Design and Construction of Free Gyro IMU Using MEMS Accelerometers

Because of the high cost of mechanical and optical gyroscopes, in recent years the low cost measurement systems based on Micro Electro Mechanical sensor (MEMS) are widely used. These systems often are integrated with radio navigation to achieve the required accuracy. MEMS gyroscopes suffer some problems like large drift and acoustic sensitivity, compare with MEMS accelerometers. So the design of low cost inertial measurement system without using the gyroscope, and based on a suitable geometry configuration of accelerometers is considered in literature in recent years. The goal of this research is to design and manufacture of such free gyroscope measurement unit. For this purpose, first an appropriate geometry configuration of accelerometer is proposed then the mathematical relationship between the output of linear accelerometers and linear and revolving acceleration of the center of mass of the structure is derived and then the angular velocities are estimated. The proposed free gyroscope IMU is constructed using the ADXL345 accelerometers as sensors and the ARM-LPC1768 microcontroller as processing unit. The experimental results using a rotating table as reference are gathered in the Lab. The results show the suitable performance of the measurements unit.