A Practical Approach to the Phase and Amplitude Error Estimation for Pseudodynamic (PSD) Testing

In PSD testing, measured signals from the experiment are used in command generation on the fly, thus making this method prone to error propagation. One way to assess the accuracy of the real-time (or fast) PSD test results is to assess the accuracy of the tracking of command displacements imposed by the hydraulic actuators. This paper introduces indicators that can be used to uncouple and quantify actuator lag/lead (i.e., phase errors) and undershoot/overshoot (i.e., amplitude errors) errors that occur while imposing the command displacements dynamically in real-time. These closed-form indicators provide monitors that are not experiment-specific and are simple to use. They use uncomplicated mathematical functions, which makes them suitable candidates for online implementation with the potential for incorporation into the control law to improve the actuator control. The procedure and the associated theoretical background are explained for each step and then the properties of the indicators are examined through several predefined command and measured signals with known characteristics. In addition, the performance of the indicators is evaluated by comparing the results with those revealed by the previous indicators.