Passivity-based adaptive delay compensation for real-time hybrid tests

This article presents a novel passivity-based adaptive delay compensation scheme for cancelling actuator dynamics in real-time hybrid testing. This scheme uses the energy added to the system by actuation hardware, to quantify a variable delay, which is subsequently used for delay compensation. It offers the advantage of correcting for tracking errors and instability in hybrid tests and can be implemented without any information of the actuator's dynamics. Thus, it offers an advantage over most conventional actuator dynamics mitigation schemes which require an accurate model of the actuator prior to testing. Experimental results compare the performance of passivity-based adaptive delay compensation with that of a state-of-the-art adaptive delay compensation scheme based on position. It was found that passivity-based adaptive delay compensation continuously updates the delay estimate while the position-based scheme only updates the delay when the system crosses zero. The performance of both schemes was found to be similar for sinusoidal inputs, mitigating phase lags of up to 35.6 degrees at 10 Hz in the hybrid system tested. Passivity-based adaptive delay compensation requires no extra hardware as it can be run on the same hardware used to drive the actuator, enabling an affordable solution applicable to a wide range of hybrid tests.