Elizaveta.Elagina's profile - activity

The problem was that the function ImuCallback doesn't accept new parameters as ordinary functions. And if it's called more than once, it sometimes works with old parameters instead of newly received. To solve this I give the angle as a global variable not as a parameter for a callback function.

I see that class TravelForward can be used for my purpose. Probably it's not the most straightforward way but it works.

I want to write a python script that makes Turtlebot ride backwards for a specified distance in meters. I have this function

def ImuCallback(data, angle):


 global stage
  quat = data.orientation
  q = [quat.x, quat.y, quat.z, quat.w]
  roll, pitch, yaw = euler_from_quaternion(q)

  sys.stdout.write("\r\033[1mGyro Angle\033[0m: [" + "{0:+.4f}".format(yaw) + " rad]  ["\
                 + "{0: >+7.2f}".format(degrees(yaw)) + " deg]"\
                 + "            \033[1mRate\033[0m: [" + "{0:+.4f}".format(data.angular_velocity.z) + " rad/s]  ["\
                 + "{0: >+7.2f}".format(degrees(data.angular_velocity.z)) + " deg/s] ")
  if angle > 0:
    if yaw > angle or yaw < 0:
      stage += 1
  else:
    if yaw > angle and yaw < 0:
      stage += 1

which makes it stop when the robot is rotating. I would like to read the distance travelled by the robot similarly as to how I read the angle of its rotation. I feel it has to be simple but I don't know how to do it. Thanks in advance!

Thnak you, I will try this.

Do you mean that I should change slam_gmapping_pr2.launch in gmapping package? Sorry, I'm a novice in this. How do I start freenect_launch in the launch file?

freenect_launch works and I can get image from the camera, so that's great, thank you, Jarvis. But I would like to use kinect for building a map and I was hoping to use gmapping. When I run roslaunch turtlebot_navigation gmapping_demo.launch I get the same error about no devices connected.

Thank you for the advice about rospy.init_node, but the problem seems to be something else. Are the bumpers only actuated when they're pressed? Apparently, they have nothing to do with my problem.

I've been trying to run python scripts on Kobuki Turtlebot in order to make it perform specific patterns on the floor. I've noticed that while executing the same script on the same spot, it provides radically different performances. This is an example of my script:

#!/usr/bin/env python

# for robot A

import rospy
from kobuki_testsuite import TravelForward 
from std_msgs.msg import Empty
from geometry_msgs.msg import Twist
from std_msgs.msg import Empty
import roslib; roslib.load_manifest('kobuki_testsuite')
import sys
import copy
import os
import subprocess

from tf.transformations import euler_from_quaternion
from math import degrees

from sensor_msgs.msg import Imu
from geometry_msgs.msg import Quaternion

global stage
stage = 1
global length
length = 1 # length in metres
global width
width = 1 
#des = 0.5  # desired angle in radians - it's negative if angle is larger than 3.14

def resetter():
    try:
        pub = rospy.Publisher('/mobile_base/commands/reset_odometry', Empty, queue_size=10)
        rospy.init_node('resetter', anonymous=True)
        rate = rospy.Rate(10) # 10hz
        for i in range(0,10):
          pub.publish(Empty())
          rate.sleep()
    except rospy.ROSInterruptException:
        pass

def ImuCallback(data, angle):
  global stage
  quat = data.orientation
  q = [quat.x, quat.y, quat.z, quat.w]
  roll, pitch, yaw = euler_from_quaternion(q)

  sys.stdout.write("\r\033[1mGyro Angle\033[0m: [" + "{0:+.4f}".format(yaw) + " rad]  ["\
                 + "{0: >+7.2f}".format(degrees(yaw)) + " deg]"\
                 + "            \033[1mRate\033[0m: [" + "{0:+.4f}".format(data.angular_velocity.z) + " rad/s]  ["\
                 + "{0: >+7.2f}".format(degrees(data.angular_velocity.z)) + " deg/s] ")
  if angle > 0:
    if yaw > angle or yaw < 0:
      stage += 1
  else:
    if yaw > angle and yaw < 0:
      stage += 1 

def publish(pub, v, sec, step):
    cnt = 0
    m = sec * 2

    while cnt < m and not rospy.is_shutdown() and stage == step: 
        pub.publish(v)
        cnt = cnt + 1
        rospy.sleep(0.5)

def rotation_anticlockwise(step, angle, r):
    rospy.Subscriber("/mobile_base/sensors/imu_data", Imu, ImuCallback, angle)
    cmdvel_topic ='/cmd_vel_mux/input/teleop'

    pub = rospy.Publisher(cmdvel_topic, Twist)
    vel = Twist() 
    print "rotation"
    print stage
    while not rospy.is_shutdown() and stage == step:
      vel.angular.z = 0.5
      vel.linear.x = 0.5 * r
      rospy.loginfo("Anticlockwise")
      publish(pub, vel, 18, step)  
      rospy.loginfo("Done")
      rospy.sleep(2)
  #    if stage == 0:
   #     vel.angular.z = 0
  #  rospy.sleep(2)

if __name__ == '__main__':
    global stage
    resetter()
    rotation_anticlockwise(1, 1.57, 0)
    resetter()
    print stage
    stage = 2
    rotation_anticlockwise(2, -0.02, 0.2 * length)

What I meant for it to do is to rotate to 90 degrees and then make a full circle with a specified radius. Most of the times I run the script I get it to rotate a bit and then stand still or rotate and then make just a part of a circle. What troubles me is I don't understand whether the problem is my script or some mechanics inside the robot. Could it be that its bumper sensors are too sensitive and make it stop unexpectedly? If so, is there a way around?

Thank you, I will try doing that!

How do I set different speed for Turtlebot wheels using python? I've been using Twist() for making the Turtlebot move forward or rotate on one spot. How do I use angular and linear for setting speed on on wheels separately? For instance, I want Turtlebot to go in a circle with a specific radius.

Thank you! I will try that.

I am using rostopic pub /mobile_base/commands/reset_odometry std_msgs/Empty to reset odometry on Turtlebot. It works fine but I want to do the same thing in a Python script. Here is my code:

import rospy
from std_msgs.msg import Empty

rospy.init_node('reset_odom')

pub = rospy.Publisher('/mobile_base/commands/reset_odometry', Empty, queue_size=10)
pub.publish(Empty())

It doesn't work. Could you point out what is wrong with it? Thanks!

Maybe I didn't get your advice right, but how do I fixate the moment it reached the desired heading given that I set only the velocity?

I have the same question. I wonder if it's possible to send the desired radian/degree as a parameter to the programme? So that when I run the script it automatically rotates a desired degree.

I guess I have installed it from apt-get. If this is the problem, how do I change my sources setup? Thanks in advance!

Hello! I have the same issue. I've tried all of the advice given above and am running out of ideas. Like the author when I run killall XnSensorServer I get no such process found and when I run XnSensorServer I get XnSensorServer: error while loading shared libraries: libOpenNI.so: wrong ELF class: ELFCLASS64. Could this be the issue? How can I fix it?

Best regards, Elizaveta