experimental study of the information signal of combined shock, tilt, and motion sensor based on the 3-axis mems-accelerometer

Modern car alarm systems are equipped with smart sensors implemented using various physical principles. These sensors have to ensure high reliability and validity of monitored parameters with a lack of false operations. First of all, shock sensor, which is a part of, essentially, entire alarm systems, as well as tilt and motion sensors are referred to the smart sensors.

Shock sensors with the sensitive elements (SE) of piezoelectric, microphone, and electromagnetic types possess a number of the essential shortcomings caused by the type of SE. It is, first of all, a narrow band of the sensitive elements, which does not allow true differentiation of shocks to the autobody from false actions, as well as a various sensitivity of sensors depending on the SE axis orientation.

Tilt sensors of electromagnetic type implemented as separate devices were seldom used because of their high cost and imperfect characteristics. Though there is still a need for such sensors. The specified shortcomings can be hardly overcome through improvement of sensitive element hangers of considered sensors. The use of the three-axial accelerometers made by MEMS technology seems to be the most perspective here.

The article presents results of pilot studies of the accelerations reached when auto-body is under shock and a car is inclined and runs. When measuring, the test board STM32F3DISCOVERY with the MEMS accelerometer LSM303DLHS is used. A level of noise and vibrations has been analysed when mounting a board on the plastic panel of the car and when operating the engine in the range from 700 to 4000 rpm. The article presents accelerations implemented under the following conditions: light shocks in different parts of the auto-body (wing, trunk, hood); strong shock (closing a door); slow and fast acceleration to the speed of 20 km/h with the subsequent braking and passage of obstacles such as "sleeping policemen".

Research results enabled us to make justification for selecting the range of accelerometer operation, as well as the accuracy of measuring acceleration, frequency of signal poll, and algorithm of filtration.

The article gives recommendations for selecting the MEMS accelerometers to be used in combined shock, tilt, and motion sensors of modern car alarm systems.