Analysis And Suppression Of Mechanical Resonance For System With Backlash And Elastic Load

In AC servo system, transmission shaft and coupling are main transmissiondevice connecting drive side and load side. But transmission device has elasticityin real system. The mechanical resonance phenomenon is generated because ofimporting of elastic load. Mechanical resonance will influence the controlperformance and precision, even make system instability. It will bring thedamage to transmission device in severe case, like wear and breaking-shaft. Inthe actual system, transmission backlash is hard to avoid. The existence ofbacklash will aggravate the harm of mechanical resonance, and bring the othersevere damage like impact. But the traditional method of suppressing mechanicalresonance cannot suppress the resonance with backlash effectively. Therefore, tosolve the resonance with backlash has important practical significance.This paper analyzes the mechanical resonance phenomenon at control pointaiming at2-mass system with elastic load and backlash. The Bode diagram canbe produced by fast identification of resonance characteristic, and thischaracteristic can be used to carry out the passive method of suppression. Thepaper proposes an effective method to suppress mechanical resonance withbacklash, and this method also can realize the adjusting of shaft-torque at anycertain value.This paper firstly researches the mechanism of mechanical resonancewithout backlash, involving resonance model and the resonance characteristics ofcontinuous and discrete system. It’s the conclusion that resonance frequency ofcontinuous system is Anti-Resonance Frequency, and resonance frequency ofdiscrete system is Natural Torsional Frequency. Further involving the backlashnonlinear factor, the effect of backlash to resonance characteristic is analyzed;the negative influence of backlash to original resonance is confirmed. Backlashis equal to reduce the elastic coefficient. When backlash is larger, the resonancefrequency reduces and resonance amplitude increases.Because normal sweeping frequency method will bring potential hazard,then aiming at conventional passive method to suppression mechanical resonance,the fast obtainment of frequency characteristic based on pseudo random binarysequence and Chirp signals is analyzed and proposed. Simulation and experimentresults verify that the method can obtain the open-loop characteristic rapidly andaccurately, and then resonance characteristic is obtained.In the end, this paper researches a suppression method based on disturbanceobserver of shaft-torque, and analyze the effect of compensating parameter andsystem stability. The reason that this method can suppress the resonance with backlash is analyzed from mechanism, that the motor inertia is increase becauseof resonance-ratio control. This paper also achieves the adjusting of shaft-torqueat any certain value by shaft-torque observer. Simulation and experiment resultsverify the effectiveness.