Research And Simulation On Hydraulic System Of Downhole Tractor

In the process of horizontal wells development,downhole equipment needs to be transported to a specific location by a downhole crawler.The wheeled crawler has the advantages of fast crawling speed and high working efficiency,while the hydraulic system can adapt to the complex working conditions of the well,so the wheeled hydraulic crawler can be better adapted to the actual production.The hydraulic system is crucial to the working performance of the crawler,and the study of the crawler hydraulic system is of great significance to improve the performance of the crawler.The main research methods and contents are as follows:(1)The mechanical model was established according to the structure of the wheel crawler dynamometer,the friction coefficient of the drive wheel furrow effect was studied,the theoretical output of the hydraulic cylinder and hydraulic motor system was obtained,and the parameters of the hydraulic cylinder,hydraulic motor and some parts of the system were calculated.(2)Preferred the scheme of valve-controlled hydraulic cylinder controlling the pushing and leaning mechanism and pump-controlled hydraulic motor controlling the driving wheel,established the mathematical model of each link of the valve-controlled hydraulic cylinder and pump-controlled hydraulic motor system,obtained the transfer functions of the two systems,established the open-loop transfer function of the system under specific working conditions,and plotted the open-loop transfer function Bode and Nyquist diagrams to judge the stability of the system.(3)Using the 1D/2D Mechanical library in AMEsim to establish the structural model of the pushing and leaning mechanism,the physical model of the valve-controlled hydraulic cylinder is built at the same time,and the hydraulic cylinder piston rod position control model with Simulink fuzzy PID is combined,and the accuracy of the mathematical model and the feasibility of the control method is verified through joint simulation.The accuracy of the piston bar position of the hydraulic cylinder under fuzzy PID control can reach 97.6%;the model of the pump-controlled hydraulic motor with load is established,and the speed characteristics of the hydraulic motor under constant load-regulated speed,variable load-fixed speed and variable load-regulated speed conditions are studied in combination with Simulink fuzzy PID.(4)A co-simulation model of Adams,AMEsim and Simulink based on Adams was established,and the feasibility of the hydraulic system was verified by studying the motion speed and displacement of the crawler in the 140 mm obstructed and barrier-free pipeline.The simulation results show when the hydraulic system is controlled by the fuzzy PID algorithm,the tractor can run smoothly in the barrier-free pipeline,and can also successfully complete the obstacle crossing in the pipeline with a 5mm height obstacle.