CONTROL SYSTEM FOR DRILLING RIG MACHINE ELECTROHYDRAULIC FEED DRIVE

Abstract

The objective of research is to develop a scientifically based approach to the synthesis of a positional control system for the hydraulic drive of a roller cone drilling machine, which ensures increased positioning accuracy, stability of transient processes, and drive efficiency under variable loads typical of the drilling process. The study has been conducted based on: the application of differential equations of hydraulic drive dynamics (equations describing the movement of the executive hydraulic cylinder, pressure dynamics in cavities, working fluid flow, and elastic properties of the hydraulic line are used); linearization of nonlinear equations (for stability analysis and controller synthesis, the hydraulic system is reduced to a linearized model in the vicinity of the operating point); modeling using transfer functions and block diagrams; Laplace transforms are used in the formation of drive transfer functions and controllers for system analysis in the frequency and time domains; methods of automatic control theory (stability analysis; controller structure selection; synthesis of P-, PI-, PID-controllers for positional control) were applied; optimization synthesis methods for calculating controller parameters that allow setting the desired eigenvalues of the closed system and ensuring the required positioning accuracy of the drive; modeling in MATLAB/Simulink (used to verify the obtained mathematical model and check the operation of the synthesized control algorithm). Theoretical and experimental research yielded the following scientific and practical results: a mathematical model of the hydraulic drive for a roller cone drilling machine was developed, considering the nonlinear characteristics of hydraulic equipment, the compressibility of the working fluid, hydraulic losses, and the dynamics of the actuating hydraulic cylinder. The model allowed us to investigate the influence of system parameters on positioning accuracy; we analyzed the dynamic properties of the drive and identified the main factors that limit the accuracy and speed of the position control system, in particular: hydraulic delays, force disturbances from the drilling process, and pressure fluctuations in the hydraulic lines; a synthesis of the positional control system was carried out using methods of automatic control theory; based on a linearized model, the choice of the regulator structure was justified and its optimal parameters were determined; an algorithm for positional feed control was proposed, which ensures stable transient processes and high accuracy of the specified position of the actuator under variable loads; a structural diagram of the control system was developed, including a feedback module, corrective links, and an executive hydraulic drive, and its operability was confirmed by modeling; the system was modeled in MATLAB/Simulink, the results of which showed: a reduction in drive positioning error improvement of system stability to disturbances; a reduction in the transition process time; a reduction in feed fluctuations during drilling.