The PAC can be paired with Parker Compax3 Series servo drives to solve registration or position capture applications. The position capture operation can be accomplished by using the MC_TouchProbe function block.
MC_TouchProbe requires an axis whose position will be captured (the Axis input) and information about how the position will be captured (the Trigger input). The Trigger input is a TRIGGER_REF structure.
For high-performance position capture, bFast should always be set to TRUE. bFast set to TRUE sets the position capture up in the drive itself for the most accurate capture. (setting bFast to FALSE set the position capture up in the PAC itself and now your accuracy will be limited by the EtherCAT update rate used)
The exact mode of capture can be defined using iTriggerNumber. The Compax3 only supports a single channel so iTriggerNumber should always be a value of 0. However, the Compax3 does allow you to configure any of the on-board digital inputs (0-7) as the trigger input for the position capture by doing a separate SDO write to object 0x2304.1. The rising or falling edge can be selected by doing a separate SDO write to object 0x2304.2 (0 = rising edge, 1 = falling edge). This is shown in the included sample project.
Once the drive's touchprobe is armed, MC_TouchProbe will hold its Busy output TRUE until the drive's touchprobe input makes the appropriate transition (rising or falling). Then, the drive will record the current position reported by the motor's encoder and MC_TouchProbe will report that position in engineering (scaled) units on its RecordedPosition output.
The sample included in this article is a PAM project archive that shows how to use MC_TouchProbe. It has one Compax3 Drive configured in its EtherCAT_Master tree and a small WebVisualization interface to allow the user to experiment with the touchprobe feature. The sample can be downloaded using the link below. Unzip and then restore project archive using PAM version 1.4 (or later).
[PAM 1.4: MC_TouchProbe -- C3 Drive (PAM 1.4).projectarchive]
[Quick link: PAC product page (North America)]
[Quick link: Compax3 product page (North America)]
June 2019 GLH