| The gyro-theodolite , which is composed of a suspended two-degree-of-freedom gyrocompass and a theodolite, is the main instrument in the engineering measurement for meridian determination. Under the condition of orientation precision, the main aim is to increase the orientation speed at present. Because the period of the motion for the two-degree-of-freedom gyrocompass is long, the orientation speed cannot be remarkably increased. Compared with that, the motion period of single-degree-offreedom gyrocompass is shorted greatly. Accordingly, the orientation speed can be increased several times. So it is important in engineering to study the single-degreeof-freedom gyrocompass.The motion for the single-degree-of-freedom gyrocompass is caused by the inertial gyro-moment that is produced by the earth抯 auto-rotation. But the inertial gyro-moment is very small. Only on the condition that the friction moment of bearings is far smaller than inertial gyro-moment, the motion for the single-degree-offreedom gyrocompass will be obtained. Thus, the key to obtain the single-degree-offreedom gyrocompass is to choose a suitable type of bearings. Permanent magnet bearings have a prominent character of no mechanical friction. A suspended singledegree-of-freedom gyrocompass with them can remove the effects of the bearing抯 friction.In this paper, we analyze the dynamic model for the single-degree-of-freedom gyrocompass restrained by permanent magnet bearings. The dynamic differential equations are obtained according to the reasonably analyzing dynamic model. The results and the responses to the initial conditions are given. The Numerical calculation is used to the results of the equations and the results are analyzed. Then the laws of the motion for the single-degree-of-freedom gyrocompass restrained by permanent magnet bearings are drew out, so does the relation between the radial stiffness of permanent magnet bearings and the period of the motion of gyrocompass.
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