Alignment of microparts using force controlled pushing

Abstract

In today’s and tomorrow’s development of new products, precise positioning and assembly of small parts is of fundamental importance. Often, such tasks require the alignment of objects with features such as edges or surface structures. In this work, we explore force controlled pushing of microparts on a planar substrate with a micromanipulator. The pushing tool is an AFM cantilever equipped with a piezoresistive force sensor. Its corse position, as well as the global manipulation strategy, is specified by the human operator. First, we present force measurements during typical pushing operations. Using these measurements, a sensor guided controller is implemented to maneuver the robot locally by detecting events such as hitting an obstacle or changing contact conditions. Using force/position macros, we are able to push the objects precisely to a desired location without exceeding a certain limit force. Experimental results demonstrate the ability of aligning microparts on a horizontal plane with micrometer accuracy relative to each other. For automated assembly applications there are two possibilities: the local controller presented in this paper can be integrated either in a passive global positioning system if the geometry of the problem is well defined. Conversely, a feedback system, e.g., with quantitative computer vision, can be used to cover a larger spectrum of object sizes and shapes