Registration

One machine revolution is defined by selecting one encoder on smarty's dual encoder module, and setting a multiplier and a divider parameter.

The fraction of a revolution between a master and a slave event is measured. Events are selected from either of the two encoder z-channel markers, or the high-speed event inputs at terminals E4 and E5. The rising edge of the signal is associated with an exact encoder edge.

The setpoint is the desired fraction of a revolution at which the slave event is expected to occur. The function block output is the error from the setpoint. Both parameters range from 0.0000 to 0.9999 revolutions.

A window, 0.0000rev to 0.5000rev, is set up around the setpoint. If the error is outside of the window, it is clamped at + or - the window value depending on whether the error exceeds 0.5 times the measured period.

Note - The maximum error output is 0.5 times the measured period.

Out of Window and Missing Event outputs are provided. Missing Event is active if the master or slave events are not present during any cycle or where the measured period exceeds 3.3 revolutions. The error tracks at the last value prior to the missing event.

Application Example - Registration on Electronic Line-Shaft, Phase-Lock

Examples include print cylinder registration and mechanical cut-to-length. The material and print or cut head rotate precisely in sync while slower corrections are applied from the registration loops.

In the following one-page framework, the primary control is from a well-calibrated and tuned electronic line-shaft, phase-lock system.

Small registration errors feed a relatively slow PI that offset the position demand in the phase-lock loop.

If the registration PI output approaches saturation, a slow MOP begins to adjust the phase-lock ratio. This allows the system to compensate for unexpected slip or stretch in the material, for example.

Application Example - Registration on Motion Control, Servo Haul-Off

Examples include bag sealer-cutters with print registration, sheeters, and folders. The servo must haul-off the precise length of material during the allowable period after the cut and prior to the commencement of the next cut.

In the following one-page framework, the primary control is from a well-tuned motion control loop using Trapezoid Motion function block.

Small registration errors feed a relatively slow PI that offsets the cut length demand in the motion loop.

If the registration PI output approaches saturation, a slow MOP begins to scale the cut length. This allows the system to compensate for unexpected slip or stretch in the material, for example.

• Available only in the dw2xx series products
• Requires library: Encoder Control (option -11)
• Requires: Dual Encoder
• Singleton function block
• Firmware versions 0x201A and later