Method and apparatus for determining the ultimate gain and ultimate period of a controlled process
First Claim
1. A method of determining an ultimate period and an ultimate gain of a controlled process, the controlled process having an input for receiving an input signal to control a parameter of the controlled process and an output for providing an output signal representative of the parameter of the controlled process, the method comprising:
- selecting at least one observation frequency;
isolating from the input signal an input sample signal corresponding to each observation frequency;
isolating from the output signal an output sample signal corresponding to each observation frequency, wherein input and output sample signals correspond to a common observation frequency to form a corresponding pair of sample signals;
determining for each corresponding pair a phase lag of the output sample signal of the corresponding pair with respect to the input sample signal of the corresponding pair;
determining for each corresponding pair a signal gain of the output sample signal of the corresponding pair with respect to the input sample signal of the corresponding pair;
determining the ultimate period based on at least one observation frequency and at least one phase lag;
determining the ultimate gain based on at least one signal gain; and
modifying the input signal to the controlled process based on the ultimate period and ultimate gain and thereby modifying the control of the parameter of the controlled process.
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Abstract
A method and apparatus determine the ultimate frequency and ultimate gain of a controlled process. The apparatus comprises a process gain and phase lag calculation module, a ultimate gain (KU) and ultimate period (TU) calculation module, and a tuning sequence control module. The tuning sequence control module initiates a tuning sequence and the process gain and phase lag calculation module samples the process input signal and the process output signal, and isolates from the process input signal and the process output signal at least one input sample signal and at least one corresponding output sample signal by bandpass filtering the process input signal and the process output signal at at least one observation frequency. The process gain and phase lag calculation module then calculates a phase lag of each output sample signal with respect to a corresponding input sample signal and a signal gain of each output sample signal with respect to a corresponding input sample signal. The ultimate period of the process is calculated from at least one observation frequency and at least one phase lag, and the ultimate gain is calculated based on at least one signal gain.
113 Citations
59 Claims
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1. A method of determining an ultimate period and an ultimate gain of a controlled process, the controlled process having an input for receiving an input signal to control a parameter of the controlled process and an output for providing an output signal representative of the parameter of the controlled process, the method comprising:
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selecting at least one observation frequency; isolating from the input signal an input sample signal corresponding to each observation frequency; isolating from the output signal an output sample signal corresponding to each observation frequency, wherein input and output sample signals correspond to a common observation frequency to form a corresponding pair of sample signals; determining for each corresponding pair a phase lag of the output sample signal of the corresponding pair with respect to the input sample signal of the corresponding pair; determining for each corresponding pair a signal gain of the output sample signal of the corresponding pair with respect to the input sample signal of the corresponding pair; determining the ultimate period based on at least one observation frequency and at least one phase lag; determining the ultimate gain based on at least one signal gain; and modifying the input signal to the controlled process based on the ultimate period and ultimate gain and thereby modifying the control of the parameter of the controlled process. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. An apparatus for automatically tuning a controller (40) in a controlled process loop (36), wherein the controlled process loop (36) includes a process (38) having a process input for receiving a control signal u(t) to control a process parameter of the process (38) and a process output for providing a process output signal y(t) representative of the process parameter, and the controller (40) having a controller output for providing the control signal u(t), and a controller input for receiving an error signal e(t) derived from the process output signal y(t), wherein control characteristics of the controller (40) are defined by controller parameters, the apparatus comprising:
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a tuning sequence control module (46) coupled to the controller (40), the tuning sequence control module (46) comprising; observation frequency selection means for selecting at least one observation frequency; controller parameter determination means for determining controller parameters based on an ultimate gain and an ultimate period; and parameter update means for providing controller parameters to controller (40); a process gain and phase lag calculation module (42) coupled to the tuning sequence control module (46), the control signal u(t), and the process output signal y(t), the process gain and phase lag calculation module (42) comprising; control signal filtering means for isolating from the control signal u(t), a control sample signal corresponding to each observation frequency; process output signal filtering means for isolating from the process output signal y(t) a process output sample signal corresponding to each observation frequency, wherein control sample signals and process output sample signals correspond to a common observation frequency to form a corresponding pair; phase lag determination means for determining for each corresponding pair a phase lag of the process output sample signal of the corresponding pair with respect to the control sample signal of the corresponding pair; and signal gain determination means for determining for each corresponding pair a signal gain of the process output sample signal of the corresponding pair with respect to the control sample signal of the corresponding pair; and an ultimate gain and ultimate period calculation module (44) coupled to the process gain and phase lag calculation module (42) and the tuning sequence control module (46), the ultimate gain and ultimate period calculation module (44) comprising; ultimate period determination means for determining the ultimate period based on at least one observation frequency and at least one phase lag; and ultimate gain determination means for determining the ultimate gain based on at least one signal gain. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43)
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44. A method of determining an ultimate period and an ultimate gain of a process having a process input for receiving a control signal and a process output for providing a process output signal, wherein the process is controlled by a controller having a controller output for providing the control signal and coupled to the process input, and a controller input that receives a feedback signal derived from the process output, thereby forming a control loop, the method comprising:
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measuring a process gain and a process phase lag of a first signal observed at first point in the control loop with respect to a second signal observed at a second point in the control loop at at least one observation frequency; determining the ultimate gain and the ultimate period based on the at least one observation frequency, at least one process gain, and at least one process phase lag; and determining parameters of the controller based on the determined ultimate gain and ultimate period. - View Dependent Claims (45)
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46. A process control system for automatically tuning a controlled process loop (36) that includes a process (38) having a process input for receiving a process input signal and a process output for providing a process output signal, the process control system comprising:
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a PID controller (40) having a controller output for producing a control signal u(t) coupled to the process input and a controller input which receives a controller error signal e(t) derived from the process output signal y(t), wherein the controlled process loop (36) is tuned by adjusting a proportional gain parameter KC, an integration time parameter TI, and a derivative time parameter TD of the PID controller (40); a tuning sequence control module (46) coupled to the PID controller (40), for selecting at least one observation frequency, initiating and controlling a tuning sequence and adjusting the proportional gain parameter KC, the integration time parameter TI, and the derivative time parameter TD of the PID controller (40) based on a determined ultimate gain and a determined ultimate period; a process gain and phase lag calculation module (42) coupled to the tuning sequence control module (46), the control signal u(t), and the process output signal y(t), for bandpass filtering from the control signal u(t) at each observation frequency a control sample signal, bandpass filtering from the process output signal y(t) at each observation frequency a process output sample signal, wherein control sample signals and process output sample signals filtered at a common observation frequencies form corresponding pairs, determining for each corresponding pair a phase lag of the process output sample signal of the corresponding pair with respect to the control sample signal of the corresponding pair, and determining for each corresponding pair a signal gain of the process output sample signal of the corresponding pair with respect to the control sample signal of the corresponding pair; and an ultimate gain and ultimate period calculation (44) module coupled to the process gain and phase lag calculation module (42) and the tuning sequence control module (46), for determining the ultimate period based on at least one observation frequency and at least one phase lag and determining the ultimate gain based on at least one signal gain.
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47. An apparatus for determining an ultimate period and an ultimate gain of a process having a process input for receiving a control signal and a process output for providing a process output signal, wherein the process is controlled by a controller having a controller output for providing the control signal and coupled to the process input, and a controller input that receives a feedback signal derived from the process output, thereby forming a control loop, the apparatus comprising:
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means for measuring a process gain and a process phase lag of a first signal observed at a first point in the control loop with respect to a second signal observed at a second point in the control loop at at least one observation frequency; means for determining the ultimate gain and the ultimate period based on the at least one observation frequency, at least one process gain, and at least one process phase lag; and means for determining parameters of the controller based on the determined ultimate gain and ultimate period. - View Dependent Claims (48)
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49. A method of determining an ultimate period and an ultimate gain of a controlled process having an input for receiving an input signal to control a parameter of the controlled process and an output for providing an output signal representative of the parameter of the controlled process, the method comprising:
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isolating from the input signal a first input sample signal corresponding to a first observation frequency by bandpass filtering the input signal at the first observation frequency; isolating from the output signal a first output sample signal corresponding to the first observation frequency by bandpass filtering the output signal at the first observation frequency determining a first phase lag of the first output sample signal with respect to the first input sample signal; determining a first signal gain of the first output sample signal with respect to the first input sample signal; determining the ultimate period based on the first observation frequency and the first phase lag; determining the ultimate gain based on the first signal gain; and modifying the input signal to the controlled process based on the ultimate period and ultimate gain and thereby modifying the control of the parameter of the controlled process. - View Dependent Claims (50, 51, 52, 53)
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54. A system for automatically tuning parameters of a controller used to control a process in a process control loop, the system comprising:
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a tuning sequence module coupled to the controller to select at least one observation frequency at which a phase lag and a gain of the process will be observed, and to determine process control parameters; an ultimate gain and ultimate period calculation module coupled to the tuning sequence control module, for determining the ultimate period based on at least one observation frequency and at least one phase lag, and for determining the ultimate gain based on at least one gain; a gain and phase lag calculation module coupled to the process, the tuning sequence control module, and the ultimate gain and ultimate period calculation module, for sampling an input signal and an output signal of the process corresponding to each observation frequency to form a corresponding pair, and for determining a phase lag and a gain of the corresponding pair; and means modifying the parameters of the controller based on the determined ultimate gain and ultimate period. - View Dependent Claims (55)
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56. A method of determining an ultimate period and an ultimate gain of a process having a process input for receiving a control signal and a process output for providing a process output signal, wherein the process is controlled by a controller having a controller output for providing the control signal and coupled to the process input, and a controller input that receives a feedback signal derived from the process output, thereby forming a control loop, the method comprising:
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measuring a gain and a phase of a first signal observed at a first point in the control loop at an observation frequency; measuring a gain and a phase of a second signal observed at a second point in the control loop at the observation frequency; determining a process gain and a process phase lag based on the measured gain and phase of the first and second signals; determining the ultimate gain and the ultimate period based on the observation frequency, the process gain, and the process phase lag; and determining parameters of the controller bleed on the determined ultimate gain and ultimate period. - View Dependent Claims (57)
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58. An apparatus for determining an ultimate period and an ultimate gain of a process having a process input for receiving a control signal and a process output for providing a process output signal, wherein the process is controlled by a controller having a controller output for providing the control signal and coupled to the process input, and a controller input that receives a feedback signal derived from the process output, thereby forming a control loop, the apparatus comprising:
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means for measuring a gain and a phase of a first signal observed at a first point in the control loop at an observation frequency; means for measuring a gain and a phase of a second signal observed at a second point in the control loop at the observation frequency; means for determining a process gain and a process phase lag based on the measured gain and phase of the first and second signals; means for determining the ultimate gain and the ultimate period based on the observation frequency, the process gain, and the process phase lag; and means for determining parameters of the controller based on the determined ultimate gain and ultimate period. - View Dependent Claims (59)
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Specification