A Linear Observer Design for Dither Removal in Ring Laser Gyroscopes

A ring laser gyro exhibits a phenomenon known as lock- in. Lock-in is the inability of a RLG to detect motion below a low rotational rate threshold. To avoid lock-in at low rotational rates, a ring laser gyro is mechanically vibrated or dithered, about its input axis. To remove this unwanted signal and to minimize data latency, dither stripping techniques have been employed. There are some dither removal techniques commonly used in RLG's. (1) dither removal by digital filtering (FIR) scheme and (2) dither stripping scheme using dither pickoff sensor. These techniques have their own advantages and disadvantages. The main drawbacks with the FIR based technique are dither components are not attenuated completely and inter gyro dither frequency interference effects are still present. In order to overcome these drawbacks, a Linear Observer based dither stripping scheme is proposed in this paper. The proposed method is efficient both in terms of highest attenuation of dither component and inter-gyro dither component interference at system level.