Research On Stability Control Of Power Haed System Of Rotary Drilling Rig

Rotary drilling rig has the characteristics of high construction efficiency and good hole forming quality.In recent years,with the rapid development of pile machinery,the number and application range of rotary drilling rig are expanding constantly.Power head system is one of the main systems in rotary drilling rig,and its stability directly affects the use of drilling rig.Because of the inconsistent performance and improper control of the power head motor components,the system pressure fluctuates in idling condition.Because of the uneven load,the rotating speed is unstable and jitter occurs in drilling conditions.Due to the large hydraulic impact,problems such as oil seal damage and motor shell cracking often occur in the soil dumping condition.In view of the above phenomena,based on the stability problem of the power head system of a drilling rig in China,this paper puts forward a stability control scheme,and finally tests the optimization scheme on the whole machine.The main content of this paper is as follows:(1)Theoretical analysis of working principle and stability influencing factors of power head system.In view of the existing problems of pressure fluctuation and oil seal,the factors affecting the stability in the transfer link were analyzed respectively,and the causes of the stability problems were summarized by surveying and mapping the relevant structures in the key motor variable mechanism,mathematical model derivation and analysis.(2)AMESim simulation model and stability analysis of power head hydraulic system.According to the principle of the system,the simulation model was built and checked.Based on the mathematical model,the simulation model and the test data of the main engine,the main cause of the pressure fluctuation in idling and drilling was identified as the instability of the motor variable.Through the orthogonal test method,it was found that the significant factor affecting the stability of the motor variable was the gap between the valve core and valve sleeve in the variable mechanism.The cause of motor damage in soil dumping condition is hydraulic shock caused by torsion strain energy of drill pipe and poor drainage of oil.(3)Research on Control Optimization of power head system.It is proposed that the pressure fluctuation problem is solved by using reasonable filtering parameters and PWM control frequency in motor control program optimization,the active pressure relief mode of large diameter oil drain check valve and the optimization of oil filling system are adopted to solve the oil seal problem.(4)Stability test and control optimization of power head system.The motor pressure fluctuation amplitude was used to evaluate the stability of idling and drilling conditions.After optimization,the motor pressure fluctuation amplitude decreased by 90.0% from20 bar to 2bar during idling,and by 94% from 50 bar to 3bar during drilling in soil layer.The stability of the earth dumping condition was evaluated by the peak of the motor drainage pressure and the motor failure rate.After optimization,the oil drainage pressure of the power head motor was reduced by 96.7% from 60 bar to 2bar.After the strategy,the tracking verification was carried out on several main engines in the market,and the failure rate was reduced from 6% to 0%,which significantly reduced the stability of the main engine power head system.