Papers by Author: Wei Ji

Abstract: In order to let the combine working in the best condition, it is necessary to control its speed according to the crop conditions in the field. The walking office of combine is analyzed in this paper. It is a high order system, some parameters will change during its working, and it is impacted by external disturbance. Then a servocontroller based on RBF neural network is designed. The model is simplified, and there are 2 parameters in it. Then a RBF neural network is established. The speed of combine, its integral value and differential value are inputted to identify the parameters. The inverse controller is established base on the simple model. The result of simulation and real vehicle tests shows that the controller can effectively adapt to changes in the internal parameters, overcome the external disturbance, and achieve the purpose of tracking a given speed.

Abstract: Existing laser honing machines all utilize the motion mode of workpiece movement. But as to complex workpiece, this mode is inappropriate to use. For example, cylinder liner, pre-casted into the engine block, is not suitable to rotate when fixed on the chuck, because the block is irregular and heavy. This equipment uses the mode of laser head rotation and linear motion. The workpiece keeps still during the laser texturing process. In this paper, the structure design and control principle of the laser machine are narrated in detail. The process of the machine is a new method of laser micro-texturing, named as “single-pulse interval of the same point many times”. The method contributes to processing microscopic or macroscopic morphology and significantly reduces the negative thermal effects of laser processing

Abstract: Nanohybrid thin films consisting of nanocrystalline TiO2 particles in poly(methyl methacrylate)(PMMA) were successfully synthesized by in-situ sol-gel and polymerization assisted by spin coating. Using titanium isoproproxide (Ti-iP), methyl methacrylate (MMA) and 3-(trimethoxysily)propyl methacrylate (MSMA) as the starting materials, nanohybrids containing up to 60% Ti-iP in PMMA were realized. The resulting nanohybrid thin films coated on quartz substrates are optically transparent and demonstrate nonlinear optical behaviour, where their nonlinear absorption increases with the loading of Ti-iP in PMMA, as confirmed by Z-scan measurements. Using pump-probe technique, these thin films are shown to exhibit an ultrafast relaxation time of ~1.5 picosecond.