Design And Analysis Of Motion And Dynamic Characteristics Of Lower Hook Mechanism Of Knot Netting Machine

Net weaving machine is a high quality and high efficiency machining equipment for fishing net weaving,the lower hook mechanism is an important mechanism for the knotting of the netting machine.The lower hook mechanism of the existing knot netting machine is driven by the mechanical cam mechanism to realize the movement of the lower hook end,therefore,there are some problems such as complex transmission structure,high impact and noise between components,low accuracy and lack of flexibility due to mechanical wear.With the development of servo control technology and the application of electronic cam in the mechanical field,using electronic cam mechanism instead of mechanical cam mechanism in the lower hook mechanism driven by servo control system can make up the above defects.In this paper,the related work is done for the lower hook mechanism of the knot netting machine.Firstly,by referring to and analyzing the research status of netting machine at home and abroad and the relevant literature of servo control technology application,combined with the application and research of electronic cam technology in the field of machinery,a compound mechanism of lower hook electronic cam of knot netting machine is proposed.According to the working principle of the lower hook mechanism,the lower hook electronic cam composite mechanism is designed.The complex trajectory motion of the lower hook is realized by driving swing guide rod mechanism and crank rocker mechanism through servo motor.Because of the large span of the lower hook plate,the inertia force generated at high speed makes it easy to bend and deform,resulting in the knot motion precision is reduced,therefore,the structure of the anti-bending mechanism of lower hook plate is designed.According to the evolution principle of member motion pair,the three dimensional model of lower hook mechanism is established.Secondly,In order to verify the motion performance of the lower hook mechanism,the kinematic analysis of the lower hook mechanism is done.Based on the design of the lower hook mechanism,according to the process requirements and the running sequence of the lower hook,the running track of the lower hook was planned by using quintic polynomial interpolation,and the motion curve of the hook was obtained.Based on the structure of the lower hook mechanism,the mathematical model of inverse kinematics parameters of the mechanism was established,the kinematics analysis of the lower hook electronic cam mechanism and the anti-bending mechanism of lower hook plate was carried out respectively,the periodic motion curves of the electronic cam and the kinematic curves of each component are obtained.the results show that the motion of each component meets the requirements of mechanical kinematics.Then,in order to improve the kinematic performance of the lower hook mechanism,the related motion parameters were optimized.In order to reduce the impact and vibration of the servo motor,particle swarm optimization algorithm was used to optimize the motion parameters of the lower hook.The optimization results show that the maximum angular acceleration amplitude of the servo motor is significantly reduced,which verifies the effectiveness of the optimization method.In order to verify the correctness of kinematic analysis of lower hook mechanism,a virtual prototype of lower hook electronic cam mechanism was established,the optimized motion parameters are used,and the kinematics simulation of the lower hook mechanism was carried out by ADAMS simulation software,the motion curve law obtained by simulation is basically consistent with the theoretical calculation results,which proves the rationality and correctness of the kinematic analysis results of the lower hook mechanism.Finally,aiming at the impact,vibration,fatigue failure and deformation of the lower hook mechanism at high speed,the mechanical characteristics of the lower hook mechanism were analyzed.According to the kinematic analysis results of the lower hook mechanism,the inertia force and inertia moment at the particle point of each component are calculated,through the force analysis of each component,the force and moment balance equations are listed,the reaction force and driving moment of each component were obtained by matrix method in Matlab.The dynamic analysis results show that the force of each component of the lower hook mechanism is reasonable,and the driving torque output by the servo motor is within the allowable range of mechanical dynamics.The statics analysis of the key parts of the lower hook mechanism is carried out,and the reliability of the hook mechanism is verified.