Abstract: The scheme by which the laser gyro mechanical dithering affects the accuracy of the attitude computation using rotation vector algorithm is researched in this paper. The attitude computation error caused by the resonance between the body attitude movement and the mechanical dithering is investigated using two sample N times-iteration algorithm. The comparability between this error and the sculling effect in specific force transformation is proposed. Two situations, that only one dither mechanism is used for the three axis RLG configuration and that the IMU is composed of three single axis laser gyros, are discussed. The power spectral density of the laser gyro sampling in IMU is analyzed under static state. It is shown that the low frequency periodic error caused by low frequency sampling of the dithered gyro will resonance with the low frequency body attitude movement. In this case attitude computation error will occur. It is pointed out that the frequency of the sampling and the rotation vector updating should be high.

Key words: laser gyro, dither bias, rotation vector, attitude computation