Ing. Gerhard Jüngling, Dipl.-Ing. Roland Glas
Conceptual Formulation
Within this final year project a robotic arm has to be designed, built and tested. This arm composed of upper and forearm should have a rotatable grabber on the bottom and it should be mounted on a frame structure. The grabber should be able to pick up the standard parts that are used in the AUT Lab. In addition on every hinge a gear motor is mounted to provide high dynamics. The objectives are
- to realise the individual control of both arms,
- the movement of both arms at the same time and
- the movement of both arms that the grabber performs a straight vertical move.
Therefore the velocity plots of the hinges have to be calculated because these plots are necessary for the software and the vertical movement of the grabber. This robotic arm is financed from the school because the project is intended for a programming practise ground for new students.
As an add-on the robotic arm could be mounted on a linear module to get a 2D portal robot. Then robotic arm is also able to move horizontal.
The arm should not be extended to a 3D area robot because the time would not suffice. In addition the control and the sensors would be to complex. Another point that should not be realised is the automatic detection of the standard parts on a conveyor which is determined under the robotic arm. The priority should be the control and positioning of the arm and not the identification of the parts.
Details on Execution
The robotic arm is mounted on a frame of Aluminium profiles and on every articulation a motor with gear is assembled. The target is to realize a straight and vertical movement of Point P1 and the single control of each motor must be possible.
The engines need a brake or a worm gear to stay at a specific position. Engine 3 is only used to hold the grabber vertical. If necessary, gears with a high reduction could be used because these gears are approximately self-locking.
The grabber should be able to pick up small practice parts from the AUT-laboratory. The two arms have the same length to assure the straight, vertical movement. The arm is mounted at a high where it is able to reach the parts on the floor when the robot arm is full extended.
The motors are equipped with encoders which report the actual position to the control software. This software simulates a programmable controller on a PC and communicates with Ethernet over a bus terminal with the engines and the grabber. The software is called TwinCAD provided by Beckhoff. The system is real time compatible and that is very important for these positioning jobs.
The bus terminal contains DC motor clamps, I/O clamps for the grabber and the sensors and a bottom clamp. The motor clamps drive the engines with a PWM signal and they are able to gather the encoder signal which is important for positioning. These is one of the basic components without the robotic arm would not work.
HTL Wien 3 Rennweg, May 2007
