Tilt Sensor with Recalibration Feature Based on MEMS Accelerometer

Abstract

The main errors of MEMS accelerometers are misalignments of their sensitivity axes, thermal and long-term drifts, imprecise factory calibration, and aging phenomena. In order to reduce these errors, a two-axial tilt sensor comprising a triaxial MEMS accelerometer, an aligning unit, and solid cubic housing was built. By means of the aligning unit it was possible to align the orientation of the accelerometer sensitive axes with respect to the housing with an accuracy of 0.03°. Owing to the housing, the sensor could be easily and quickly recalibrated, and thus errors such as thermal and long-term drifts as well as effects of aging were eliminated. Moreover, errors due to local and temporal variations of the gravitational acceleration can be compensated for. Procedures for calibrating and aligning the accelerometer are described. Values of thermal and long-term drifts of the tested sensor, resulting in tilt errors of even 0.4°, are presented. Application of the sensor for monitoring elevated loads is discussed.

MEMS Inertial Sensor Calibration Technology: Current Status and Future Trends

“…Some crucial existing calibration methods. Box 1 represents the combination of a lowprecision turntable and cube fixture [66]; box 2 represents the tilt sensor with 3D-printed housing [22]; box 3 represents other autonomous calibration methods that do not require a turntable.…”

“…Keep the accelerometer system coordinate system consistent with the turntable test coordinate system, and test each sensitive axis of acceleration vertically up and down with the help of high-precision turntable. Once each sensitive axis senses the acceleration of g and then −g, the bias b (Equation ( 8)) and the scale factor s (Equation ( 9)) are calculated [22].…”

“…The use of specially designed cube housings can be easily and quickly recalibrated by the user in order to eliminate such considerable errors as thermal and long-term drifts as well as effects of aging, keeping the sensitive axes aligned with respect to the external mechanical datum [22].…”

“…Figure 1 shows the cost price of MEMS inertial sensors with varying degrees of accuracy in various application scenarios. Tables 1 and 2 MEMS inertial sensor errors are mainly related to the following factors: the misalignment and nonorthogonality of the sensitivity axes; the thermal and long-term drifts of the output signals (affecting both the bias and the scale factor); errors related to the installation and manufacture of sensors and aging of the silicon structure; variable bias due to thermal effects; and some uncertain noise sources or random errors [19][20][21][22]. Given these facts, this paper focuses on existing calibration techniques for MEMS inertial sensors and briefly analyses them.…”

“…At the same time, certain calibration and test standards must be followed [24]. Using the method of error calibration, deterministic errors, such as offset, scale factor, nonorthogonality, misalignment and so forth, associated with the unknown orientation of the accelerometer and gyroscope sensitivity axes, thermal and long-term drifts of the output signals, installation and manufacture of sensors, aging of the silicon structure and so on can be effectively eliminated or compensated for [22]. This allows the sensor operating parameters to be accurately determined under given operating conditions, thereby increasing the accuracy and reliability of the sensor.…”