Research On Stability Of Main Hoist Down Of Rotary Drilling Rig Based On Active And Passive Control

Rotary drilling rig has become an essential piling machine in domestic infrastructure construction.As one of the most important systems,the main hoist system often causes system pressure fluctuation in descending condition due to improper matching of inherent parameters of the system or unreasonable program control,and then appears the descending instability phenomenon,affecting the working efficiency and quality of the main engine.Based on this,this paper mainly conducts the following research:(1)Establishment of theoretical models of braking system and balancing valve system.Through hydraulic principle analysis,it is concluded that the main factors affecting the stability of the main hoist down are the response of the braking system and the stability margin of the balance valve system,and a theoretical model is established to preliminarily identify the parameters affecting the response of the braking system and the stability margin of the balance valve system.(2)The AMESim simulation model of the main hoist hydraulic system is established.Through component entity mapping and sample characteristics,the internal structure and control parameters of components were defined,and then the component simulation model was built.The accuracy of the model was verified through static check.Finally,the simulation model of the main hoist system was built from points and surfaces.(3)Stability margin analysis and active and passive control optimization.Firstly,the braking system response is simulated and analyzed,and the influence of the braking system response on the stability of the main hoist system is determined quantitatively.Then,based on the classical control theory,the sensitivity and proportion of the influence parameters on the stability margin of the system were analyzed in the frequency domain.And for the two parameters with the highest proportion,namely,the motor displacement and the pilot damping diameter of the balance valve,the mathematical model of the stability margin based on the coupling of the two parameters was simulated and fitted based on the empirical design margin of the system.Finally,the time domain simulation of main hoist downdraft stability was carried out,and combined with the analysis results in frequency domain and time domain,a two-level strategy was proposed,namely active control which is dynamic control of motor displacement and passive control which are optimization of pilot damping diameter of balance valve and triangular throttling groove width of balance valve spool.(4)Whole machine test verification of main hoist down stability.Taking the pressure fluctuation amplitude reduction ratio of pump port,motor oil inlet and motor oil return port as the index,the pressure fluctuation amplitude reduction ratio is 90.86%,87.99%and 93.73% respectively through dynamic control of motor displacement.By optimizing the damping diameter,the amplitude reduction ratio of pressure fluctuation is 88.20%,85.27% and 86.59%,respectively.By optimizing the balanced spool throttling groove,the amplitude reduction ratio of pressure fluctuation is 91.25%,87.99% and 89.84%,respectively.The active control strategy,namely,the dynamic control of the motor displacement,is more convenient,while the passive control strategy,namely,the optimized damping diameter and the balanced spool throttling groove,are more universal.Both optimization strategies on two levels can improve the stability of main hoist downdraft,and thus improve the working efficiency and quality of the main engine,which can provide guidance for the design of the main hoist system of the fully electronic and hydraulic controlled rotary drilling rig.