The speed control research on rotary valve driven by micromotor in MWD

The rotary valve speed control, extremely affected by nonlinear dependence of rotary valve load torque on rotation angle, affects the generation of drilling fluid pressure PSK signal and its quality. Based on load torque calculation model, the load torque feed forward compensation is used in linearized correction of rotation speed control system to enable the motor voltage to vary according to the calculation model. Additionally, the calculation model is also used in compensating the influence of serious nonlinearity in rotary valve load torque on rotation speed control. By means of closed-loop proportional-integral-derivative (PID) control which is formed by negative feedback of speed and the PID parameter values determination rule which is created by attenuating control of transient component in step response of rotary valve speed, the rapid servo control of rotary valve speed is realized. Simulink Simulation indicates that the closed-loop speed control system of rotary valve is able to track the change of control voltage pulse quickly and strongly suppress the interference influences from flow measurement error and load torque calculation model deviation.

Automated summary

This study investigates the influence of nonlinear dependence of rotary valve load torque on rotation angle in the rotary valve speed control system. It proposes the use of load torque feed forward compensation and closed-loop PID control with negative feedback for rapid servo control.