A subband coding approach to control under limited data rates and message losses

For the design of networked control systems, we employ a subband coding technique to efficiently use the available data rate. Such coding schemes have widely been used in the area of signal processing for data compression in communication and storage. Compared to conventional subband coding methods, the proposed approach is more suitable from the control perspective in that frequency characteristics of a controller is directly used. In particular, the proposed scheme has three features. First, on the coder side, it uses a controller consisting of a filter bank whose outputs can be viewed as subband signals of the control input. Second, on the decoder side is another filter bank for reconstruction of those subband signals. This decoder is capable of taking account of random message losses that occur during the communication over a channel and is designed via an H∞ type method. Third, for the quantizers in the coder, an optimal bit allocation scheme is developed.