Encoder Concept - General Information
Encoders are required for position measurement (path and angle measurement) with high precision. Speed and acceleration can be derived from the position measurement. During path measurement, the resolution of these sensors is in the micrometer range and during angle measurement in the range of few thousandth degrees.
Encoder types:
oIncremental encoder generates information on position, angle, and number of rotations in type-specific number of lines (number of steps/rotation). The number of lines per rotation defines the resolution. The relevant position is determined by counting these steps from a reference point. A reference run is required to determine an absolute position.
oAbsolute value encoder generates information on position, angle, and number of rotations in type-specific number of angular steps. A unique reference sample is assigned to each angular step. The number of existing code samples per rotation defines the resolution. As an absolute position is assigned to each code sample, no reference run is required. There are two types of rotating encoders. Encoders that can turn only one rotation and then begin at 0 (Single-Turn-Encoder) again, and encoders that can turn several rotations (Multi-Turn-Encoder).
Encoders are as used motor encoders in the PacDrive system (Motor feedback system) and as position encoders in machine mechanics.
oAn absolute encoder is always used for the motor encoder.This is also used to store the electronic nameplate. This means that the parameters of the motor are automatically known to the PacDrive system, which makes configuration of the system much easier.
oIncremental encoders as well as absolute encoders are used as position encoders on the machine mechanics. This depends on the machine concept.
Master encoders are speed or position sources and thus can be engine encoders or position encoders.
Possible Master Encoder:
oLXM
oVirtual encoder
oPhysical Master Encoder (SinCos)
oIncremental encoder
oLogical encoder
oSum encoder
oSum Master Encoder
oEncoder network for sync encoder Input
To use and manipulate signals of a speed and position source in the PacDrive system independently many times, the logical encoder was integrated in the system as “Software encoder”.
Tasks of the logical encoder:
oCoupling various encoder types to a “Standard encoder”
oCoupling multiple logical encoders to a master encoder
oGenerating position values from the Master encoder speed value
oManipulating the master encoder speed signal
oSoftware gear (multiplication) of the speed signal
oAdding a speed signal to the speed signal of the master encoder
oSoftware coupling
oRealizing a phase displacement trough the system
oMaster position source for electronic curve (“x-axis”)
oMaster position source for cam switch
To add speed signals in the PacDrive system, the Sum Master Encoder was integrated in the system.
Tasks of the sum master encoder:
oRegistration Correction
The positive deviation of the print mark is compensated by feeding a correction curve via the Sum encoder.
oOverlapping a corrective curve to the actual curve (phase shift)
When, for example, compensating a changing pressure angle of the belt drive, a constant production velocity can be achieved by feeding a corrective curve via the Sum Master Encoder.
The sum encoder was integrated in the system for adding speed position signals in the PacDrive system.
Tasks of the sum encoder:
oRegistration Correction
The position deviation of the print mark is compensated by feeding a correction curve via the Sum encoder.
oOverlapping a corrective curve to the actual curve (phase shift).
When, for example, compensating a changing pressure angle of the belt drive, a constant production velocity can be achieved by feeding a corrective curve via the Sum encoder.
NOTE: In practice, addition of positions appears difficult, because for example, a jump occurs in the “output position” of the Sum encoder on resetting a “source position”.
Therefore, the Sum Master Encoder must be used. This problem does not occur in this encoder. As speed is added here.
