Homing

Overview

Homing is used to mechanically move a motor (connected to a mechanism) to a specific location on the machine, referred to as “home”. Motion tasks then use this home as a reference point for movements that must base a known position on this reference point. Motor movement is usually controlled by a variety of limit switches (end of travel) and a home reference switch. Using these reference points with the logic of the drive allows the machine to find and set the home reference point.

Using Homing

The AKD includes a variety of homing methods (set with HOME.MODE) to accommodate your machine needs:

  • Home using current position (HOME.MODE 0)
  • Find limit input (HOME.MODE 1)
  • Find input limit then find zero angle (HOME.MODE 2)
  • Find input limit then find index (HOME.MODE 3)
  • Find home input (HOME.MODE 4)
  • Find home input then find zero angle (HOME.MODE 5)
  • Find home input then find index (HOME.MODE 6)
  • Find zero angle (HOME.MODE 7)
  • Move until position error exceeded (HOME.MODE 8)
  • Move until position error exceeded, then find zero angle (HOME.MODE 9)
  • Move until position error exceeded, then find index (HOME.MODE 10)
  • Find index signal (HOME.MODE 11)
  • Home to home-switch, including mechanical stop detection (HOME.MODE 12)
  • Home to feedback position (HOME.MODE 13)
  • Home to home-switch for rotary applications (HOME.MODE 14)
  • Find next feedback zero position (HOME.MODE 15)
  • Find home input with dual edges (HOME.MODE 16)
  • Absolute Mode - Calculate and save offset (HOME.MODE 17)
  • Find home input, then find next feedback zero position (HOME.MODE 18)

Each of these homing methods offers a different way to achieve a home reference point based on your particular system mechanics. All homing methods provide the options of adjusting the acceleration, deceleration, and speed for homing moves. In addition, once the homing move is completed, you can either set an offset position or make an offset move as required. Homing modes, guidance for mode selection, and homing examples are included in Selecting and Using Homing Modes.


  • When using any of the methods that use homing switches and limits, please refer to the Input/Output section for proper wiring techniques.

Home Default Window

The Home window provides a means to select your homing method and configure the homing settings. This window also provides a simple controls to start homing and confirm homing success.

Mode Selection:

Use this box to select the appropriate homing mode. Homing modes are described below in Selecting and Using Homing Modes. The active options in the Settings area change depending on the homing mode selected.

Settings:

  • Acceleration: Sets the acceleration ramp used during the homing procedure.
  • Deceleration: Sets the deceleration ramp used during the homing procedure.
  • Direction: Sets the start direction for homing movement.
  • Distance: Sets a prescribed distance you want the motor to move once the home reference point is found. A zero value (default) corresponds to the axis actively returning to the defined position found during the homing process.
  • Position: Sets the current position to a prescribed value once the home reference point is found.
  • Position Lag: Sets the position error threshold, which is used for indicating home reference when using the hardstop modes 8 and 9.
  • Velocity: Sets the initial velocity used for homing moves.
  • Velocity Factor: In modes where a limit is reached, and direction is reversed, the velocity factor allows you to reduce the velocity as a precentage of the homing velocity.
  • Positive/Negative Limit Switch/Home Reference/Peak Current: These fields appear based on the mode selected. For homing to limits and home reference, this field will indicate how the digital inputs are configured as well as provide a link to the digital input page. For Homing to a hard stop, the Peak Current field allows you to set the peak current limit desired during homing.

Controls:

  • Found: When the home reference is found, then this indicator is green.
  • Done: When the home move is complete, this indicator is green.
  • Active: This indicator will be green while the Home move is taking place.
  • Error:This indicator will be red if something in the homing sequence failed.
  • Position Feedback: This window reports the current value for PL.PFB.
  • Auto Homing: Allows the system to auto-home on power up.
  • Start/Stop: Click this button to start or stop the selected homing method.

Selecting and Using Homing Modes


  • When homing to a limit switch, the limit switch must remain in the triggered state while the motor decelerates to zero and begins to reverse. A very low acceleration rate combined with a high approach velocity may overshoot the switch and cause it to become active. This action will cause a homing error fault.


  • When homing to a limit switch, the limit switch must remain in the triggered state while the motor decelerates to zero and begins to reverse. A very low acceleration rate combined with a high approach velocity may overshoot the switch and cause it to become active. This action will cause a homing error fault.


  • When homing to a limit switch, the limit switch must remain in the triggered state while the motor decelerates to zero and begins to reverse. A very low acceleration rate combined with a high approach velocity may overshoot the switch and cause it to become active. This action will cause a homing error fault.

Using Homing: Advanced

The various homing methods in the AKD offer several options for setting up your home reference.  When using any of the methods that use homing switches and limits, please refer to the Input/Output section for proper wiring techniques.

Related Parameters and Commands

HOME Parameters

PL.FB

CAP0.MODE, CAP1.MODE : Sets index capture method

Digital Inputs and Outputs

DIN Parameters

DOUT Parameters