Evaluation of vision-based robot control configurations for reconfigurable assembly

Steed, Clint Alex (2016-03)

Thesis (MEng)--Stellenbosch University, 2016.

Thesis

ENGLISH ABSTRACT: This thesis considers vision based robot control for a reconfigurable manufacturing cell. Reconfigurable manufacturing systems are aimed at rapidly adapting to fluctuations in market demand, shorter product life cycles and product customization. Computer vision is a promising component of such manufacturing systems, in particular aiding the flexibility to handle a range of products with reduced set-up time and fewer fixtures. The objective of the research presented here was to develop a simulation-based approach to compare eye-in-hand and fixed camera vision-based control within a reconfigurable assembly cell. These configurations have dissimilar system costs and system performance characteristics. The research used a KUKA six degree of freedom articulated arm robot, a DVT Legend 540 camera and a Cognex ism-1100 camera, as well as the software supplied with the cameras. The simulation was aimed at predicting the throughput rate of multiple eye-in-hand and fixed camera configurations, where configurations include varying the numbers of reconfigurable singulation units, positions of machines, parts being singulated, etc. The throughput rates for different configurations can then be compared to their costs and ease of reconfiguration. The simulation uses a holonic control system that was designed based on the ADACOR architecture. The thesis describes in detail the holons used, including their hardware, data structures and responsibilities. A multi-agent system was implemented for high-level control and some of the agents communicated with their respective lower-level controllers during validation testing. In the simulation, software (including KUKA Simpro and some custom software) replaced the hardware and low-level controllers. Tests on a number of physical laboratory configurations were used to validate the simulation. The simulation's application is demonstrated in a number of experiments in which cell configurations and machine performance were varied. For example, for a particular situation simulated, these experiments showed that the eye-in-hand configuration has a competitive cost to performance ratio when tasks have a significant waiting period (pallet exchange time, tasks deployed sparsely, etc.). In most experiments, however the fixed camera configuration performs better. The simulation allowed “hardware in the loop” testing, which also makes it a useful tool for development of the cell.

AFRIKAANSE OPSOMMING: Hierdie tesis ondersoek visie-gebaseer robotbeheer vir 'n herkonfigureerbare vervaardigingsel. Herkonfigureerbare stelsels is daarop gemik om vinnig aan te pas by skommelinge in die markaanvraag, korter produklewensiklusse en produk-aanpassings. Rekenaarvisie is 'n belowende onderdeel vir sulke stelsels, in besonder vir die buigsaamheid hantering van 'n reeks produkte met verminderde opsteltyd en verminderde gebruik van setmate. Die doel van navorsing wat hier aangebied word, was om 'n simulasie-gebaseerde benadering te ontwikkel vir die keuse tussen "eye-in-hand-" en vaste-kamera-beheer in 'n herkonfigureerbare samestelling-sel. Hierdie konfigurasies het verskillende eienskappe ten opsigte van stelselkoste en -werkverrigting. Die navorsing het 'n Kuka ses vryheidsgraad geartikuleerde-arm-robot, 'n DVT Legend 540 kamera and 'n Cognex ism-1100 kamera, asook die programmatuur wat met die kameras voorsien word, gebruik. Die simulasie is daarop gemik om die deursetkoers van verskillende "eye-in-hand-" en vaste-kamera-konfigurasies te voorspel, waar konfigurasies verskillende aantal herkonfigureerbare singulasie-eenhede, posisies van masjiene, onderdele wat gesinguleer word, ens. insluit. Die deursetkoerse van verskillende konfigurasies kan dan met hul koste vergelyk word. Die simulasie gebruik 'n holoniese beheerstelsel, gebaseer op die ADACOR argitektuur. Die tesis beskryf in detail die holons wat gebruik is, insluitend hul hardeware, datastrukture en verantwoordelikhede. 'n Multi-agent-stelsel is geïmplementeer vir die hoë-vlak-beheer en sommige agente het met hul onderskeie laer-vlak-beheerders tydens validasie-toetse gekommunikeer. In die simulasie is die hardeware en lae-vlakbeheerders vervang met programmatuur (insluitend Kuka Sim Pro en sommige doelgemaakte programmatuur). Toetse op 'n aantal fisiese laboratorium-konfigurasies is gebruik om die simulasie te valideer. Die simulasie se toepassing is gedemonstreer in 'n aantal eksperimente waarin selkonfigurasies en masjienprestasie gewissel is. Byvoorbeeld, vir 'n spesifieke konfigurasie wat gesimuleer is, het die eksperimente getoon dat die "eye-in-hand"-konfigurasie 'n laer koste-tot-prestasie-verhouding het wanneer take 'n beduidende wagtydperk (ruiltyd vir pallette, take yl ontplooi, ens.) het. Die simulasie het "hardeware in die lus" toetsing moontlik gemaak, wat dit ook 'n nuttige hulpmiddel maak tydens die ontwikkeling van die sel.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/98803
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