Steering Platform Control Based On Disturbance Observer

The steerable drilling stabilization platform is a key link in the rotary steerable drilling tool.Its accurate and rapid control directly determines the efficiency and reliability of the drilling.Due to the complex and varied environment and the influence of various frictions,it is difficult to establish an accurate mathematical model of the stable platform.Therefore,some traditional control strategies can not meet the control requirements for the stable drilling platform.In this paper,the control method combining the disturbance observer and the sliding mode variable structure control theory is applied to realize the control of the stable drilling platform.Aiming at the uncertainty caused by the friction problem of the rotating steerable drilling platform and various unknown disturbances,the steerable drilling platform based on the Disturbance Observer(DOB)is proposed to control the platform with a simple structure and a small amount of computationin oderto suppress of interference.PIDDOB is used to restrain the uncertain interference experienced by the system to meet the control requirements of system performance.The Lugre model is simulated in Matlab.The control effect of the control system under the influence of nonlinear factors is studied.The robustness of the stable platform system under the influence of parameter perturbation and unknown disturbance torque is analyzed.By designing the disturbance observer to compensate the unknown interference of the stable platform and the error of the internal model,the anti-interference ability of the system is improved.By simulating the control strategy,the experimental results show that under the control method,the steerable drilling platform system can suppress the external disturbance,and overcome the influence of the nonlinearity and the influence of the parameter perturbation to some extent.The accuracy is significantly improved.In order to further improve the tracking speed of the stable platform to the tool face angle and reduce the error of the control system,a Sliding Mode Variable Structure Control based on Disturbance Observer(SMVSCDOB)control method is proposed.This method is based on the uncertain disturbance term in the system.By designing the controller,the disturbance observer and the sliding mode variable structure are combined to compensate the uncertainty in the system,reduce the friction interference and influence of unknown interference ontracking performance of stable platform control system.The stability of the closed-loop system controlled by SMVSCDOB is proved by Lyapunov theory.Comparing the SMVSCDOB control method with the methods of PID,PIDDOB,SMVSC,etc.,it can be seen that SMVSCDOB can effectively compensate the adverse effects caused by the frictional disturbance to the stable platform control system.To the unknown disturbance torque,after adding the disturbance observer,the tracking performance of the system isincreased,meanwhile the chattering of the control input is reduced..The simulation results show that the proposed method SMVSCDOB can better track the tool face angle,reduce the system error,suppress the friction interference,and make the system more robust.