Limitations on Control System Performance

Many different factors such as process dynamics, disturbances, process uncertainties and actuator saturation have to be considered when designing a control system. It is important to be aware of factors that limits the achievable performance. In this paper we attempt to formulate some problems that capture the essence of the design problem in a simple way. Results of this type are a complement to computational tools for control system design. They make it possible to quickly make a preliminary assessment before doing massive design computations. They are also useful in process design to determine potential difficulties and to give hints for redesign.