Trajectory Planning Algorithm Python ROS Program

asked 2019-06-19 09:24:53 -0500

691TReilly gravatar image

I am currently trying to write a Python ROS program which can be executed as a ROS node (using rosrun) that implements the defs declared in a separate Python file arm.py (available at: https://github.com/nortega1/dvrk-ros/...). The program initially examines the current cartesian position of the arm. Subsequently, when provided with a series of points that the arm must pass through, the program calculates a polynomial equation and given a range of x values the program evaluates the equation to find the corresponding y values.

Within the arm.py file there is a publisher set_position_cartesian_pub that sets the Cartesian position of the arm as follows:

self.__set_position_cartesian_pub = rospy.Publisher(self.__full_ros_namespace + '/set_position_cartesian', Pose, latch = True, queue_size = 1)

However, I am unsure how to pass the x and y values (I'll calculate the z values at a later date) to the publisher in the python program that I am creating. This is what I have written thus far:

#!/usr/bin/env python

import rospy
from tf import transformations
from tf_conversions import posemath
from std_msgs.msg import String, Bool, Float32, Empty, Float64MultiArray

    from geometry_msgs.msg import Pose, PoseStamped, Vector3, Quaternion, Wrench, WrenchStamped, TwistStamped

def callback(data):
  rospy.loginfo(data.pose)

def currentPositionListener():
    rospy.init_node('currentPositionListener', anonymous=True)
    rospy.Subscriber('/dvrk/PSM1/position_cartesian_current', PoseStamped, callback)
    rospy.spin()

def lagrange(f, x):

 total = 0
    n = len(f)
    for i in range(n):
            xi, yi = f[i]

            def g(i, n):
                g_tot = 1
                for j in range(n):
                    if i == j:
                    continue
                xj, yj = f[j]
                g_tot *= (x - xj) / float(xi - xj)

            return g_tot

        total += yi * g(i, n)
    return total

def newPositionListener():
    rospy.Subscriber('/dvrk/PSM1/set_position_cartesian', PoseStamped, trajectoryMover)
    rospy.spin()

def trajectoryMover(data):
    points =[(0,0),(45,30),(23,10), (48,0)]
    xlist = [i for i in range(100)]
    ylist = [lagrange(points, xlist[i]) for i in range(100)]
    for x, y in zip(xlist, ylist):
        data.pose.x = x
        data.pose.y = y
        data.pose.z = 0

if __name__ == '__main__':
    currentPositionListener()
    newPositionListener()

Any help would be greatly appreciated!

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