Signal Filtering for Control – Why and How

Signal filtering is performed to remove undesirable aspect of a signal, often higher frequency components termed noise. For control purposes, filtering may be needed for effective derivative action and to avoid excessive manipulated variable movement, which can come from proportional and derivative contributions. However, excessive filtering can have a detrimental effect on loop performance leading to sluggish performance or worse, instability. This presentation considers the key reasons to filter a signal, the impact of filtering on key loop metrics, and the types of filters to consider. Illustrative examples are provided to support the recommendations.