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5-12 Operation MN1904
In summary , the following rules can be used as a guide:
H KPROP: Increasing KPROP will speed upthe response and r educe theeffect of disturbances
and load variations. The side effect of increasing KPROP is that it also increases the
overshoot, and if set too high it will cause the system to become unstable. The aim is to set
the Proportional gain as high as possible without getting overshoot, instability or hunting on
an encoder edge when stationary (the motor will buzz).
H KVEL: This ga inhas adampingeffect,and canbe increasedto reduce any overshoot. IfKVEL
becomes too large it will amplify any noise on the velocity measurement and introduce
oscillations.
H KINT: This gain has a de-stabilizing effect, but a small amount can be used to reduce any
steady state errors. B y default, KINTMODE is set so that the KINT term is either ignored, or
is only applied during periods of constant velocity.
H KINTLIMIT: The integration limit det ermines t he maximum value of the effect of integral action.
This is specified as a percentage of the full scale demand.
H KDERIV: This gain has a damping effect. The Derivative action has the same effect as the
velocity feedback if the velocity feedback and feedforward terms are equal.
H KVELFF: This is a feed forward term and a s such h as a different effect on the servo system
than the previous gains. KVELFF is outside the closed loop and therefo re does not have an
effect on system stability. This gain allows a f aster response to demand speed changes with
lower following errors, for example you would increase KVELFF to reduce the following error
during the slew section of a trapezoidal move. The trapezoidal test move can be used to
fine-tune this gain. This term is especially useful with velocity controlled servos
H KACCEL: This term is designed to reduce velocity overshoots on high acceleration m oves.
Due to the quantization of the positional data and the speed of the servo loop, for the
acceleration feed forward term to a ffect the servo loop the acceleration of the axis must
exceed 1,000,000 encoder counts per second.