Task4_Final_Code_Modified

#!/usr/bin/env python3


import cv2                                          #for importing opencv 
import numpy as np                                  #useful in the array operations
import roslib                                       #roslib is an internal library to write tools
import sys                                          #module to handle runtime environment
import rospy                                        #for use of pytho with ROS
from geometry_msgs.msg import Twist
from sensor_msgs.msg import Image                   #importing the image type sensor message
from sensor_msgs.msg import LaserScan
from nav_msgs.msg import Odometry
from tf.transformations import euler_from_quaternion
from cv_bridge import CvBridge, CvBridgeError       #for importing CvBridge used to convert the ROS format images to opencv format
import tf2_ros                              #imporing tf2
import geometry_msgs.msg                    #for geometry messages
import tf_conversions                       #importing tf_conversions
import moveit_commander                     #moveit commander for motion planning
import moveit_msgs.msg                      #moveit messages
import actionlib                            #for importing for providing standard interface e.g. for returning point cloud
import math                                 #for importing the math library




######## COLOR THRESHOLDING AND FILTERING ########
'''
h_min ----> Min value of Hue
s_min ----> Min value of Saturation
v_min ----> Min value of Value
h_max ----> Max value of Hue
s_max ----> Max value of Saturation
v_max ----> Max value of Value
'''

tomatoColor = [[0, 37, 117, 0, 250, 255]]       #Defining the HSV color space of red tomatoes with format [h_min, s_min, v_min, h_max, s_max, v_max]

###################################################


### GLOBAL VARIABLE ####

imgContour = None                           #imgContour is declared of the type None and it will hold the final image
depth_image = np.empty((480,640),float)     #this is a 2D array that hold the depth value of every pixel of the frame
midX = 0                                #this is the middle value of the entire span of the contour in the x - axis
midY = 0                        #this is the middle value of the entire span of the contour in the y - axis
linear_vel = 0.0
angular_vel = 0.0

maxCounter = 0

regions = {                 #this is to hold the laser values of paricular regions
        'bleft':  0.0  ,
    }


flagPose = True         # this flag is used to first set the arm to a particular pose before starting the detection of the tomatoes 
flag = False           #this is to start detection and motion of the bot once the arm is set to a particular pose

flagEndMotion = False

ArucoId = -1            #this variable is used to hold the current aruco id of the marker visible ---> it is initialized to an invalid id of -1

pose = [0.0] * 4        #initializing the pose variable

flagDetect = False         #this variable is to check if the tomato is visible in the frame of the camera

flagExecution = True       #this variable is used to check if the execution of the motion of the arm was successful or not

# Motion Stage to handle the stage of motion of the agribot

motionStage = [False] * 15          #boolean list with all values False is defined
motionStage[0] = True               #the first stage is set to true to start the motion

#######################



class Ur5Moveit:

    # Constructor
    def __init__(self):

        self._planning_group = "arm"                                        #for defining arm as the planning group as arm for moving the arm
        self._commander = moveit_commander.roscpp_initialize(sys.argv)      #initializing the moveit commander
        self._robot = moveit_commander.RobotCommander()
        self._scene = moveit_commander.PlanningSceneInterface()
        self._group = moveit_commander.MoveGroupCommander(self._planning_group)     #setting the planning group
        self._hand_group = moveit_commander.MoveGroupCommander("gripper")  #this is to initialize a new group called the _hand_group so that the opening and closing of the gripper can be controlled
        self._display_trajectory_publisher = rospy.Publisher(
            '/move_group/display_planned_path', moveit_msgs.msg.DisplayTrajectory, queue_size=1)

        self._exectute_trajectory_client = actionlib.SimpleActionClient(
            'execute_trajectory', moveit_msgs.msg.ExecuteTrajectoryAction)
        self._exectute_trajectory_client.wait_for_server()

        self._planning_frame = self._group.get_planning_frame()
        self._eef_link = self._group.get_end_effector_link()
        self._group_names = self._robot.get_group_names()
        self._box_name = ''

        # Current State of the Robot is needed to add box to planning scene
        self._curr_state = self._robot.get_current_state()


    def gripper_robot(self,state):                      #this function is used to control the gripper and it accepts the state variable for setting the state of the gripper
        if state == 1:                                  #state 1 means that the gripper will be in the closed state
            self._hand_group.set_named_target("close")  #this is to set the target to a pre-defined pose of the gripper as close
            plan2 = self._hand_group.go()               #this line plans and executes the instructions given by moveit
        elif state == 0:                                #state 0 means that the gripper will be in the open state
            self._hand_group.set_named_target("open")   #this sets the state to open
            plan2 = self._hand_group.go()

    def arm_robot(self,state):                          #this function is for taking the arm to predefined pose 
        if state == 1:                                  #When the state of the arm is set to 1 then the arm goes to the Drop_Pose
            self._group.set_named_target("Drop_Pose")   #Drop_Pose has been designed to drop the picked up tomatoes effectively in the bucket
            plan3 = self._group.go()                    #For planning and execution of the Drop_Pose ---> go() function handles both the work
        elif state == 0:                                #State 0 is for the Plant_Perception pose ---> using this pose the TF of all the tomatoes of the plant is collected at time 0
            self._group.set_named_target("Plant_Perception")
            plan3 = self._group.go()
        elif state == 2:
            self._group.set_named_target("Plant_Perception_2")
            plan3 = self._group.go()

    def go_to_pose(self, arg_pose):                                     #this function takes the arm to a specific pose

        global flagExecution

        pose_values = self._group.get_current_pose().pose               #for displaying the current pose of the arm

        self._group.set_pose_target(arg_pose)                           #for setting the target pose of the arm
        flag_plan = self._group.go(wait=True)  # wait=False for Async Move  #for taking the arm to the planned pose

        pose_values = self._group.get_current_pose().pose

        list_joint_values = self._group.get_current_joint_values()              #for getting the current joint values of the joints


        if (flag_plan == True):                                 #this flag is used to display whether the planning and the execution was successful
            flagExecution = True
            rospy.loginfo(
                '\033[94m' + ">>> go_to_pose() Success" + '\033[0m')
        else:
            flagExecution = False
            rospy.logerr(
                '\033[94m' + ">>> go_to_pose() Failed. Solution for Pose not Found." + '\033[0m')

        return flag_plan

    # Destructor
    def __del__(self):
        moveit_commander.roscpp_shutdown()                              #for shutting down the moveit commander
        rospy.loginfo(
            '\033[94m' + "Object of class Ur5Moveit Deleted." + '\033[0m')




def callback_depth(data_depth):             #this callback is for accessing the depth image

    global depth_image                  #this is to update the value in the global depth_image variable

    try:
        bridgeDepth = CvBridge()                #for creating the bridge object
        depth_image = bridgeDepth.imgmsg_to_cv2(data_depth, "32FC1") #for converting the depth image into depth matrix if 32FC1 encoding  ----> each pixel value is stored as one channel floating point with single precision
    except CvBridgeError as e:          #for handling errors
        print(e)


#$$$$$$$$$$$$$$$$$$$THIS SECTION IS USED SO THAT WE CAN READ THE ARUCO ID OF THE MARKER VISIBLE$$$$$$$$$$$$

def callback_Aruco(data):

    global ArucoId

    try:
        bridge = CvBridge()
        frame = bridge.imgmsg_to_cv2(data, "bgr8")
        frame = cv2.cvtColor(frame, cv2.COLOR_BGR2RGB)

        # load the dictionary that was used to generate the markers
        dictionary = cv2.aruco.Dictionary_get(cv2.aruco.DICT_7X7_1000)

        # initializing the detector parameters with default values
        parameters =  cv2.aruco.DetectorParameters_create()

        # detect the markers in the frame
        corners, ids, rejectedCandidates = cv2.aruco.detectMarkers(frame, dictionary, parameters=parameters)

        if len(corners) > 0:
            # Flatten the ArUco IDs list
            ids = ids.flatten()
            # loop over the detected ArUCo corners
            for (markerCorner, markerID) in zip(corners, ids):
                ArucoId = str(markerID)
                rospy.loginfo(ArucoId+" Reached")
    except CvBridgeError as e:
        print(e)

#$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$








def getContours(img):           #this function is used to draw contours in their appropriate places
    global imgContour  
    global midX                 
    global midY
    global depth_image
    global flagDetect           #this variable will be set to true if the tomato is visible in the frame of the camera
    global maxCounter
    depth = 0                   #initial value of depth is taken to be 0
    cx = 320.5                  #the mid point of the x-axis is 320.5
    cy = 240.5                  #the mid point of the y-axis is 240.5
    fx = 554.387                #the focal length for x is 554.387
    fy = 554.387                #the focal length for y is 554.387
    contours, hierarchy = cv2.findContours(img, cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_NONE)       #this is for getting all the contours that can be formed on the image
    x, y, w, h = 0, 0, 0, 0     #x, y, w, h are for getting the bounding rectangle dimensions for the drawing the contour
    midX = 0            #mid of x is set to 0
    midY = 0            #mid of y is set to 0
    counter = 0  #this counter is used to label the child frame ------> that means it's value is used to give unique label to every contour and hence giving unique value to every tomato
    for cnt in contours:                #for loop is for iterating over all the contours that needs to be drawn
        area = cv2.contourArea(cnt)         #this function is used to return the area of every contour that can be drawn on the image ---> that means every red tomato visible currently
        if area > 600:                   #this is for filtering the noise ---> that means if the area is >600 then it means we are looking at something substantial and we need to draw contour on that and broadcast the TF for that
            flagDetect = True            #the flagDetect is set to true so that the bot is slowed down so that the depth value of the tomatoes can be accessed easily
            peri = cv2.arcLength(cnt, True)     #this is to get the perimeter of the contour

            approx = cv2.approxPolyDP(cnt, 0.02 * peri, True)       #0.02 is a factor ---> it can be adjusted for better detection

            x, y, w, h = cv2.boundingRect(approx)               #this returns and stores the value of x, y, w, h

            cv2.circle(imgContour, (x+(w // 2), y+(h // 2)), max(h // 2, w // 2), (255, 0, 0), 2)   #this is the circle drawing function that draws image on imgContour with center x+(w/2) and y+(h/2) the next parameter is to get the radius of the circle that is the max of the entire spread
            cv2.circle(imgContour, (x+(w // 2), y+(h // 2)), 1, (255, 0, 0), -1)    #the (255, 0, 0) ----> is in the BGR format so max of blue and 0 values of red and green makes the circle blue in colour
            midX = x + w // 2       #this is the mid of the circle
            midY = y + h // 2       #this is the mid of the circle


            if midX != 0 and midY != 0 and midX <= 640 and midY <= 480:     #as the frame of the output image is 640 x 480 pixels so this is to prevent accessing values that are out of bound by any case
                depth = depth_image[midY][midX]         #the depth value is registered for the point (midX, midY)

                X = depth*((midX-cx)/fx)            #conversion to the world coordinates
                Y = depth*((midY-cy)/fy)            #conversion to the world coordinates
                Z = depth                           #conversion to the world coordinates


                br = tf2_ros.TransformBroadcaster()     #setting up the TF2 broadcaster
                t = geometry_msgs.msg.TransformStamped()        #broadcasting is stamped for every object
                t.header.stamp = rospy.Time.now()       #the head stamp is the current time that we use this makes it unique
                t.header.frame_id = "camera_link2"          #as the camera on the arm has the camera_link2 so we are using that
                t.child_frame_id = "obj"+str(counter)           #this is the naming convention where the is given as obj + value of the counter -----> obj1, obj2 etc.

                cv2.putText(imgContour, t.child_frame_id,               #this function is used to put text on the imgContour, the text is the child_frame_id, at the point (midX, midY) 
                (midX, midY), cv2.FONT_HERSHEY_SIMPLEX,         #cv2.FONT_HERSHEY_SIMPLEX ----> is the font used to label the image
                0.5, (255, 0, ), 2)             #0.5 is the font scale, (255, 0, 0) is for giving blue colour and 2 is the thickness


                ''' In this section we are trying to get the depth of the tomato visible ---> by doing this we will ensure that we accuate the arm only when the depth of the visible tomato
                is upto a certain limit so that we are unnecessarily don't try to pick up tomatoes on the other side of the plant and in doing so hit the plant and damage the arm'''

                depth = depth_image[midY][midX-w//2]    #the depth value is re-adjusted so that we ensure that the depth value that we get is for the tomato and not the thing just around the tomato because we are not stopping to check the depth value but we are drifting with a small value
                if depth <= 0.80:      #over here the depth value that allows us to pick the tomatoes on the side where the bot is standing is 0.80

                    '''In this section we will only broadcast the TF when the tomato visible is in the depth range from where it can be picked'''    

                    t.transform.translation.x = Z          #this is for transforming the world coordinates to the camera frame that is on the arm
                    t.transform.translation.y = -X         #this is for transforming the world coordinates to the camera frame that is on the arm
                    t.transform.translation.z = -Y         #this is for transforming the world coordinates to the camera frame that is on the arm

                    q = tf_conversions.transformations.quaternion_from_euler(0, 0, 0)       #for conversion euler to quaternion
                    t.transform.rotation.x = q[0]
                    t.transform.rotation.y = q[1]
                    t.transform.rotation.z = q[2]
                    t.transform.rotation.w = q[3]

                    br.sendTransform(t)         #for broadcating the TF 

                counter = counter+1 #as this loop loops through the number of times equal to the number of unique contours that can be drawn then if the counter is incremented same number of times it will have unique value starting from 1 for every contour
                if counter > maxCounter:
                    maxCounter = counter
        else:
            flagDetect = False              #flagDetect is set to false if the tomato is not visible
            maxCounter = 0
    cv2.imshow("Result",imgContour)         #this is for displaying the final image with all the contours on it
    cv2.waitKey(1)          #this is for adding a 1 millisecond delay

    return x + w // 2, y + h // 2  # for mid of the box is returned using this



def callback(data):         #this callback is for color detection
    global imgContour     
    try:
        bridge = CvBridge()
        frame = bridge.imgmsg_to_cv2(data, "bgr8")      #the ROS format image is converted to bgr8 format -----> that is the format that is used in opencv
        imgContour = frame.copy()               #this function is used to copy the frame image to the imgContour
        imgHSV = cv2.cvtColor(frame, cv2.COLOR_BGR2HSV)         #this is used to convert the image to HSV image
        x, y = 0, 0
        for color in tomatoColor:       #this for loop goes through the tomatoColor list and gets the h_min, h_max, s_min, s_max, v_min, v_max value for the red colour
            lower = np.array(color[0:3])        #this is for forming the lower range of the HSV colour space ----> i.e. h_min, s_min, v_min
            upper = np.array(color[3:6])        #this is for forming the upper range of the HSV colour space ----> i.e. h_max, s_max, v_max
            mask = cv2.inRange(imgHSV, lower, upper)            #for masking the image 
            x, y = getContours(mask)   
    except CvBridgeError as e:          #for handling the error
        print(e)


def moveBot():                      #this function is to move the bot with a particular velocity

    '''The stage structure prevents other stages from getting triggered that are not supposed to be triggered ----> this is important as the bot is not moving in a straight line but is moving 
    in an environment where the bot has to cross the same locations multiple times so the pose value of the bot will remain same at these locations so to prevent the other stages from getting triggered
    the stage variables are used'''

    global linear_vel
    global angular_vel
    global motionStage              #this is the boolean array defined as global variable
    global pose                     #we are accessing the pose of the bot so that we can keep a track of position of the bot 
    global flagDetect  #this flag is used to check any tomato is visible in the frame of the camera that is larger than a specific filtering threshold value
    global flagEndMotion
    if motionStage[0] is True:
        if pose[1] >= -0.56:
            motionStage[0] = False          #we are using a step-wise trigger stage where the execution of one stage triggers the execution of the other stage
            motionStage[1] = True
        else:
            rospy.loginfo("Started Run !")
            linear_vel = 0.5               #Intial velocity is 0.5
            angular_vel = 0.0 
    elif motionStage[1] is True:
        if pose[1] >= 7.22:
            motionStage[1] = False
            motionStage[2] = True
        else:
            if flagDetect is True:      #the flagDetect is used in this way that whenever a tomato is visible the speed of the bot is reduced to 0.02 so that the depth value of the tomato can be accessed correctly
                linear_vel = 0.02
                angular_vel = 0.0 
                Pcontroller()
            else:
                linear_vel = 0.2       #if the bot is moving in between the rows but no tomato is visible in the frame of the bot then it will move with a speed of 0.2
                angular_vel = 0.0
                Pcontroller()           #when the bot is moving between the rows the precision in distance is maintained using the P-Controller
    elif motionStage[2] is True:
        if pose[2] <= 0:
            motionStage[2] = False
            motionStage[3] = True
        else:
            if pose[1] <=8.27:      #pose[1] ---> is the y value of the bot
                linear_vel = 0.3
                angular_vel = 0.0
            elif pose[2] > 0:
                linear_vel = 0.0
                angular_vel = 1.0           #while turning the angular velocity of the bot is 1.0
    elif motionStage[3] is True:
        if pose[0] < -0.647 and pose[2] > -1.6 and pose[2] < -1.5:
            motionStage[3] = False
            motionStage[4] = True
        else:
            if pose[0] >= -0.647:
                linear_vel = 0.3
                angular_vel = 0.0
            elif pose[2] < -1.6 or pose[2] > -1.5:
                linear_vel = 0.0
                angular_vel = 1.0
    elif motionStage[4] is True:
        if pose[1] < 7.7:
            motionStage[4] = False
            motionStage[5] = True
        else:
            linear_vel = 0.3
            angular_vel = 0.0
    elif motionStage[5] is True:
        if pose[1] < 0.0:
            motionStage[5] = False
            motionStage[6] = True
        else:
            if flagDetect is True:
                linear_vel = 0.02
                angular_vel = 0.0 
                Pcontroller()
            else:
                linear_vel = 0.2
                angular_vel = 0.0
                Pcontroller()
    elif motionStage[6] is True:
        if pose[1] < -1.3 and pose[2] > 0:
            motionStage[6] = False
            motionStage[7] = True
        else:
            if pose[1] > -1.3 and pose[2] < -1.0:
                linear_vel = 0.3
                angular_vel = 0.0
            elif pose[2] < 0:
                linear_vel = 0.0
                angular_vel = 1.0
    elif motionStage[7] is True:
        if pose[0] > 2.3:
            motionStage[7] = False
            motionStage[8] = True
        else:
            if pose[0] <= 2.3:
                linear_vel = 0.5
                angular_vel = 0.0
    elif motionStage[8] is True:
        if pose[2] > 1.56:
            motionStage[8] = False
            motionStage[9] = True
        else:
            linear_vel = 0.0
            angular_vel = 1.0
    elif motionStage[9] is True:
        if pose[1] >= 7.22:
            motionStage[9] = False
            motionStage[10] = True
        else:
            if pose[1] < -0.56:
                linear_vel = 0.3
                angular_vel = 0.0
            elif flagDetect is True:
                linear_vel = 0.02
                angular_vel = 0.0 
                Pcontroller()
            else:
                linear_vel = 0.2
                angular_vel = 0.0
                Pcontroller()
    elif motionStage[10] is True:
        if pose[2] < 0:
            motionStage[10] = False
            motionStage[11] = True
        else:
            if pose[1] <=8.27:
                linear_vel = 0.3
                angular_vel = 0.0
            elif pose[2] > 0:
                linear_vel = 0.0
                angular_vel = 1.0
    elif motionStage[11] is True:
        if pose[2] > -1.6 and pose[2] < -1.4:
            motionStage[11] = False
            motionStage[12] = True
        else:
            if pose[0] >= 0.97:
                linear_vel = 0.3
                angular_vel = 0.0
            elif pose[2] > -1.4 or pose[2] < -1.6:
                linear_vel = 0.0
                angular_vel = 1.0
    elif motionStage[12] is True:
        if pose[1] < 7.7:
            motionStage[12] = False
            motionStage[13] = True
        else:
            linear_vel = 0.3
            angular_vel = 0.0
    elif motionStage[13] is True:
        if pose[1] < 0.0:
            motionStage[13] = False
            motionStage[14] = True
        else:
            if flagDetect is True:
                linear_vel = 0.02
                angular_vel = 0.0 
                Pcontroller()
            else:
                linear_vel = 0.2
                angular_vel = 0.0
                Pcontroller()
    elif motionStage[14] is True:
        if pose[1] <-1.39:
            motionStage[14] = False
            flagEndMotion = True
        else:
            if pose[1] >= -1.39:
                linear_vel = 1.0
                angular_vel = 0.0
    else:
        stopMotion()                        #this will stop the bot when it returns to the start after all execution
    
        
        

def stopMotion():               #this function is to set the value of the linear_vel and angular_vel to 0 to stop the bot
    global linear_vel
    global angular_vel
    linear_vel = 0.0
    angular_vel = 0.0



def odom_callback(data):        #callback funtion for odom to get the correct position of the bot 
    global pose
    x  = data.pose.pose.orientation.x
    y  = data.pose.pose.orientation.y
    z = data.pose.pose.orientation.z
    w = data.pose.pose.orientation.w
    pose = [data.pose.pose.position.x, data.pose.pose.position.y, euler_from_quaternion([x,y,z,w])[2]]




def laser_callback(msg):                #callback function for laser
    global regions
    regions = {
        'bleft':  min(min(msg.ranges[680:720]),3.2)  ,          #this will get the left side value of the distance using the laser
    }



def Pcontroller():     #function for the proportional controller --> this has been used so that the bot is able to correct its path if it gets deflected form its path
    global angular_vel
    global regions
    kp = 10             #the correction factor for the P-Controller is kept 10 so as to attain faster correction
    angular_vel = kp * (regions['bleft']-0.70) #when the left value of the distance as calculated by the laser is 0.70 then the angular_vel is 0 and any deflection from this value will set a certain angular_vel to correct that deflection





def main(args):                                                                         #this is the main method

    rospy.init_node('object_detection_manipulation', anonymous=True)                                 #for initializing the node with name object_detection
    tfBuffer = tf2_ros.Buffer()                                                         #for setting the buffer
    listener = tf2_ros.TransformListener(tfBuffer)                                      #for using the TF listener
    ur5 = Ur5Moveit()                                                                   #for setting up the ur5 object of Ur5Moveit class
    depth_sub = rospy.Subscriber("/camera/depth/image_raw2", Image, callback_depth)     #for setting the depth image subscriber
    image_sub = rospy.Subscriber("/camera/color/image_raw2", Image, callback)           #for setting the color image subscriber
    image_sub_aruco = rospy.Subscriber("/ebot/camera1/image_raw", Image, callback_Aruco)
    rospy.Subscriber('/ebot/laser/scan',LaserScan, laser_callback)      #setting up the subscriber
    rospy.Subscriber('/odom', Odometry, odom_callback)  #setting up the subscriber
    pub = rospy.Publisher('/cmd_vel',Twist,queue_size=10)   #setting up the publisher
    
    ur5_pose_1 = geometry_msgs.msg.Pose()                                               #for using the pose 
    velocity_msg = Twist()

    velocity_msg.linear.x = 0
    velocity_msg.linear.y = 0
    pub.publish(velocity_msg)
    global linear_vel
    global angular_vel
    global flagPose
    global flag
    global ArucoId
    global flagDetect
    global flagExecution
    global maxCounter
    global flagEndMotion
    flagNewPose = False         #to get to a new pose to make the accuation of the arm from this new pose in case it fails the first time

    hold = ''
    
    while not rospy.is_shutdown():                      #while loop


        if flagEndMotion is True:           #gets triggered when the bot returns to its start location after completing the motion
                stopMotion()                                    #to stop the motion when the allignment of the aruco 
                velocity_msg.linear.x = linear_vel
                velocity_msg.angular.z = angular_vel
                pub.publish(velocity_msg)
                rospy.loginfo('Mission Accomplished!')
                break

        #####FOR TAKING THE ARM TO THE PLANT PERCEPTION POSE########
        if flagPose is True:
            flagPose = False
            ur5.arm_robot(0)
            rospy.sleep(0.1)
            flag = True

        ##########################################################
        elif flag is True:

            for i in range(maxCounter+1):       #this loop actually checks which tomato is in the permissible depth range 
                try:
                    trans = tfBuffer.lookup_transform('base_link', 'obj'+str(i), rospy.Time(0))      #for getting the TF of obj0 ----> tomato in the scene
                    hold = str(i)
                except (tf2_ros.LookupException, tf2_ros.ConnectivityException, tf2_ros.ExtrapolationException):
                    continue

                if hold != '':
                    break


            if hold == '':  #if no tomato is visible the hold will be blank string so the bot will keep moving
                moveBot()                           #if the TF of the bot is not available then the bot has to keep moving
                velocity_msg.linear.x = linear_vel
                velocity_msg.angular.z = angular_vel
                pub.publish(velocity_msg)          #publishing the value to the bot

                '''If the tomato is not visible then the aruco id is set to an invalid id ---> this will prevent the bot from alligning to the previous marker when the tomato is visible , 
                this is very important because if it is set to some valid id as 0 then when we are trying to allign the bot to the marker it will already have TF of some valid marker and 
                it will try to move to that marker to allign itself insead of moving slowly forward and alligning to the marker that is visible or will get visible in moving forward
                instead of alligning to the previous marker'''

                ArucoId = '-1' #set to invalid id -1

                continue       #to continue with the next iteration if we get some exception

            ##########################################################################################################

            '''In this section we are alligning the Aruco Marker ----> as we have set the aruco id to invalid id -1 so when the TF is check it will definitely not be available so the 
            bot will drift with a small velocity till the time the marker becomes visible ---> when the marker becomes visible not the task is to center the marker so that the bot is exactly 
            in the front of the trough this is done using the while loop and the bot is moved forward and backward accordingly to bring the center of the marker to a region that is greater than -0.01
            and less than 0.01 ---> over here we have taken a small region so that overcorrection is not triggered and that loop will get stuck'''

            try:
                transAruco = tfBuffer.lookup_transform('sjcam_link', 'aruco'+ArucoId, rospy.Time(0))
            except (tf2_ros.LookupException, tf2_ros.ConnectivityException, tf2_ros.ExtrapolationException):
                velocity_msg.linear.x = 0.1             #till the time the TF of the aruco is not available then the bot is moving with a small velocity of 0.1
                velocity_msg.angular.z = 0.0
                pub.publish(velocity_msg)
                continue
            while transAruco.transform.translation.y > 0.01 or transAruco.transform.translation.y < -0.01:  #when the TF is available but the center of the Aruco is not in the range 
                if transAruco.transform.translation.y > 0.01:   #if the bot has moved forward by any chance then a negative velocity will bring it back
                    velocity_msg.linear.x = -0.1
                    velocity_msg.angular.z = 0.0
                    pub.publish(velocity_msg)
                elif transAruco.transform.translation.y < -0.01:        #if the bot has moved backward then a positive velocity will do the work
                    velocity_msg.linear.x = 0.1
                    velocity_msg.angular.z = 0.0
                    pub.publish(velocity_msg)
                transAruco = tfBuffer.lookup_transform('sjcam_link', 'aruco'+ArucoId, rospy.Time(0))    #the TF is continuously read so that we are able to allign the aruco properly

            ##########################################################################################################

            stopMotion()                                    #to stop the motion when the allignment of the aruco 
            velocity_msg.linear.x = linear_vel
            velocity_msg.angular.z = angular_vel
            pub.publish(velocity_msg)

            trans = tfBuffer.lookup_transform('base_link', 'obj'+hold, rospy.Time(0))  #the TF of the tomato is read again when the bot is completely stopped so that the TF of the tomato is perfectly correct

            rospy.loginfo('obj'+hold+' Identified at '+ArucoId)


            #************************************************************VARIABLE DEFINITIONS******************************************************#


            tomato_Position_X_Transform = trans.transform.translation.x           #for storing the x value of transform for the tomato 2
            tomato_Position_Y_Transform = trans.transform.translation.y           #for storing the y value of transform for the tomato 2
            tomato_Position_Z_Transform = trans.transform.translation.z           #for storing the z value of transform for the tomato 2

            base_link_Position_X = 0.16                  #this is the x position of the base_link ----> our reference point
            base_link_Position_Y = 0                     #this is the y position of the base_link ----> our reference point
            base_link_Position_Z = 0.53                  #this is the z position of the base_link ----> our reference point


            #######OFFSETS FOR INCORPORTING THE OFFSETS IN CALCULATION OF THE ACTUAL POSE AND THE POSE OF THE END EFFECTOR##########

            '''These offsets are calculated so that the gripper exactly reached the tomatoes and does not go to some other location because the actual perception is from either the camera or
            the depth camera and all the calculations of distance ----> in this case depth is from the depth camera ----> but the gripper is not exactly at the location of the depth camera
            so to remove the error we are calculate these offsets'''

            offset_x_1 = 0.16
            offset_y_1 = 0.4
            offset_z_1 = 0.02

            offset_x_2 = 0.1
            offset_y_2 = 0.25

            ########################################################################################################################


            ####TO SET THE ORIENTATION OF THE GRIPPER######

            ur5_pose_1.orientation.x = -0.20426466049594807
            ur5_pose_1.orientation.y = 0.9759094471343439
            ur5_pose_1.orientation.z = -0.07502044797426752
            ur5_pose_1.orientation.w = 0.01576806431223178

            ###############################################

            #*****************************************************************************************************************************************#
        

            ###############################ACTUATION FOR THE TOMATO#######################################

            

            ur5_pose_1.position.x = base_link_Position_X + tomato_Position_X_Transform + offset_x_1
            ur5_pose_1.position.y = base_link_Position_Y + tomato_Position_Y_Transform - offset_y_1
            ur5_pose_1.position.z = base_link_Position_Z + tomato_Position_Z_Transform

            ur5.go_to_pose(ur5_pose_1)
            if flagNewPose is True and flagExecution is False:  #this will ensure that when the arm has moved to the new pose of perception the steps after that will only be triggered if it reaches the tomato from this pose
                continue

            if flagExecution is False and flagNewPose is False:              #this variable is used to ensure that the steps after this are only actuated when this step is successfully actuated
                ur5.arm_robot(2)        #this is the new pose for perception ---> the arm will move to this pose if the planning fails from the first pose
                rospy.sleep(0.1)
                flagNewPose = True
                continue
            rospy.sleep(0.1)

            ur5_pose_1.position.x = base_link_Position_X + tomato_Position_X_Transform + offset_x_2
            ur5_pose_1.position.y = base_link_Position_Y + tomato_Position_Y_Transform - offset_y_2
            ur5_pose_1.position.z = base_link_Position_Z + tomato_Position_Z_Transform + offset_z_1

            ur5.go_to_pose(ur5_pose_1)          #actuation is done in 2 steps to make it precise
            rospy.sleep(0.1)

            ur5.gripper_robot(1)
            rospy.sleep(0.1)

            rospy.loginfo('obj'+hold+' Picked')     #to display the picked up message

            ur5.arm_robot(1)
            rospy.sleep(0.1)
            ur5.gripper_robot(0)
            rospy.sleep(0.1)

            rospy.loginfo('obj'+hold+' Dropped in '+'Basket')       #to display the drop message

            ######################################################################################################

            flagPose = True                #to set this variable to true again so that the arm positions itself correctly after picking up the tomato
            flag = False               #this will prevent further execution till the arm has not positioned itself correctly
            hold = ''
            flagNewPose = False

    del ur5             #to delete the ur5 object

if __name__ == '__main__':
    main(sys.argv)                  #for calling the main method