Acceleration Sensors in Automotive Electronics

The best center of gravity position can be selected by measuring the inertia of the smart car, and the smart car can be accurately positioned in straight lines, curves, ramps, drifting and other running states; the acceleration sensor can predict the path in advance and determine when the braking effect is best. It also solves the balance and direction recognition of the upright walking car model.

Therefore, a design based on three-axis acceleration sensor in smart car control and path recognition is proposed. This design uses three-axis acceleration sensor MMA7260Q to measure the acceleration signal of the smart car in motion, and uses embedded single chip MC9S12XSl28B as the core controller to sample the acceleration signal, A/D conversion, and then store the characteristic data in EEPROM. It solves the problem of smart car motion path analysis and obtains the car acceleration in real time, so as to obtain the running status of the car more comprehensively, which makes it possible to control the smoothness and better road condition recognition.

In the upright walking car model, applying the same principle and selecting the optimal center of gravity can effectively solve the balance and direction recognition of the upright walking car model, thereby speeding up the driving speed of the car model.

Market research firm IHS iSuppli pointed out that thanks to the rapid popularization of automobile safety regulations and automobile safety system applications in recent years, the market for composite MEMS inertial sensors for automotive applications is expected to reach US$163 million in 2013, a significant increase of 77%.

IHS said that as more cars are equipped with safety systems, the use of these types of sensors in cars is increasing rapidly. Last year, the market for this type of sensor grew by about 338% to $92 million, a significant increase from $10 million in 2011.

A composite inertial sensor is a multi-sensor element that integrates an accelerometer and a gyroscope in a single package. It provides inertial input for the electronic stability control system (ESC) in the car to avoid or reduce the occurrence of skidding.

"In North America, Europe and other places with mature regulations, such as Australia, Japan, Canada and South Korea, cars are required to use ESC systems," said Richard Dixon, principal analyst for MEMS and sensors at IHS. However, "there are still huge business opportunities in some untapped areas, such as China, which provides a larger market, which will obviously affect the global penetration of ESC. However, from another perspective, it will also bring huge growth drivers and momentum to the overall automotive composite sensors."

VTI's inclination sensors consist of high quality silicon capacitive sensor elements and interface electronics assembled in a specific application package. The silicon capacitive inclination sensor element is made of single crystal silicon and glass. This design ensures reliability, unprecedented accuracy and excellent stability over time and temperature. Typically a component can withstand accelerations of more than 40,000g (1g = acceleration due to the earth's gravity).

There is no plastic deformation and hysteresis in single crystal silicon, it is either successfully made or completely destroyed. The cantilever dual capacitance sensing element is equipped with overload protection, which can measure acceleration in two directions.

The core of the inclination sensor is the symmetrical capacitor block of the micromechanical acceleration sensor element, which consists of three silicon wafers isolated from each other by thin glass films. The middle silicon wafer is a cantilever multi-ray structure, and the large mass block on it, the capacitance and the elastic coefficient can independently obtain the best results. This is exactly why good measurement results are obtained in the low g value range. The gravity and acceleration forces acting on the silicon wafer cause the single crystal silicon electric beam to oscillate and bend. This deviation can be measured by the change in the distance between the capacitors with two metal films as electrodes. The micromechanical wafer can make relatively large capacitance and capacitance changes easily detected.