Anti-disturbance Compound Control Strategy Of Continuous Wave Mud Pulser Based On Sliding Mode Observer

In the process of continuous development of drilling technology,more and more information needs to be transmitted from the downhole to the ground.Therefore,the cost and speed of information transmission are required to be higher and higher.Because the date rate of continuous wave mud pulse is more than 10 times that of the traditional positive pulse mode,and it is economical and reliable.Therefore,it has become the latest technology of underground information mud pulse telemetry system.Permanent magnet synchronous motor is selected as the driving motor of continuous wave mud pulser because of its small size and easy maintenance,it drives the rotary valve of pulser to rotate and generates mud pressure pulse carrier to transmit downhole information.At the same time,it is affected by the variable resistance torque of drilling fluid,which leads to the decline of dynamic performance and further affects the quality and distance of information transmission.Improving motor control performance is the key to improve the quality of information transmission from the perspective of source.During the operation of the motor,it will be affected by the variable resistance torque of drilling fluid,and the variable resistance torque is affected by many factors,such as the flow rate,the opening of rotary valve and so on.In order to solve this problem,a compound control strategy based on sliding mode observer is proposed to improve the dynamic performance of the motor.Firstly,based on the traditional reaching law,an improved variable exponential reaching law is proposed.Compared with the traditional reaching law,this reaching law does not add new parameters,but it can reduce the chattering and improve the dynamic performance of the motor,and its feasibility is proved theoretically.Then,based on the improved variable exponential approach law,a sliding mode controller of speed loop is designed to realize the sliding mode control of PMSM.The simulation results of different controllers in Matlab/Simulink show that the sliding mode controller based on improved variable exponential reaching law is superior;In order to further improve the disturbance rejection performance of the motor,the sliding mode observer is designed by using the improved variable exponential reaching law.The observer is proved to be excellent by tracking and comparing the fitted hydraulic torque curve in Matlab/Simulink;The observer and controller designed in this paper are combined to observe and estimate the disturbance including the torque of drilling fluid resistance,and then compensate to the input of current loop in proportion to realize the compound control of the driving motor.The simulation results show that the disturbance rejection compound control strategy based on sliding mode observer can effectively improve the dynamic response speed of the driving motor and enhance its disturbance rejection.Using the continuous wave mud pulse remote transmission platform to simulate the underground information transmission,the modulation and demodulation of2 FSK information are simulated and modeled;Finally,the information transmission of the continuous wave mud pulse remote transmission system is compared under the two different control strategies,PI control and compound control in this paper.The results showed that improving the motor control performance is really beneficial to improve the information transmission quality.