trajectory_lock.py

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#! /usr/bin/env python
# Copyright (c) 2009, Willow Garage, Inc.
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#       this software without specific prior written permission.
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# author: Vijay Pradeep


# This is a super simple script to change the trajectory setpoint to
# the current position of the joints.  This is designed to work with
# the JointSplineTrajectoryController, and has to live live in the same
# namespace as the controller, in order to link up correctly to the
# "<controller>/command" and "<controller>/state" topics".

import sys
import time
import rospy

from trajectory_msgs.msg import *
from pr2_controllers_msgs.msg import *

rospy.init_node("trajectory_lock")

if len(sys.argv) < 2:
    print "Using default joint bound of .08 per joint"
    joint_bounds = [.08]*10
else:
    joint_bounds = [float(x) for x in rospy.myargv()[1:]]

def callback(msg):
    global pub

    max_error = max([abs(x) for x in msg.error.positions])

    exceeded = [abs(x) > y for x,y in zip(msg.error.positions, joint_bounds)]

    print "All: %s" % "  ".join(["% .4f" % x for x in msg.error.positions] )

    if any(exceeded):
        print "Exceeded: %.4f" % max_error

        # Copy our current state into the commanded state
        cmd = trajectory_msgs.msg.JointTrajectory()
        cmd.header.stamp = msg.header.stamp
        cmd.joint_names = msg.joint_names
        cmd.points.append( trajectory_msgs.msg.JointTrajectoryPoint())
        cmd.points[0].time_from_start = rospy.Duration(.125)
        cmd.points[0].positions = msg.actual.positions
        pub.publish(cmd)
    else:
        print "Small: %.4f" % max_error

global pub
pub = rospy.Publisher("command", trajectory_msgs.msg.JointTrajectory, queue_size=10)

rospy.Subscriber("state", pr2_controllers_msgs.msg.JointTrajectoryControllerState, callback)

rospy.spin()