Automatic hull height control system for a hydrofoil vehicle

摘要

934,094. Automatic control of hydrofoil craft. NORTH AMERICAN AVIATION Inc. Jan. 8, 1962 [Feb. 27, 1961], No. 642/62. Class 38 (4). [Also in Group XXXIII] In an automatic control system for a waterborne vehicle having a hull and hydrofoils a reference signal is generated representing the height at which it is desired that the hull travel above the sea and means are provided for limiting said signal to prevent contact with the sea and broaching of the hydrofoils. As shown, Fig. 6A, an adjustable height reference signal is fed from a generator 30 to a limiter 31 which modifies the amplitude of the reference signal to prevent it exceeding an upper limit or falling below a lower limit. The modified reference signal is compared with the output of an height senser 32 in a summing means 33 to provide a signal indicative of deviation from the desired height. The height senser 32 has a flat response from zero frequency to a frequency representative of the highest wave frequency to which the control system is to be subjected. The deviation signal is fed to a hydrofoil servo actuator 34 to control the attitude of the hydrofoils so as to tend to reduce the deviation to zero. A low-frequency filter 35 prevents high-frequency components of the actual height signal from affecting the response of the servo system; alternatively, the filter can be connected between the summing means 33 and servo 34. The upper and lower reference limits provided by limiter 31 are dependent on the output of a wave height detector 37 which is connected to the wave height senser 32. The elements 31, 37, 32, 35 are arranged so that the limiting is in accordance with Fig. 4 where 2H is the waveheight, trough to crest, and the hatched lines are the upper and lower limits of the hull. The wave-height detection function of detector 37 is accomplished by a high-pass filter having a cut-off frequency approximately equal to the cut-off frequency of the low-pass filter 35. Vertical acceleration is reduced by feeding the servo 34 from an accelerometer 38 through an equalization device 40 which provides a signal to the servo which is a function of both the vertical acceleration and the first integral of vertical acceleration. A signal from an accelerometer switch 41 is fed to the servo 34 and a throttle servo 42 to reduce the vehicle speed and cause the hydrofoil effect to become inoperative under sea state conditions which cause excessive contouring by an automatically controlled vehicle. An integrator 39 is connected in parallel to the output of the summing means 32 and servo 34 to reduce the steady-state height error to a minimum.