Structure Design And Simulation Research Of Mems Micromirror For Smart Concentrating Window

In daily life,when the outdoor light intensity is high,in order to prevent glare,people generally reflect or scatter part of the sun light through external devices such as curtains and window paper.When the indoor light is insufficient,they can only rely on indoor lighting devices.Adjusting light leads to a serious waste of light resources.Today’s smart windows can already adjust indoor lighting by adjusting the sunlight transmittance of the windows,but they cannot intelligently adjust indoor temperature and light intensity and maximize the use of sunlight.The combination of MEMS technology and windows makes it possible to maximize the use of light resources of smart windows.Because of its small and easy-to-control,MEMS micro-mirrors can be deflected following the change of the light position,and the incident sunlight can be adjusted in a controllable angle.The intelligent concentrating window studied in this paper can control the MEMS micro-mirror array to condense light while adjusting the light,and converge the light to the high-efficiency photovoltaic cells arranged above the balcony to generate electricity.However,most of the MEMS micro-mirrors developed at home and abroad are small in size and unable to achieve large controllable deflection angles.The research on MEMS micro-mirrors with large mirror sizes and controllable deflection angles carried out in this paper has broad market prospects and scientific significance.,the main research contents are as follows:1.The domestic and international status of smart windows,photovoltaic building integration and micro-electromechanical technology are expounded,and the concept and advantages of smart concentrating windows are put forward.Then,the four driving modes of MEMS micro-mirrors of electrostatic,electro-thermal,piezoelectric and electromagnetic are compared and analyzed,and the research objectives and contents of the electro-thermal and piezoelectric-driven MEMS micro-mirrors is determined.2.2D and 3D modeling software are used to establish the light control mirror and condenser mirror model schematic diagram of the intelligent concentrating window,and the concentrating battery and inverter are selected.According to the weather data of Qingdao,the factors that affect the power generation,such as the solar altitude angle H_s,the solar azimuth angle A_s,the micromirror spacing d_s,and the micromirror fixed end length L_f,are analyzed.Then the theoretical formula is used to calculate the power generation of the smart concentrating window,and finally the photovoltaic system simulation software Pvsyst is used to simulate the equivalent power generation.The error between the theoretical calculation value and the simulation value is 2.5%.3.The driving principle of the electrothermal MEMS micro-mirror is analyzed,and a thermo-electric-mechanical model is established,and an improved cantilever MEMS micro-mirror structure is proposed.The simulation model is established by COMSOL Multiphysics simulation software to optimize the structural parameters that affect the deflection angleθand light reflection area of the micro-mirror,such as the mirror length L_mir,the mirror width W_mir,the thickness of the thermal expansion material,and the fixed end length L_f.The improved MEMS micromirror accounts for 93%of the mirror surface area,and can be deflected from 0 to 96.53°in the voltage range of 0 to 1.5V,which basically meets the needs of condensing windows,finally,the analysis of the optimized structure such as vibration mode and cantilever beam stress is performed.4.The driving principle of piezoelectric-driven MEMS micro-mirror is studied and the piezoelectric materials are compared.The principle analysis of piezoelectric MEMS micro-mirror based on displacement amplification mechanism is carried out and the torsional mechanics model is established.In the micro-level,using COMSOL simulation software to establish a finite element model,three piezoelectric micromirrors with different lever magnification structures are proposed.Under a voltage of 0～50V,the three piezoelectric micromirrors can achieve 0～26.89°,0～36.67°,0～30.51°deflection angle to meet the deflection requirements of the condensing mirror Then,the displacement magnificationαand the deflection angle-voltage linearity△of the three structures are compared and analyzed.Finally,the performance of the four micromirror structures proposed in this paper is compared and the MEMS micro-mirror structure suitable for different mirror surfaces is obtained.