FB_ALY_StepResponse_1Ch

Step Response 1Ch identifies parameters of the step response of a PT2 track. These include the delay time T_e, the compensation time T_b, the settling time T_cs, and the time of maximum t_m.

To detect whether the track is steady, a local minimum or maximum is searched for. If this is within the tolerance band (marked in gray), it is assumed that the track is steady. Only then is the settling time set.

The algorithm starts when a new setpoint is outside the previously stored tolerance band.

Syntax

Definition:

FUNCTION_BLOCK FB_ALY_StepResponse_1Ch
VAR_OUTPUT
    ipResultMessage: Tc3_EventLogger.I_TcMessage;
    bError: BOOL;
    bNewResult: BOOL;
    bConfigured: BOOL;
    bExecuting: BOOL;
    fbEquivalentDeadTime: FB_ALY_Timespan;
    fbEquivalentTimeConstant: FB_ALY_Timespan;
    fbSettlingTime: FB_ALY_Timespan;
    fbTimeMax: FB_ALY_DateTime;
    fError: LREAL;
END_VAR

Outputs

Name	Type	Description
ipResultMessage	I_TcMessage	Contains more detailed information on the current return value. This special interface pointer is internally secured so that it is always valid/assigned.
bError	BOOL	This output is `TRUE` if an error occurs.
bNewResult	BOOL	When a new result has been calculated, the output is `TRUE.`
bConfigured	BOOL	Displays `TRUE` when the function block is successfully configured.
bExecuting	BOOL	`TRUE` if the parameter identification is active.
fbEquivalentDeadTime	FB_ALY_Timespan	Delay time of the track. Timespan between the start of the step response and the intersection of the inflectional tangents with the start value.
fbEquivalentTimeConstant	FB_ALY_Timespan	Compensation time of the track. Timespan between the intersection point of the inflectional tangents with the start value and the intersection point of the inflectional tangents with the setpoint.
fbSettlingTime	FB_ALY_Timespan	Settling time of the track.
fbTimeMax	FB_ALY_DateTime	Time of the maximum overshoot.
fError	LREAL	Difference between input value and setpoint.

Methods

Name	Definition location	Description
Call()	Local	Method for calculating the outputs for a specific configuration.
Configure()	Local	General configuration of the algorithm with its parameterized conditions.
Reset()	Local	Resets all internal states or the calculations performed so far.
SetChannelValue()	Local	Method for passing values to the algorithm.

Sample

VAR
    fbStepResponse : FB_ALY_StepResponse_1Ch;
    fbSystemTime : FB_ALY_GetSystemTime;
        
    fThresholdReversal : LREAL;
    bUseRelativeTolerance : BOOL;
    fErrorTolerance : LREAL;
    bConfigure : BOOL := TRUE;
    
    fInput : LREAL;
    fSetpoint : LREAL;
END_VAR

// Get current system time
fbSystemTime.Call();

// Configure algorithm
IF bConfigure THEN
    bConfigure := FALSE;

    fbStepResponse.Configure(fThresholdReversal, bUseRelativeTolerance, fErrorTolerance);
END_IF

// Call algorithm
fbStepResponse.SetChannelValue(1, fInput);
fbStepResponse.SetChannelValue(2, fSetpoint);
fbStepResponse.Call(fbSystemTime.tSystemTime)

Requirements

Development environment	Target platform	Plc libraries to include
TwinCAT v3.1.4024.0	PC or CX (x64, x86)	Tc3_Analytics

Further Information