Qualitative transitions in object reorienting behaviour. 1. The effects of varying friction

We investigate the topology of the space of possible pushing behaviour for 2.5D objects of arbitrary outline. We do this by studying the push-stability diagram (PSD) derived by Brost (1985, 1988), which is a generalisation of a result of Mason´s. In this paper, we show how to derive a PSD for arbitrarily curved objects, and investigate how changes in the friction between pushing and pushed objects affect the topology of the PSD for any given object. This leads us to include an extra axis on the PSD, resulting in an extended PSD. This representation makes explicit the topological changes in the operation space of possible reorientation behaviours for any given 2.5D object, leading to the possibility of using it in the design of feeders