Unable to publish to /smoother_cmd_vel

I am working on Bunker robot from Agile Robotics..

I can control the robot via RF transmitter and also through CAN protocol.I have created a python script through which I can pass on coordinates to the robot and it will move to that point. After enabling the Robot base frame, it seems that the topic that i need to publish my coordinates is "/smoother_cmd_vel". Below is my attach script but i still cant publish it.

import rospy
from nav_msgs.msg import Odometry
from tf.transformations import euler_from_quaternion
from geometry_msgs.msg import Point, Twist
from math import atan2

x = 0.0
y = 0.0 
theta = 0.0

def newOdom(msg):
  global x
  global y
  global theta

  x = msg.pose.pose.position.x
  y = msg.pose.pose.position.y

  rot_q = msg.pose.pose.orientation
  (roll, pitch, theta) = euler_from_quaternion([rot_q.x, rot_q.y, rot_q.z, rot_q.w])

rospy.init_node("speed_controller")

sub = rospy.Subscriber("/odom", Odometry, newOdom)
pub = rospy.Publisher("/smoother_cmd_vel", Twist, queue_size = 1)

speed = Twist()

r = rospy.Rate(4)

goal = Point()
goal.x = 5
goal.y = 5

while not rospy.is_shutdown():
    inc_x = goal.x -x
    inc_y = goal.y -y

    angle_to_goal = atan2(inc_y, inc_x)

    if abs(angle_to_goal - theta) > 0.1:
        speed.linear.x = 0.0
        speed.angular.z = 0.3
    else:
        speed.linear.x = 0.5
        speed.angular.z = 0.0

    pub.publish(speed)
    r.sleep()    

looking for some suggestions.Thank you and good day