Semi-automatic compensation of the propagation delay in fault-tolerant systems

In control systems the jitter is a major problem since in a time-varying system the theoretical results for analysis and design of time-invariant systems cannot be used directly. Reducing the jitter increases the stability of the closed control-loop thus leading to enhanced reliability. This paper presents a general model that can be applied to bus topologies as well as to star topologies. Based on this model an algorithm is presented that allows to improve the precision of a set of distributed clocks by measuring the propagation delay of the communication lines and compensating the jitter introduced by the propagation delay. Some fault-tolerant architectures already provide means for coping with propagation delays but require manually entering the values in a configuration-tool. With this algorithm the system supports this errorprone task by providing validity checks for the entered values or measuring these values automatically thus rendering this maintenance step obsolete.