Patent GB-1279708-A (GB)
Title: Analogue computer for solution of non-linear boundary-value problems
Inventor: GESHELIN BORIS MIKHAILOVICH
IPC: G06G7/46
Filed: 1969-08-19
Abstract: 1279708 Analog simulation VSESOJUZNY NEFTEGAZOVY NAUCHNO - ISSLEDOVATELSKY INSTITUT 19 Aug 1969 41341/69 Heading G4G  An analog computer for the solution of problems arising from non-linear processes, e.g. physico-chemical processes, under known boundary conditions, comprises initial-condition (4, Fig. 1, not shown) and boundary-condition (7) function generators connected to a variableresistance network (1) simulating the parameters of the medium being processed, an integrator (2) for adding the voltages generated at the nodes of the network (1) the integrator and the network being connected to a non-linear function generator 3 adapted to simulate the relations between the parameters of the medium and to continually readjust the resistances of the network (1). The computer comprises, in addition, a non- linear function generator (6) connected in a loop with resistance network and adapted to simulate accumulation of potential energy in the medium. A further non-linear function generator (5) is connected in a loop with the integrator 2 and is adapted to simulate physico-chemical reactions in the medium. Fig. 2 shows a typical node a of the resistance network, there being as many nodes as is necessary for a solution of the problem, each node comprising four identical resistance units I and also, if required a boundary-condition resistance unit II. The resistance units consist of n branches where n is the number of components of the medium. They contain variable voltage sources 12 1  ... 12 n , variable resistances 11 1  ... 11 n , and measuring resistances 10 1  ... 10 n , 14 1  ... 14 n . Each node is also connected to a variable capacitor 17 controlled by the potential-energy function generator 6 which accepts directly the voltage at the node. Integrators 2 1  ... 2 n  are respectively connected to measuring resistances 10 1  ... 10 n  and 14 1  ... 14 n  belonging to node a. The initial conditions are set up in the function generator 4 which supplies voltages to integrators 2 and the boundary conditions, represented by time functions of current and voltage, are generated in generator 7 and fed to the resistance unit II. Considering conditions in resistance unit I of node a only, current flowing in a controlled resistance 11, produces a voltage drop across resistance 10, which is applied to an adder 18, and to a sense detector 19 1 . The latter is connected to switches 20 1 , 21 1  which operate so that if a current is sensed flowing towards the node, a voltage from the output of the adder belonging to the adjacent node on the right is conveyed by conductor 24 1  to the integrator 22 1 . If current is sensed flowing away from the node, the switches operate to apply the output of adder 18 1  to the integrator 22 1 . The new value of the output of integrator 22 1  is fed to the non- linear physico-chemical simulator 5 together with the voltage at node a and the voltage across the measuring resistance 10 1 . The output of simulator 5 is fed back to the integrator 22 1 . The function generator 31 is also supplied with the same voltages as simulator 5, and the output fed to control the value of resistance 11 1  and voltage source 12 1 . The above applies to all the branches of the resistance units I at all the nodes. A multichannel read-out (8), controlled by a periodically operating device (9), is connected to the integrators 2 and the relevant measuring resistors of the resistance units I. The device (9) is also connected to the initial and boundary condition generators 4 and 7.