Measurable Signal Decoupling with Dynamic Feedforward Compensation and Unknown-Input Observation for Systems with Direct Feedthrough**

Several feedforward decoupling and estimation problems are treated here in a unified setting, and their exact geometric solution is extended to the general case where the direct feedthrough matrices of all the systems involved are possibly non-zero. To this end, the concepts of selfboundedness and self-hiddenness are generalised and investigated within the general context of non-strictly proper systems. Then, for each problem considered, solvability conditions are provided as well as the explicit structure of the solving compensator or observer.