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Look, no hands - Machines could take on the fiddliest assembly work

点击量:   时间:2017-04-25 06:02:04

By Justin Mullins San Francisco MINIATURE robots will use electric fields to manipulate components in the future, replacing human fingers on the assembly line. Researchers at the University of California are developing microassembly lines capable of putting together the tiny electronic components necessary for the next generations of disc drives, flat screen displays and microsensors. Conventional robotic manipulation is almost impossible with components that are smaller than a millimetre. Large robotic arms cannot position very small components accurately. Humans have to do the job using tweezers and a microscope. Also, with very small components, forces such as electrostatic attraction and surface tension from moisture come into play. “With large robots, the problem is how to pick things up. On the small scale, it’s how to let them go,” says Ken Goldberg, the engineer at Berkeley who leads the project. Goldberg and his colleagues Karl Böhringer and Michael Cohn have come up with a novel way of overcoming these unwanted sticky forces. They place submillimetre silicon components on rapidly vibrating surfaces, which makes them dance around like droplets on a hotplate, so they don’t stick. The researchers then place the vibrating components in an electric field between the parallel plates of a capacitor. By drilling a pattern of holes in one of the capacitor plates, the researchers can create a similar pattern in the electric field. The silicon components simply drop into each hole in the field and become trapped. Once one component has fallen into a hole no other components can follow. While acknowledging that the work is in its early stages, Goldberg says the approach has two huge advantages. First, a large number of components can be positioned at the same time—a concept known as parallel assembly. Manipulating a component with tweezers is painfully slow. Secondly, the system requires no feedback mechanisms to monitor and adjust the position and orientation of the components as they move. On modern robotic assembly lines, the sensors that do this work greatly increase the complexity of the system. “Our goal is sensorless control,” says Goldberg. The researchers started by assembling small arrays of tiny silicon slivers. Larger arrays of hundreds of components should be possible with two years. Parallel assembly will be invaluable for making laptop screens, says Goldberg. Each group of four liquid crystal pixels is controlled by a much smaller transistor that sits at the corner where they meet. The scale is similar to a person standing at the point where four football pitches meet, says Goldberg, making it impossible to place the transistors accurately. In parallel assembly the transistors would be made in large numbers on wafers of silicon, cut up and then assembled into an array using electric fields to position them. The flat screen would then be pressed down onto this array. When the vibrations stopped, the electrostatic forces would make the transistors stick to the screen like raisins in pastry. Charles Leader, a production engineer at Hewlett-Packard in Santa Clara,