sr_grasp

Tools for running grasps (moveit_msgs/Grasp) on the Shadow Hand. Handles pre and main grasps, interpolating the motion over a configuarable amount, using the position controllers. Can optionally stop the grasp on contact with the finger tactile sensors.

Also contains:

• grasp_planner - A simple grasp planner for the shadow hand.
• isr_grasp.utils - A python library.

grasp

Quick Start

Start either your real Shadow Hand (with position controllers) or a simulated one:

roslaunch sr_hand gazebo_hand.launch

Then start the grasp node:

rosrun sr_grasp grasp

Now start the quick grasp tool, which provides a quick command line way to run a full hand grasp:

rosrun sr_grasp quick_grasp
[INFO] [WallTime: 1420469735.467177] [2088.184000] Loaded grasps from file: /home/hand/indigo_ws/src/shadow_robot/sr_grasp/resource/grasps.yaml
[INFO] [WallTime: 1420469735.467525] [2088.184000] Looking for hand...
[WARN] [WallTime: 1420469738.040228] [2089.002000] No tactile topic found. This is normal for a simulated hand
[INFO] [WallTime: 1420469738.040807] [2089.002000] Found

Grasps:
0 - Power Grasp Vertical
1 - Pinch Horizontal
2 - Basic full grab
Current grasp: Power Grasp Vertical
Number select grasp, z zero hand, g grasp, p pre-grasp, q quit
: 

Working with grasp files.

Sets of grasps can be stored in YAML files containing a top level array of moveit_msgs/Grasp objects serialised to YAML the same way rostopic does. Although most of the fields are optional you must have an id and will need at least one pre-grasp posture and grasp posture. sr_grasp contains some example files in the resource directory.

quick grasp reads it’s ~grasps_file param to get the file name of grasps to use, defaulting to grasps.yaml in the sr_grasp package. So to use another file:

rosrun sr_grasp quick_grasp _grasps_file:=foo.yaml

You can use the n command to create a new grasp using the current hands pose as the grasp pose. The s command will re-write the file with the current list of grasps.

Actionlib

The main interface to the node is via actionlib, it exposes the sr_robot_msgs/Grasp action on the grasp/ topic. See the quick_grasp script for a python example of using this interface.

grasp_planner

Node implementing the sr_robot_msgs/PlanGrasp action to generate grasps. Currently returns a single, hardcoded grasp.

sr_grasp.utils

Python lib. Exports a mk_grasp function for quick generation of moveit_msgs/Grasp messages.

from sr_grasp.utils import mk_grasp

grasp = mk_grasp({
    'LFJ3': 1.4, 'RFJ3': 1.4, 'MFJ3': 1.4, 'FFJ3': 1.4,
    'LFJ0': 2.0, 'RFJ0': 2.0, 'MFJ0': 2.0, 'FFJ0': 2.0,
    'THJ1': 0.4, 'THJ2': 0.36, 'THJ3': 0.2, 'THJ4': 1.23, 'THJ5': 0.06, 
})

Converting sr_hand XML grasps

sr_hand has some grasps classes, interpolater and gui that work with an XML file found in sr_hand/scripts/sr_hand/grasps.xml. You can convert them to new style moveit messages in YAML using:

rosrun sr_grasp convert_xml.py sr_hand/scripts/sr_hand/grasps.xml > converted.yaml

Then load them up to play with:

rosrun sr_grasp quick_grasp _grasps_file:=converted.yaml

Changelog for package sr_grasp

1.4.0 (2015-04-07)

• First release