GB1408636A - Control devices - Google Patents

Abstract

1408636 Automatic control of acceleration and position FRANCE ARMED FORCES MINISTER OF 21 Sept 1972 [21 Sept 1971] 43853/72 Headings G3N and G3R The position of a craft (e.g. a drilling vessel) is controlled by the combination of signals from accelerometers and from a navigational system which determines positional errors with respect to a reference frame, there being at least three accelerometers, at least two of which detect translational acceleration in orthogonal planes and which are corrected for errors arising from rotational movements of the craft. In the embodiment a ship 9 is acted upon by wind, current and swell forces represented by box 13 and thrust Fxn produced by a propeller 10. The ship may have bow and stern laterally acting propellers in addition to the normal drive propeller, and it may be a submarine with vertical thrust propellers. Each propeller has a separate control channel like the one shown. Accelerometer signals from 14 are processed in a P+I unit 15 and control the propeller via a summer 12 and a non- linear circuit 11 which compensates for the non- linear thrust/control signal relationship. The gain of circuit 11 and the phase angle (time constant) in unit 15 are automatically adjusted by an arrangement 16 also Fig. 10 (not shown) which applies pertubations to the thrust via summer 12 and notes the result on the accelerometer output; if this differs from values set on potentiometers adjustment to 11 and 15 is made. Signals from wind, current and swell detectors 25 are applied to a circuit 26, also Fig. 11 (not shown) in which the parameters of the ship are modelled, the resulting response being applied as anticipatory signals to the summer 12. The final input to the summer 12 comprises the output of a position error detector 17, 18 which uses a conventional radio, sonar or anchored reference source and is not disclosed in detail. This output may have its co-ordinates changed at 20 and is filtered by a low pass filter 21. The circuit 20 may respond to a circuit Fig. 12 (not shown) which calculates the resultant thrust due to wind, current and swell, to change the ships heading so as to minimize this thrust. In the complete system three accelerometers are mounted on a gyro stabilized horizontal platform, Fig. 6 (not shown), two orthogonal translational ones and one angular one. Their outputs are compensated for the tangential effect of pitch and roll by two further accelerometers (39, 40) on the ship's frame, and the output of resolvers (37, 38) on the gyro gimbals, by an accurate circuit Fig. 7 (not shown) or a simpler, approximate one Fig. 9 (not shown). A switch 22 provides for manual operation by controller 24. Provision is made for manual control of one channel concurrently with automatic control of the others.