PWM Control Study On Output Force Of The Downhole Hydraulic Guide Anti-deviation Mechanism

A certain type of drilling tool is one of novel oil automatic vertical drilling tools.To achieve automatic anti-deviation, the core component of the drilling tool is hydraulicguide anti-deviation mechanism. Due to not able to adjust anti-deviation force of thedrilling tool continuously, it affects the accuracy and efficiency of the downholeanti-deviation severely. In this paper, electronic control method is applied to adjustanti-deviation force of drilling tool continuously with not changing the existingstructure and parameters of the drilling tool.The guide anti-deviation mechanism of the drilling tool is a micro hydraulic powersystem, whose core component is the valve-controlled cylinder pressure control systemwith single piston pump. Its flow is low and discontinuous. The maximum outputpressure (the maximum anti-deviation force) of this system is set by the relief valve.Based on establishing theory models and analyzing on flow-pressure characteristics ofthe system, a special PWM control method is put forward to achieve the continuouscontrol of the drilling tool’s anti-deviation force through adjusting the system outputpressure, which is smaller than the maximum output pressure set by the relief valve.The theory of PWM control method is to actively control the leakage of hydraulicsystem using the two-position, two-way solenoid valve of the guide anti-deviationmechanism. Then, the impact of the action delay time of the check valve spool on theon-off switching moment of the solenoid valve is analyzed detailedly in the paper. Inorder to realize the special PWM control method, the PWM control principles andworking characteristics of the solenoid valve are analyzed. On the basis of furtherelucidating the PWM control theory of the system, a practical PWM control strategy isproposed and the function relationship between the system output pressure and PWMparameters is deduced. In addition, co-simulation research on the system PWM controlis completed by the AMEsim and Matlab/Simulink software. In the guidance of thetheory and simulation analysis, experimental test of the PWM control effect is conducted for the hydraulic guide anti-deviation mechanism. The experimental resultsshow that: the PWM control method, which has no strict requirements for the on-offswitching moment of the solenoid valve, is feasible for the special hydraulic system.