Tuning mechanically linked axes

Tuning Mechanically Linked Axes

Method 1: Tune individually, then as system

  1. Tune the cylinders individually while not connected to the mechanical system. Make sure to tune very conservatively, because if you tune it too aggressively (high gains), the system can have problems when connected to the mechanical system

  2. Connect the cylinders, then send simultaneous moves as you continue to tune the system.

Method 2: Tuning as a linked system

  1. Setting the Proportional gain very low on each axis, and do very short, simultaneous moves.

  2. As you increase the Proportional gain, you should see the control improving. As the control improves, make the moves longer.
    Make similar adjustments to the gains on all the cylinders to keep them tracking roughly the same position.

General Tips:

  • You can use the Send All button in the Command Tool to send command simultaneously.

  • Once you have obtained some initial control, you can use the Tuning Wizard with Existing Plot and choose gains with the Gain Calculator. If you have identical cylinders and valves on each axis, which is usually the case, you can do this on just one axis, and then anytime you change gains, make sure to write the same gains to the other axis before doing the next move

It might be a good idea to put the axes that are linked mechanically into a halt group. That way in case you make a mistake commanding one cylinder you might be able to keep from braking something.

What is considered a ‘very low’ Proportional gain? I found myself with two systems I was having to tune while mechanically linked in the past 6 months and faced difficulties. One a two axis and the other with six axes total, three to move a bed up and down and three to move the bed left and right.

What is considered a low gain depends on how much your position units can vary. For a system that can moves in inches, a Proportional gain of 1 would be considered low. An equivalent gain for the same system called in mm would be 0.04.

The key thing to remember is to initially make short moves so you don’t have to worry about tracking over the length of the moves.