A closed loop parametrical identification procedure forcontinuous-time constant linear systems is introduced. Thisapproach which exhibits good robustness properties with respect toa large variety of additive perturbations is based on thefollowing mathematical tools:(1) module theory;(2) differential algebra;(3) operational calculus.Several concrete case-studies with computer simulationsdemonstrate the efficiency of our on-line identification scheme.

We are extending to linear recurrent codes, i.e., totime-varying convolutional codes, most of the classic structuralproperties of fixed convolutional codes. We are also proposing anew connection between fixed convolutional codes and linear blockcodes. These results are obtained thanks to a module-theoreticframework which has been previously developed for linear control.

For constant linear systems we are introducing integralreconstructors and generalized proportional-integralcontrollers, which permit to bypass the derivative term in theclassic PID controllers and more generally the usual asymptoticobservers. Our approach, which is mainly of algebraic flavour, isbased on the module-theoretic framework for linear systems and onoperational calculus in Mikusiński's setting. Several examplesare discussed.