The ADRC Algorithm For Dynamic Point-the-Bit Rotary Steerable Drilling Tool

The dynamic point-the-bit rotary steerable drilling technology represents the highest level of drilling automation technology in the world today,which can be used to drill directional hole while drilling.The quality of wellbore and the accuracy of drilling trajectory are related to the performance of the control system.In the thesis the self-developed dynamic point-the-bit rotary steerable drilling tool(DPRSS)prototype was taken as the object,then the control algorithm and its disturbance was analysed deeply from simulation and experiments.By analyzing the limitation and performance of control algorithm,some improvements and validations have been achieved,which provides theoretical and experimental basis for the development of rotary steerable drilling tool with independent intellectual property rights.Firstly,the background and development status of current rotary steerable drilling technology at home and abroad are introduced in the thesis,in which the principle and advantages of current commercial rotary steerable drilling tool are analysed,too.Secondly,the sencond generation dynamic point-the-bit rotary steerable drilling tool prototype,which is self-developed by laboratory,was taken as the object to analyse and introduce the control method,mechanical structure and directional principle of drilling tool.Therefore the control objective of the drilling tool was detemined in the thesis,the control scheme was designed,too.Thirdly,the thesis has finished the establishment and perfection of control system model,meanwhile the ADRC algorithm was applied in the stable platform speedloop and position loop with the relevant parameters being designed.Fourthly,A load torque compensation method,which is based on longberg observer,was given in the thesis.Various factors that interfere with the work of steerable mechanism of drilling tool in actual condition are analysed.Meanwhile the limitation of ADRC algorithm in disturbance rejection was analysed too.Then by combining the design of relavant parameters with the actual engineering indexes,the adverse influence of control accuracy,which is caused by complex condition,was effectively suppressed by the given method.Moreover,the simulation and actual experiment results of stable platform speed loop and stable platform toolface loop were compared and analysed by the control system.Finally,the speed loop and position loop of stable platform were simulated and tested.The data shows that by using the ADRC controller based on the bandwidth method or the settling time method,the settling time of the stable platform speed loop is less than 0.23 s,and its overshoot is less than 5.00%.In the same conditionthe settling time of stable platform position loop is less than 0.47 s,and its overshoot is less than 8.76%.The stable fluctuation of toolface angle,which was caused by sticksllip condition,can be controlled in the range of-15.60°to 10.78°.Compared with the conventional ADRC controller,the improved ADRC controller based on longberg observer can reduce the sudden change range of speed form-4.21rps～0.49 rps to-1.91rps～0.48 rps.Meanwhile,the improved ADRC controller can also reduce the stable fluctuation of toolface angle in the condition of stickslip form-15.60°～10.78°to-9.38°～7.00°.