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Aiming to online suppress the mechanical resonance existed generally in electromechanical servo system, this paper proposed an effective method based on extremum seeking control (ESC). Firstly, the theoretical analysis of 2-mass model with elastic load is carried out to obtain the mathematical expression and physical phenomenon of mechanical resonance. Then, a single variable ESC-based scheme is employed to identify the resonance frequency by introducing a band-pass filter with variable center frequency. Furthermore, based on the identified resonance frequency, the multivariable ESC is applied to design a parameter self-adjusting notch filter to suppress the resonance quickly online. In addition, an adaptive adjusting law of disturbance signal amplitude of ESC is designed to accelerate the convergence as well as eliminate the unexpected steady state oscillation existing in those parameters to be optimized. Finally, the effectiveness and superiority of this method are verified sufficiently by simulations.

To increase the suppression rate of surplus torque of load simulator, this paper proposes a high-performance model-based extended state observer(ESO) to estimate the total disturbance and compensate the system as the nominal model of actual system. First the third-order model-based ESO is designed for a class of second-order systems in which the model information is used in ESO structure to improve performance. And a parameter tuning method with better noise suppression ability and observation performance, instead of the classic pole-placement method, is used to obtain accurate disturbance observation, which can effectively enhance the surplus torque suppression ability of the load simulator. Furthermore, experiments on actual load simulator are conducted to verify the effectiveness and superiority of this method.