PID Gain Schedule VI

Owning Palette: PID VIs

Requires: Full Development System

Selects a set of PID gains from a gain schedule for the control of processes that require different sets of gains for different regions of operation, such as highly nonlinear processes. Use the DBL instance of this VI to implement a single control loop. Use the DBL Array instance to implement parallel multi-loop control.

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PID Gain Schedule (DBL)

	gain scheduling value specifies the current input value to use to select PID gains from the gain schedule.
	PID gain schedule specifies the gain schedule for the proportional, integral, and derivative gain parameters. Specify the maximum values for the PID gain schedule in ascending order. This VI uses the first set of PID gains in the array for all gain scheduling values less than the corresponding maximum value. If you define a maximum setpoint value and the actual setpoint rises above that value, this VI continues to behave as if the maximum setpoint value were still in effect. PID gains 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. max value specifies the maximum value of the range of the gain scheduling value.
	index out returns the index of the element in the PID gain schedule array corresponding to the PID gains out output.
	PID gains out returns the current PID gains from the gain schedule. 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 Gain Schedule (DBL Array)

	gain scheduling value specifies the current input value to use to select PID gains from the gain schedule.
	PID gain schedule specifies the gain schedule for the proportional, integral, and derivative gain parameters. Specify the maximum values for the PID gain schedule in ascending order. This VI uses the first set of PID gains in the array for all gain scheduling values less than the corresponding maximum value. If you define a maximum setpoint value and the actual setpoint rises above that value, this VI continues to behave as if the maximum setpoint value were still in effect. PID gains 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. max value specifies the maximum value of the range of the gain scheduling value.
	index out returns the indexes of the elements in the PID gain schedule array corresponding to each element of the PID gains out output array.
	PID gains out returns the current PID gains from the gain schedule. 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 Gain Schedule Details

You can use the DBL Array instance of this polymorphic VI in multi-loop PID control applications. In this case, the length of the gain scheduling value input determines the length of the output array. Other input arrays do not necessarily need to be the same length as the gain scheduling value input. This VI resizes other input arrays to the same length as the gain scheduling value input as follows:

• If the input array is longer than the gain scheduling value input, the input array is truncated to the length of the gain scheduling value input. Additional values in the array are not used.
• If the input array is shorter than the gain scheduling value input, the last value of the input array is repeated until the size matches that of the gain scheduling value input.

In this manner, an input value that should be used for each output calculation does not need to be specified repeatedly in the array passed into this VI. Instead, the array can consist of a single value that is used for each output calculation.

Example

Refer to the Gain Scheduling Simulator VI in the labview\examples\control\PID directory for an example of using the PID Gain Schedule VI.

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