CPB Modbus RTU Technical Manual

Cyclic Synchronous Position

Overview

Description

In this mode, the controller receives an absolute position preset via the fieldbus at fixed time intervals (referred to in the following as a cycle). The controller then no longer calculates any ramps, but rather only follows the presets.

The target position is transferred cyclically (via PDO). Bit 4 in the controlword does not need to be set (unlike the Profile Position mode).

Note: The target is absolute and, thus, independent of how often it was sent per cycle.

Synchronization with the SYNC object

To achieve smooth movement, the controller should synchronize with the SYNC object (depending on the field bus). This SYNC object is to be sent by the higher-level controller in regular intervals. Synchronization occurs as soon as the controller is switched to the Operational NMT mode.

Note: Where possible, it is recommended that a time interval of the SYNC object be used for transfer of the target position.

Controlword

In this mode, the bits of controlword 6040h have no special function.

Statusword

The following bits in object 6041h (statusword) have a special function:

Bit Value Description
8 0 The controller is not in sync with the fieldbus
8 1 The controller is in sync with the fieldbus
10 0 Reserved
10 1 Reserved
12 0 Controller does not follow the target; the preset of 607Ah (Target Position) is ignored
12 1 Controller follows the target; object 607Ah (Target Position) is used as the input for position control.
13 0 No following error
13 1 Following error

Bit 11: Limit exceeded: The demand position is above or below the limit values set in 607Dh.

Object entries

The following objects are necessary for controlling this mode:

  • 607Ah (Target Position): This object must be written cyclically with the position set value.
  • 607Bh (Position Range Limit): This object contains the preset for an overrun or underrun of the position specification.
  • 607Dh (Software Position Limit): This object defines the limitations within which the position specification (607Ah) must be located.
  • 6065h (Following Error Window): This object specifies a tolerance corridor in both the positive and negative direction from the set specification. If the actual position is outside of this corridor for longer than the specified time (6066h), a following error is reported.
  • 6066h (Following Error Time Out): This object specifies the time range in milliseconds. If the actual position is outside of the position corridor (6065h) for longer than this time range, a following error is triggered.
  • 6085h (Quick-Stop Deceleration): This object contains the braking deceleration for the case that a quick-stop is triggered.
  • 605Ah (Quick-Stop Option Code): This object contains the option that is to be executed in the event of a quick-stop.
  • Only if closed loop is activated: 6080h (Max Motor Speed): Maximum speed
  • 60C2h:01h (Interpolation Time Period): This object specifies the time of a cycle; a new set value must be written in 607Ah in these time intervals.

    The following applies here: cycle time = value of 60C2h:01h * 10value of 60C2:02 seconds.

  • 60C2h:02h (Interpolation Time Index): This object specifies the time basis of the cycles. Currently, only value 60C2h:02h=-3 is supported; this yields a time basis of 1 millisecond.
  • 60B0h (Position Offset): Offset for the position set value in user-defined units
  • 60B1h (Velocity Offset): Offset for the speed set value in user-defined units
  • 60B2h (Torque Offset): Offset for the torque set value in tenths of a percent

The following objects can be read in this mode:

  • 6064h (Position Actual Value)
  • 606Ch (Velocity Actual Value)
  • 60F4h (Following Error Actual Value)
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