Hello, I am having the 1.6.16s ros-fuerte-simulator gazebo with Ubuntu 12.04 (64bit). I am having a similar problem as this post:

link:Hector_Quadrotor Gazebo - Quadrotor x/y position does not update

The difference is I can control the quadrotor in the two demos but not when I tried to control the robot with my own code. The one extra thing is my robot pose is not updated as well after I publish the msg. So basically right now when I publish a twist message to '/cmdvel' and then I check the state with /gazebo/getmodel_state', the linear and angular component under twist are all zero. Does anyone know why? Here's my code (without the part that I set my robot's pose):

---

def init(self, proj, shareddata, velocityTopic='/cmdvel'):

    self.pose_handler = proj.h_instance['pose']
    print self.pose_handler.model_name
    try:
        #open a publisher for the base controller of the robot
        self.pub = rospy.Publisher(velocityTopic, Twist)

        # for the pr2, use /base_controller/command
        # the turtlebot takes /cmd_vel
    except:
        print 'Problem setting up Locomotion Command Node'


def sendCommand(self, cmd):

    #Twist is the message type and consists of x,y,z linear velocities
    #and roll, pitch, yaw orientation velocities (x,y,z)
    twist=Twist()

    #Positive x is forward on robots in Gazebo
    twist.linear.x=cmd[0]*4   

    #Angluar z is yaw or rotation in the xy plane
    twist.angular.z=cmd[1]*1.5

    try:
        #Publish the command to the robot
        self.pub.publish(twist)
        rospy.wait_for_service('/gazebo/get_model_state')
        gms = rospy.ServiceProxy('/gazebo/get_model_state', GetModelState)
        resp = gms(self.pose_handler.model_name,'world')
        print >>sys.__stdout__,'resp:' + str(resp)
    except:
        print 'Error publishing Twist Command'

---

Thank you for your help.