Phaser

Names

Description

MLPhaInit

Initializes a phaser Pipe Block.

MLPhaReadActPhase

Gets the actual phase value of a phaser block.

MLPhaReadPhase

Gets the phase value of a phaser block.

MLPhaReadSlope

Gets the phase slope value of a phaser block.

MLPhaWritePhase

Sets the phase value of a phaser block.

MLPhaWriteSlope

Sets the phase slope value of a phaser block.

  • There is a delay when using an external encoder.
    The delay is five cycles:
         2 cycles to read the encoder from the AKD via EtherCAT,
         1 cycle for computing,
         2 cycles for sending the new position set point to the AKD).
    This lag error is speed proportional (5 cycles * speed).
    A Phaser block can be used to compensate for this lag.

Purpose

A Phaser produces a flow of output values which are offset (phase shifted) a specified amount from its input. A typical application of a Phaser is to provide independent phase adjustment capability on an axis.

The Phaser has some similarities with the Gear pipe block, however its intended use is quite different.

  • The typical application for a Phaser pipe block is to drive a periodic system: a machine where the axes are globally increasing (or decreasing) their position.
  • The Gear pipe block, with OFFSET and RATIO parameters, is intended for bounded applications (applications where the integral of speed on a complete cycle is zero).
    • Using the wrong one at the wrong place will cause unnecessary complications.
    • In addition, you must always consider the position as the input value (and not the speed).

When executing, the phaser block is in one of these states:

State

Description

Applying Phase
  • Entered when the programmed Phase value is reached.
  • Exits to the Changing phase state whenever a new value is programmed via the MLPhaWritePhase function changes the Phase Offset target.

Changing Phase
  • Entered when a new value is programmed.
  • Exits to the Applying Phase state when the programmed phase offset is reached.
  • The current Phase offset value is slewed to the new phase offset by the amount of the slew value.

Standby
  • Entered when the Block is initialized.
  • Exits to the Changing Phase state when the Phase value is changed via the MLPhaWritePhase command.

Parameters

Parameter

Description

Phase

The amount of phase adjustment.

  • The phase value can be negative.
    • A negative phase value is subtracted from the input value.
  • Phase is expressed in User units.

PhaseSlope
  • User-defined rate at which phase changes are implemented.
    • Expressed in user logical units per second.
  • A slow rate parameter is used to limit the implementation of step changes of phase.

StandbyValue
  • The output signal value assumed by the phaser output when the phaser is in a stopped condition.
  • Expressed in user logical units.
  • This is the output from the Phaser Block until the MLPhaWritePhase function is executed.

Examples: Phaser Function

Figure 1: Changed Phase value

Figure 2: Changed Slope value


  • % MODULO_POSITION is in the equation to take into account the modulo (periodicity) of the value.

Associated Data

  • OutputValue: Output value of the data flows.
  • IsReady: Boolean set to TRUE when the pipe block is ready.