Guaranteed performance for sampled-data systems with generalized higher-order hold

The paper investigates the digital control of continuous-time processes, where continuous stochastic disturbances act directly on the continuous part of the system, which is typical for motion control of marine vehicles. Instead of zero-order hold, which is normally used, the digital computer and the continuous process are connected by hold elements of arbitrary order. On basis of the parametric transfer function concept, the paper presents a rigorous description of this class of sampled-data system. This description allows to find optimal controllers by using polynomial and numerical methods. For the practically relevant problem, where the disturbances are only known to belong to a certain class, a minimax solution is presented, which guarantees a certain performance for any admissible disturbances. The effect of higher-order hold is briefly discussed on basis of an examples.