【作者】 王艳萍；

【导师】 董玮；

【作者基本信息】 吉林大学 ， 电路与系统， 2010， 硕士

【摘要】 MEMS潜在的影响力和各种传导机制的广泛应用,使得各种新型MEMS产品逐步实现商业化,微机械加速度传感器就是其中特别重要的一种,它已经广泛渗透到人们日常的社会生产生活中。但是它的电容变化非常小,必须和检测电路一起使用,才能发挥其应有的功能,所以对检测电路的设计要求越来越高,检测电路的检测精度和电路性能的高低对加速度传感器来说至关重要。差分电容式加速度计的上下极板两电容共同组成差分电容,其电容变化直接反映加速度,而且与加速度是线性正比关系。本论文所研究的就是差分电容式微加速度计的检测电路,包括以下几部分:(一)对MEMS技术做一下简单的介绍,在此基础上讨论微机械加速度传感器的国内外研究现状及应用,对其进行了分类,并分别介绍了各种传感器的性能特点和工作原理。对需要检测的微加速度计的比较重要的特性指标分别进行讨论。(二)讨论电容式微加速度计的测控原理,介绍其工作原理,并在此基础上将传感器分为变面积和变间距两种,重点介绍采用差分电容结构设计制作的加速度传感器,对开关电容、AC桥式、谐振式和电荷放大四种检测电路进行比较,最终选择电荷放大电路。(三)结合要检测的微加速度计的自身特点和选用的电荷放大检测电路,拟定了检测电路的总体方案。并设计了各电路模块,之后为了验证方案的合理性,对电路的性能进行了模拟仿真,最后建立了加速度加载系统,对制作的器件施加加速度,测量不同加速度时电压的变化情况,并对数据进行了处理,拟合出了电压变化量随加速度的变化曲线。更多还原

【Abstract】 As today’s MEMS technology is becoming increasingly mature,MEMS has been well applied in the production of complex micron structures, devices and systems.The potential impact of MEMS and the extensive use of a variety of transmission mechanisms, make a variety of new MEMS products progressive realizing commercialization.Micro-mechanical acceleration sensor is one particularly important of MEMS products.Because of small size, high sensitivity and low power consumption,it has become a very important device to measure the acceleration. Micro-acceleration sensor has broad range of applications, such as medicne, automotive, industrial control and other areas,and it has become a research hotspot around the world. In the future, MEMS accelerometer will also play an important role in the field of aerospace.However, the capacitance variation of micro-accelerometer is very small.So in the real applications,it must be used together with the detection circuit.Only in this way,it can perform its proper function.Therefore, the demand for the design of the detection circut is increasingly critical , the detection accuracy and circuit performance is critical to all of the acceleration sensors.The upper and lower plates of differential capacitive accelerometer are composed of differential capacitance, and the capacitance variation directly reflects the acceleration, the acceleration is linear proportional relationship with the capacitance variation. This thesis is the study of differential capacitive micro-accelerometer detection circuit,and it includes the following sections:At the beginning of thesis, we make a simple introduction to the MEMS technology.Based on this ,we discuss the research status of micro accelerometer and its application in the automotive, military and other fields.According to the working mechanism of the sensor ,micro accelerometers are classified,and the performance characteristics and working principle of various sensors are introduced. At the same time, the performance indexes of accelerometer are introduced.Next we discuss the measurement and control principle of capacitive micro-accelerometer, and the working principle of the acceleration sensors is introduced. Based on this, acceleration sensors are divided into two types including gap variation and area variation.We highlight the differential capacitive acceleration sensor made by laboratory,the sensitive element use a four-beam model.Four forms of detection circuits including switched-capacitor, AC bridge, resonant amplification and charge amplification detection circuit,are analyzed and compared in detail. The charge amplification circuit is chosed as the detection circuit, because its sensitivity and resolution are ideal for testing. In this circuit, the parasitic capacitance and stray capacitance will not affect the capacitance change detection, and we do not have to consider the problem of potential shielding.Then combining with the inherent characteristics of micro accelerometer and the use of charge amplification detection circuit, we developed an overall program of the detection circuit. This is a key part of the thesis, the program mainly includes seven modules, named power supply circuit ,carrier generation circuit,charge amplifier,band-pass filter circuit, phase-shifting circuit, phase-sensitive demodulation circuit, low pass filter circuit, voltage conversion circuit and data acquisition circuit.Charge amplifier,band-pass filter circuit and phase-shifting circuit are called the front-end charge amplifier. The design of power supply circuit,carrier generation circuit and front-end amplifier is emphasized.The positive and negative output voltage regulator composed of LM7805 and LM7905 is used as the power supply module.Sine wave is generated by DDS, mainly using the VHDL to describe hardware circuits, and finally generate the sine wave of 10kHz. Charge amplification circuit realize the conversion from capacitance to voltage, two carriers with the same amplitude,same frequency and contrast phase are its input. The output voltage variation only associated with capacitance variation. The output waveform of charge amplifier circuit has glitches and interference.The waveform will be improved after band-pass filter circuit.The role of phase-shifting circuit is to ensure the phases of demodulation inputs completely inverting. The role of low-pass filter is to preserve the useful DC signal of demodulation,while the voltage conversion circuit is to make the voltage range become benefitly observed. After the last module circuit,acceleration change which is in the form of a digital voltage will be displayed in the LCD.After that,to verify the design of the circuit is right or not, we make simulations for the detecton circuit,mainly on the power supply circuit, front-end amplifier.After the simulation of key circuits,we find the design of evry circuit module is reasonable. On this basis, we have made the circuit PCB layout and the real-time measurement of evry module in the PCB.Finallly we find the output waveforms coincide the simulation results of each module.Finally we have design the detection system which consist of the DC speed controller, DC motor and tachometer.And using this detection system,the voltage were measured and recorded when acceleration is not loaded or loaded on the accelerometer.And after data were processed ,the voltage variation curves with the acceleration were fitted out.From the fitting curve,we obtained key performance indicators of the MEMS accelerometer,their results are as follows: sensitivity is about 80mV / g, range is about and the precision of about 1.64%.±12g更多还原