PID Online Autotuning VI

Owning Palette: PID VIs

Requires: Full Development System

Controls the parameters of a PID controller based on the autotuning technique of the polymorphic instance you select. You can use this VI in applications with other PID VIs, such as PID or PID Advanced, to construct and tune a PID controller. You must manually select the polymorphic instance to use.

Example

Use the pull-down menu to select an instance of this VI.

Select an instance PID Online Autotuning (Step Open Loop)PID Online Autotuning (Step Closed Loop)PID Online Autotuning (Relay Feedback)PID Online Autotuning (PID Relay)

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PID Online Autotuning (Step Open Loop)

Note  Use this instance for step open loop tuning, which assumes that you can model any process as a first-order lag and a pure dead time.

	autotuning parameters specifies various parameters used for the autotuning process. type of controller specifies which parameters to return as the output of the tuning process. 0 P—Specifies to return only the proportional parameters. 1 PI—Specifies to return the proportional and integral parameters. 2 PID—Specifies to return the proportional, integral, and derivative parameters. relay cycles specifies the number of setpoint relay cycles to use to determine the ultimate gain and period. More cycles result in more accurate parameter estimation; however, slower systems might require more time for numerous cycles. relay amplitude specifies the amplitude of the setpoint relay action. The setpoint relay is between setpoint – relay amplitude and setpoint + relay amplitude. control specification specifies the desired response performance of the PID parameters determined by the autotuning process. 0 normal—Specifies a normal response performance. 1 fast—Specifies a fast response performance. Faster response generally results in a smaller rise time. 2 slow—(Default) Specifies a slow response performance. Slower response generally results in less overshoot. PV noise level specifies an estimation of the noise level of the process variable. This value is used as the hysteresis for the setpoint relay action.
	manipulated variable specifies a quantity or condition to vary as a function of the actuating error signal so as to change the value of the directly controlled variable. The manipulated variable also can be referred to as the controller output.
	setpoint specifies the setpoint value, or desired value, of the process variable being controlled.
	process variable specifies the measured value of the process variable being controlled. This value is equal to the feedback value of the feedback control loop.
	PID gains in specifies the proportional gain, integral time, and derivative time parameters of the controller. proportional gain (Kc) specifies the proportional gain of the controller. The default is 1. In the equation that defines the PID controller, KC represents the proportional gain. integral time (Ti, min) specifies the integral time in minutes. The default is 0.01. derivative time (Td, min) specifies the derivative time in minutes. The default is 0.
	dt (s) specifies the�interval, in seconds, at which this VI is called. If dt (s) is less than or equal to zero, this VI uses an internal timer with a one millisecond resolution. The default is –1. Use the same dt (s) value as you use for the PID or PID Advanced VI.
	reinitialize? specifies whether to reinitialize the internal parameters, such as the integrated error, of the controller. Set reinitialize? to TRUE if your application must stop and restart the control loop without restarting the entire application. The default is FALSE.
	autotune? specifies to begin autotuning. Wire this input from a Boolean control with latched mechanical action and a default value of FALSE. The default is FALSE.
	setpoint out returns the updated setpoint value.
	process variable out returns the value of the process variable. If autotune? is TRUE, this output returns 0.
	tuning completed? returns TRUE when the autotuning process is complete. You can use this output to determine when to update the PID gains in.
	PID gains out returns the updated PID gain parameters upon completion of the autotuning process. Normal output values are identical to the values in the PID gains in input. proportional gain (Kc) returns the proportional gain of the controller. integral time (Ti, min) returns the integral time in minutes. derivative time (Td, min) returns the derivative time in minutes.
	tuned PID gains returns the tuned proportional gain, integral time, and derivative time parameters of the controller. proportional gain (Kc) returns the proportional gain of the controller. integral time (Ti, min) returns the integral time in minutes. derivative time (Td, min) returns the derivative time in minutes.

PID Online Autotuning (Step Closed Loop)

Note  Use this instance for closed-loop tuning.

	autotuning parameters specifies various parameters used for the autotuning process. type of controller specifies which parameters to return as the output of the tuning process. 0 P—Specifies to return only the proportional parameters. 1 PI—Specifies to return the proportional and integral parameters. 2 PID—Specifies to return the proportional, integral, and derivative parameters. relay cycles specifies the number of setpoint relay cycles to use to determine the ultimate gain and period. More cycles result in more accurate parameter estimation; however, slower systems might require more time for numerous cycles. relay amplitude specifies the amplitude of the setpoint relay action. The setpoint relay is between setpoint – relay amplitude and setpoint + relay amplitude. control specification specifies the desired response performance of the PID parameters determined by the autotuning process. 0 normal—Specifies a normal response performance. 1 fast—Specifies a fast response performance. Faster response generally results in a smaller rise time. 2 slow—(Default) Specifies a slow response performance. Slower response generally results in less overshoot. PV noise level specifies an estimation of the noise level of the process variable. This value is used as the hysteresis for the setpoint relay action.
	manipulated variable specifies a quantity or condition to vary as a function of the actuating error signal so as to change the value of the directly controlled variable. The manipulated variable also can be referred to as the controller output.
	setpoint specifies the setpoint value, or desired value, of the process variable being controlled.
	process variable specifies the measured value of the process variable being controlled. This value is equal to the feedback value of the feedback control loop.
	PID gains in specifies the proportional gain, integral time, and derivative time parameters of the controller. proportional gain (Kc) specifies the proportional gain of the controller. The default is 1. In the equation that defines the PID controller, KC represents the proportional gain. integral time (Ti, min) specifies the integral time in minutes. The default is 0.01. derivative time (Td, min) specifies the derivative time in minutes. The default is 0.
	dt (s) specifies the�interval, in seconds, at which this VI is called. If dt (s) is less than or equal to zero, this VI uses an internal timer with a one millisecond resolution. The default is –1. Use the same dt (s) value as you use for the PID or PID Advanced VI.
	reinitialize? specifies whether to reinitialize the internal parameters, such as the integrated error, of the controller. Set reinitialize? to TRUE if your application must stop and restart the control loop without restarting the entire application. The default is FALSE.
	autotune? specifies to begin autotuning. Wire this input from a Boolean control with latched mechanical action and a default value of FALSE. The default is FALSE.
	setpoint out returns the updated setpoint value.
	process variable out returns the value of the process variable. If autotune? is TRUE, this output returns 0.
	tuning completed? returns TRUE when the autotuning process is complete. You can use this output to determine when to update the PID gains in.
	PID gains out returns the updated PID gain parameters upon completion of the autotuning process. Normal output values are identical to the values in the PID gains in input. proportional gain (Kc) returns the proportional gain of the controller. integral time (Ti, min) returns the integral time in minutes. derivative time (Td, min) returns the derivative time in minutes.
	tuned PID gains returns the tuned proportional gain, integral time, and derivative time parameters of the controller. proportional gain (Kc) returns the proportional gain of the controller. integral time (Ti, min) returns the integral time in minutes. derivative time (Td, min) returns the derivative time in minutes.

PID Online Autotuning (Relay Feedback)

Note  Use this instance for relay feedback tuning, which applies an on-off relay in a closed-loop test in order to obtain controlled oscillations and extract values for ultimate gain and ultimate frequency. This technique also incorporates hysteresis to reduce noise.

	autotuning parameters specifies various parameters used for the autotuning process. type of controller specifies which parameters to return as the output of the tuning process. 0 P—Specifies to return only the proportional parameters. 1 PI—Specifies to return the proportional and integral parameters. 2 PID—Specifies to return the proportional, integral, and derivative parameters. relay cycles specifies the number of setpoint relay cycles to use to determine the ultimate gain and period. More cycles result in more accurate parameter estimation; however, slower systems might require more time for numerous cycles. relay amplitude specifies the amplitude of the setpoint relay action. The setpoint relay is between setpoint – relay amplitude and setpoint + relay amplitude. control specification specifies the desired response performance of the PID parameters determined by the autotuning process. 0 normal—Specifies a normal response performance. 1 fast—Specifies a fast response performance. Faster response generally results in a smaller rise time. 2 slow—(Default) Specifies a slow response performance. Slower response generally results in less overshoot. PV noise level specifies an estimation of the noise level of the process variable. This value is used as the hysteresis for the setpoint relay action.
	manipulated variable specifies a quantity or condition to vary as a function of the actuating error signal so as to change the value of the directly controlled variable. The manipulated variable also can be referred to as the controller output.
	setpoint specifies the setpoint value, or desired value, of the process variable being controlled.
	process variable specifies the measured value of the process variable being controlled. This value is equal to the feedback value of the feedback control loop.
	PID gains in specifies the proportional gain, integral time, and derivative time parameters of the controller. proportional gain (Kc) specifies the proportional gain of the controller. The default is 1. In the equation that defines the PID controller, KC represents the proportional gain. integral time (Ti, min) specifies the integral time in minutes. The default is 0.01. derivative time (Td, min) specifies the derivative time in minutes. The default is 0.
	dt (s) specifies the�interval, in seconds, at which this VI is called. If dt (s) is less than or equal to zero, this VI uses an internal timer with a one millisecond resolution. The default is –1. Use the same dt (s) value as you use for the PID or PID Advanced VI.
	reinitialize? specifies whether to reinitialize the internal parameters, such as the integrated error, of the controller. Set reinitialize? to TRUE if your application must stop and restart the control loop without restarting the entire application. The default is FALSE.
	autotune? specifies to begin autotuning. Wire this input from a Boolean control with latched mechanical action and a default value of FALSE. The default is FALSE.
	setpoint out returns the updated setpoint value.
	process variable out returns the value of the process variable. If autotune? is TRUE, this output returns 0.
	tuning completed? returns TRUE when the autotuning process is complete. You can use this output to determine when to update the PID gains in.
	PID gains out returns the updated PID gain parameters upon completion of the autotuning process. Normal output values are identical to the values in the PID gains in input. proportional gain (Kc) returns the proportional gain of the controller. integral time (Ti, min) returns the integral time in minutes. derivative time (Td, min) returns the derivative time in minutes.
	tuned PID gains returns the tuned proportional gain, integral time, and derivative time parameters of the controller. proportional gain (Kc) returns the proportional gain of the controller. integral time (Ti, min) returns the integral time in minutes. derivative time (Td, min) returns the derivative time in minutes.

PID Online Autotuning (PID Relay)

Note  Use this instance for PID relay tuning, which connects a relay and an extra feedback signal with the setpoint and keeps the PID controller in the loop with the relay.

	autotuning parameters specifies various parameters used for the autotuning process. type of controller specifies which parameters to return as the output of the tuning process. 0 P—Specifies to return only the proportional parameters. 1 PI—Specifies to return the proportional and integral parameters. 2 PID—Specifies to return the proportional, integral, and derivative parameters. relay cycles specifies the number of setpoint relay cycles to use to determine the ultimate gain and period. More cycles result in more accurate parameter estimation; however, slower systems might require more time for numerous cycles. relay amplitude specifies the amplitude of the setpoint relay action. The setpoint relay is between setpoint – relay amplitude and setpoint + relay amplitude. control specification specifies the desired response performance of the PID parameters determined by the autotuning process. 0 normal—Specifies a normal response performance. 1 fast—Specifies a fast response performance. Faster response generally results in a smaller rise time. 2 slow—(Default) Specifies a slow response performance. Slower response generally results in less overshoot. PV noise level specifies an estimation of the noise level of the process variable. This value is used as the hysteresis for the setpoint relay action.
	manipulated variable specifies a quantity or condition to vary as a function of the actuating error signal so as to change the value of the directly controlled variable. The manipulated variable also can be referred to as the controller output.
	setpoint specifies the setpoint value, or desired value, of the process variable being controlled.
	process variable specifies the measured value of the process variable being controlled. This value is equal to the feedback value of the feedback control loop.
	PID gains in specifies the proportional gain, integral time, and derivative time parameters of the controller. proportional gain (Kc) specifies the proportional gain of the controller. The default is 1. In the equation that defines the PID controller, KC represents the proportional gain. integral time (Ti, min) specifies the integral time in minutes. The default is 0.01. derivative time (Td, min) specifies the derivative time in minutes. The default is 0.
	dt (s) specifies the�interval, in seconds, at which this VI is called. If dt (s) is less than or equal to zero, this VI uses an internal timer with a one millisecond resolution. The default is –1. Use the same dt (s) value as you use for the PID or PID Advanced VI.
	reinitialize? specifies whether to reinitialize the internal parameters, such as the integrated error, of the controller. Set reinitialize? to TRUE if your application must stop and restart the control loop without restarting the entire application. The default is FALSE.
	autotune? specifies to begin autotuning. Wire this input from a Boolean control with latched mechanical action and a default value of FALSE. The default is FALSE.
	setpoint out returns the updated setpoint value.
	process variable out returns the value of the process variable. If autotune? is TRUE, this output returns 0.
	tuning completed? returns TRUE when the autotuning process is complete. You can use this output to determine when to update the PID gains in.
	PID gains out returns the updated PID gain parameters upon completion of the autotuning process. Normal output values are identical to the values in the PID gains in input. proportional gain (Kc) returns the proportional gain of the controller. integral time (Ti, min) returns the integral time in minutes. derivative time (Td, min) returns the derivative time in minutes.
	tuned PID gains returns the tuned proportional gain, integral time, and derivative time parameters of the controller. proportional gain (Kc) returns the proportional gain of the controller. integral time (Ti, min) returns the integral time in minutes. derivative time (Td, min) returns the derivative time in minutes.

Example

Refer to the Autotuning PID Online and Inline VI in the labview\examples\control\PID directory for an example of using the PID Online Autotuning VI.

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