Microelectromechanical-systems (MEMS) technology uses micro fabrication techniques to combine microelectronics capabilities with the mechanical properties of microsensors. Increasingly, MEMS gyroscopes and accelerometers are used in a large number of devices for both consumer and industrial applications.
Active suspensions, for example, require four extremely stable and accurate sensors mounted on the wheels in order to achieve a greater degree of ride quality and car handling, thus allowing for better traction and control. Another application is to prevent passengers on the front seat from being thrown out of the passenger compartment in case of an accident.
The benefits of these MEMS approaches include high efficiency, small size, and low cost. Automobile MEMS sensors play a key role, solving safety challenges in an extremely accurate and stable design. In fact, electronic safety systems based on MEMS technology can ensure compliance with functional safety standards, enabling designers to more efficiently achieve their goals. Demand is stronger than ever for enhanced safety and security in the automotive industry, which is propelling growth and development in the MEMS market.
MEMS加速度计和陀螺仪都从这种增长中受益。加速度计测量一个，两个或三个正交轴的加速度。它们通常用于计算重力加速度的倾斜度或方向，并测量振动和冲击。为了为特定应用选择正确的加速度计，设计人员必须考虑不同的项目变量，包括传感器结构，共振，可靠性，稳定性，带宽和能源消耗以及成本。
In contrast, MEMS gyroscopes provide a simple way to measure angular velocity (or rotation motion) in easy-to-install packages on the printed-circuit board (PCB). They’re a popular choice for feedback systems as a sensitive element for motion control.
有关MEMS加速度计的更多信息
大多数加速度计的传感器都是硅品种。这些设备通常分为两种基本类型 - 它们基于电容或热方法。
根据应用的不同，由于多种原因，使用MEMS热加速度计可能是有利的。例如，电容式方法可能更适合于检测车祸和/或激活安全气囊。相反，热方法最适合电子稳定性控制（ESC），因为它基于密封腔内加热气体分子的对流原理。
1.显示的是用于测量MEMS传感器容量变化的电图。当电容器的几何形状即将改变时，检测是基于容量变化。
通过非常准确的传感器，可以检测由于加速度（或倾斜度）差异较小而导致的温度曲线变化。另一方面，电容性mems通过通过加速力敦促的微观晶体结构来利用压电效应。反过来，这会导致电应力。它们是本质上的宽带传感器（> 5 kHz），对于低G设备，机械共振频率接近2 kHz。检测临时型变化的一种典型方法是测量能力的变化，电容器可以作为传感器和执行器进行操作(Fig. 1)。
电容式加速度计需要两个DIE溶液（一个用于传感器元件，另一个用于应用程序特定的集成电路或ASIC），以测量高振动环境中的倾斜度。在大多数情况下，传感器元素需要比ASIC更大的几何形状。对于它的部分，MEMS热传感器将传感器和电子设备整合到单个单片IC中，从而导致一个较小的设备，从而简化了组装过程。
MEMS Gyroscopes
大多数可用的MEMS陀螺仪基于带有两个肿块的Diapason构型，它们在相反的方向上连续振荡。当施加角力时，每个质量上的科里奥利强度也朝相反的方向起作用。所得能力的变化与角速度（ω）成正比。该速度转换为模拟或数字陀螺仪的输出电压(Fig. 2)。
在噪声方面，MEMS陀螺仪有助于角速度。这种固有的噪声代表陀螺仪的输出信号的变化，当时它处于静态惯性状态（即没有旋转）和环境免疫力（或没有振动或颠簸）的条件。
2. MEMS陀螺仪使用科里奥利效应来测量角速度。当质量（M）沿V的方向移动并应用角度旋转ω时，质量将沿箭头方向经历力（F科罗洛斯) due to Coriolis's strength.
The most common parameters for describing such noise behavior are rate noise density (RND) and angular random walk (ARW). The RND factor typically uses a unit of degrees/sec /√Hz and provides a simple mode to predict total noise based on the gyroscope frequency response. The ARW factor, on the other hand, typically uses grading units/√hour , and is often more useful when analyzing the impact of noise on angle estimation for specific time periods.
下一步是什么？
As the automotive industry continues to undergo a massive transformation, new features like advanced safety and driver-assistance systems continue to evolve. The various sensors already available, such as pressure and temperature, will still be used in vehicles. Yet other types of sensors will certainly be implemented in autonomous driving to support safety functions.
此外，科学和工程的进步将导致新材料和加工方法。他们将实现针对用于汽车应用的下一代MEMS技术和传感器的胶片设计和制造，例如高级驾驶员辅助系统（ADAS）。
Inside the cabin, for example, automotive companies are designing MEMS microphone solutions to offer new voice-control functions with noise-to-noise ratios in the range of 60 to 70 dB. Such microphones offer a high signal-to-noise ratio (SNR) and good sensitivity with a surface-mount assembly processes. Moreover, they offer less variation in sensitivity over temperature, with significant advantages in terms of performance, reliability, and manufacturability for a multitude of safety applications in the automotive industry.
In addition, a gyroscope can be used to activate the electronic-stability-control (ESC) braking system to prevent accidents when the car is, for example, traveling along a narrow curve(Fig. 3)。当倾斜状况或额叶事故发生时，陀螺仪也可用于激活安全气囊。在包括汽车多样性的机器中，它可用于测量方向，以在丢失GPS信号时保持数字地图上的移动方向（Dead-Reckoning Systems）。
3. Within feedback systems, the MEMS sensor performs the feedback task and, therefore, the control response is associated.
噪声与运动控制
显然，MEMS陀螺仪和加速度计已经有助于使汽车更加安全 - 他们在车辆控制系统中的大量存在可显着提高驱动稳定性。MEMS设备还构成了系统的核心，在大多数情况下，该系统需要噪声过滤，自适应学习算法以及重置由于温度变化和振动引起的效果的任何不平衡的能力。
Keep in mind, though, that the noise of MEMS systems can have a direct influence on the key performance criteria in motion-control systems. Thus, it should be carefully considered in the design process.
还请记住，新的MEMS市场正在出现：纳米电机机电系统（NEMS）。由于其灵敏度，这些纳米纳米设备能够获得很小的传感器，以检测原子水平的应力和振动。
纳米技术有望提高现有汽车技术的性能，从而提高发动机效率和油耗。这些设备通过传感和控制功能提高了微电子和力学的计算能力，从而提供了高水平的功能积分和低功率操作。
