Papers by Author: Jian Wang

Abstract: Photovoltaic grid-connected power generation is the inevitable development trend of solar photovoltaic systems,grid inverter is an essential part of photovoltaic grid-connected power generation. With the developed three phase current type PWM inverter device as the research object, and symmetry rules sampling method is applied to the inverter, through the method combined by the computer simulation and experiment research, the device was verified by simulation and experimental .The results show that: This method could not only effectively reduce the DC side inductance volume of the current-mode PWM inverter , and it could make output AC currents sinusoidal and in phase with grid voltages, but also improve the efficiency of the system, it will be more suitable for photovoltaic grid-connected.

Abstract: According to needs of aspheric lens grinding and measurement with X/Y/Z 3-axis grinding machines, a CAM system is designed and implemented. The system, based on the parallel grinding geometry model, has realized the function of grinding locus planning, form error compensation, NC program auto-generation, on-machine measurement, grinding wheel on-machine measurement, simulation and technical database. To verify the stability of this CAM system, experiments were performed with three independent machining experiments. The experimental results indicate that the system realized the whole process of aspheric grinding, and it improved the machining efficiency and automation. Especially, this system adopted on-machine form error compensation technology and improved the machining accuracy. By implementing the error compensation integrated in the CAM system, the surface form error of a 430mm×430mm aspheric lens is decreased from PV8.2µm to PV4.1µm. The grinding accuracy was improved 100%.

Abstract: The causes of machining errors are very complicated and apt to mutual influence in aspheric grinding, so it is difficult to improve machining accuracy by control one cause. To compensate the machining error of large aspheric grinding, an error-compensation technique using on-machine profile measurement system in three axes grinding machine are presented. To verify the effectiveness of the compensation machining and the reliability of the measurement system, experiments on high-precision grinding machine were performed. Moreover, the compensation machining with the on-machine measurement substantially decreases the machining errors and improve machining accuracy by more than 45%, compared with the non-compensation machining.

Abstract: In the traditional precision machining, it is easy to introduce positioning error because of the separation of the machining and the measurement. In order to solve this problem, an online measurement technique for aspheric grinding has been put forward. It measured the workpiece with sensor which was fixed to the high-precision machine tool. It processed data with the algorithm of Two-dimensional weighted average filtering and curve fitting based on Gauss-Newton and Levenberg-Marquardt least-square method. The experimental results indicated that the fitting residual error was less than 3×10-6 mm. In the grinding process, the measurement error was of the order of the magnitude of 10-3 mm. It can be concluded that the technique measures the surface exactly, and improves the machining accuracy effectively by providing accurate data for compensation.

Abstract: The computer-controlled chemical polishing (CCCP) techniques based on the Marangoni effect have been developed to manufacture precision optics on polished fused silica surface. In this study, we present the Marangoni confined chemical-etching process in which the material removal on optical surfaces can be accomplished by etching with buffered HF solution. The process shows stable characteristics and good repeatability while the etching depth can be controlled in the order of ten nanometers. We also present the experimental results of this technology for fabrication of phase corrector and continuous phase plate. Results show that the CCCP’s deterministic sub-aperture-polishing characteristics make it possible to correct the surface error and imprint complex phase structure with spatial scale-length of several millimeters onto optical surface.