Patent GB-964537-A (GB)
Title: Three dimensional function generator
IPC: G06G7/30
Filed: 1961-11-16
Abstract: 964, 537. Function generators. BOEING CO. Nov. 16, 1961 [Jan. 16, 1961], No. 41106/61. Heading G4G. [Also in Division H3] In a generator which produces an output z = f (x, y) from two inputs x and y there is included a matrix of z elements having energization inputs connected together in rows distributed along an x scale and having voltage outputs connected together in colums distributed along a y scale and selective energizing means responsively connected to the x input and operable to progressively vary the energization state of the individual rows between predetermined lower and upper limits as x progressively varies. Each z element has predetermined x and y co-ordinates and is adapted when its row is at a maximum energization to produce a voltage output related to the value of function z for the associated x and y coordinates. A y selector is responsively connected to the y input and is operable to apply to the generator output the summation of output voltages in the y column to which the instantaneous value of y corresponds. The potentiometers Zp are set so as to provide values related to z according to the equation z = f (x, y) for certain discrete pre-chosen values of x and y, and an output z is obtained by adding together the voltages produced by all the Zp potentiometers in rows caused to be energized by a given value of x in a column corresponding to a given value of y. For values of x and y between the pre-chosen ones, two distinct systems of linear interpolation are used. The rows corresponding to the pre-chosen x values are energized by voltage sources E x1 , E x2  &c. (see Division H3), the outputs of which can be made to vary say from 0 to 50 volts in a small continuous range of x values, but remain constant outside this range. The levels at which the circuits start to energize are set on the potentiometers Txl, Tx2 &c., and the width of range x which they cover is set on the feedback potentiometers Fxl, Fx2, &c. If the discrete chosen x intervals are all the same, then the potentiometers will all be set to the same positions. Any x value thus consists of a number of whole outputs and a part output from these energizers. Feedback is provided through an operational amplifier 38, which accommodates the non linearity of the energizers and the tolerances on the threshold settings. Interpolation for y co-ordinates is achieved by switching the outputs from adjacent columns through appropriate gates y0, y1 &c. to the output line, so that an output between the value provided by each column is obtained whose value depends upon the time spent switched to one column compared with the time spent switched to the other. This is carried out using binary circuit drivers Ey 1  Ey 2  &c., which are activated or deactivated according to the settings of potentiometers Ty 1 , Ty 2  &c. For a given y input there will be a definite adjacent pair where one driver is activated and the next is not. This will allow a given y gate to open, together with a feedback F 1  or F 2  &c. The feedback potentiometers Fy 1 , Fy 2  &c. are set so as to feed back voltages in opposition to the input y when the appropriate gate is open, and this will cause the input to change at a rate proportional to the voltage feedback until the highest activated binary becomes deactivated, and the z output is taken from the next column. The input to the binaries will rise again until the one previously activated is again activated, and the cycle is repeated. Thus the outputs from two adjacent columns are switched into the output for times which will produce the required interpolated value on the output line. A filter network together with the output amplifier 66 ensures that a steady output is provided. To allow for possible changes of sign in z a negative slope generator 48 is provided with inputs taken from the x energizers and an output which is added to the z column outputs, to produce the final output representing the required function.