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US 4,265,263 AGranted
Non-linear level controller
AssigneePhillips Petroleum Company
InventorJames W. Hobbs
Life of this patent
Estimating the term…
Abstract
A non-linear level controller is provided in which the proportional term is a function of the actual liquid level in a vessel compared to the actual liquid level in the vessel at a previous time. The integral term is a function of the actual liquid level in the vessel compared to a set point which is representative of the desired liquid level in the vessel. Both the proportional term and the integral term are modified by a variable gain factor which is a non-linear function of the liquid level being controlled. The proportional term and integral term are combined to provide the controller output which is utilized to manipulate a flow of liquid from the vessel in which the liquid level is being controlled.
Claims14
A non-linear level controller for controlling the level of a liquid in a means for containing said liquid comprising:
- means for establishing a first signal (LP) representative of the actual level of said liquid at a time T.sub.1 ;
- means for establishing a second signal (L) representative of the actual liquid level of said liquid at a time T.sub.2, said time T.sub.2 being later in time than said time T.sub.1 ;
- means for subtracting said first signal from said second signal to establish a third signal representative of the change in liquid level (DL) between said time T.sub.1 and said time T.sub.2 ;
- means for establishing a variable gain factor (VGF) which is a non-linear function of the level of said liquid;
- means for multiplying said third signal by said variable gain factor to establish a fourth signal representative of (VGF)*(DL);
- means for establishing an incremental proportional output (DP) in response to said fourth signal;
- means for establishing a fifth signal (SP) representative of the desired level of said liquid;
- means for subtracting said fifth signal from said second signal to establish a sixth signal representative of the integral error (E);
- means for multiplying said sixth signal by said variable gain factor to establish a seventh signal representative of (VGF)*(E);
- means for establishing an incremental integral output (DI) in response to said seventh signal;
- means for combining said incremental proportional output and said incremental integral output to produce a total incremental output (DF);
- means for adding said total incremental output to the total incremental output of said non-linear level controller at said time T.sub.1 to establish a position output (FS);
- and
- means for manipulating the flow of liquid from said means for containing said liquid in response to said position output to thereby control the level of said liquid in said means for containing said liquid.
11 more elements
A method for controlling the level of a liquid in a means for containing said liquid comprising the steps of:
- establishing a first signal (LP) representative of the actual level of said liquid at a time T.sub.1 ;
- establishing a second signal (L) representative of the actual liquid level of said liquid at a time T.sub.2, said time T.sub.2 being later in time than said time T.sub.1 ;
- subtracting said first signal from said second signal to establish a third signal representative of the change in liquid level (DL) between said time T.sub.1 and said time T.sub.2 ;
- establishing a variable gain factor (VGF) which is a non-linear function of the level of said liquid;
- multiplying said third signal by said variable gain factor to establish a fourth signal representative of (VGF)*(DL);
- establishing an incremental proportional output (DP) in response to said fourth signal;
- establishing a fifth signal (SP) representative of the desired level of said liquid;
- subtracting said fifth signal from said second signal to establish a sixth signal representative of the integral error (E);
- multiplying said sixth signal by said variable gain factor to establish a seventh signal representative of (VGF)*(E);
- establishing an incremental integral output (DI) in response to said seventh signal;
- combining said incremental porportional output and said incremental integral output to produce a total incremental output (DF);
- adding said total incremental output to the total incremental output of said non-linear level controller at said time T.sub.1 to establish a position output (FS);
- and
- manipulating the flow of liquid from said means for containing said liquid in response to said position output to thereby control the level of said liquid in said means for containing said liquid.
11 more elements
Apparatus for establishing a variable gain factor (VGF) for a non-linear level controller comprising:
- means for establishing a first signal (L) representative of the actual level of a liquid in a means for containing said liquid;
- means for establishing a second signal (SP) representative of the desired level of said liquid in said means for containing said liquid;
- means for establishing a third signal representative of the high limit (HL) for the level of said liquid in said means for containing said liquid;
- means for establishing a fourth signal representative of the low limit (LL) for the level of said liquid in said means for containing said liquid;
- means for setting said variable gain factor equal to 1.0 if the level of said liquid is less than the magnitude of said fourth signal;
- means for setting said variable gain factor equal to (SP-L)/(SP-LL) if said level is greater than the magnitude of said fourth signal;
- means for setting said variable gain factor equal to (L-SP)/(HL-SP) if the level of said liquid is greater than the magnitude of said second signal;
- and
- means for setting said variable gain factor equal to 1.0 if the level of said liquid is greater than the magnitude of said third signal.
6 more elements
A method for establishing a variable gain factor (VGF) for a non-linear level controller comprising the steps of:
- establishing a first signal (L) representative of the actual level of a liquid in a means for containing said liquid;
- establishing a second signal (SP) representative of the desired level of said liquid in said means for containing said liquid;
- establishing a third signal representative of the high limit (HL) for the level of said liquid in said means for containing said liquid;
- establishing a fourth signal representative of the low limit (LL) for the level of said liquid in said means for containing said liquid;
- setting said variable gain factor equal to 1.0 if the level of said liquid is less than the magnitude of said fourth signal;
- setting said variable gain factor equal to (SP-L)/(SP-LL) if said level is greater than the magnitude of said fourth signal;
- setting said variable gain factor equal to (L-SP)/(HL-SP) if the level of said liquid is greater than the magnitude of said second signal;
- and
- setting said variable gain factor equal to 1.0 if the level of said liquid is greater than the magnitude of said third signal.
6 more elements
Dependencies are inferred from the claim text.