Analog Computation Of The Attitude Parameters Of Rotary Steering Drilling Tool

Real-time parameters near the drill hole are one of the basis of Rotary Steering Drillingtechnology. In order to control hole trajectory effectively, high precision attitude parameters,such as the tool face angle and well-inclination angle, is necessary. Usually, attitudeparameters are measured by inertial devices, for example, the accelerometers, the flux gates orgyroscopes.Based on the working principle and ways of trigonometric function generator, wecomplete the design of arcsine circuit to realize the well-inclination angle computation. Testson the designed circuit with discrete and continuous signals are realized. In discrete testing,multi-point fitting is adopted to process experimental data. In continuous measurement,features of the input and output signals in time-domain and frequency-domain are analyzed.The tool face angle is computed by the circuit based on the combination of trigonometricfunction generator AD639and analog multiplication/division.Combined with the Strap-down Inertial Navigation System and the reference-frametransformation, the trigonometric function relations between output of attitude sensors andattitude parameters is derived. Thus，we can get the formulas of the well-inclination angle, toolface angle and azimuth angle. In order to compute the attitude parameters directly, the inversetrigonometric function circuits are designed. Finally, the circuits to give priority to the chips oftrigonometric function generator AD639and analog multiplication/division AD734is designedto realize the computation of the well-inclination angle and tool face angle.In order to reduce the nonlinear distortion of the sensors and improve the accuracy of thesignal, non-orthogonal coordinate system is adopted to complete the attitude parameters’measurement. And in this paper, the computation scheme used in the non-orthogonalmeasurement is proposed. In view of weak signal of the sensors’ output in the smallwell-inclination angle, judgment and amplifying circuit of small signal based on the analogswitches is proposed.Experimental results show that the proposed circuit is feasible, the average error ofattitude angle computed is smaller, and thus the circuit can be used for the analog computationof attitude parameters.