Mechanical Analysis of Stable Platform for Rotary Steerable Drilling Tool

Stable platform is a typical mechanical and electrical integrated control system that servo control and inertia technology are combined, which is also the control core of rotary steerable system. Its structural stiffness determines whether the system can work normally or not. Therefore the structural principle of stable platform control shaft is introduced in this paper. Based on its structural characteristics and stress conditions, the mechanical analysis model and finite element model is obtained with some reasonable simplifications. Since downhole vibrating acceleration has a great impact on the stiffness of the control shaft, three typical acceleration states are given, acceleration perpendicular to the control shaft, downwards along the direction of the control shaft and upwards along the direction of the control shaft. The lateral and longitudinal stiffness of the model is analyzed by finite element method, results of which show that the vibrating acceleration no more than 15g is safe for the stable platform control shaft. The analytical results also show that the maximum displacement occurred on the upper end of the lower turbine generator. Through the analysis of this paper, the constraint conditions for the rotary steerable drilling tool are obtained and the theoretical basis for application of the tool structure is provided.