SYSTEM-IDENTIFICATION FOR A PHOTODIODE-BASED MONITORING-SYSTEM

A laser-based system to monitor fiber load level in carding has been developed based on silicon PIN-photodiodes. It is desirable to establish more accurately the dynamic characteristics of the sensing system and in particular the interaction between the sensors, the sensing circuitry and the data acquisition equipment. An experimental set up that allows to evaluate the dynamics of the entire monitoring system is here presented, along with experimental results. This set up allows to determine an experimental transfer function and frequency response curves for the sensing system. In addition to this, results from the system identification procedure can be extended to develop a linearized transfer function of the sensor. Additional input-output tests can tl;en be used to determine the parameters of such linear model from an analysis of the impulse response; a linear model of the sensor can then be used on the feedback path of a controller design based on these sensors. This technique can be extended to other processes on which controller design is under consideration and dynamic characteristics of the corresponding sensors are unknown.