The Goals of Robust Control Techniques

Robust control is normally used to handle systems with uncertainties & disturbances and with high performances. The objective of robust control is to be able to design controllers that achieve a desired level of performance and also, be able to handle a collection of uncertainty structures specified by the designer. A typical approach is to try to maximise the tolerated uncertainty bounds.

The robust control techniques are based on a formal description of the control problem where the stability and performance objectives must be fulfilled for any plant, S, belonging to a family G. The family of plants may be described by parameter variations, as bounds in frequency response, etc.

Two problems are the core of robust control methodologies:

Analysis – establishing if a regulator, designed with any methodology, will withstand a known modelling error structure and size, in terms of:

• Robust stability (RS) – excluding the possibility of an unstable closed loop for the available modelling error estimation.
• Robust performance (RP) – asserting that the performance objectives will be fulfilled for any plant in the uncertain family.

Synthesis – determining a regulator that maximises tolerable modelling error for a given performance level, or alternatively, determining the maximum performance level for a given modelling error description.

You may also read:

• Control Modes in Automation Systems
• The Performance Limits for PID Controllers
• Hierarchical Control Strategies for a Process Plant
• Basic Steps to Consider in Designing a Control System
• 5 Control Techniques – Their Features & Applications
• Key Causes of Uncertainty in Control Systems