Gyro-Free Inertial Measurement Unit With Unfettered Accelerometer Array Distribution and for the Object With Position Change in Center of Gravity

Previous gyro-free inertial measurement units (GF-IMU) usually suffered from installation errors induced by mutual placements and mutual sensing directions of accelerometers, and underlying mechanism for eliminating the effect of position change in the center of gravity (PCGC) was not presented clearly. This paper reports a GF-IMU compensating for the effect of PCGC and installation errors by using two parallel mounted accelerometers as a group in designing accelerometer array configuration. The underlying kinematics is first developed and indicates that subtraction of accelerations within a group can remove the effect of PCGC. Nine acceleration subtractions from nine independent groups with irrelevant sensing directions and arbitrary installation distances can determine the square of angular velocity and angular acceleration directly, which does not induce installation errors. Then three configurations fitting different requirements are proposed based on three accelerometer placement rules. The motion quantities at the center of gravity (GC) can also be obtained if mutual installation distance among different groups is known. The validity and performance of schemes are finally verified by SimMechanics simulations. The rotational motion measurement scheme proposed in this paper does not need to know mutual placement information of accelerometers as well as the GC position, which greatly simplifies its installation, and make it possible to develop a convenient product for the rotational motion measurement with only accelerometers.