Patent ID: 6598617
Filing Date: 2003-07-29
Classification: G05D,Y10T

Abstract:
In a liquid flow system comprising a plurality of reservoirs connected in series by pipelines or open channels including at least one first reservoir (V1) and a level sensor, at least one inflow (F0) and at least one outflow (F1), each said inflow and outflow including flow measuring devices and said outflow including a flow manipulation device, the improvement comprising a cascaded variable bias feedforward and feedback flow and level control system for maintaining liquid levels in said reservoirs while substantially eliminating flow and level oscillations, said control system comprising the following:(a) a nested control module comprising: (i) a proportional only level controller for maintaining a desired liquid level in the at least one first reservoir (V1), said proportional only level controller in electrical communication with the level sensor of said at least one first reservoir (V1), and (ii) a PID flow controller adapted to control the flow manipulation device of the at least one first reservoir outflow (F1), wherein said nested control module proportional only level controller is adapted to respond to the level sensor of said at least one first reservoir (V1) and a calculated bias value resulting from the total inflow (F0) to said at least one first reservoir (V1) to produce an output signal that is cascaded to the nested control module PID flow controller to become a set point thereof.