كنترل ارتعاشات چتر در ماشين ابزار به كمك مواد هوشمند پيزوالكتريك

چكيده انگليسي :

Vibration Control of Chatter in Machine Tools by Piezoelectric Smart Materials Seyed Mohammad Karim Tabatabaei tabatabaei@me iut ac ir November 1 2009 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Supervisor Dr Saeed Behbahani Behbahani@cc iut ac irAbstract Metal cutting has a troublesome obstacle in achieving perfect surface finishing while increasingproductivity and in high speed machining named chatter It also has a deteriorating effect on the machine toollife and safety of the machining operation Chatter is an unstable self excited vibration which may happen dueto a variety of reasons Regenerative effect is the most dominant reason of chatter occurrence which has beenstudied in this dissertation In this thesis active control methods for chatter vibration by means of piezoelectricactuator are presented After presenting dynamic equations of machine tool vibration and governing equation of chatteroccurrence possibility of improvement in stability lobes by means of changing different structural parametersare investigated Stability lobes diagram is one of the standard methods for chatter evaluation It specifies the boundaryof stable and unstable machining conditions Generating of stability lobes based on machine tool structuralproperties involves a complex and point by point procedure of drawing which makes it impossible to offer ananalytical formulation between machine tool properties and stability lobes to be used for analytical controllerdesign methods i e pole placement Therefore in this research activity possibility of stability lobes estimationby polynomial equations and presentation of stability specifications by closed analytical equation and thesimplest form of equations is presented Due to powerful specifications of piezoelectric smart materials such as their fast response and highaccuracy a piezoelectric sensor and a piezoelectric actuator have been used with the aim to active control ofchatter vibration Both analytical solution and numerical optimization methods are used for active vibrationcontrol Analytical solutions are based on frequency domain analysis of the controller effect on the governingequations of chatter Performance of a PID controller in increasing the minimum points in stability lobes isinvestigated A PD controller is designed analytically for moving stability lobes in order to stable machiningcondition In other part of this research a genetic algorithm optimization has been used to design optimum activecontroller for chatter vibration suppression As mentioned generation of stability lobes which specifies theboundary of stable and unstable machining conditions involves a point by point complex and time consumingcalculations which makes it impossible to present an inverse evaluation This means that no closed form andanalytical calculation to specify how far a machining condition is from the boundary of instability based on thecontrolled structural specifications of the machine tool can be presented for using in controller designing Toovercome this problem a genetic algorithm in controller designing has been used The main idea in this designmethodology is changing structural properties by active controller and in turn moving stability lobes inhorizontal and vertical directions with the aim to make the machining working point i e specific spindle speedand width of cut far from unstable boundary by considering minimum energy consumption A comprehensivetransfer function for the controller is considered which can be implemented by Op Amp Performance of thedesigned mechatronic system on chatter suppression has been evaluated in both frequency and time domain andsatisfactory results have been achieved Key Words Chatter Stability lobe Piezoelectric Active control Genetic Algorithm

طباطبايي، محمد كريم

كنترل ارتعاشات چتر در ماشين ابزار به كمك مواد هوشمند پيزوالكتريك

دياگرام پايداري , كنترل فعال , الگوريتم ژنتيك