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publishing to /cmd_vel gives error

asked 2018-11-14 06:50:53 -0500

girpon gravatar image

hey everyone,

i am trying to let my jackal drive with this custom node :

#! /usr/bin/env python

import rospy
from geometry_msgs.msg import Twist
from sensor_msgs.msg import LaserScan

def callback(msg):
seconds = rospy.get_time()
if int(seconds) % 3 == 0:
    move.linear.x = 0
    move.linear.y = 1
    move.angular.z = 0
elif int(seconds+1) % 3 == 0: 
    move.linear.x = 0
    move.angular.z = -0
    move.linear.x = -2
    move.angular.z = -2


sub = rospy.Subscriber('/kobuki/laser/scan', LaserScan, callback)
pub = rospy.Publisher('/cmd_vel',Twist,queue_size=10)
move = Twist()


however it returns the error : /clock not being published etc. you probably know the error.

but /clock definetely is running, and my jackal isnt moving. rostopic info /cmd_vel does state its subscribing the node i want. maybe its worth it to state that this script DOES work with the turtlebot in gazebo.

greetings girpon

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Rather strangely you code will only publish a cmd_vel message when it receives a LaserScan message. So my first though is that there are no LaserScan messages being published and therefore no cmd_vel Twist messages.

PeteBlackerThe3rd gravatar image PeteBlackerThe3rd  ( 2018-11-14 08:30:17 -0500 )edit

I second @PeteBlackerThe3rd about no laser data being published, it probably works with the turtlebot because you subscribe to the topic /kobuki/something, kobuki being the mobile base of the turtlebot but not related to the jackal robot.

Delb gravatar image Delb  ( 2018-11-15 03:11:53 -0500 )edit

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answered 2018-11-14 07:43:48 -0500

dhindhimathai gravatar image

updated 2018-11-14 07:46:15 -0500

First of all, your code does not seem to be properly indented.

Did you check if the result of rosparam get use_sim_time is false? If not please try rosparam set use_sim_time false and look if it works.

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Asked: 2018-11-14 06:50:53 -0500

Seen: 274 times

Last updated: Nov 14 '18