Patent GB-1292741-A (GB)
Title: Optimizing control systems
Inventor: SMITH LAWRENCE RAY
IPC: G05B13/02
Filed: 1969-10-15
Abstract: 1292741 Adaptive control WESTINGHOUSE ELECTRIC CORP 15 Oct 1969 [24 Oct 1968 28 April 1969] 50670/69 Heading G3R A plurality of process variables are perturbed at different frequencies or phases so chosen that their effects are distinguishable in a signal which is a function of the variables so that each of these effects may be integrated over the perturbation cycle to produce corrective signals for the variables so as to maximize or minimize the function by control of each variable. In Fig.1, a process 30 is influenced by a number of uncontrolled variables 31 and signals 37, 38 produced by measurement of two process variables are compared with set values 35, 36 so that any differences are effective through analogue controllers 33, 34 to correct the variables by controlling the process through lines 39, 40. A digital counter type clock and modulation source 55 applies a number of alternating signals through lines 56 to channels 49, 50, 51 &c. so that each signal perturbates a different process variable through one of lines 32. The perturbation signals are of different phase or frequency and so related to each other that each perturbation of the process is identifiable with a perturbation of one process variable only. Signals 45, produced by measurement of the perturbated variables, are applied to an analogue or digital computer 46 which compares them with limiting values, weights them according to the comparison, and produces a single signal corresponding in magnitude to the overall performance of the process. This signal appears with opposite polarities in lines 47, 48. In each channel, e.g. 49, MOSFET gates, e.g. 70, 71, periodically apply samples of each half cycle of the perturbation to an integrator 87 which periodically produces at 97 a signal corresponding to deviation of the process performance from a minimum or maximum. Such outputs are stored capacitively at 95 and applied through appropriate lines 32 to correct each variable at the end of each period. Sampling times are so arranged and filters provided that the effect of noise in the integrator is reduced. Modulation frequency may be varied in a random manner by a Zener diode noise generator. If computer 46 detects excessive errors, e.g. due to a disturbance, it applies a signal through line 113 to reset clock 55 and integrator 87 to zero periodically so that the signal stored at 95 continues to effect control of the process until the condition is passed. A gate 119 may be opened to cause the controlled variable to follow a manually or automatically variable signal applied at 352. Bumpless transfer to and from such form of control is ensured by store 95. Guard potential plates (not shown) minimize leakage in the integrator, storage and other MOSFET circuits. Feed-forward control may be provided by signals (not shown) applied at 99. An application is described for maintaining maximum pumping efficiency by automatically controlling the pitch of the vanes of a pair of turbine pumps arranged in parallel to supply fluid to a common main. Efficiency is computed by multiplying a signal dependent on the rate of fluid-flow by a signal dependent on the pressure drop across the pumps and dividing by a signal dependent on the rate of supply of fuel or energy to the engine or motor driving the pumps. The rate of fluid-flow is also compared with a desired value so that any difference automatically controls the engine or motor speed to maintain a constant fluid-flow. Electrical signals dependent on engine temperature, torque and speed and on pump vane position are also applied to the control system.