Multirate control for computation saving

Jiagen Ding, Federico Marcassa, Shang-Chen Wu, Masayoshi Tomizuka

Abstract: This brief paper considers multirate control from the viewpoint of computation saving. When a digital control system involves multiple actuators with different bandwidths, feedback loops may be closed at different rates: a fast rate for a high bandwidth loop and a slow rate for a low bandwidth loop. Multirate implementation of a single loop controller is possible by decomposing the control algorithm to fast and slow rate blocks. Such implementations of digital controllers will reduce the total amount of computation. The slow rate part of the controller may be further decomposed and interlaced so that computation saving by multirate control may be distributed uniformly at all fast rate sampling instances. The performance of multirate control implementations for computation saving are applied to the dual actuator track following problem of computer hard disk drives (HDDs). The experimental results show that the multirate implementations achieve regulation performance of the position error signal at about the same level as the single-rate implementation while realizing significant computation saving.