Advanced Control Options

Cogging Compensation

Cogging is an effect caused by magnetic interaction between motor rotor and stator. It results in torque ripples over the motor revolution, which leads to uneven motion or generally unsatisfying performance of the motor at low velocities. This phenomena is of particular concern in economic motor models, but can be compensated on a software level. The feature is currently accessible for advanced developers through the SOMANET SDK.

Feedforward Torque Control and Dynamic Offset Torque

On top of the desired velocity input, the position and velocity controllers also accept a desired ‘offset torque’, which is a dynamically changeable torque value that will be added to the torque value generated by the velocity PI controller. This applies to the simple PID position controller, to the cascaded position controller and to the velocity controller. The offset torque can be updated at full EtherCAT communication frequency (1 kHz in most configurations) and is given in the unit of per thousands of rated torque.

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The feature can be used if the high level robot control contains a model or any other knowledge of feedforward control, e.g. acceleration feedforward or gravity compensation. As this value should be fed dynamically with continuously updated values, it is not accessible in OBLAC Drives, but through the EtherCAT parameter 0x2300.

Please check out further functionality of OBLAC Drives:

  • Learn how to make your drive part of a higher level robotic control structure:

Drive Control via EtherCAT

  • Get to know the different Control Modes and Controller Types that are available additionally to the ones that you have just been using:

Control Modes and Controller Types

  • Learn more about automatic and manual approaches for Controller Tuning:

Controller Tuning