Encoder

Depending on their operating modes, encoders determine the actual position, actual velocity or the actual acceleration. Actual values often fluctuate heavily, so a parameterisable filter is available for each mode in order to ensure a reasonable resolution. A wide variety of encoders versions is supported. Both absolute and incremental encoders are available. On top of this, there are simulation encoders and special encoders for the determination of force. The encoder parameters include the scaling, zero offset shift and the modulo factor. In addition, the encoder data includes the parameters for the software end locations and for the reference travel.

Interface

Every encoder that is not of the "simulation" type must be associated with an actual value acquisition module.

Encoder types

Simulation encoders
Absolute, with 24 or 25 bits, and 12 and 13 bit single turn encoders (M3000)
Incremental, with 24 bits (M31x0, M3100, M2000)
Incremental, with 16 bits (KL5101)
Absolute SSI with 24 bits (KL5001)
Absolute/incremental BISSI with 16 bits (KL5051 and PWM Terminal KL2502_30K (frq. cnt. pulse mode) )
Absolute analog input with 16 bits (KL30xx)
SERCOS "Encoder" POS
SERCOS "Encoder" POS and VELO
Binary incremental encoders (0/1)
Absolute analog input with 12 bits (KL2510)
T&R Fox 50 module (24 bits absolute (SSI))
Force acquisition from Pa, Pb, Aa, Ab
Incremental with 16/20 bits (AX2000)
Incremental with 32 Bit
Incremental with variable bit mask (max. 32 bits)
Incremental NC backplane

Encoder parameters

Parameter	Data type	Unit	Description
ENCODER mode	ENUM		Operation mode of the encoder: POS = the actual position is determined. POSVELO = the actual position and the actual velocity are determined. POSVELOACC = the actual position, actual velocity and the actual acceleration are determined.
Encoder counting direction inverted	BOOL		Counting direction inverted: FALSE = the polarity of the axis movement agrees with the counting direction of the acquisition hardware. TRUE = the polarity of the axis movement is in the opposite sense to that of the counting direction of the acquisition hardware.
Scaling factor	float	mm/INC	Incremental evaluation: this factor is used to convert the displacement increments into axis positions.
Zero offset shift	float	mm	With absolute encoders: this value is added to the encoder position in order to determine the axis position. It is used to specify the machine-dependent zero point.
Modulo factor	float	mm	With rotary axes: this is the "distance" represented by one rotation. If the actual value is acquired, for instance, in degrees, 360.0 should be entered here.
OPERATING MODE: min. end position monitoring	BOOL		Activation and deactivation of the monitoring of the minimum end position.
Software end position, min.	float	mm	Location of the minimum end position
OPERATING MODE: max. end position monitoring	BOOL		Activation and deactivation of the monitoring of the maximum end position.
Software end position, max.	float	mm	Location of the maximum end position
Actual position filter time	float>0	s	Filter time for the PT1 filtering of the actual position.
Actual velocity filter time	float>0	s	Filter time for the PT1 filtering of the actual velocity.
Actual acceleration filter time	float>0	s	Filter time for the PT1 filtering of the actual acceleration.

PT1 filter

A PT1 filter is a transfer function that performs convex interpolation between a new value x_n and an old value (from one cycle ago) x_a. The filter time parameter (>= 0.0) in seconds is to be entered. If l=Saf cycle time/(Saf cycle time+filter time), then x = l x_n + (1-l) x_a, l Î [0.0,1.0]. If the filter time is close to 0.0, the new value has a high weighting. If the filter time is long, the older value has relatively high weighting.

Referencing parameters

Parameter	Data type	Unit	Description
Search direction for referencing cam inverted	BOOL		Search direction inverted: FALSE = cam is looked for in the direction of positive movement. TRUE = cam is looked for in the direction of negative movement.
Search direction for sync pulse inverted	BOOL		Search direction inverted: FALSE = synchronization pulse is looked for in the direction of positive movement. TRUE = synchronization pulse is looked for in the direction of negative movement.
Reference position	float	mm	The axis position that is assigned to the synchronization pulse that is active during homing. If the actual position of the axis is acquired in any unit other than mm, then that unit must be used here too.
External sync pulse	BOOL		Reserved

SERCOS Axes

The modulo scaling (only in the weighting of the position data in the modulo display (S-0-0076 bit 7)) determines the modulo value at which the position data begins again at 0. This value must agree with the value set at the drive (S-0-0103) if the position is to be correctly indicated and controlled.

When TwinCAT is active and SERCOS is at least in Phase 2, the value can be read off via "Calculate". Download and Upload can be used to write or read the value to and from the running TwinCAT system.