The Optimization Of Hydraulic Correction Mechanism's Output Force With Low Frequency PWM Control In Vertical Drilling Tools

The AADDS drilling tool discusses in this paper is a new type of oil automatic vertical drilling tool.To achieve automatic anti-deviation,the core component of the drilling tool is hydraulic guide anti-deviation mechanism.In the premise of not changing the existing structure,component and parameters of the drilling tool,the research is on the basis of proposed method that applying PWM control to AADDS automatic vertical drilling tool to implement the downhole anti-deviation force adjusting continuously.However,the previous PWM control method would cause the anti-deviation force fluctuate large,which brought the low stability of well deviation's relative azimuth.To solve this problem,the optimum research about achieving the continuous adjustment of downhole anti-deviation force is put forward.The guide anti-deviation mechanism of the drilling tool is a micro hydraulic power system which driven by single piston pump,the flow of the system is low and discontinuous.In order to realize the continuous control of the output anti-deviation force of the drilling tool and reduce the fluctuation range of the anti-deviation force.Based on the original single pulse width modulation technology,the multi pulse width modulation technique is introduced.With analysis of the flow-pressure characteristic of the system by theoretically modelling,this paper proposes the method that control the on-off time of the two-position two-way solenoid valve several times in a drill pipe rotation period,which is also the cycle of pulse width modulation.Through the multi pulse width modulation,the increasing oil volume in the anti-deviation cylinder,would discharge several times instead of once in a cycle.In this way,it could improve the stability of anti-deviation cylinder's pressure and output anti-deviation force effectively.In order to realize this kind of multi pulse width modulation control,The modulation principle and working characteristics of the multi pulse width modulation of the solenoid valve are analyzed.The parameters that be required for in the multi pulse width modulation can be calculated by the mathematical model of the hydraulic controlsystem.It also develop simulation research on the modulation control of multi pulse width modulation by using Matlab/simulink software.Under the guidance of theory and simulation analysis,the experimental test of the effect of the multi pulse width modulation control of the hydraulic guide anti-deviation mechanism is carried out.The results show that the optimized multi pulse width modulation technique can effectively reduce the fluctuation range of the modulation pressure of the anti-deviation cylinder,thus improve the stability of the pressure and output anti-deviation force of the cylinder.