Application Of The Electromagnetic Damping To The Suspended Two-Degree-of-Freedom Gyrotheodolite

The suspended two-degree-of-freedom gyrocompass is the kernel part in the gyro-theodolite. Decreasing the north-finding time of the gyrocompass is practically important to the improvement of the complete machine performance. The traditional methods of the true-north measurement used in suspended gyrocompass need a sampling time for the oscillation period of the gyro-wheel axis at least. With the two-degree-of-freedom gyrocompass as the researching object, a new implement method which can decrease the north-finding time is introduced using the coaxial electromagnetic damper.Firstly based on the compound motion theory, the influence of earth rotation on the motion of the gyrocompass is analyzed. Using the motion of center of mass theorem and Euler kinetics equation , the motion differential equations of the suspended two-degree-of-freedom gyrocompass are established; The working principle of Electromagnetic Damper is discussed, thus the complicated calculation of the eddy current is converted into resistance calculation. A diagram method is used to calculate the eddy circuit resistance and the equation between the magnetizing current and the electromagnetic damping torque are offered. Combined with the former two equations, the motion differential equation of gyrocompass added with magnetic damping is suggested and this first order differential equations are solved using the integral transformation. Based on the obtained solution, the reasons affecting the north-finding time of the gyrocompass are discussed using second-order oscillating system theory. A new method is proposed that gyro-wheel axis can point to true north directly without restriction of the oscillation period by controlling the electromagnetic damping, thus reducing the north-finding time. Using Matlab to simulate the motion process of gyrocompass, the survey time are compared by changing the coefficients of the electromagnetic damping moment。The results show that the shorter survey time can be obtained using the sectional damping coefficients method. The results of decreasing time are compared under the sectional damping consisting oftwo segment with various coefficients and different time boundary between two adjacent segment considering the existing experiment condition. Finally the simulation experiment system is constructed and the time of system entrying into homeostasis are measured under the situations of the fixed damping and the sectional damping. The result shows that the sectional damping method is effective in realization. Based on the experiment data, this method can be applied to the gyro-theodolite and is proved the feasibility of reducing the measurement time.