【作者】 刘鹏；

【导师】 孔繁森；

【作者基本信息】 吉林大学 ， 机械制造及其自动化， 2010， 博士

【摘要】 镗削加工处于半封闭状态,刀杆悬伸较长,刀具的后刀面和内孔的摩擦较大,切削系统易处于不稳定状态,极易发生振动。因此,对于镗杆在镗削过程中的振动控制就显得尤为重要和迫切。随着智能材料和智能自适应结构等现代结构材料的兴起,对结构进行振动的主动控制或主-被动混合控制在技术实现上进展迅速。鉴于机械加工领域对抑制切削振动的迫切需求和结构振动主动控制在工程领域巨大的应用空间,以及主、被动控制的有机结合可以更好地对振动进行有效控制,本文以镗削过程中刀具普遍存在的振动作为研究对象,结合切削系统本身的动力学特性,采用压电元件作为传感器和执行器,分别采用主动控制方法和主-被动混合控制方法对镗杆所产生的振动进行有效抑制。主动控制方法根据以振抑振的思想,将压电元件与镗杆结构相整合,通过调节外加主动电源的增益值来对镗杆的振动进行抑制。为了整合传统被动控制方法鲁棒性强、低能耗和控制效果稳定的优点,作者进而提出了一种整合R-L分流回路的主-被动振动混合控制系统。仿真和实验研究结果证明,这种方法能够对切削过程中镗杆所产生的振动进行有效抑制。更多还原

【Abstract】 1 IntroductionAll objects which have elasticity and quality can be vibratile. Vibration and noise have the enormous influence on the performance of mechanical system, operator’s physical and moral integrity as well as the processing quality, and so on; It’s an important problem in the field of technology about how to prevent and control vibration effectively. Boring processing is at half seal condition, the boring bar extends longways, and the back surface of the cutter has a big friction with the inner hole, which can result in the non-steady state of the system and vibration easily. Therefore, it’s very important and urgent to control the vibration in the course of the boring process.With the grow up of intelligent materials and intelligent adaptive structures, AVC and active-passive hybrid control techniques have a rapid development in the case of technical implementation. According to the imperious demands of supressing cutting vibrations and the giant developing space of AVC on the field of structures active vibraition control, for the sake of combining AVC with PVC and controlling cutting vibrations more effectively, this paper considered the common cutting process as the researching object and used AVC and APPN techniques respectively to supress the cutting vibrations of the boring bar integrated piezoelectric components as sensors and actuators. On the basis of using vibration to suppress vibration, the AVC technique integrated piezoelectric components with the boring bar, and suppressed the cutting vibration of boring bar to change the gains of vibration. The simulation and experiments results show that this method can control the low-frequency vibration of the boring bar during the cutting process. However, the obvious disadvantages of AVC technique will limit the robust performances of AVC system, and will disppate more energies. In order to solve above problems, the author proposed an active-passive hybrid control system integrated with RL shunting circuits, and analysized and estimated the vibration controlling performences with simulation experiments. This hybrid system can suppress the vibration more effectively on the premise of saving more energies. The simulating and experimenting results show that the APPN method will have a widerspread engineering application space because of the simple structures, less dissipation of energies and high robost properties.2 Piezoelectric equations and the sensor-driven modelPiezoelectric effect was found by the Curie brothers in 1880. Pierre Curie was Early on the contact of pyroelectric crystal symmetry phenomenon and this allowed the two brothers not only found the existence of electric field under pressure, but also predicted that if a certain direction in the crystal pressure, it would produce the piezoelectric effect. Then, sphalerite, sodium chlorate, boron stone, tourmaline, quartz, calamine, topaz, tartaric acid, sucrose and potassium tartrate crystal (Rochelle salt), etc., were observed to have the piezoelectric effect. Inverse piezoelectric effect from the Lippman was foreseen under the first principle of thermodynamics, and in subsequent years confirmed by the Curie brothers.1884, Woldemar Voigt formally established the relationship between elastic modulus and electric vector by the crystal symmetry principle. Experiments confirmed that in all 32 class crystal,20/21 lack of symmetry of crystal class can produce the piezoelectric effect. Piezoelectric materials based on inverse piezoelectric effect, can be made into sensors and actuators to use.3 Design of intelligent boring bar model containing piezoelectric transducerBoring system generally can be simplified into a number of boundary conditions including a one-dimensional distributed structure. For bore lathe processing, since the boring bar does not rotate, the stiffness of the workpiece is much higher than the boring bar itself, and the boring bar’s torsion resistance is far higher than the bending resistance. Therefore, Vibration System boring bar as a weak link in the main model, is simplified as a cantilever Euler-Bernoulli bending project (Figure 1).Figure 1 Vibration boring system dynamic model Boring vibration system dynamics model can be described as4 The build of Hybrid control system modelFigure 2 is integrated with the RL shunt circuit of the piezoelectric intelligent boring bar main-passive hybrid control system diagram of the system by the boring bar structure of the matrix, piezoelectric sensors, piezoelectric actuators, active control, active voltage source and other components. It works as follows:the piezoelectric sensor paste the boring bar structure, used to detect the vibration of the system which will sense the signal after amplification by the charge voltage in the form passed to the controller, the controller will send its processed active voltage source, the final will be the high voltage in series with the RL shunt circuit to both ends of the piezoelectric actuator, which reacts in the boring bar, the actuator is configured to position the sensor with the principles of configuration are arranged in the boring bar of the root;at the same time, shunt circuit through the controller parameters in real time to adjust, and ultimately boring bar vibration on the main-passive hybrid control.Figure 2 active-passive hybrid control of piezoelectric intelligent boring bar diagramHybrid control system dynamic equation shown in Figure 2 can be expressed in matrix form Hybrid control system dynamic equation shown in Figure 5.1 can be expressed in matrix form in which, q is the structure of the generalized displacement vector for the circuit in the charge, Ms, C, and s were boring bar structure of the mass, damping and stiffness matrix, L, R, and Kp were shunt circuit inductance, resistance and equivalent capacitance of piezoelectric elements for the mechanical structure and electric field coupling term, f is the cutting force, the control voltage. What is more,(χ2-χ1)is the length of the piezoelectric film,h31is piezoelectric constant,ε33 is the dielectric constant of piezoelectric ceramics.We completed the physical coordinates to modal coordinates transformation. Equation (2) is called the piezoelectric vibration boring bar’s main-passive hybrid control model. The system describes a mode. The first one mode shunt circuit by the introduction of elections. It is noteworthy that the original system to increase the vibration absorber will cause the system to an additional degree of freedom. Take the characteristic function as a cantilever beam comparison function, the first i order generalized coordinates and first i modal coordinates (i=1,2,3,…,N) is very similar. More importantly, because the modal analysis generated by infinite-order mode in the optimization process is not applicable, in most cases, we need to truncate and approximate the model.更多还原