Sampling time selection and its effect on direct digital and adaptive control algorithm implementation

The influence of sampling time on the performance of several digital control algorithms is examined through the use of simulations. Good control can be achieved at coarse sampling rates by using a `true digital´ design, and proportional-integral-plus is found to be a particularly simple, general purpose, digital control algorithm that works well with coarse sampling. Finally, the load disturbance rejection properties of coarse sampling controllers are investigated, and it is suggested that there is a `worst case´ during the sampling cycle time at which load disturbances can occur. It is therefore recommended that the controller should be designed for this condition, thereby ensuring acceptable performance for all other cases