Architecture

 

Architecture

System Requirements

GrabControl requires two Altivar variable speed drives with support of flux vector control (closed loop) motor mode. One of the drives controlling hold axis and the other one controlling the close axis.

Both hold and close axes must be equipped with encoders and both Altivar drives must be configured to run in flux vector control motor control mode. The FB works with incremental encoders. The positions of both axes are stored in non-volatile memory.

The hold and close axes must have identical linear speeds and encoder resolutions.

Vertical movement must be limited in upwards direction by an emergency limit switch.

Environment

The following equipment are required to use GrabControl function block:

oEcoStruxure Machine Expert controller

oTwo Altivar variable speed drives

oTwo encoder interface cards for Altivar variable speed drives (not necessary for drives with an embedded encoder interface.)

oTwo incremental encoders, typically 1024 PPR (Pulses Per Revolution)

oEquipment for communication between the controller and drives.

The following equipment is typically used in conjunction with GrabControl function block:

oA two-axis joystick for control of close and hold axes.

NOTE: The function block supports analog and digital joysticks.

oThree buttons for resetting the calibration values and setting calibration of open and closed grab positions (can be done via HMI).

oAdditional button(s) on the joystick for extended functions like scraping and rapid opening.

oTwo buttons, selector or potentiometer for direct modification of hold torque during closing on stack. These buttons are useful when materials of various densities are transported.

oOptional strain gauge weighing system for enabling automatic closing on stack only when the grab is on the stack.

The hold motor is working in a torque limited mode during automatic closing on stack. If activation of the automatic closing on stack function must be suppressed while the grab is mid-air, the user application must take into account the enabling and disabling of the automatic closing on stack function. The situation often results in a detected over speed fault reported by the Altivar drive.

Data Flow Overview

The following figure is the internal Structure of the GrabControl function block