Research On Handling Technology And Micro-stress Assembly For Miniature Parts

With the development of micro technology, micro system has been used more and more widely. Therefore, the assembly of miniature part, the characteristic size of which is within 0.01-10mm, becomes increasingly common. Recently, plenty of mature precision assembly systems have been applied in assembly of micro products, most of which is designed for simple structure and less components. But for the products with complex structure and more components, precision assembly systems are still in experimental research stage. According to the project assembly requirement, a precision assembly system based on machine vision and force feedback was developed. It adopts modular design and mainly consists of manipulator module, vision measuring module, the feeding module, worktable and the control system with human-computer interface. The modules cooperate with each other to complete the assembly task. As the essential component of manipulator module, combined gripper integrated with a vacuum gripper and a clamping gripper can manipulate various kinds of parts. Considering the requirement of measurement and assembly, a practical assembly strategy was developed. An experiment is carried out to demonstrate that control strategy and software architecture used in the assembly system meet the performance requirement of product.Miniature parts have the characteristics of lightness, smallness, thinness, softness in practical application, even efficient specially-designed equipments can also do damage to the fragile parts and consequently lower the output. In order to solve difficult assembly task of miniature part, a concept for micro-stress assembly was proposed, that is, stresses will not be introduced in the process of picking up and releasing parts. However, it is difficult to achieve accurate force control due to unknown environment. A method based on passive compliant control and active force control was used to control the force introduced during the process of assembly. The passive compliant structures can rely on its own coordination to control the manipulating force and improve the flexibility of assembly system. In order to achieve active force control, an impedance control based on force method was used, which can control the motion of gripper according to the change of contact force between the gripper and the parts.