Gripper Cuff Control Example

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The Gripper Cuff Control example demonstrates basic cuff/gripper interaction on the robot. In this example, connects cuff buttons to gripper open/close commands: 'Circle' Button will open gripper, 'Dash' Button will close gripper, Cuff 'Squeeze' will turn on Nav lights.


This program demonstrates the usage of gripper, cuff, lights interface to control the close and open actions of the gripper and navigation light. The main() function creates an instance of the GripperConnect class which connects the gripper buttons to various callback functions. If you would like to follow along with the actual source code for the example on GitHub, it can be found through this link for gripper cuff control example.


$ rosrun intera_examples -h


Important Arguments:

-g or --gripper : The gripper limb to control.

-n or --no-lights : Specify the argument will not trigger lights on cuff while grasping.

-v or --verbose : Specify the verbose will print the debug statements from rospy, default value is rospy.INFO

usage: [-h] [-g {['right']}] [-n] [-v]

SDK Gripper Button Control Example

    Connects cuff buttons to gripper open/close commands:
        'Circle' Button    - open gripper
        'Dash' Button      - close gripper
        Cuff 'Squeeze'     - turn on Nav lights

    Run this example in the background or in another terminal
    to be able to easily control the grippers by hand while
    using the robot. Can be run in parallel with other code.

optional arguments:
  -h, --help            show this help message and exit
  -g {['right']}, --gripper {['right']}
                        gripper limb to control (default: both)
  -n, --no-lights       do not trigger lights on cuff grasp
  -v, --verbose         print debug statements

Code Walkthrough

Now, let's break down the code.

30 import argparse
31 import sys
33 import rospy
35 from intera_interface import (
36     Gripper,
37     Lights,
38     Cuff,
39     RobotParams,
40 )

This imports the intera interface for accessing the Cuff, Lights and the Gripper class.

43 class GripperConnect(object):
44     """
45     Connects wrist button presses to gripper open/close commands.
46     Uses the Navigator callback feature to make callbacks to connected
47     action functions when the button values change.
48     """
50     def __init__(self, arm, lights=True):
51         """
52         @type arm: str
53         @param arm: arm of gripper to control
54         @type lights: bool
55         @param lights: if lights should activate on cuff grasp
56         """
57         self._arm = arm
58         # inputs
59         self._cuff = Cuff(limb=arm)
60         # connect callback fns to signals
61         self._lights = None
62         if lights:
63             self._lights = Lights()
64             self._cuff.register_callback(self._light_action,
65                                          '{0}_cuff'.format(arm))

Instances of the cuff and the lights are created.

67         try:
68             self._gripper = Gripper(arm)
69             if not (self._gripper.is_calibrated() or
70                     self._gripper.calibrate() == True):
71                 rospy.logerr("({0}_gripper) calibration failed.".format(
73                 raise
74             self._cuff.register_callback(self._close_action,
75                                          '{0}_button_upper'.format(arm))
76             self._cuff.register_callback(self._open_action,
77                                          '{0}_button_lower'.format(arm))
78             rospy.loginfo("{0} Cuff Control initialized...".format(
80         except:
81             self._gripper = None
82             msg = ("{0} Gripper is not connected to the robot."
83                    " Running cuff-light connection only.").format(arm.capitalize())
84             rospy.logwarn(msg)

If the gripper attached, create the instance of the gripper then verify if the gripper was already in a calibrated state, the cuff actions will be registered afterwards. Failed to calibrate the gripper will raise error. If the gripper is not attached, warning message will appear.

87     def _open_action(self, value):
88         if value and self._gripper.is_ready():
89             rospy.logdebug("gripper open triggered")
91             if self._lights:
92                 self._set_lights('red', False)
93                 self._set_lights('green', True)

The method opens the gripper and set cuff light when button sends a True value.

 95     def _close_action(self, value):
 96         if value and self._gripper.is_ready():
 97             rospy.logdebug("gripper close triggered")
 98             self._gripper.close()
 99             if self._lights:
100                 self._set_lights('green', False)
101                 self._set_lights('red', True)

The method closes the gripper and set cuff light when button sends a True value.

103     def _light_action(self, value):
104         if value:
105             rospy.logdebug("cuff grasp triggered")
106         else:
107             rospy.logdebug("cuff release triggered")
108         if self._lights:
109             self._set_lights('red', False)
110             self._set_lights('green', False)
111             self._set_lights('blue', value)

This method assigns the boolean value that was signalled to the light interface.

113     def _set_lights(self, color, value):
114         self._lights.set_light_state('head_{0}_light'.format(color), on=bool(value))
115         self._lights.set_light_state('{0}_hand_{1}_light'.format(self._arm, color),
116                                                                  on=bool(value))

Set light color according to the provided params.

118 def main():
119     """SDK Gripper Button Control Example
120     Connects cuff buttons to gripper open/close commands:
121         'Circle' Button    - open gripper
122         'Dash' Button      - close gripper
123         Cuff 'Squeeze'     - turn on Nav lights
124     Run this example in the background or in another terminal
125     to be able to easily control the grippers by hand while
126     using the robot. Can be run in parallel with other code.
127     """
128     rp = RobotParams()
129     valid_limbs = rp.get_limb_names()
130     if not valid_limbs:
131         rp.log_message(("Cannot detect any limb parameters on this robot. "
132                         "Exiting."), "ERROR")
133         return
134     if len(valid_limbs) > 1:
135         valid_limbs.append("all_limbs")
136     arg_fmt = argparse.RawDescriptionHelpFormatter
137     parser = argparse.ArgumentParser(formatter_class=arg_fmt,
138                                      description=main.__doc__)
139     parser.add_argument('-g', '--gripper', dest='gripper', default=valid_limbs[0],
140                         choices=[valid_limbs],
141                         help='gripper limb to control (default: both)')
142     parser.add_argument('-n', '--no-lights', dest='lights',
143                         action='store_false',
144                         help='do not trigger lights on cuff grasp')
145     parser.add_argument('-v', '--verbose', dest='verbosity',
146                         action='store_const', const=rospy.DEBUG,
147                         default=rospy.INFO,
148                         help='print debug statements')
149     args = parser.parse_args(rospy.myargv()[1:])

The gripper option, the light and verbose options are parsed from the command line arguments, as entered by the user.

153     rospy.init_node('sdk_gripper_cuff_control_{0}'.format(args.gripper),
154                     log_level=args.verbosity)
156     arms = (args.gripper,) if args.gripper != 'all_limbs' else valid_limbs[:-1]
157     grip_ctrls = [GripperConnect(arm, args.lights) for arm in arms]
159     print("Press cuff buttons for gripper control. Spinning...")
160     rospy.spin()
161     print("Gripper Button Control Finished.")
162     return 0
164 if __name__ == '__main__':
165     sys.exit(main())

The node is initialized and an instance of the GripperConnect is created.