P - Proportional gain - stiffness and response
Closes the loop, react quickly, according to the sign of the error
D - Derivative term - provides damping. - if D is too large - causes vibrations
Structural resonances and distributed components (things are not perfect
in nature) contribute to high frequency dynamics, which is amplified by too large D gain
I - Integral gain - Accuracy
- Causes overshoots
- Can cause instability
- Larger I implies faster convergence
As long as there is any (even a slightest) error due to friction, the integrator keeps building up
the control signal until it becomes large enough to overcome friction, and eventually makes the motor
rotate to reduce the error.
Low KI → slow growing of signal (response delay)
High KI → overshoot and instability
source from courseware of university of moratuwa
原文：http://www.cnblogs.com/zhanghankui/p/7866888.html