Off-line displacement error correction method for servo-hydraulic testers

Purpose: This paper presents an approach towards improving the test rig performance in reproduction of random excitation to which a prototype hydraulic damper is subjected. The method is intended to be implemented as a software solution without modifications either in hardware or the settings of the servo-hydraulic tester. These are the conditions of fatigue tests when a specific signal sequence (block) is repeated until failure of the sample.Design/methodology/approach: Experimental validation of the proposed correction method was conducted using a servo-hydraulic test rig and a transfer function inverse model which was identified based on the operational data.Findings: The proposed method, both in the frequency and time domain, improves the tracking of the test signal and allows an accuracy of more than 95% to be gained using the best fit measure in the case of reproduction of coloured noise signals.Research limitations/implications: It is possible to consider more advanced model-based methods for performing off-line error correction, e.g. state-space models.Practical implications: The proposed method was validated and implemented in the LabVIEW software to automatically perform the correction of the test signal before the test. The method was validated for the test rig with and without the tested object.Originality/value: The paper proposes an off-line control strategy that improves the reproduction of the load signal in case of repeatable test sequences achieving more than 99% agreement between the applied and measured load.