Design and Implementation of Servo Control of Strap-Down Automatic Vertical Drilling System

To solve the problem of deviation control during fast drilling through formations tending to deflection in vertical wells,and realize the deviation correction and prevention actively,the research on servo control of the strap-down automatic vertical drilling tool has been carried out.A three-ring closed-loop control model including position loop,speed loop and current loop was adopted to establish the hardware configuration and software architecture of the servo control system in which the incremental digital PID control law was used to realize the fast and accurate and reliable adjustment to the system.By studying current dynamic step response,the motor output shaft position and the disc valve tool face angle control effect,analyzing the dynamic and static characteristics of the servo control system,the servo control system was ultimately designed then put into field application.Under laboratory conditions,the static control precision of the motor output shaft position was less than 0.2°,the dynamic step response of current loop reached 1.2 ms,and the velocity adjust range was 0 to 300 r/min.Those results show that the servo-control has high control accuracy,good dynamic performance and wide adjustment range,and is able to realize real-time control.In field application in Well Anshun 1,the deviation of the output disc valve tool face angle and the input designated restoring tool face angle was less than 2°,resulting in inclination control of less than 2.8°/100 m.The servo control system of the strap-down automatic vertical drilling tool can respond quickly and control the motor output shaft position accurately to realize deviation correction and prevention in vertical wells.