SAJ 8000m Series, Руководство пользователя

Страница: 112 / 153

8000m Series
- 111 -
longest value, and the differential time to zero. Only use proportional control to let
the system start operating, and then adjust the PID setting to monitor the deviation
between feedback and setting(static error). If the static error keeps in the direction
of PID setting adjustment(i.e. As increasing the PID setting, and the feedback is
always less than the setting after the system reaching a stable state), then it is
needed to increase the proportional gain, or it is needed to decrease the gain.
Repeat this procedure until the static error is fairly small( it is hard to get rid off
static error).
Integral Control (I): With a deviation appears between PID feedback and setting,
PID controller will give an output which is accumulating continuously. If the
deviation exists, the output of adjustment will keep on increasing, until the
deviation disappears. Integral control can eliminate static errors effectively. With
the integral control getting too strong, repeating overshoot will appear, resulting in
unstable state of system and finally oscillation. The feature of oscillation under
strong integral control is the PID feedback will swing around the PID setting, and
the amplitude will keep on increasing until oscillating happen. For adjustment of
the integral time, it is commonly modified from long to short, step by step, while
monitoring the effect of adjustment, until it meets the requirement of speed to
become stable.
Differential Regulation (D): When the deviation between PID feedback and setting
is varying, PID controller will give an output which is proportional to the varying
rate of deviation. The output will be relative to varying rate and direction of the
deviation only, not the deviation’s direction and value. The effect of differential
regulation is to regulate the system by the varying trend of feedback signal. Thus it
will control the variation of feedback signal. Differential regulation should be used
with extreme caution, because it could easily lead to the amplification of system
interference, especially the interference in high frequency.