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I am working on MAV control in GPS denied environment using px4flow and Lidar sensor.While in simulation and during experiments on real vehicle, MAV doesnt stay at its position and drifts in random direction. I am using /mavros/local_position/pose msg to provide setpoints to the MAV. Currently it just have to takeoff hover and land at the same position. What might be causing this? Here is the code for your reference.

import rospy

from geometry_msgs.msg import Point, PoseStamped

from mavros_msgs.msg import * from mavros_msgs.srv import *

class fcuModes: def init(self): pass

def setTakeoff(self):
rospy.wait_for_service(‘mavros/cmd/takeoff’)
try:
 takeoffService = rospy.ServiceProxy(‘mavros/cmd /takeoff’,mavros_msgs.srv.CommandTOL)
 takeoffService(altitude = 3)
 except rospy.ServiceException, e:
 print “Service takeoff call failed: %s”%e

def setArm(self):
rospy.wait_for_service(‘mavros/cmd/arming’)
try:
armService = rospy.ServiceProxy(‘mavros/cmd/arming’,    mavros_msgs.srv.CommandBool)
armService(True)
except rospy.ServiceException, e:
print “Service arming call failed: %s”%e

def setDisarm(self):
rospy.wait_for_service(‘mavros/cmd/arming’)
try:
armService = rospy.ServiceProxy(‘mavros/cmd/arming’,     mavros_msgs.srv.CommandBool)
armService(False)
except rospy.ServiceException, e:
print “Service disarming call failed: %s”%e

def setStabilizedMode(self):
rospy.wait_for_service(‘mavros/set_mode’)
try:
flightModeService = rospy.ServiceProxy(‘mavros/set_mode’,     mavros_msgs.srv.SetMode)
flightModeService(custom_mode=‘STABILIZED’)
except rospy.ServiceException, e:
print “service set_mode call failed: %s. Stabilized Mode could not be     set.”%e

def setOffboardMode(self):
rospy.wait_for_service(‘mavros/set_mode’)
try:
flightModeService = rospy.ServiceProxy(‘mavros/set_mode’,     mavros_msgs.srv.SetMode)
flightModeService(custom_mode=‘OFFBOARD’)
except rospy.ServiceException, e:
print “service set_mode call failed: %s. Offboard Mode could not be     set.”%e

def setAltitudeMode(self):
rospy.wait_for_service(‘mavros/set_mode’)
try:
flightModeService = rospy.ServiceProxy(‘mavros/set_mode’,     mavros_msgs.srv.SetMode)
flightModeService(custom_mode=‘ALTCTL’)
except rospy.ServiceException, e:
print “service set_mode call failed: %s. Altitude Mode could not be     set.”%e

def setPositionMode(self):
rospy.wait_for_service(‘mavros/set_mode’)
try:
flightModeService = rospy.ServiceProxy(‘mavros/set_mode’,     mavros_msgs.srv.SetMode)
flightModeService(custom_mode=‘POSCTL’)
except rospy.ServiceException, e:
print “service set_mode call failed: %s. Position Mode could not be set.”%e

def setAutoLandMode(self):
rospy.wait_for_service(‘mavros/set_mode’)
try:
flightModeService = rospy.ServiceProxy(‘mavros/set_mode’,     mavros_msgs.srv.SetMode)
flightModeService(custom_mode=‘AUTO.LAND’)
except rospy.ServiceException, e:
print “service set_mode call failed: %s. Autoland Mode could not be    set.”%e

class Controller:

def init(self):
# Drone state
self.state = State()
# Instantiate a setpoints message
self.sp = PositionTarget()
# set the flag to use position setpoints and yaw angle
self.sp.type_mask = int(‘010111111000’, 2)
# LOCAL_NED
self.sp.coordinate_frame = 1

# We will fly at a fixed altitude for now
# Altitude setpoint, [meters]
self.ALT_SP = 1.5
# update the setpoint message with the required altitude
self.sp.position.z = self.ALT_SP
# Step size for position update
self.STEP_SIZE = 2.0
# Fence. We will assume a square fence for now
self.FENCE_LIMIT = 5.0

# A Message for the current local position of the drone
self.local_pos = Point(0.0, 0.0, 1.0)

# initial values for setpoints
self.sp.position.x = 0.0
self.sp.position.y = 0.0

# speed of the drone is set using MPC_XY_CRUISE parameter in MAVLink
# using QGroundControl. By default it is 5 m/s.

# Callbacks

## local position callback

def posCb(self, msg):
self.local_pos.x = msg.pose.position.x
self.local_pos.y = msg.pose.position.y
self.local_pos.z = msg.pose.position.z

## Drone State callback

 def stateCb(self, msg):
  self.state = msg

## Update setpoint message

 def updateSp(self):
self.sp.position.x = self.local_pos.x
self.sp.position.y = self.local_pos.y

def x_dir(self):
 self.sp.position.x = self.local_pos.x + 5
 self.sp.position.y = self.local_pos.y

def neg_x_dir(self):
  self.sp.position.x = self.local_pos.x - 5
  self.sp.position.y = self.local_pos.y

def y_dir(self):
  self.sp.position.x = self.local_pos.x
  self.sp.position.y = self.local_pos.y + 5

def neg_y_dir(self):
  self.sp.position.x = self.local_pos.x
  self.sp.position.y = self.local_pos.y - 5

def main():

  rospy.init_node(‘pos_ctrl’, anonymous=True)

# flight mode object

modes = fcuModes()

cnt = Controller()

rate = rospy.Rate(20.0)

rospy.Subscriber(‘mavros/state’, State, cnt.stateCb)

# Subscribe to drone's local position

rospy.Subscriber(‘mavros/local_position/pose’, PoseStamped, cnt.posCb)

# Setpoint publisher    

sp_pub = rospy.Publisher(‘mavros/setpoint_raw/local’, PositionTarget,  queue_size=1)

# Make sure the drone is armed

while not cnt.state.armed:
modes.setArm()
rate.sleep()

# We need to send few setpoint messages, then activate OFFBOARD mode,   to take effect

k=0
while k<10:
sp_pub.publish(cnt.sp)
rate.sleep()
k = k + 1

#  activate OFFBOARD mode

modes.setOffboardMode()

# ROS main loop

while not rospy.is_shutdown():
x=0
while x<500:
 rate.sleep()
 cnt.updateSp()
 sp_pub.publish(cnt.sp)
 rate.sleep()
 x= x + 1

 modes.setAutoLandMode()

 if name == ‘main’: try: main() except rospy.ROSInterruptException:   pass
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