【作者】 许宝忠；

【导师】 刘铁根；

【作者基本信息】 天津大学 ， 光学工程， 2010， 博士

【摘要】 本文重点研究了成形脉冲YAG激光生成技术及其在激光熔覆、焊接中的应用。成形脉冲是指激光器的脉冲波形可以按照软件预先设置形状的技术,其通过改变脉冲持续期间激光功率密度的分布,适应了不同材料、不同加工对激光能量变化的要求,从而能够获得最佳的加工效果。论文主要从理论研究、建模分析、成形方式与控制系统设计和应用实验等几个方面对成形脉冲技术进行了逐步深入的研究:通过对激光弛豫振荡过程以及光与物质相互作用等理论的分析,论证了通过软件预置激光脉冲形状实现成形控制输出技术方案的可行性;根据最优控制理论,成形脉冲系统采用了峰值电流双环反馈控制技术,运用状态空间平均法为其建立了交流小信号动态模型,根据等效功率级的传递函数为电压控制器外环设计了补偿网络;以ARM微处理器为控制核心,设计了成形脉冲激光控制系统,完成了成形脉冲编辑和驱动设计,实现了成形脉冲激光输出;用成形脉冲激光对飞机发动机受损叶片进行了激光熔覆修复和锂离子电池安全阀激光焊接的实验研究,并对熔覆层组织结构进行了金相分析和显微硬度分析,获得了预期的效果。工作中的主要创新点:1.实现了脉冲YAG激光输出波形的预先设置,针对不同材料和不同加工方式对激光能量变化的需求,可以设置多种激光波形。2.采用峰值电流双环反馈控制技术控制激光束的功率,实现了成形脉冲YAG激光输出。3.用成形脉冲YAG激光对飞机涡轮发动机受损叶片进行了熔覆修复实验研究,获得了高质量熔覆层,实现了形状修复和功能修复,这项成果具有重要的技术意义、经济意义和低碳环保价值。4.在计算机上开发出专用激光脉冲波形编辑软件,脉冲波形经USB下载至成形脉冲控制系统,由后者驱动斩波环节实现成形脉冲。更多还原

【Abstract】 This dissertation is focused on the pulse-shaping YAG laser technology and its applications in laser cladding and laser welding. Pulse-shaping is a technique that the pulse waveform of laser can be shaped in accordance with the software pre-set, which meets requirements on the laser energy for different materials, different processing and therefore get the best processing results by changing power density distribution of the laser pulse duration.The main contents of the dissertation include theoretical investigation, modeling analysis, shaping method, control system design and application experiments. Based on theory analysis of laser principal, relaxation oscillation as well as the interaction between light and matter, the feasibility of technical solutions that the laser waveform can be controlled by the method of software pre-set has been approved. According to optimal control theory, double-loop feedback control technology was applied for pulse-shaping system. AC small-signal dynamic modeling using state space averaging method was set up for the technology and a compensation network for voltage controller through transfer function of the equivalent power stage was also designed. The study also finished the design of control system for pulse-shaping based on ARM and completed the editing, driven design and download for waveform on the computer, and in the meanwhile realized the method of pulse-shaping. The research work also includes experiments of laser cladding repair for aircraft engine damaged blades and laser welding for lithium-ion battery tab using pulse-shaping technology. Metallographic analysis and microhardness evaluation for cladding layer were also conducted which demonstrated inspiring results.The major innovations in the work are summarized as follows:1. The realization of the output of the programmable waveform for pulse YAG laser, based on the request of the laser energy for different materials and different processing methods, a variety of laser waveform can be set.2. The application of double-loop feedback control technology based on peak current-mode in the field of the power electronics to the control of the laser beam power, and realized programmable pump pulse generation.3. The fulfillment of the experiments of laser cladding repair for damaged aircraft turbine engine blades using pulse-shaping laser, and got high quality cladding layer, and realized recovery of shape and functional. The results have important significance of economy and low-carbon value of environment.4. Specific software for setting of the laser waveform on the computer, waveform should be downloaded to pusle-shape control system via USB, and the latter drove chopper electrical for achieving of pulse-shaping.更多还原