Study on the Reconfigurable Control Method for the Fault-Tolerant of the Dynamic Point-the-Bit Rotary Steerable System

Abstract

The dynamic point-the-bit rotary steerable system (DPRSS) is the state-of-the-art directional drilling equipment which realized downhole closed-loop toolface control. To guarantee steering precision, the DPRSS is equipped with different kinds of sensors, such as the gyro, fluxgate, and accelerometer, meanwhile, a compound control structure is also adopted. However, the sensors are possibly damaged in the high-temperature and high-pressure harsh drilling conditions, the DPRSS will turn to be invalidated. To improve system reliability, this paper presents a reconfigurable control method which includes fault-detection mode, reconfigurable toolface estimator, reconfigurable controller, and reconfiguration mechanism. Considering the complete failure of the sensors in the toolface estimator, the fault-detection mode is performed during the ‘making a connection’ nonproductive process. The reconfigurable toolface estimator is designed with various estimation methods, including single sensor estimation and multi-sensor data fusion. The reconfigurable controllers are designed with the model-based active disturbance rejection control (ADRC) and the conventional ADRC algorithms. The numerical simulation was performed by using the sensor error models, and the root mean square error index were provided. Based on the simulation results, the reconfiguration mechanism is designed to determine the optimal reconfiguration control method in the presence of sensor failures. The reconfigurable control method makes full use of all health sensors, the probability for high precision steering increases from 0.512 to 0.768, which shows that the proposed method improves the system reliability to a large extent.