Ashwin27's profile - activity

Hello Nikhil, I moved forward with the Nav2d package by Sebastien mentioned in the answer below. I highly recommend it, it's a great place to start.

Using Gazebo, I place a husky robot in a completely unknown environment (currently the willowgarage map). My basic objective is to make the husky autonomously navigate itself through the entire world with the sole aim of mapping the entire area. Basically, if anyone could tell me how to combine an exploration algorithm such as frontier_exploration with gmapping, I would greatly appreciate it. Most tutorials out there use teleoperation, which really defeats the purpose I'm trying to achieve.

Thank You!

Sure, that's quite alright. Please do look at it a little later when you're free, I would greatly appreciate your help.

Hello Andromeda,

I've uploaded the tf_views graph and the ros graph to the drive folder. The map that I'm using is a willow garage map in Stage, I have uploaded a screenshot of the same.

Thank you, Lebowski and David. I modified the code as you guys suggested and solved the error.

goal_m.target_pose.header.frame_id = "/map";
goal_m.target_pose.header.stamp = ros::Time();

goal_m.target_pose.pose.position.x =mCurrentMap.getOriginX() + (((double)goal_x+0.5) * mCurrentMap.getResolution());

goal_m.target_pose.pose.position.y = mCurrentMap.getOriginY() + (((double)goal_y+0.5) * mCurrentMap.getResolution());

goal_m.target_pose.pose.orientation.w= 1.0;

Hello,

I am currently implementing a simulation wherein a robot is supposed to explore and map an unknown environment. An exploration algorithm decides on a frontier cell for a robot to move towards and then sends it to move_base which does the rest. This works for some time, but then move_base begins to provide a faulty path, one that cuts right through a high cost route, as shown in the figure. The drive folder in the link also contains the rqt_graph, tf tree and a screenshot of the Stage simulation.

At this stage, the robot stops moving and continuously displays the warning:

Unable to get starting pose of robot, unable to create global plan

This is then followed by the errors: Cannot clear map because pose cannot be retrieved and Aborting because a valid plan could not be found. Even after executing all recovery behaviors.

If I then teleoperate the robot a bit and restart the whole process, it continues exploring for a while again, till move_base plans another path through a high-cost region.

Am I making any obvious mistakes here? Should I retune my costmap parameters? Is there any way I can make move_base provide an alternate that does not traverse through the high cost region?

If anyone has any suggestions at all on how I can prevent this from happening, please share them, I would greatly appreciate it.

Thank You.

Thanks for the reply, David! The quaternion error doesn't pop up anymore, but now it displays this error: The robot's start position is off the global costmap. Planning will always fail, are you sure the robot has been properly localized?

I have an occupancy grid map and an exploration algorithm that provides me with 2 dimensional co-ordinates to travel to. The mapping and goal generation are working perfectly. Unfortunately, an error arises when I send the goal to move_base. The robot does not move and I get the following error:

The robot's start position is off the global costmap. Planning will always fail, are you sure the robot has been properly localized?

This is the part of the code that sends the goal:

MoveBaseClient ac("move_base", true); 
move_base_msgs::MoveBaseGoal goal; 
goal.target_pose.header.frame_id = "base_link"; 
goal.target_pose.header.stamp = ros::Time::now(); 
goal.target_pose.pose.position.x = goalx; 
goal.target_pose.pose.position.y = goaly;
goal.target_pose.pose.orientation.w = 1.0;     //Edit made based on David Lu's answer
ac.sendGoal(goal);

where goalx and goaly are integers that contain the map co-ordinates of the goal. MoveBaseClient has been defined earlier, as given in this link.

Also, if someone has links/documentation on move_base, quaternions in ROS or examples of sending goals to move_base apart from this tutorial link, please post them as well, I would be extremely grateful. I haven't perfectly understood how to programmatically send goals to move_base.

Thank You!

And thank you so much! It really is brilliant of you to offer so much help.

Sorry about that, Sebastien, I downloaded the packages again and it's working now. Although, yes, the Husky's odometry does seem to be causing issues. Still, it's running now, I'll try to figure the rest out and keep you posted, if I get the maping to run better.

I've uploaded a screenshot of my rqt_console here. I called the StartMapping service at #19, after which the Navigator was initialised. After this, it just continuously prints the tf error. The robot does not move.

Oh, my mistake, sorry about that. The reason I tried /cmd instead of /cmd_vel was because nothing is being published on cmd_vel. /cmd does have something published on it once I start Mapping.

Hello,

I am currently trying to implement the navigation_2d package using Gazebo with a Husky Robot Model and am facing several problems. Is there anyone out there who has managed to successfully implement the navigation_2d package in Gazebo?

EDIT: So far, I have managed to successfully launch Gazebo, however I believe there is an error in the tf tree. The following warning is seen when the launch is started:

Node: /Operator Time: 05:30:35.510000000 (1970-01-01) Severity: Warn Published Topics: /rosout

Waiting on transform from base_link to odom to become available before running costmap, tf error:

Location: /tmp/buildd/ros-hydro-costmap-2d-1.11.11-0quantal-20140919-0015/src/costmap_2d_ros.cpp:Costmap2DROS::Costmap2DROS:95

The launch file, tf tree, rqt_graph and images of the simulation once launched, can be found here.

When the command to start mapping is issued, the following error is printed:

Could not get robot position: "map" passed to lookupTransform argument target_frame does not exist.

Basically, I do not understand why the robot fails to localize. If it is an error in the tf tree, do I need to modify the sdf file of the Husky IIRC? The simulation, despite inputting the laser scan data, does not localize the robot nor create a map. Any help at all will be gratefully accepted. I apologize for the overload of information.

Thank you.

Does it depend on the version of gazebo you're using? Or do I have to make changed in the husky's urdf file again? I'm currently using gazebo-1.9. Would updating it help solve this error.