L_TB1P_FrictionCompensation

This FB includes the "Friction identification" and "Friction compensation" functions.

By means of the "Friction identification" function ( xIdent = TRUE), the friction characteristic can be automatically identified.

For this, the FB accepts the drive control on request and carries out the identification.

For saving the automatically identified friction characteristic, four memory locations are provided. The selection of memory locations 1 ... 4 is effected via the input dwSelectCurve .

The friction characteristic includes 65 values which are equally distributed across the speed range of 0 ... lrMaxSpeedIdent .

With the "Friction compensation" function ( xEnableFrictionCurve = TRUE), a speed-dependent compensation of the friction torque can be executed on the basis of a linear characteristic or friction characteristic that has been automatically determined before.

The friction characteristic to be used is selected via the dwSelectCurve input.

If the input dwSelectCurve is = 0 or unassigned, a parameterisable linear characteristic is used for the friction compensation.

		L_TB1P_FrictionCompensation
BOOL	-	xIdent	xBusy	-	BOOL
BOOL	-	xFollowerActive	xDone	-	BOOL
LREAL	-	lrActReelSpeedIn	xError	-	BOOL
LREAL	-	lrActTorqueIn	eErrorID	-	L_IE1P_Error
DWORD	-	dwSelectCurve	xStop	-	BOOL
BOOL	-	xEnableFrictionCurve	xEnableFollower	-	BOOL
LREAL	-	lrSetReelSpeed	lrSetReelSpeedOut	-	LREAL
LREAL	-	lrFrictionAdapt	lrSetFrictionTorqueOut	-	LREAL
BOOL	-	xInvertOutput
LREAL	-	lrMaxSpeedIdent
LREAL	-	lrAccDecIdent
LREAL	-	lrFilterTimeSpeed
LREAL	-	lrFilterTimeTorque
LREAL	-	lrFilterTimeReelSpeed
LREAL	-	lrLinearCompStart
LREAL	-	lrLinearCompEnd
ARRAY [1...66] OF LREAL	-	alrFrictionCurve1
ARRAY [1...66] OF LREAL	-	alrFrictionCurve2
ARRAY [1...66] OF LREAL	-	alrFrictionCurve3
ARRAY [1...66] OF LREAL	-	alrFrictionCurve4

Inputs and outputs

Name Data type	Information/possible settings
alrFrictionCurve[1...4] ARRAY [1...66] OF LREAL	Friction characteristics 1 ... 4

Name

Data type

Information/possible settings

alrFrictionCurve[1...4]

ARRAY [1...66] OF LREAL

Friction characteristics 1 ... 4

Inputs

Name Data type	Information/possible settings
xIdent BOOL	TRUE	Friction identification: Start identification of the friction characteristic.
xFollowerActive BOOL	Interface for feedback that setpoint generation has been enabled (e.g. SMC_FollowVelocity.bBusy)
lrActReelSpeedIn LREAL	Current speed of the motor shaft (actual speed value) Unit: rev/s
lrActTorqueIn LREAL	Current torque (actual torque value) Unit: Nm
dwSelectCurve DWORD	Friction identification ( xIdent = True) Selection of the memory area in which the friction values identified are stored. Selection '1' ... '4': memory area 1 ... 4
dwSelectCurve DWORD	Friction compensation ( xEnableFrictionCurve = TRUE, xIdent = FALSE) Selection of the characteristic for friction compensation. Selection '0': linear friction characteristic, adjustable via ... lrLinearCompStart lrLinearCompEnd lrLinearCompEndReelSpeed ) Selection '1' ... '4': friction characteristic identified (memory area 1 ...4)
xEnableFrictionCurve BOOL	Activate friction compensation.
	TRUE	Friction compensation is activated.
	FALSE	The friction torque is reset to '0'.
lrSetReelSpeed LREAL	Speed setpoint for the friction characteristic Unit: rev/s
lrFrictionAdapt LREAL	Value for the proportional evaluation of the friction characteristic Unit: % (1 º 100 %)
xInvertOutput BOOL	TRUE	The lrSetFrictionTorqueOut output signal is shown in an inverted fashion.
lrMaxSpeedIdent LREAL	Maximum speed for friction identification Unit: rev/s
lrAccDecIdent LREAL	Acceleration for friction identification Unit: rev/s ²
lrFilterTimeSpeed LREAL	Filter time constant for the actual speed value for friction identification Unit: s Initial value: 0.0 (with this value, the filter is not active.)
lrFilterTimeTorque LREAL	Filter time constant for the actual torque value for friction identification Unit: s Initial value: 0.0 (with this value, the filter is not active.)
lrFilterTimeReelSpeed LREAL	Filter time constant for the speed setpoint for friction compensation Unit: s Initial value: 0.0 (with this value, the filter is not active.)
lrLinearCompStart LREAL	Initial friction torque for friction compensation
lrLinearCompEnd LREAL	End friction torque for friction compensation
lrLinearCompEndReelSpeed LREAL	Speed at end friction torque for friction compensation

Outputs

Name Data type	Value/meaning
xBusy BOOL	TRUE	The "Friction identification" or "Friction compensation" function is active.
xDone BOOL	TRUE	The "Friction identification" or "Friction compensation" function has been completed successfully.
xError BOOL	TRUE	An error has occurred. For details see eErrorID .
eErrorID L_IE1P_Error	If xError = TRUE: Error number for the error that has occurred.
xStop BOOL	xStop is set to TRUE if the friction identification process is aborted and can be used to control an external STOP function.
xEnableFollower BOOL	xEnableFollower is set to TRUE for activating a setpoint interface (e.g. SMC_FollowVelocity).
lrSetReelSpeedOut LREAL	Speed setpoint for friction identification Unit: rev/s
lrSetFrictionTorqueOut LREAL	Current friction torque Unit: Nm

Identifying the friction characteristic automatically

How to proceed:

Select the memory location for the characteristic.

Define the memory location (1 ... 4) in which the characteristic is to be saved via the dwSelectCurve input after the identification process has been carried out successfully.
Start identification process.

Set the xIdent input to TRUE.

Friction identification process

The basic function "Speed follower" is activated.

The xBusy output changes to TRUE.

With the acceleration set in lrAccDecIdent , the drive is accelerated to the maximum speed set in lrMaxSpeedIdent .

When the drive has reached the maximum speed, it is braked to a standstill again with the acceleration set in lrAccDecIdent .

The friction characteristic is saved in the memory area selected via the input dwSelectCurve .

After a successful identification process, ...

the xBusy output is set to FALSE;

the xDone output is set to TRUE.

The identification is executed according to the following state machine:

State machine for the friction identification

Aborting the friction identification process

If the xIdent input is reset to FALSE, the active identification process is cancelled immediately. Resetting the xFollowerActive input to FALSE also results in the immediate abort of the process.

The xBusy output is reset to FALSE.

The xStop output is set for one cycle and can be used to control an external Stop function.

The cause of abort is shown via the eErrorID output.

Smoothing the actual value signals

If incremental encoders are used, it may be required to filter the actual speed value signal.

The time constant for the filter can be set via the lrFilterTimeSpeed input. A setting of '10 ms' is sufficient in most cases.

Filtering the actual torque signal can be also helpful for smoothing the friction characteristic. The time constant for this filter can be set via the lrFilterTimeTorque input.

Activating the friction compensation

Friction compensation is active if the xIdent input is set to FALSE and the xEnableFrictionCurve input is set to TRUE.

The current speed is preselected via the lrSetReelSpeed input.

If the actual speed value exceeds the maximum value defined in the characteristic, the characteristic is extrapolated linearly.

Use of a linear characteristic

If the input dwSelectCurve is = 0 or unassigned, a linear characteristic is used for the friction compensation.

The linear characteristic is defined via parameters lrLinearCompStart , lrLinearCompEnd , and lrLinearCompEndReelSpeed :

lrLinearCompStart = initial friction torque at speed '0'

lrLinearCompEnd = end friction torque at speed lrLinearCompEndReelSpeed

Use of a previously automatically identified friction characteristic

If the dwSelectCurve input = 1 ... 4, the friction characteristic saved in the corresponding memory location is used instead of the linear characteristic.

Temperature compensation

Via the lrFrictionAdapt input, a gain for the characteristic on a percentage basis is specified, for instance in order to compensate changes in the friction torque due to temperature changes.

Smoothing the speed setpoint

For smoothing the lrSetReelSpeedOut speed setpoint, a filter time constant can be specified via the lrFilterTimeReelSpeed input.

Display of the precontrol signal

The precontrol signal generated is provided at the lrSetFrictionTorqueOut output. By setting the xInvertOutput input to TRUE, this signal can be output in an inverted manner (change of direction of rotation).