Motion: Diagnostics & Tuning

UniLogic enables you to perform single-parameter tuning and run Diagnostics using a motion scope trace that enables you to view the performance of your system.

Once your system hardware is set up and connected, you can import Ready-made Motion code, and use the HMI Tuning screens the code provides to tune your system.

Tuning Overview

Optimizing servo performance will improve settling time, steady state error, and the overall system responsiveness. In general, proper configuration (system rigidity and inertia ratios) should result in acceptable servo performance that satisfies the application requirements.

You should tune the Servo under the conditions of the working environment.
If there is no need, do not increase gains.

Servo Loops

In the closed-loop servo system, every command is based on the previous command's feedback error.

3. Position Loop, third loop	2. Velocity Loop, second loop	1. Current Loop, internal loop
This loop is active only at “Position control” commands The position feedback usually comes from the motor position sensor (encoder) Its gains are configurable, and they are application dependent	This loop is active at “Velocity control” and “Position control” commands The velocity feedback is provided by the motor’s position sensor values, divided by time Its gains are configurable, and they are application dependent	The fastest loop: always active The current feedback is provided by embedded current measurement sensors It is automatically predefined for every motor It is not affected by the system’s mechanics

The next graph shows the progression of tuning to minimize Over/undershoot and minimize vibration, to reach a steady state within tolerance limits.

The Ready-made motion code provided by Unitronics includes HMI screens with options for simple and manual tuning.

To access them, select the Tuning tab, and then select Simple or Manual.

Simple Single-parameter Tuning

Use the Slider to adjust the gain, or enter values in the fields:

Increase “Servo Gain” parameter until it starts fluctuating. (multiply by 2)
Decrease “Servo Gain” (divide the last increased value by 2) until it stops fluctuating

Manual Tuning

The Inertia Detection test performs 3 clockwise revolutions, and the 3 counter-clockwise
Please note that Limit switches are ignored during this test, and that velocity and acceleration are not changeable

Select Manual Tuning; note the Advanced checkbox is not checked by default. Touch the Advanced checkbox to reveal additional parameters.
Perform inertia detection (Fn009), note that values are in kg.cm²

Divide that value by motor inertia, as listed in the motor's technical specifications, and enter the resulting value in % into Servo gain (Pn106).

If you cannot perform the preceding calculation, set the “Servo gain” to 500

Tune the velocity loop ( Pn102,103).

Increasing Pn102 increase the axis responsiveness.
Increasing Pn103 decreases the axis responsiveness.

Tune the position loop (pn104).
If position loop is too low increase torque filter value (Pn105).

Motion Diagnostics

On the Solution Explorer, under Motion Diagnostics, there are the Diagnostic Trace and the Parameters selections.

When you enter online mode, use the Diagnostics trace to see the real-time performance of your system.

Note that you can:

Mouse-over the toolbar on the left of the screen to select View options.
Click on the scope screen and move your cursor back and forth to see different points in the session.
Zoom in and out via your mouse wheel.

Select Parameters on the Solution Explorer to view actual values.

Upload Axis Parameters to PC: When you configure an axis, the values you enter in the Axis Struct are written to the axis at power-up. When you enter values from the HMI, the axis functions according to these values, but the values you have entered will be overwritten at power-up.

To overwrite the values in the axis struct, use the ribbon option shown below,Upload Axis Parameters to PC.