A Method for Verifying Measurements and Models of Linear and Nonlinear Systems

Abstract

A method has been developed to help verify system models and measurements and identify system nonlinearities. This method involves measuring the response of physical systems with a swept sine measurement device, such as the HP3562(3) A Control Systems Analyzer (CSA)1, and simulating system models with a dynamic system simulation tool, such as SIMULINK, using swept sine input. The input-output time sequences obtained from the simulations are analyzed in a similar fashion as done by the CSA to enable more accurate comparisons. A parallelism between swept sine measurements and describing functions is exploited to allow this method to be used in identifying nonlinear systems. Using the measured and simulated frequency response functions as a guide the designer can iteratively improve the model of the system and verify the correctness of the measurements.