Recursive least square algorithm-based acceleration harmonics identification for an electro-hydraulic shaking table

ABSTRACT Hydraulic shaking tables are important mechanical environmental simulators for such fields as aerospace, nuclear industry, automobile and civil engineering to measure the specimen’s reliability under vibration condition. Sinusoidal shaking tests are widely used in practical applications, but its acceleration response usually contains higher harmonics, due to the nonlinearities in the system. The harmonic distortion lowers the system control performance. A harmonic identification scheme is thus developed by utilizing a transversal filter based on recursive least square method to provide harmonic information for further harmonic cancellation. A harmonic generator generates the harmonic vector, and the parameter vector of the filter is updated by incrementing its old value by an amount equal to the product of the estimation error and the gain vector. The amplitude and phase of each harmonic including the fundamental response are then directly computed from the time-varying parameter vector. Each harmonic is also directly decomposed from the harmonic vector and the estimated parameter vector. Experimentations performed on an electro-hydraulic shaking table are carried out to validate its efficiency and accuracy.