2.4.2.6 Velocity Auto-tuning
Note
This feature is available since OBLAC Drives 19.0
The general purpose of the velocity control loop auto-tuning is to design controller gains based on user
specifications and the identified model of the set-up. The procedure calculates gains for the PI velocity
controller.
2.4.2.6.1 Prerequisites
Before conducting velocity auto-tuning check the following:
1. The System Identification has been executed successfully.
2. The obtained model corresponds to the current configuration of the system. Otherwise the identification
procedure should be repeated.
3. If there is a gearbox in between, the gear ratio should be specified.
4. Make sure that the sensors are mounted properly and calibrated.
2.4.2.6.2 Limitations
The procedure uses a linear mathematical model of the system. If there are strong nonlinearities there will
be a difference between the actual and the requested performance.
Max bandwidth of 100 Hz is specified because of 1 kHz EtherCAT frequency.
2.4.2.6.3 How to use
1. The controller gains are updated automatically every time the sliders are dragged and released.
2. There are 2 sliders that allow users to specify the demanded performance of the control loop:
Damping ratio is a parameter of an oscillatory system that reduces oscillations. In the velocity control
loop, this parameter controls overshoot and rise time. The damping ratio can be divided into 2 regions:
Underdamped < 1: overshoot is allowed, results in a sharper response.
Example of a velocity control loop step response with a damping ratio of 0.4:
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