Vacuum Gripper Interface

Controlling the Vacuum Gripper

This is the main API for interacting with Baxter's vacuum grippers, and is instantiated by:

from baxter_interface import Gripper

right_gripper = Gripper('right')
left_gripper = Gripper('left')

Its main uses are:

Sending suck/release commands to the gripper
Querying the state/properties of the gripper
Reacting to grippers being plugged/unplugged
And controlling aspects of how the gripper acts (vacuum threshold, etc.)

Reading the Vacuum Gripper Sensor

The vacuum gripper sensor falls under the Analog IO category in baxter_interface. To read the vacuum sensor, choose either left_vacuum_sensor_analog, right_vacuum_sensor_analog as your component when initializing AnalogIO: Inside an init'd shell:

[baxter - http://p12345:11311] foo@bar:~/ros_ws$ python

>>> import rospy, baxter_interface
>>> rospy.init_node("vacuum_test")
>>> l_vacuum_sensor = baxter_interface.AnalogIO('left_vacuum_sensor_analog')

To query the sensor's state:

>>> l_vacuum_sensor.state()
11.0

Alternatively, it is possible to query the vacuum sensor from either of these ROS topics:

/robot/analog_io/<left\right>_vacuum_sensor_analog/state
/robot/analog_io/<left\right>_vacuum_sensor_analog/value_uint32

eg.

$ rostopic echo /robot/analog_io/left_vacuum_sensor_analog/state
---
timestamp: 
  secs: 1418760984
  nsecs: 575399546
value: 20.0
isInputOnly: True
---
timestamp: 
  secs: 1418760984
  nsecs: 585399929
value: 19.0
isInputOnly: True
---

These values being output via Python and ROS are analog values being read from the vacuum sensor. They can range from 0-255, and the breakdown is as follows:

Vacuum Sensor Readings
Value Range	Meaning
`0-46`	The vacuum gripper is likely not attached to an object
`47-175`	The vacuum is likely attached to an object (usually around `150` when grasping)
`176+`	There is likely a short between 5V and signal on the sensor