Research Of Trajectory Tracking Control Methods For Rotary Steerable Systems

Rotary steerable system(RSS)is a new type of directional drilling that has been applied in oil and gas drilling operations in recent years.RSS has a number of advantages including low cost,high rate of penetration,smooth borehole trajectory,horizontal well extension and so on.In actual applications,there exist violent nonlinearity,time-variation,delay characteristics and other factors which influence control performances in the RSS.These leads system difficult to track ideal predetermined borehole trajectory accurately,and even makes system deviate from predetermined trajectory.Therefore,it has important theoretical significance and practical value to study the trajectory tracking problems for RSS.Taking the trajectory tracking control and platform construction for RSS as research object,main contributions of this dissertation include:1.A push-the-bit RSS trajectory model is introduced,and 2-dimension and 3-dimension trajectory state space equations of this model are deduced.The stability of system model is analyzed.2.State feedback controller based on stability compensation observer has been proposed for 2-dimension RSS trajectory model.Stability compensation observer is designed by integral sliding model variable structure control method,and stability compensation of delay characteristics in system is realized.An improved genetic algorithm named NSGA-II has been used to optimize system parameters.Compared with traditional state feedback control based on state observer,the proposed method in this paper has advantages in performance indices such as convergence speed,accuracy,and oscillation elimination.3.A cooperative trajectory tracking control algorithm based on interval type-2 fuzzy control and reinforcement learning has been proposed for 3-dimension RSS trajectory model.First,interval type-2 fuzzy controller which is adopted to deal with nonlinearity and delay characteristics of the system.Then,the actor-critic networks controller is designed to optimize drilling trajectory,and the accuracy and smoothness are improved.The control effects are enhanced further by using Low-pass filter to fuse and filter the control signals.4.The electrical integrated platform of drilling system are constructed.In the platform design,CAN bus is used to realize signal acquisition and control,and PLC is used to realize stepper motor control.The CAN bus and OPC protocol are used to communicate with slave computer for different modules respectively,and the signal acquisition,transmission and control are realized in the industrial control computer.The visualization interface of drilling trajectory are realized,and it is convenient to observe real-time downhole trajectory.