XML format description

The following describes the format used to wrap the geometric information describing the problem single XML file. Meshes, kinematic models and task domain/problem are given in separate files. The xml file contains information about the initial geometric state, and invariants such as grasps, surfaces supporting stable placements, stable objects poses, movability, initial attachments.

General structure

The file is overall structured as follows:

 1 <problem>
 2    <objects>
 3       object1
 4       object2
 5       ...
 6    </objects>
 7 
 8    <robots>
 9       robot1
10       robot2
11       ...
12    </robots>
13 </problem>

Grasps, SSSP, and SOP are relative to objects, therefore object description follows the following template:

 1 <obj>
 2    <name>obj1_name</name>
 3    <geom>filename.obj</geom>
 4    <pose>...</pose>
 5    <moveable>true/false</moveable>
 6    <grasps>
 7       <gf>...</gf> and/or
 8       <gc>...</gc> 
 9    </grasps>
10    <sssp>...</sssp>
11    <sop>...</sop>
12    <attachments>...</attachments>
13 </obj>

Parameters

All numerical values are expressed in standard units: meters (distances) and radians (angles).

Single values

Example:

<torso>0.15</tordo>

The initial value for the torso joint is 15cm.

Vectors

Vectors are used for 3D vectors (e.g., rotation axis), but also to specify robot configurations (e.g., arm configurations).

Example:

<left_arm>0.5 0.0 0.0 -0.16 0.0 -0.11 0.0</left_arm>

Transformation matrices

Transformation matrices are used to represent the initial poses of objects, or the initial pose of a robot's base. A 3x4 transformation matrix is represented by a 12-uplet (row-wise):

≃ <tag>a0 a1 a2 a3 b0 b1 b2 b3 c0 c1 c2 c3</tag>

Grasps

Grasps can be specified in two ways:

• discrete set of grasps: a list of grasp frames (<gf>...</gf>)
• continuous set of grasps: a template grasp and a rotation axis (<gc>...</gc>)

Xml attributes are used to specify grasp types (up to the TMP planner to use it or not):

<gf type="top_grasp">0.0 0.0 1.0 -0.0015 0.0 -1.0 0.0 0.027 1.0 0.0 0.0 -0.051</gf>
<gf type="side_grasp">0.0 0.0 1.0 -0.005 0.0 1.0 0.0 0.005 -1.0 0.0 0.0 0.123</gf>

in the case of continuous grasps, a template frame and a rotation axis are given:

<gc type="top_grasp">
   <template>0.0 0.0 1.0 -0.0015 0.0 -1.0 0.0 0.027 1.0 0.0 0.0 -0.051</template>
   <axis>0.0 0.0 1.0</axis>
</gc>

SSSP

The surfaces supporting stable placements are specified by 6 values (xmin, xmax, ymin, ymax, zmin, zmax) representing a rectangular region in the reference frame of the object. In the example below, the SSSP of disc2 and disc3 boils down to a single point because it is assumed that the discs should be perfectly aligned when stacked on top of each other. The SSSP of table is a rectangular area matching the position and dimensions of the surface of the table.

Remark: A list of points defining a polygon may be used later for non trivial shapes.

SOP

The stable object poses are defined similarly to continuous grasps: a template rotation and a rotation axis (both expressed in the world frame of reference.

Remark: SSSP and SOP tags are simple xml nodes in the example, but we could aim at something more general and define them as lists. In this way, we could approximate non-square SSSP by several rectangles (or polygons), and similarly allow for several SOP for objects (upright, upside-down, lying on the side). (to be discussed)

Initial object attachments

Although this is not allowed in this problem, if disc2 was moved, disc1 would also move, just as a tray with objects on it. We can represent this as a list tied to the "parent" object.

Example

Example for problem1 (disc3 and pegs omitted for clarity).

 1 <problem>
 2    <objects>
 3 
 4       <obj>
 5          <name>disc1</name>
 6          <geom>cylinder1.obj</geom>
 7          <pose>1.0 0.0 0.0 0.7 0.0 1.0 0.0 0.2 0.0 0.0 1.0 0.028)</pose>
 8          <moveable>true</moveable>
 9          <grasps>
10             <!-- discrete set of grasps for that object -->
11             <gf>0.0 0.0 1.0 -0.0015 0.0 -1.0 0.0 0.027 1.0 0.0 0.0 -0.051</gf>
12             <gf>0.0 0.0 1.0 -0.0015 0.0 1.0 0.0 0.0 -1.0 0.0 0.0 0.051</gf>
13             .....
14          </grasps>
15          <sssp>false</sssp> <!-- no sssp for disc1 -->
16          <sop>
17             <template>1.0 0.0 0.0 0.0 1.0 0.0 0.0 0.0 1.0</template> <!-- all z-rotations of the -->
18             <axis>0.0 0.0 1.0</axis>                                 <!-- "natural" position     -->
19          </sop>
20          <attachments>false</attachments> <!-- nothing attached to disc1 -->
21       </obj>
22 
23       <obj>
24          <name>disc2</name>
25          <geom>cylinder2.obj</geom>
26          <pose>1.0 0.0 0.0 0.7 0.0 1.0 0.0 0.2 0.0 0.0 1.0 -0.038)</pose>
27          <moveable>true</moveable>
28          <grasps>
29             <!-- continuous set of grasps for that object -->
30             <gc>
31                <template>0.0 0.0 1.0 -0.0015 0.0 -1.0 0.0 0.027 1.0 0.0 0.0 -0.051</template>
32                <axis>0.0 0.0 1.0</axis>
33             </gc>
34          </grasps>
35          <sssp> <!-- sssp = single point -->
36             <xmin>0.0<xmin><xmax>0.0<xmax>
37             <ymin>0.0<ymin><ymax>0.0<ymax>
38             <zmin>0.065<zmin><zmax>0.065<zmax>
39          </sssp>
40          <sop>
41             <template>1.0 0.0 0.0 0.0 1.0 0.0 0.0 0.0 1.0</template> <!-- all z-rotations of the -->
42             <axis>0.0 0.0 1.0</axis>                                 <!-- "natural" position     -->
43          </sop>
44          <attachments> <!-- disc1 attached to disc2 -->
45             <name>disc1</name>
46          </attachments>
47       </obj>
48 
49       ...
50 
51       <obj>
52          <name>table</name>
53          <geom>table_narrow.obj</geom>
54          <pose>1.0 0.0 0.0 0.9 0.0 1.0 0.0 -0.4 0.0 0.0 1.0 -0.87)</pose>
55          <moveable>false</moveable>
56          <sssp> <!-- sssp = horizontal rectangular region -->
57             <xmin>-0.68<xmin><xmax>0.0<xmax>
58             <ymin>0.0<ymin><ymax>0.83<ymax>
59             <zmin>0.78<zmin><zmax>0.78<zmax>
60          </sssp>
61          <sop>false</sop> <!-- does not really apply to the table (moveable=false) -->
62          <attachments> <!-- does not apply, but for the sake of example -->
63             <name>peg1</name>
64             <name>peg2</name>
65             <name>peg3</name>
66             <name>disc3</name>
67          </attachments>
68      </obj>
69 
70       ...
71 
72    </objects>
73 
74    <robots>
75       <robot>
76          <name>pr2</name>
77          <urdf>models/pr2.urdf</urdf> <!-- or some other format -->
78          <basepose>1.0 0.0 0.0 0.0 0.0 1.0 0.0 0.0 0.0 0.0 1.0 0.0)</basepose>
79          <movebase>false</movebase> <!-- in problems 1 and 2, the base should not move -->
80          <torso>0.1</torso>
81          <left_arm>0.5 0.0 0.0 -0.16 0.0 -0.11 0.0</left_arm>
82          <right_arm>-0.5 0.0 0.0 -0.16 0.0 -0.11 0.0</right_arm>
83       </robot>
84    </robots>
85 
86 </problem>