Design of measurement while drilling system based on inertial sensors

With the development of urban infrastructure, the trenchless technology has been widely applied in many applications, especially in the field of pipeline or subway construction. In these applications, the attitude and position information of the bit is indispensable in the process of drilling. Currently, Measurement While Drilling Systems (MWD systems) are generally based on radiolocation or single accelerometer measurement. In that case, the precisions of these MWD systems are limited due to the presence of disturbances. Aiming at this defect, a new MWD system with multiple sensors based on inertial technology is developed in this paper. Note that the measuring range of angle of traditional method is limited, we propose a new while-drilling unit which contains two 3-axis accelerometers fixed on two different planes with a certain angle as redundancy. With the help of the temperature sensor and geomagnetic sensor in the while-drilling unit, temperature compensation and credibility estimation are available. The attitude and position information of the bit, as well as the credibility, is calculated by ARM microprocessor. The method of data calculating is also described in details. Compared with traditional MWD system, this new MWD system obtains a better anti-disturbance property and can produce more reliable measurements information.