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2014-01-28 17:27:11 -0500 marked best answer Using move_base to turn wheels?

Hello,

I am currently using move_base(with default local and global planners) to get the robot in the desired position. My problem is that when my robot(2 wheeled, built using real wheelchair) is told to move forward right or forward left, it is making a path that goes around too much to get there. In other words, if the robot is located at (0,0) and is commanded to move to (1,1), it is not turning its wheels enough to get there more directly and rather makes a curvy path with large radius than necessary. Is there a parameter that I can tweak to make the radius of path smaller?

I would appreciate any help, Thank you.

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2013-05-11 11:07:55 -0500 asked a question Resetting odometry(pose) information

Hello,

I am conducting an experiment that compares different navigation algorithms for a short distance (<4~5m) using a turtlebot, by plotting the sequences of locations contained in the odom messages. Since I am concerned with only short distances, I am not willing to use any localization to estimate the precise pose(location) of the robot.

The problem is that because I am relying only on odometry information (i.e. how much wheels have turned) to estimate the pose of the robot, odometry messages contain different pose information even for a same location. As a result, everytime I switch between navigation algorithms I need to turn off and turn on the turtlebot package in order to start at (0,0).

Is there a way to manually set the pose of the robot without turning on and off the turtlebot package? I am using turtlebot_bringup minimal.launch.

Thank you in advance.

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2012-09-01 06:08:02 -0500 asked a question How to get the time on bag file?

Hello,

I am trying to graph robot's distance from a particular point over time. I have a bag file, and wondering if I can get the duration in the bag file. For instance, if I play a x.bag file, I have the following information:

[PAUSED] Bag Time: 1346096057.781698 Duration: 1.680327 / 19.253778

Is there a way to get that duration in a code?

2012-09-01 06:03:23 -0500 commented question Using move_base to turn wheels?

Thank you all for your help guys. I found that it was the problem with the PID controller, which was written by some guy before me. PID controller was set such that it limits the gain in angular velocity - quite amused that move_base actually take PID parameters into account.

2012-08-30 11:39:00 -0500 asked a question Moving and stopping when using TrajectoryPlannerROS and carrot_planner

Hi,

I am currently using base_local_planner/TrajectoryPlannerROS as my local planner, and carrot planner as global planner. Everything seems to work fine, execept that when these are used to execute a path, my robot moves a little and stops to plan another global path from the new location to the goal, continue moving, and stops to plan and so on. It seems like when the robot is out of the planned path even by little, it stops to replan.

Is there a way to allow the robot to be out of the global path a little bit? I looked at many different parameters including path_distance_bias, but it does not seem to have any effects on the behaviour.

Any help would be appreciated.

2012-08-30 05:14:46 -0500 commented answer Mechanism for calculating smooth trajectory?

Hi again. Instead of goal_passer, I used carrot_planner and like you said it is much faster than navfn. However, when I use carrot_planner it will move for sometime and stops, and continue moving. Do you know what might be causing this movement?

2012-08-30 03:47:43 -0500 commented answer Mechanism for calculating smooth trajectory?

Hi, I checked out goal_passer, but the wiki page is empty. Do you know what it does? Right now it is just rotating in one place, with 0 linear velocity.

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2012-08-28 14:15:17 -0500 asked a question Mechanism for calculating smooth trajectory?

Hi,

I have a wheelchair robot, and I have written by own path planner. My path planner gives a set of waypoints to reach the goal, each ~1m apart, and a path is re-planned every time there is something observed by Kinect. I have been sending these waypoints to move_base to get to these waypoints, treating them as a goal to move_base node. However, I realized that move_base is slow in adapting to a new goal when there is a goal already being pursued.

I just need a mechanism that computes a smooth trajectory given a two points (current position and the goal), by taking account of the current robot's velocity and position. I do not need obstacle avoidance, costmap update, recovery method and etc, which I presume is slowing down the move_base node. Is there a such node in ROS? I think base_local_planner is somehow publishing the velocity (cmd_vel topic) with a given plan, however I do not really have a plan but only two points.

Any help would be appreciated.

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2012-08-24 15:57:05 -0500 commented question transformPoint using tf::Transform?

I took a look at time travel tutorial in tf wiki: http://www.ros.org/wiki/tf/Tutorials/Time%20travel%20with%20tf%20%28C%2B%2B%29, but it does not explain about transforming a point.

2012-08-24 15:56:22 -0500 asked a question transformPoint using tf::Transform?

Hi,

I need to save a transform (world->Kinect frame) at a specific time, and use this transform to convert a point in world coordinate frame to a point in that old Kinect frame after several seconds.

To do this, I first tried using tf::Listener::transformPoint. However, to my knowledge the only way to save a transform at a specific time is by using tf::lookupTransform, which can save the transform at specific time in tf::Transform type. My problem is that in this tf::Transform type, there is no function such as transformPoint.

Am I left to implement such function myself, or is there a one that is named differently?

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2012-08-13 02:29:14 -0500 commented question Using move_base to turn wheels?

Yes, I am sure I did otherwise the robot would not move at all. My problem is that the planners in move_base are planning paths that are too curvy (i.e. radius larger than necessary), and was wondering if there is anything I can do to make this smaller.