| In the fight against hijacking,criminals often keep hostages in closed rooms.In this case,it is critical to learn about the layout of the room,the location of the terrorists and the hostages in real time.Therefore,with the support of Criminal investigation department,this research group developed a drilling device utilizing torsional vibration drilling in low noise.It can drill a small hole on the building wall at a relatively low noise without being detected by criminals.In this paper,theoretical analysis,structural improvement and experimental study of the device are carried out through simulation and testing.1.During the drilling of the building wall,self-excited vibration will appear,which will produce broken noise.The drilling process is simplified as a spring-mass-band self-excited vibration system.The velocity conditions of self-excited vibration,and the influence of eccentric excitation and electromagnetic excitation on self-excited vibration is studied by means of simulation and experiment.The feasibility of suppression the self-excited vibration during drilling process through torsional vibration is verified.2.Due to the problem of unstable self-synchronization of vibrating motor during drilling,the excitation mode is changed to electromagnetic excitation,and the excitation module is improved.The design and calculation of the plate spring in the excitation module are emphasized,so that the drill bit can produce the effect of vibration drilling.3.The structure of the plate spring is optimized according to the fracture of the plate spring.The natural frequency of the torsion direction of the actual drilling device is tested by resonance method.The noise source identification experiment of two kinds of drilling devices is carried out,it is found that the drilling noise of the improved device is obviously reduced.According to the noise problem of stepping motor,the structure improvement scheme of drilling device is put forward. |
PDF Full Text Request