A variable structure parallel observer system for periodic measurement output

This paper proposes the variable structure parallel observer system (VSPOS), a multirate estimation technique for discrete time systems, to compensate for output measurements that are only periodically available. The VSPOS is an extension of the original parallel observer system. The VSPOS is based upon a stable discrete-time sliding mode observer with an attractive boundary layer driving a Luenberger observer and running in parallel. The resulting observer system provides stable state estimates for each control step despite incomplete measurements. The VSPOS is applied to a second order resonance model with nonlinear uncertainties/disturbances as proof of concept, and a stability proof and error bounds are provided.