magistrsko delo
Mario Klenovšek (Author), Matjaž Mihelj (Mentor), Sebastjan Šlajpah (Co-mentor)

Abstract

Zaradi premika industrije od masovne proizvodnje k masovnemu prilagajanju je željo po popolni avtomatizaciji industrijskega procesa izrinila želja po delni avtomatizacij. Pri delni avtomatizaciji gre predvsem za sodelovanje med robotom in človekom pri izdelavi skupnega izdelka. Pri takšnih aplikacijah postane velik problem zagotavljanje varnosti delavcev, ki si delijo delovni prostor z robotom. Da bi bili namerni ali nenamerni kontakti med operaterjem in strojem varni, so v zadnjih letih izšli številni standardi, ki pokrivajo področje varnosti. Ti dokumenti zahtevajo izvedbo detajlne analize tveganj vsake izdelane sodelovalne aplikacije. S pomočjo analize se ugotovi morebitne nevarne kontakte, pri katerih je potrebno izmeriti silo kontakta. Izmerjene vrednosti morajo biti manjše, kot so dopustne meje podane v standardih. Do sedaj so se meritve izvajale s togo vpetim merilnim sistemom. Pri teh trkih se ne upošteva mase in naravne reakcije prostega segmenta telesa ob trku. Začetna študija je temeljila na standardu ISO/DIS 21260, ki je bil kasneje izbrisan ter je služila zgolj kot dokaz koncepta. V tej študiji smo ocenili sile trkov, ki smo jih pomerili s pomočjo merilne celice pritrjene na linearnih vodilih. Merilni sistem je bil prosto gibljiv v smeri trka. Pri meritvah smo merilnemu sistemu dodajali uteži, s čimer smo posnemali dinamiko različnih delov človeškega telesa. Rezultati so pokazali statistično signifikantno povezavo med hitrostjo gibanja robota in maso merilnega sistema ter izmerjeno silo trkov. Nova izdaja standarda ISO/DIS 10218--2:2021 opisuje sistem za merjenje dinamičnih trkov, vendar se ta merilna metoda trenutno še ne uporablja. Obstoječi merilni sistem, uporabljen v prejšnji študiji, smo nadgradili z zamenjavo merilne celice. Uporabili smo 1D merilno celico s piezo kristalnim elementom za višjo frekvenco vzorčenja. Zamenjali smo obstoječa linearna vodila, ki so uporabljala drsne puše, z vodili, ki uporabljajo kroglične ležaje. S tem smo zmanjšali trenje pri gibanju merilnega sistema. Poleg tega smo naredili preprost sistem za kompenzacijo gravitacije, ki preprečuje neželeno premikanje merilnega sistema pri merjenju trkov v navpični smeri. Za zagotovitev čim bolj zanesljivih meritev smo uporabili umerjene vzmeti in gume komercialno dostopnega merilnega sistema. Nov merilni sistem smo pritrdili na vrh robotskega manipulatorja, da bi s tem pokrili večji del delovnega prostora in avtomatizirali postopek merjenja. Robotski programi so bili zasnovani v simulacijskem okolju, ki smo jih prenesli v krmilnike robotov. Primerjali smo trke v različnih točkah delovnega prostora, pri različnih smereh in hitrostih robota ter različnih masah merilnega sistema. Rezultati so pokazali, da hitrost robota in masa merilnega sistema močno vplivata na silo trkov, medtem ko imata smer in točka udarca manjši vpliv. Na podlagi izmerjenih vrednosti je možno presoditi varnost trkov v izbranih točkah delovnega prostora. Če so kontakti pri določenih masah znotraj mej podanih v standardu, lahko za te kontakte trdimo, da so varni. Kontakte, ki presegajo limite, je potrebno bodisi preprečiti, bodisi robotu omejiti hitrost ali moč.

Keywords

sodelujoči roboti;merilni sistemi;merjenje trkov;varnost;sila;standardi;magisteriji;

Data

Language: Slovenian
Year of publishing:
Typology: 2.09 - Master's Thesis
Organization: UL FE - Faculty of Electrical Engineering
Publisher: [M. Klenovšek]
UDC: 007.52(043.3)
COBISS: 77940483 Link will open in a new window
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Downloads: 42
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Other data

Secondary language: English
Secondary title: Analysis of collaborative robot dynamic impacts
Secondary abstract: In recent years, the industry shifted from mass production to mass adaptation, so the need for partial automation of the industrial process overcame full automation. Partial automation covers the cooperation between a robot and a human in the production of a product. In such applications, the safety of workers who share a workspace with a robot becomes a significant problem. Several standards have been issued in recent years to ensure that intentional or unintentional contacts between the operator and the machine are as safe as possible. These documents direct a detailed risk analysis of each developed collaborative application. The analysis is used to identify potentially dangerous contacts where contact force must be evaluated. The measured values must be lower than the permissible limits given in the standards to ensure safety. To date, such measurements have been performed with a rigidly mounted measuring system. These types of measurements do not consider the mass and natural reactions of the free segment of the human body after impact. The initial proof-of-concept study was based on a standard ISO/DIS 21260 that was later deleted. In this study, we assessed impact forces measured by a force sensor mounted on linear rails. The force sensor was freely movable in one direction. In the experiment, different weights were added to the measurement system mimicking different dynamics of human body parts. Results showed a statistically significant correlation between robots velocity and mass of the measurement system and impact forces. The new edition of ISO/DIS 10218--2:2021 covers a transient collision measurement system, but this measurement method is currently not in use. We improved the existing measurement system used in the previous study by replacing the force sensor with a 1D measuring force cell with a piezo crystal element for a higher sampling frequency. We replaced the existing rails that used sliding bushings and used ball bearings, thus reducing friction. In addition, we constructed a simple gravity compensation system to prevent unwanted movement of the measuring system while measuring impact in the vertical direction. We used calibrated springs and rubber pads of a commercially available system to ensure the most reliable measurements possible. We attached the new measuring system onto a robot to cover a larger part of the workspace and automate the measuring process. Robotic programs were designed in a simulation environment, which enabled us to export the constructed programs to the controllers of the robots. We compared collisions in different points within the selected part of the workspace at different directions, the robot's speeds, and the mass of the measurement system. Results showed that the robot's speed and mass of the measurement system significantly affect impact forces, while the direction of impact and the impact point have a smaller effect. Based on the measured values, it is possible to assess the safety of the contacts at selected points in the work area. If the contacts at specific masses are within limits given in the standard, we can say that these contacts are safe. Contacts that exceed the limits must be prevented, or the robot's speed or power must be limited.
Secondary keywords: Collaborative robot;measuring system;force measurement;safety;force;standard.;
Type (COBISS): Master's thesis/paper
Study programme: 1000316
Embargo end date (OpenAIRE): 1970-01-01
Thesis comment: Univ. v Ljubljani, Fak. za elektrotehniko
Pages: XIX, 99 str.
ID: 13539704