Mechanism design and grasping control of compliant mechanical gripper for gangue sorting robot

CHEN Kaiyun; ZHAO Wenya; ZHANG Chenyang; GONG Fankang

doi:10.13225/j.cnki.jccs.2024.1487

Abstract：Mechanical gripper is the key to realize coal gangue separation by intelligent gangue separation robot.In the process of intelligent separation of coal and gangue,there are some problems such as large difference of gangue particle size,wet and slippery surface,large impact force of dynamic grabbing and mechanical fatigue of long-term continuous op-eration,which lead to low comprehensive separation rate of coal and gangue.In view of the above problems,this paper designs a new type of compliant mechanical gripper by combining passive compliant mechanism with active compliant control.Firstly,the sorting process of gangue sorting robot is analyzed.Based on the kinematic characteristics and physic-al characteristics of gangue,a mechanical gripper scheme with passive compliant mechanism is proposed.The flexible transmission element is used to replace the traditional rigid structure,the rubber buffer gasket is set on the contact surface of the claw,and the multi-stage buffer system is constructed by integrating the universal ball stud,the torsion spring and the rubber-coated bearing.By optimizing the structural parameters of the mechanical gripper,the stiffness of the mechan-ical gripper system is further improved,its service life is prolonged,and its grasping stability is enhanced.Secondly,based on the multi-source real-time feedback data such as force,displacement and velocity,the admittance-impedance hybrid controller is integrated to realize the adaptive compliance control in the process of gangue grabbing.Finally,the position and particle size parameters of gangue are obtained by building a visual recognition and positioning system,and a mul-tivariate gangue sorting test is designed:50 groups of samples of 3 kinds of materials and 3 kinds of particle size grades are selected to carry out 50 groups of comparative tests to test the grasping performance of the compliant mechanical grip-per and verify the effectiveness of the compliant grasping control algorithm.The test shows that the compliant mechanical gripper designed in this paper can adapt to a larger range of gangue particle size,reduce the dynamic grasping impact force,reduce the mechanical loss,improve the reliability of gangue grasping,and the comprehensive separation rate of gangue is 94％.The experiment proves that the design of the mechanical mechanism of the compliant mechanical gripper is reasonable,the stiffness improvement method of the mechanical gripper based on parameter optimization is feasible,and the compliant grasping control algorithm based on admittance-impedance hybrid control is effective.The research res-ults will provide technical support for improving the comprehensive sorting rate of the gangue sorting robot and prolong-ing the service life of the mechanical gripper.