Reconstructibility and Controllability Analysis in Bandwidth Limited Industrial Networked Control Systems

This paper studies structural properties of bandwidth limited Industrial Networked Control Systems in which the number of simultaneous network accesses is limited. Conventional control theory assumes that the measured output is available as a vector at each time instant and the input vector can be applied simultaneously to the actuator. However, when the system is bandwidth limited, it is not possible to instantly read all of the sensors and nor it is possible to apply the whole input (control) vector to the actuator. As a result, a system which is controllable (reconstructible) for its own, may not preserve this property when the communication medium is bandwidth limited. The communication medium therefore changes the overall system structural properties. This is of utmost importance since existing control and estimation algorithms are based on the assumptions that the whole output vector (input vector) is read from sensors (applied to actuators) instantly. We assume that communication medium is shared among both sensors and actuators. It is shown that controllability and reconstructibility analysis could not be performed independently (as inherently assumed or ignored by previous works in this field). For the special case of equidistant sequences with separate read/write cycles, we prove that controllability and reconstructibility analysis’s can be done independently if a specific procedure is followed. Examples are included to clarify the results.

Keywords:

Networked control and estimation , Communication sequence , Controllability , Reconstructibility