USING FILTERING TO IMPROVE PERFORMANCE
Michel Ruel · 2003
When a disturbance occurs, the controller needs time to reduce the error to zero. If the loop is tuned properly, the response time will be reduced. If the loop is tuned too aggressively, cycling and overshoot can occur. In all cases, the response time will limit the ability of the controller to remove too fast disturbances. If the disturbances are too fast, the controller will be useless. Such fast disturbances are called “noise”. This noise will go through the controller and will appear also on the controller output. To reduce the noise, a filter is used; if the filter time constant is selected properly, only the disturbances will be applied to the controller, the noise being removed or reduced by the filter.