GB827728A - Improvements in or relating to an analogue device for determining the output response of a system - Google Patents

Abstract

827,728. Electric analogue calculating. LANDIS & GYR A.G. Feb. 13, 1956 [Feb. 11, 1955], No. 4488/56. Class 37. Analogue apparatus for determining the output response of a system (which may be hydraulic, hydro-mechanical, thermal or electrical) to a variable physical amplitude input, according to the transfer function of the system, comprises a stationary first transparent carrier medium recorded with the transfer function in variations of density against a timebase; means traversing a second opaque carrier medium at predetermined velocity past a fixed origin point at which the input is recorded on the second medium as a variable transparent area recording of which the width transverse to the direction of motion of the carrier is a function of the instantaneous value of the input; means projecting parallel light through the two media to derive emergent light of intensity representing the products of magnitudes of recorded input and transfer functions at corresponding points on their abscissal axes over the whole timebase of the recorded transfer function; and a photo-cell receiving the emergent transmitted light to generate an electric signal representing the sum of all such products, which is recorded and/or indicated. A transfer function of time f = a 1 (t) (Fig. 1) represents the output variation of a system in response to an input pulse function e 1 (t) of unit magnitude, and may be recorded (Fig. 2) on a carrier medium 1 against a timebase represented by abscissal displacement. The pulse function e 1 (t) is similarly recorded by pen 2 at an abscissal origin point on carrier medium 3, moving at velocity v giving an accurate time scale and shown as displaced by a time interval T after recording. For compression or expansion of the time scale, the traversal velocity is increased or decreased. When e 1 (t) is unity, the resultant instantaneous product is a 1 (t) 1 and is zero for e 1 (t) = 0. An input function e varying with time recorded by pen 2 on moving carrier medium 3 (Fig. 3) is equivalent to a sequence of adjacent pulse functions the height of each corresponding with the appropriate ordinate of the input function, whereby continuous summation of the respective products of the ordinate of each pulse of the series at its instantaneous point on the abscissal axis of the input function with the corresponding ordinate value of the transfer function a 1 , varying with time, yields the resultant output function. For step function input signals E 1 t (Fig. 4), the transfer function may be replaced by the difference between the asymptotic value A 1 (00) for t = oo and the instantaneous value A 1 (t) thereof (Fig. 5, not shown). In Fig. 6 a carrier medium 11 having bands of variable density representing the magnitudes of successive ordinates of a characteristic transfer function disposed along an abscissal axis, is uniformly illuminated from a light source 10, and transmits light through a transparent carrier medium 14 laterally movable parallel to the abscissal axis, which is coated with opacity removable by pen 15 at a fixed origin point to leave a transparency whose corresponding ordinal displacements represent values of a variable input magnitude at successive instants of recording. The intensity of emergent light beams at corresponding points on the abscissal axes of the media represent the products of the instantaneous values of the input function and the transfer function at such points, and fall upon a photo-cell 17 operating a recorder 18 in response to a time variable signal representing the sum of the products of the two functions at all corresponding points on the abscissal axis of the transfer function.