A method for the identification of hydraulic damper characteristics from steady velocity inputs

The research presented in this paper investigates the possibility of precise experimental identification of steady damper characteristics. The paper considers velocity sensitive and nominally symmetric hydraulic dampers. The proposed identification methodology is based on a piecewise constant velocity excitation. One goal of the paper is to analyze the transient nature of the damper response in the context of finite permissible piston displacements and first order transient effects due to elastic elements in the damper structure. The proposed methodology is formalized in a framework suitable for experimental design, allowing the detailed study of steady state damper performance. The second goal of the paper is to demonstrate the practical application of the proposed methodology. It is applied to the case of a safety critical hydraulic damper used for stability augmentation in production helicopters. The research work presented shows that this methodology can be used for identification in a finite but relatively wide range of piston velocities. The case study demonstrates a successful example of damper property identification where the resulting characteristics prove useful as a tool for model validation. Finally, the identification results are related to the results of a more traditional test with harmonic piston excitation.