شبيه سازي و ارائه طرح پيكربندي مناسب ربات در فرآيند ماشينكاري

چكيده انگليسي :

Simulation and Presentation of Proper Configuration Scheme for Manipulator of Robot in Robotic Machining Iraj Lirabi i lirabi@me iut ac ir Date of Submission 25 Apr 2011 Department of mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 IranDegree M Sc Language FarsiDr S M Safavi mosafavi@cc iut ac ir Abstract The use of industrial robots have remarkably increased during the past decade and its applications include a wide variety from simple and repetitive tasks like loading and unloading to highly sophisticated tasks like assembly operations Among these broad uses of industrial robots when it comes to machining operations because of large work space of industrial robots their flexibility ability to track complicated paths and high added value of machining process they are considered as the next generation of machine tools Notwithstanding the advantages brought about by the implementation of robotic machining systems robots compared to conventional machine tools have less stiffness It is largely due to the serial and coupled structure of the manipulator of the robot Moreover regarding the high machining forces and weaker structure of manipulator stability of robotic machining operation is considerably more sensitive than general machining methods Generally in order to study the stability of machining operation the possibility of occurrence of a phenomenon called chatter vibrations is surveyed This kind of vibrations is referred to as self excited vibrations and is strongly influenced by the dynamics of machining operation and chip formation Unlike common machining processes in robotic machining the stability of the process is dependent upon the configuration of the manipulator with which machining is fulfilled Therefore according to the nonlinear coupled structure of the manipulator the mechanical properties of the robot will change This causes the limit of chatter to vary from configuration to configration in the working space of the manipulator In this thesis a model is provided for detecting chatter vibrations in robotic machining by using the most important chatter mechanism and the dynamic model of robot Thus chatter stability lobes could be extracted from the model by running the simulations Furthermore by means of time domain approach for chatter analysis an objective function is obtained which is capable of numerically assessing the possibility of chattering in various machining conditions On the other hand by using a redundant kinematic structure of a given manipulator the number of inverse kinematic solutions to position the endeffector excessively increases Now the question is that which one of the configuration solutions best fits the necessities of a stable machining operation In fact the objective is to find the configuration having the best mechanical properties in order to achieve chatter free robotic machining operation In the next step by putting the transfer function of each configuration in the chatter analysis model the corresponding value could be extracted for the objective function according to the cutting parameters of the machining operation Finally the optimal configuration can be achieved by choosing the configuration possessing the least value acquired for the objective function It is shown that by using the presented method to detect the chatter vibrations in robotic machining process it is possible to survey the machining stability and choose the best machining variables through off line simulations based on dynamic and kinematic parameters of the manipulator Thus robotic engineers and process planners could manage to spend less time on trial and error to choose robotic machining parameters Hence the machining time could be decreased and the efficiency of process can be increased Key words Robotic Machining Chatter Vibrations Dynamic Model Kinematic Redundancy Time Domain Analysis

ليرابي، ايرج

شبيه سازي و ارائه طرح پيكربندي مناسب ربات در فرآيند ماشينكاري

ماشينكاري ربات , ارتعاشات چتر , مدل ديناميكي , ساختار سينماتيكي فزوني , تحليل حوزه ي فركانس