| Harmonic reducer is one of widely used reducers in small and medium load industrial robots.Due to it's sophisticate structure,complex assembly process and high requirement of assembly precision,it's difficult to achieve automated assembly.Therefore,most of the assembly processes are completed manually,and the operation process is backward and the cost is too high.Based on the actual assembly requirements of a robotic company's harmonic reducer,this thesis designs the assembly system for the key assembly processes such as press-fit,screw-lock and large-diameter O-ring assembly for harmonic reducer assembly.In-depth study of the key issues involved in determining the position of the threaded hole,the O-ring feeding and inspection the result of O-ring assembly.This thesis mainly completed the following work:(1)Research on assembly process of harmonic reducer and mechanical design of assembly systemThe structure of a certain type of harmonic reducer is analyzed.The involved assembly process is researched,and the key assembly problems are extracted.Based on the automated assembly theory,the robot type selection and overall layout of the assembly system are carried out.The core equipment in the assembly unit,such as end effector and press machine,are selected and designed.(2)Overall design of the control systemThe control requirements and main tasks of the assembly system are analyzed,and the control architecture of the robot control cabinet-PLC-Iolink is designed to satisfy the control requirements.With PLC as the main control station and robot control controller as the slave station,the hardware selection,control system configuration,Control program of assembly system PLC terminal and robot terminal are completed.(3)Research on thread hole search method based on laser displacement sensorAiming at the problem that the position of the workpiece and the position of the threaded hole are uncertain during the screw locking process in the industrial field,a method of determining workpiece's pose and searching center of circular hole by laser displacement sensor is proposed.It can be applied to various workpieces without designing special fixture.In addition,a search strategy is designed for the common annular group hole workpiece.Finally,experimental verification shows the effective of method.(4)Research on screwing processFor the specific technical problems of screwing,based on the requirements of locking and disassembling a variety of different size screws,the selection of the feeding and screwing equipment is completed,and redesigned the screwing equipment to fit the end effector finger grip;For the screwing equirements,the Screw function module(SFM)and the feeding device control program are written;For the screw-disassembly requirements,the force sensor-assisted disassembly process is designed;the test meets the requirements of the screw-locking process involved in the assembly of the harmonic reducer..(5)Research on Key technology of large-diameter ratio O-ring assembly on the end face of partsThe totally assembly process of the O-ring consists of three parts: feeding,assembly and assembly result detection.Due to its large geometric size and strong flexibility,the large wire diameter ratio O-ring cannot be fed and assembled in the traditional way.For the large diameter-diameter ratio O-ring,a versatile feeding scheme is designed,and the dynamic analysis of the O-ring unsuperimposed state in the feeding process of the O-ring is achieved;Static analysis of the O-ring superposition state during the feeding process,the prototype of the feeding device was designed based on analysis results.Aiming at the problem of O-ring assembly on end face,a low-cost,high-reliability assembly scheme realized by fixture is designed.For the detection effect of the O-ring assembly result,the assembly result detection and fault handling are performed by means of the machine vision.Finally,the test proved that the prototype of the feeding machine and the assembly result can satisfy the demand. |
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