Probe Unit function
A probe unit is a hardware-oriented functional group that can store the current axis position for a parameterizable event. The event may be an edge of a digital input in the drive, for example. The position is stored immediately without significant delay for subsequent evaluation by the control system.
The probe unit of the drive can be used for event-driven position sensing through the application program (MC_TouchProbe), or for registering a reference position during homing (MC_Home) if the NC referencing mode is set to hardware latch.
In any case, the probe unit must be parameterized before it can be used. The following parameterization description refers to an AX5000 drive (SoE), although it can also be used more generally for the parameterization of a SERCOS drive.
Parameter overview
Parameter | Value | EtherCAT transition (startup) | Description |
|---|---|---|---|
S-0-0303 | 405 | P -> S | Allocation of real-time Control bit 2 |
S-0-0307 | 409 or 410 | P -> S | Allocation of real-time Status bit 2 |
S-0-0169 | 1, 2, 3 | P -> S | Probe control parameter |
S-0-0170 | 3 | S -> O | Probing cycle procedure command |
Parameter | Description |
|---|---|
S-0-0130 | Probe value positive edge |
S-0-0131 | Probe value negative edge |
Probe unit parameterization
The probe unit is controlled via an AX5000 configuration dialog. In multi-channel devices a probe unit is available for each channel.
In the first step a signal source (Mux1) for triggering the probe unit is selected. Digital drive inputs 0 to 7 are available for selection. To parameterise the probe unit for homing with evaluation of the encoder zero track, select Mux 2, which is the only option offering reference signal feedback.
The trigger signal can be linked with a further signal source (Mux 2). In the simplest case only one signal source is used, and the linkage logic is set accordingly.
A signal parameter determines whether the positive or negative signal edge is evaluated (Pos Edge or Neg Edge). The decision to use a particular signal edge is therefore made during drive parameterisation and cannot be made later in the control program.
The modifications entered during these initial configuration steps can be stored in the startup list for the drive, so that they are transferred to the drive on system startup. In the Startup List dialog save the modified parameters by clicking Accept All and or exit the dialog with OK.
Linking the probe unit with the NC
In a further configuration step, the probe unit for the drive is linked with the NC controller. The control system operates the probe unit via the SERCOS real-time bits in the master control word and the drive status word and retrieves the latch position from the drive process data.
Startup list
To configure the real-time bits the drive startup list is extended (New...).
To enable activation of the probe unit set S-0-0303 to 405 (95 01).
The drive response is signalled in a status bit. To this end S-0-0307 is set to 409 (99 01) for a positive signal edge and 410 (9A 01) for a negative signal edge.
Finally the probe unit function must be activated. This can be achieved by setting the command S-0-0170 to 3 during startup. Please note that the drive only accepts this value during the EtherCAT transition S->O.
Process data
To enable the control system to evaluate the measured value, the value is included in the process data and linked with the NC axis. On the drive side one measured value is available for the positive signal edge and one for the negative signal edge.
Right-click in the PDO Content list to add a new value. Depending on the configuration the value of S-0-0130 or S-0-0131 is stored in the process data.
The measured value is automatically linked with the NC axis when a link is created between the axis and the drive. If the link was already established before the configuration described here, the link can be cancelled and recreated to ensure that the measured value is linked.
Startup parameter overview
