Skip to content

Object Parts

Jump to bottom
GuiHome edited this page Apr 24, 2016 · 1 revision

Object Parts

A grip can be applied in many different object parts. For the purpose of defining a suitable set of canonical grips we have to consider a discretization of objects in parts. Then a canonical grip will be defined according to the relative hand-object posture and to the object parts that experience the dominant oppositional forces.

Whereas for a small object we may only consider its center part, objects whose dimensions exceed certain thresholds may be discretized into graspable parts. Let us consider a threshold D (e.g. 5 cm), relative to the robot perception and control precision, below which we consider a single part. Also let us consider the object dimensions along its main axes of inertia (dx, dy, dz) sorted by increasing size (see definition of Reference Frames for objects). We consider the following discretization (the numbering of the parts is assigned as the indices a C++ 3D array):

1 part

        (dx <= dy < D) and (dy <= dz < D) and (dz < D)

The object has a single part :

  • center

2 parts

        (dx <= dy < D) and (dy < D) and (D <= dz < 2D)

The Z dimension is divided in two identical parts, thus the object has two parts :

  • Z+ or top end
  • Z- or bottom end

3 parts

        (dx <= dy < D) and (dy < D) and (2D <= dz )

The Z dimension is divided in three identical parts (if dz < 3D), or extremes with dimension D and the center with the remaining (if dz >= 3D). The object has three parts :

  • Z+ or top end
  • Z0 or center middle part
  • Z- or bottom end

4 parts

        (dx < D) and (D <= dy <= dz < 2D) and (D <= dz < 2D)

The Y and Z dimensions are divided in two identical parts, thus the object has four parts:

  • (Z+,Y+) or top-left end
  • (Z+,Y-) or top-right end
  • (Z-,Y+) or bottom-left end
  • (Z-,Y-) or bottom-right end

6 parts

        (dx < D) and (D <= dy < 2D) and (2D <= dz )

The Y dimension is divided into two identical parts and the Z dimension is divided in three identical parts (if dz < 3D), or extremes with dimension D and the center with the remaining (if dz >= 3D). The object has six parts :

  • (Z+,Y+) or top-left end
  • (Z+,Y-) or top-right end
  • (Z0,Y+) or centermiddle-left part
  • (Z0,Y-) or centermiddle-right part
  • (Z-,Y+) or bottom-left end
  • (Z-,Y-) or bottom-right end

8 parts

        (D <= dx <= dy < 2D) and (D <= dy <= dz < 2D)

Both X, Y and Z dimensions are divided into two identical parts. The object has eight parts :

  • (Z+,Y+,X-) or front-top-left corner
  • (Z+,Y-,X-) or front-top-right corner
  • (Z-,Y+,X-) or front-bottom-left corner
  • (Z-,Y-,X-) or front-bottom-right corner
  • (Z+,Y+,X+) or back-top-left corner
  • (Z+,Y-,X+) or back-top-right corner
  • (Z-,Y+,X+) or back-bottom-left corner
  • (Z-,Y-,X+) or back-bottom-right corner

9 parts

        (dx < D) and (2D <= dy <= dz)

The Y and Z dimensions are divided in three identical parts (if dy,dz < 3D), or extremes with dimension D and the center with the remaining (if dy,dz >= 3D). The object has nine parts :

  • (Z+,Y+) or top-left end
  • (Z+,Y0) or top-centermiddle end
  • (Z+,Y-) or top-right end
  • (Z0,Y+) or centermiddle-left part
  • (Z0,Y0) or center part
  • (Z0,Y-) or centermiddle-right part
  • (Z-,Y+) or bottom-left end
  • (Z-,Y0) or bottom-centermiddle end
  • (Z-,Y-) or bottom-right end

12 parts

        (D <= dx <= dy < 2D) and (2D <= dz)

The X and Y dimensions are divided into two identical parts and the Z dimension is divided in three identical parts (if dz < 3D), or extremes with dimension D and the center with the remaining (if dz >= 3D). The object has twelve parts :

  • (Z+,Y+,X-) or front-top-left corner
  • (Z+,Y-,X-) or front-top-right corner
  • (Z0,Y+,X-) or front-centermiddle-left part
  • (Z0,Y-,X-) or front-centermiddle-right part
  • (Z-,Y+,X-) or front-bottom-left corner
  • (Z-,Y-,X-) or front-bottom-right corner
  • (Z+,Y+,X+) or back-top-left corner
  • (Z+,Y-,X+) or back-top-right corner
  • (Z0,Y+,X+) or back-centermiddle-left part
  • (Z0,Y-,X+) or back-centermiddle-right part
  • (Z-,Y+,X+) or back-bottom-left corner
  • (Z-,Y-,X+) or back-bottom-right corner

18 parts

        (D <= dx < 2D) and (2D <= dy <= dz)

The X dimension is divided into two identical parts and the Y and Z dimensions are divided in three identical parts (if dy,dz < 3D), or extremes with dimension D and the center with the remaining (if dy,dz >= 3D). The object has eighteen parts :

  • (Z+,Y+,X-) or front-top-left corner
  • (Z+,Y0,X-) or front-top-centermiddle part
  • (Z+,Y-,X-) or front-top-right corner
  • (Z0,Y+,X-) or front-centermiddle-left part
  • (Z0,Y0,X-) or front-center part
  • (Z0,Y-,X-) or front-centermiddle-right part
  • (Z-,Y+,X-) or front-bottom-left corner
  • (Z-,Y0,X-) or front-bottom-centermiddle part
  • (Z-,Y-,X-) or front-bottom-left corner
  • (Z+,Y+,X+) or back-top-left corner
  • (Z+,Y0,X+) or back-top-centermiddle part
  • (Z+,Y-,X+) or back-top-right corner
  • (Z0,Y+,X+) or back-centermiddle-left part
  • (Z0,Y0,X+) or back-center part
  • (Z0,Y-,X+) or back-centermiddle-right part
  • (Z-,Y+,X+) or back-bottom-left corner
  • (Z-,Y0,X+) or back-bottom-centermiddle part
  • (Z-,Y-,X+) or back-bottom-right corner

26 parts

        (2D <= dx <= dy <= dz)

The X, Y and Z dimensions are divided in three identical parts (if dx,dy,dz < 3D), or extremes with dimension D and the center with the remaining (if dx,dy,dz >= 3D). The object has twenty-six parts :

  • (Z+,Y+,X-) or front-top-left corner
  • (Z+,Y0,X-) or front-top-centermiddle part
  • (Z+,Y-,X-) or front-top-right corner
  • (Z0,Y+,X-) or front-centermiddle-left part
  • (Z0,Y0,X-) or front-center part
  • (Z0,Y-,X-) or front-centermiddle-right part
  • (Z-,Y+,X-) or front-bottom-left corner
  • (Z-,Y0,X-) or front-bottom-centermiddle part
  • (Z-,Y-,X-) or front-bottom-right corner
  • (Z+,Y+,X0) or top-left part
  • (Z+,Y0,X0) or top-center part
  • (Z+,Y-,X0) or top-right part
  • (Z0,Y+,X0) or left-center part
  • (Z0,Y-,X0) or right-center part
  • (Z-,Y+,X0) or bottom-left part
  • (Z-,Y0,X0) or bottom-center part
  • (Z-,Y-,X0) or bottom-right part
  • (Z+,Y+,X+) or back-top-left corner
  • (Z+,Y0,X+) or back-top-centermiddle part
  • (Z+,Y-,X+) or back-top-right corner
  • (Z0,Y+,X+) or back-centermiddle-left part
  • (Z0,Y0,X+) or back-center part
  • (Z0,Y-,X+) or back-centermiddle-right part
  • (Z-,Y+,X+) or back-bottom-left corner
  • (Z-,Y0,X+) or back-bottom-centermiddle part
  • (Z-,Y-,X+) or back-bottom-right corner

Clone this wiki locally