Robot control systems can be considered complex systems, the design of a controller involving the determination of the dynamic model for the system. This in itself can be a complicated task due to non-linearities, multiple axis (degrees of freedom) control and the constantly changing working environment. Problems arise when the theoretical model produced for such a system is not accurate. When developing a controller using conventional techniques a design scheme has to be produced, usually based on a model of the system. In addition kinematics equations must be derived to take into account the physical boundaries of the system. The work outlined in this thesis utilises fuzzy logic control to address these control issues. Fuzzy logic provides functional capability without the use of a system model and has characteristics suitable for capturing the approximate, vaiying values found in real world systems. Initial development of a single axis fuzzy logic control system was implemented on a Dainichi industrial five-axis robot, replacing the existing control and hardware systems with a new developmental system. The concept of fuzzy logic and its application to control highlights the potential advantages that fuzzy logic control (PLC) can provide when compared to the more conventional control methodologies. Additional new control hardware has been interfaced to an existing robot manipulator, making it possible to compare PLC and PIDVF (Proportional Integral Derivative Velocity FeedforwardlFeedback) controllers for single axis development. Average response time and overshoot for a given set point were compared for each system. The results proved that, using a basic PLC minimal overshoot and fast rise times could be achieved in comparison to the commercial PIDVF system. Further research concentrated on the development of the control software to provide multiple axis control for an industrial robot using a continuous path algorithm. The more from single axis to multiple axis control provided a much more complex control problem. A novel and innovative process for the fuzzy controller was implemented with up to three axes reaching the target point simultaneously. Control of the industrial robot was investigated using methods that were more suited to real time controL The most significant change was a reduction in the number of fuzzy rules when compared to single axis control. During robot control no adaptation of the rule base or membership functions was carried Out Ofl line; only system gain was modified in relation to link speed and joint error within predetermined design parameters. The fuzzy control system had to manage the effects of frictional and gravitational forces whilst compensating for the varying inertia components when each linkage is moving. Testing based on ISO 9283 for path accuracy and repeatability verified that real time control of three axes was achievable with values of 938tm and 864tm recorded for accuracy and repeatability respectively. The development of novel industrial robot real time multi-axis fuzzy controller has combined new control hardware with an efficient fuzzy engine addressing inverse kinematics, scaling and dynamic forces in order to provide a viable robot control system.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:369240 |
| Date | January 2001 |
| Creators | Breedon, Philip James |
| Publisher | Nottingham Trent University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://irep.ntu.ac.uk/id/eprint/10298/ |
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