wheel odometry publisher not rotating vehicle, some error in code. The forward and backward is working great only rotation is the problem.

edit

It goes forward and backward when rotating the robot. I am using wheel rpm values to convert to odometry data please guide if theres anything wrong or i have missed out something.

please check the code i think i couldnt spot the error in the code.

import rospy
from geometry_msgs.msg import PoseStamped
from nav_msgs.msg import Odometry
from std_msgs.msg import Float32
from geometry_msgs.msg import Point, Pose, Quaternion, Twist, Vector3
import tf
import math

def leftVelCallback(vel):
    global leftVel
    leftVel = vel.data

def rightVelCallback(vel):
    global rightVel
    rightVel = vel.data

rospy.init_node('odometry_publisher')

odom_pub = rospy.Publisher("odom", Odometry, queue_size=10)
rospy.Subscriber("/left_vel", Float32, leftVelCallback)
rospy.Subscriber("/right_vel", Float32, rightVelCallback)
odom_broadcaster = tf.TransformBroadcaster()

x = 0.0
y = 0.0
th = 0.0

vx = 0
vy = 0
vth = 0

leftVel = 0
rightVel = 0

wheeltrack = 0.63
wheelradius = 0.10

current_time = rospy.Time.now()
last_time = rospy.Time.now()
r = rospy.Rate(5)

while not rospy.is_shutdown():
    current_time = rospy.Time.now()
    average_rpm_x = (leftVel + rightVel) / 2
    average_rps_x = average_rpm_x / 60
    linear_velocity = (average_rps_x * (2 * math.pi * wheelradius))
    average_rpm_a = (rightVel - leftVel)
    average_rps_a = average_rpm_a / 60
    angular_velocity = (average_rps_a * ( 2 * math.pi * wheelradius)) / wheeltrack

    vx = linear_velocity
    vy = 0
    vth = angular_velocity
    print(vx)
    print(vth)
# //compute odometry in a typical way given the velocities of the robot

    dt = (current_time - last_time).to_sec()
    delta_x = (vx * math.cos(th) - vy * math.sin(th)) * dt
    delta_y = (vx * math.sin(th) + vy * math.cos(th)) * dt
    delta_th = vth * dt

    x += delta_x
    y += delta_y
    th += delta_th

    odom_quat = tf.transformations.quaternion_from_euler(0, 0, th)


# # //send the transform
    odom_broadcaster.sendTransform(
    (x, y, 0.),
    odom_quat,
    current_time,
    "base_link",
    "odom"
    )
# //next, we'll publish the odometry message over ROS
    odom = Odometry()
    odom.header.stamp = current_time
    odom.header.frame_id = "odom"

    odom.pose.pose = Pose(Point(x, y, 0.), Quaternion(*odom_quat))

    odom.child_frame_id = "base_link"
    odom.twist.twist = Twist(Vector3(vx, vy, 0), Vector3(0, 0, vth))

    #  //publish the message
    odom_pub.publish(odom)
    last_time = current_time
    r.sleep()
    rospy.loginfo("Published Odom")