Research On Efficient Automated Micro Assembly Technology

Micro assembly technology is used for producing 3D micro structures, solving the problem of process compatibility, and distributed manufacture. The micro components are devied by their different manufacture process or function. Then they are manufactured and followed by an assembly process. This process likes macro manufacture rather than traditional micro manufacture process. It is one of the key technologies to realize millimeter or sub-millimeter robotic systems.After more than ten years research, the biggest problem remained of micro assembly is the unsatisfactory assembly efficiency. At microscopic level, the dominant adhesion forces between micro objects affect micro handling dramatically. The handing success rate and positioning accuracy of micro objects are influenced by them. However, the main component of adhesion forces, van der Waals force, electrostatic force and surface tension force are related to the ambient environmental relative humidity condition. In order to obtain an effective micro handling efficiency, we should understand how environmental parameters affect micro handling efficiency. Moreover, the speed of serial micro assembly is very slow comparing with that of parallel micro process. Hence we must reduce the time consuming of assembly a micro part.This dissertation investigated the environment influences on micro handling efficiency. By choosing suitable environmental parameters, we could obtain the best handling efficiency while the experimental configuration is not changed. Furthermore, In order to improve the handling speed and stability, a vision servo automated micro assembly system was developed. The main research subjects of this dissertation are detailed as follows:1. Micro objects are handled by an adhesive type micromanipulator (a gold coated tungsten tip) in atmosphere environment. And how the handling efficiency varies with the ambient environmental relative humidity level are investigated. The experimental results indicate that both the contact interface cracking process and adhering process during micro object handling operation are remarkably affected by the environmental humidity. The micro object release success rate increases with the environmental humidity, and the pickup success rate also shows a tendency of increase but followed by a rapid decrease. For our adhesive type manipulator, the best handling efficiency will be obtained when the environmental relative humidity is between 65% and 85%. It is possible to obtain a satisfactory handling efficiency by controlling the environmental humidity in a proper range.2. A piezoelectric driven micromanipulator is developed. It can be used to handle micro objects with shapes of sphere, cubic, cylinder and so on. The displacement of the micromanipulator is measured by a vision feed back system. By considering the elastic ratio of the end-effectors, the grasping force is controlled by applying an extra driven voltage after the end-effectors contact a micro object. The micromanipulator generates a displacement of about 200μm while a driven voltage of 70 V is applied. The displacement resolution is sub-micron. The grasping force resolution is about 200 nN.3. An environmental controllable automated micro assembly system is developed. The environmental control system can adjust the air pressure, temperature and relative humidity of the working chamber. The vision servo micro assembly system is full automated. It can focus and calibrate the microscope system, recognize micro objects and measure their positions, control the displacement and grasping force of the micromanipulator, and so on. The microscope calibration precision is sub-micron while the magnification ratio of the microscope is 18×. The system can assemble a micro object within 10 seconds automatically. The success rate of handling polymer spheres is about 93%.