MA Chicheng1,2,LUO Yajun2,ZHANG Xinong2,CHENG Xiangmeng1,SHAO Mingyu1
JOURNAL OF VIBRATION AND SHOCK. 2018, 37(23): 197-203.
Manipulators are usually designed to carry or move goods,and their mass may move or change its magnitudes in transmission,so manipulators belong to time-varying mass structures.Here,manipulators were simplified as flexible beam structures with time-varying mass to investigate their dynamic characteristics and vibration active control.The dynamic control equation of a flexible beam with time-varying mass was derived with the mode superposition method and the material constitutive equation.The transient responses of the system were computed,and its dynamic characteristics and vibration laws were analyzed.Then,vibration active control of this structure was studied.For the mass time-varying feature of the system,a fuzzy PID controller was designed to study vibration active control for this system.Vibration suppressions were simulated under different operational conditions,and the results were compared with those using a classical PID controller.Considering shortages of FFT in non-stationary signal analysis,the time-frequency analysis technique was utilized to decompose the collected vibration signals and obtain their energy distribution information in time-frequency domain.Hence,the control effects of the two controllers were compared more accurately.The numerical simulations showed that due to the system’s variable mass feature,the system doesn’t have natural frequencies,but has a resonance frequency band; both two control strategies of PID and fuzzy PID can realize the system’s vibration control,but the fuzzy PID controller has a stronger robustness and higher self-adaptability,so improving its parameters can effectively enhance the vibration control effect.