Research And Design For Dither Bias System Of Mechanically Dithered Ring Laser Gyroscopes

As an ideal part of inertia navigation, the mechanically dithered ring laser gyro (MDRLG) has been widely used overseas. But its development in our country is unsuccessful yet. One of the reasons is that the research on dither bias system is not deep enough, and performance of the dither bias system can not meet the demands of lock-in error canceling. In this article , dither bias and dither bias system is studied in theory and experiment. New technologies such as finite element analysis, computer simulation and computer aided control system design are introduced. A high performance dither bias system is developed.Based on the dither bias theory, the demands of lock-in error canceling on dither bias system are educed. The demands are: the dither mechanism should have high resonant frequency and large dither amplitude; the dither controller should keep the bias level stable; the noise injection device should inject a steady noise whose amplitude changes once a dither period into the dither motion. These demands are used to instruct the design and research on dither bias system.The approaches to improve the performance of dither mechanism are discussed. Aim at overcome the shortcomings of traditional method, finite element analysis method is introduced in resonant frequency design and stress analysis. A new design method for dither mechanism is developed. A new type of dither mechanism with high performance is designed by using this method.A dither controller should have an amplitude control loop and a resonant frequency-track loop. Computer simulation technology is used to solve the non-linearity problem of amplitude control loop. System identification method is used to find the transfer functionof the loop. CACSD method is used to design the loop. A self-oscillation loop is design to track the resonant frequency.The problems of noise type, noise inject mode, noise intensity, and noise inject efficiency are studied. A scheme of noise producing and injecting is developed. The target of noise injection is achieved and the dynamic lock-in error is canceled. The influence of noise intensity on dynamic lock-in error is studied. It is found that noise intensity of 2% is adequate.Experiments are done on the newly developed MDRLG. Its random walk coefficientis 0.0163 %/fe , RMS precision of drift is 0.09/fc, and scale factor precision is less than10ppm. The experiment result can approve that the gyro has a preferable precision, the dither bias system work perfectly and the target of dither bias is achieved.