【作者】 吕必达；

【导师】 郑堤；

【作者基本信息】 宁波大学 ， 机械电子工程， 2009， 硕士

【摘要】 随着现代电子应用和光学技术的发展,非球面光学零件以其极佳的光学特性受到了研究者的广泛关注。非球面光学零件的表面精度是决定其应用价值的关键。现有的光学抛光加工是依赖于高精密器械,采用柔顺研抛的控制方式完成的。但高精密设备的价格昂贵,限制了非球面光学零件的广泛应用。为了降低非球面光学零件的加工成本,研究基于普通数控车床的非球面加工方法及工具系统,对非球面零件的精密加工和广泛应用无疑具有重要的理论意义和工程价值。普通数控车床在机床精度不高的情况下,可以通过安装附加工具,利用柔顺控制来实现研抛精加工。当前柔顺控制的瓶颈在于力/位混合控制中的力/位强耦合:研抛工具的位姿因工位而异,研抛力的大小和工位存在着直接的关系,给控制系统的研发带来极大的困难。为了降低力/位混合控制的难度,本文提出了力/位混合控制解耦的原理和方法,即通过采用合适的力控制装置,结合数控轨迹规划保证加工过程中研抛力的方向始终与工件表面法向一致,使研抛力的大小和方向不随加工位置变化而变化,实现力/位混合控制解耦。针对这一思路,本文提出了在普通NC数控车床上安装研抛工具系统,进行非球面柔顺研抛精加工原理和方法研究。工具系统的力伺服装置是由磁流变液(MRF)阻尼器与伺服电机组合而成的。传统的力伺服器一般采用电机或者液压机构,其主要特点是力与位移相伴而生,紧密耦合在一起,无法实现对力的单独控制。本文采用的MRF力矩伺服装置可以不依赖位移而对力矩实施控制,且具有快速响应和输出力矩无级可调的特性,是柔顺研抛加工中的一种比较理想的力伺服器。本文借助虚拟样机技术,运用运动学、动力学仿真软件ADAMS,建立了MRF阻尼器的仿真等效模型,在此基础上建立了工具系统整体虚拟样机。对研抛工具系统中的关键部件——自适应研抛头的结构进行了仿真分析与结构优化,并通过实验验证了仿真分析结果的正确性。接着,对工具系统的作业空间进行了数学建模及优化。通过对工具系统输出研抛力的稳定性仿真和实验研究发现,有必要设计控制系统以进一步提高工具系统输出稳定性。在建立系统的动力学模型的基础上,完成了控制系统的理论设计。ADAMS和MATLAB/SIMULINK联合仿真结果表明,增加控制环节后,工具系统的输出稳定性得到了有效的提高。更多还原

【Abstract】 With the development of modern electronic and optical technologies, researchers’attention is collected by aspheric optical parts for its excellent optical properties. As is known to all, the surface quality determines the using value of optical parts. So far, the optical polishing finished in high-precision instrument, which will make a substantial increase in processing cost, and restrict the widespread use of aspheric parts. In order to reduce the manufacturing cost of aspheric parts, a new method of aspheric manufacturing and tools based on the common NC lathe is studied. Undoubtedly, it has theory meanings and project value for the widespread use of aspheric parts.Because the machining accuracy of common NC lathe is not high enough, polishing can be carried out working with an additional tool and compliant control. One nodus of the compliant control is the force/position coupling in the force/position hybrid control, i.e., there exist different tool poses at the different positions and also need various polishing force servo in processing. The polishing force has something to do with the processing station, which will make a great difficulty to design a force servo control system. In this thesis, a method of decoupling the force/position hybrid control is proposed. In specific word, with the proper force servo and motion track, the direction of polishing force is kept same to the normal direction of parts’surface, and force can be controlled independently of position. At the same time, a tool system which is fixed in the common NC lathe is designed to study the aspheric manufacturing method. Generally, servo motor or hydraulic mechanism is used as force servo, whose force providing depends on the displacement. To meet the control of force servo, a new type of torque servo system consisted of Magnetorheological Fluids (MRF) damper and servo motor is proposed. For the advantage of rapid response and damping adjustable stepless of MRF damper, it will play a good role in the force servo in the active compliant control.In this thesis, using the virtual prototyping technology and the strategy of force/position hybrid control decoupling, a simulation equivalent model of MRF and the virtual prototype of the tool system are established in the kinematics and dynamics simulation software ADAMS. After analyzing the structure of the polishing tool, optimization which is validated by simulation outcome and experiment is put forward. Then, A mathematical modeling for operation space of the tool system is built. According to the simulation outcome, a control system is designed based on the dynamic model of the tool system to improve the force output stability of the tool system. ADAMS and MATLAB/SIMULINK co-simulation shows that the force servo property of the tool system has been improved with the control system.更多还原