Gain Scheduling¶

Depending on the application, the “optimal” tuning for the cascaded PID controller may differ between different operating points. If there is only one tuning available, it has to be a compromise not using the full potential of the hardware.

This feature allows the user to apply controller gains which will change dynamically regarding the current speed. This technique can be used within the cascaded position controller to compensate for nonlinear effects, especially stiction / friction in the mechanics.

../../../../../_images/gain_schedule_structure2.png

For velocities (in rpm) below a user-defined value, a set of PID values determined best for slow motion is used. Likewise, for velocities (in rpm) above a user-defined value, a set of PID values determined best for fast motion is used.

The PID values between these values are interpolated linearly.

../../../../../_images/linear_interpolation2.png

Note

Please note that this feature is at the moment experimental. It is currently accessible only directly via EtherCAT through the parameter 0x2013:1 … 0x2013:18. The gain scheduling feature is only available in Cascaded PID mode which is selected in object 0x2002.

0x2002 Position control strategy

Selects the control structure used for position control.

0x2013 Gain Scheduling

Parameters needed for Gain Scheduling