Measurement of force sensory information in ultraprecision assembly tasks

Automation of assembly tasks has previously been tackled by many researchers. They mostly focused on the geometric constraints related to a considered task, e.g., relative configuration change between the peg and the hole. Such an approach, however, has a limited validity in the sense that, unlike ultraprecision assembly studied in the present study, it assumes that the dimensional tolerance is fairly large so that it allows change to the relative configuration of the two mating parts in an obvious fashion. The paper investigates what makes highly precise assembly tasks very difficult from the viewpoint of automation of the tasks. Tolerance considered in the present study is in the range of 3-9 μm. We focus on force sensory information involved in a high-precision peg-in-a-hole task of a polygon mirror unit because a position-based analysis under such a narrow dimensional tolerance seems inappropriate. A variety of insertion experiments are conducted by skilled and unskilled subjects for comparison purposes in which associated force signals are measured and analyzed