Determination of the dynamic characteristics of a multi-point excitation system using electrodynamic shakers and control of their exciting force

Electrodynamic shakers can be used as vibration exciters for structure strength and fatigue tests. The Real-Time Waveform (RTW) control of the exciting force that is produced using multiple electrodynamic shakers can help simulate the working conditions of the Structure Under Test (SUT). In this study, a cantilever aluminum plate forced using two shakers is employed as an experimental structure to analyze the dynamic characteristics of the system. An equivalent model under forced vibration with two Degrees of Freedom (DOFs) is used to analyze the dynamic characteristics of the test system. The Transfer Function Matrix (TFM) of the system is also presented. The relationship between the TFM and dynamic characteristics of the system is described through model analysis. Modal testing and TFM measurements are conducted to validate the dynamic model. The shakers at the control points are coupled because of the flexibility of the SUT. A stable Feedforward Decoupling Compensator (FDC) based on the Structure Invariance Principle (SIP) is then employed for RTWcontrol. Additionally, an adaptive algorithm based on the Recursive Least squares Method (RLSM) is used to improve the controller's robustness. The force controller including its sensitivities and calculation errors for the TFM is discussed. The experiment on RTW control shows that the adaptive controller performs better than the conventional controller around the system's and subsystems' natural frequencies, but the limitation of the adaptive controller is such that the reference signals should be linearly independent.