Research On Adaptive Suppression Technology Of Mechanical Resonance In AC Servo System

The AC servo system is gradually used in automation equipment,and its control accuracy is also improved.However,the flexible connection between the motor and the load in some servo systems can cause mechanical resonance,thereby reducing the control accuracy of the system and even causing damage to the equipment.Aiming at the problem of mechanical resonance of servo system,the online identification and real-time suppression technology of mechanical resonance of AC servo system are studied.And a corresponding experimental platform to verify the identification and suppression technology is built.For the two-mass system with flexible connection,the mechanism of mechanical resonance is analyzed,and the two-mass system model is established.The influence of the stiffness coefficient of the transmission system and inertia ratio on the resonance is studied.And the different characteristics of the resonance in the open-loop and closed-loop speed systems of the flexible load servo system are analyzed.An online resonance suppression method based on adaptive notch is proposed,which realizes the online identification of mechanical resonance characteristics and suppression.Aiming at the problem of large calculation of Fourier transform,a mechanical resonance feature identification scheme based on FPGA is designed.By implementing the fast Fourier transform in FPGA,the real-time is improved.By analyzing the spectral characteristics of the quadrature-axis current,the on-line identification of resonance characteristics is realized.The real-time performance and accuracy of the FPGA-based fast Fourier transform are verified through experiments,and a simulation model is established to verify the feasibility of the resonance identification scheme.Aiming at the problem that the frequency and amplitude of mechanical resonance will change with the operating environment such as the inertia ratio,a scheme for dynamic suppression of mechanical resonance based on an adaptive notch is proposed.The parameters of the notch filter are dynamically adjusted according to the results of the resonance identification.The effects of the notch center frequency,notch width and notch depth parameters on the notch effect are analyzed with the notch filter model.A digital notch filter is designed using a bilinear transform discretization method.Within a certain quantization error range,the digital notch filter bit width of the coefficients and the output data are determined.According to the identified resonance frequency and amplitude,the parameter design method and parameter update strategy of digital notch filter are studied.The effect of dynamic suppression of the mechanical resonance of the notch filter is verified by simulation.An experimental platform for mechanical resonance suppression is set up to verify the proposed online resonance suppression method based on adaptive notch.In the experiment,different inertia ratios are changed,and the mechanical resonance characteristics can be quickly identified within 1s.After notch filtering the steady state fluctuation of the motor speed is within 1%.The experimental reuslts show that this method can effectively identify the resonance characteristics and suppression resonance.