Nonlinear Correction Of The Rotary Valve Load Torque And Analysis On The Rotary Speed Control Method

The research on the information transmission from the underground to the ground is a hotspot in the field of modern drilling engineering.Measure while drilling(MWD)is a kind of modern drilling engineering supporting technology,of which drilling fluid pressure wave generator is the core device.The fast follow-up control of the rotating speed of the rotary valve determines the effect of the signal modulation,and has a significant influence on the transmission of the pressure signal.Therefore,the research of speed control of rotary valve can provide theoretical guidance and technical support for the development of MWD system.According to the structural design and rotor force analysis of rotary valve,the mathematical model and characteristic analysis of the load torque of the rotary valve are carried out.Based on the mathematical model of the axial force of the rotary valve,polynomial fitting of the load torque of the rotary valve was built,and rotation angle and speed equation under motor drive of rotary valve was established on this basis.By nonlinear compensation,elimination of nonlinear characteristics of control,the linearization of the rotational speed equation is realized,and the open loop control model of rotary valve is established.According to this,the influence mechanism of the disturbance on the rotational speed of the rotary valve is analyzed.Besides,the forward PID control is used to establish the PID closed loop control model in complex frequency domain,the mathematical model of the influence of the deviation of the rotation speed,the measurement error and the load torque on the rotational speed output is established.With the reasonable selection of PID parameters,using residue method and Simulink simulation,the theoretical calculation and simulation analysis of the rotating speed of the rotating valve under the influence of disturbance has been done.Theoretical research and simulation analysis show,with the optimization of PID parameters,linearization correction method of rotary valve speed control system based on feedforward compensation,fast follow-up control of rotary valve speed and high interference rejection ability can be done.It provides a theoretical basis for speed control of rotary valve.