Regulator gains
Speed loop gains are the most critical adjust because they greatly depend on the mechanical load characteristics
(inertias, frictions, coupling stiffness, resonances,...).
- Proportional speed gain (KPv): defines the proportional gain of the controller which acts on the speed error.
The higher this parameter value, the faster the speed loop response.
- Integral speed gain (KIv): defines the integral gain of the controller which acts on the speed error. The higher
this parameter value, the better the axis stiffness.
- Integrator low frequency limit (KIvf in Hz): defines the low frequency value from where the controller
integrator term is saturated. This parameter is used for reducing the motor heating in applications with large dry
frictions due to the mechanical load.
- Damping gain (KCv): defines the proportional gain of the controller which acts only on the speed feedback.
This parameter allows to reduce the speed loop overshoot in response to a step like set point change .
- Derivative speed gain (KDv): defines the derivative gain of the controller which acts on the speed error.
- Derivator high frequency limit (KDvf in Hz): defines the high frequency value from which the controller
derivative term is saturated.
- Gain scaling factor (KJv): defines a multiplying factor for all speed regulator gains. This parameter is scaling
the speed regulator gains in order to avoid any saturation when large values are required. This parameter allows
also to adjust the servo loop stability in case of load inertia changes.
The Current command filter is a 3rd order, low pass type, with 3 adjustable cut-off frequencies. Each cut-off
frequency value can be freely adjusted according to the application for the filtering of high frequency noise or the
filtering of mechanical resonances.
The Speed measurement filter is a 1st order, low pass type, with 3 selectable time constant values. The higher
the time constant value, the lower the speed measurement noise, but also the lower the speed loop gains
because of the increased speed measurement delay. The Speed measurement filter time constant is selected
according to the motor position sensor resolution and the acceptable noise level in the speed measurement.
Position loop gains influence mainly the servo motor behaviour during the displacements (following error,
position overshoot, audible noise, ...).
- Proportional position gain(KPp): defines the proportional gain of the controller which acts on the position
error. The higher this parameter value, the better the axis stiffness and the lower the following error.
- Feedforward speed 1 gain(KFp): defines the feedforward speed amplitude corresponding to the speed input
command. This term allows to reduce the following error during the motor displacement. Its value is set to the
max (65536) after the autotuning procedure if a following error as small as possible is required.
- Feedforward speed 2 gain(KBv): defines the feedforward speed amplitude corresponding to the viscous
frictions. This term allows to reduce the viscous friction effect during the motor displacement. The gain value is
equal to the damping gain value + the viscous friction compensation term. After the autotuning procedure, the
feedforward speed 2 gain is set equal to the damping gain value if a following error as small as possible is
required. The viscous friction compensation term can be calculated by measuring the current⁄speed ratio at
various motor speed values.
- Feedforward acceleration gain(KAv): defines the feedforward acceleration amplitude corresponding to the
acceleration input command. This term allows to reduce the following error during the motor acceleration and
deceleration phases. Its value is calculated by the amplifier during the auto-tuning procedure if a following error as
small as possible is required.
When the autotuning procedure is executed, the motor + mechanical load specifications are identified and the
appropriate gain values are calculated according to the user selected requirements (controller type, filter type,
bandwidth value, ...). All gain values can then be modified manually by the user if required.
