Zhiping,

A few questions off the top of my head:

* Does your odometry for the robot look reasonable? To check this you can do
things like rotate the robot in place and set a large decay time on laser
scans to see if the drift looks reasonable. You'd hope to see scans more or
less fall on top of each other during subsequent rotations.

* Have you looked at navigation relevant topics in rviz to make sure that
you've configured the costmap to take laser data into account? You can find
a tutorial on this here:
http://www.ros.org/wiki/navigation/Tutorials/Using%20rviz%20with%20the%20Navigation%20Stack.
If the costmap doesn't show laser data, then the robot will likely hit
walls.

* Have you configured the acceleration limits of your robot correctly? If
not, this could result in the robot being unable to follow a straight path.
The following section of the navigation setup tutorial highlights the
parameters you should think about changing:
http://www.ros.org/wiki/navigation/Tutorials/RobotSetup#Base_Local_Planner_Configuration

* What frame are you using for the global costmap? It should probably be
your odometric frame if you're running with an empty map, meaning you
wouldn't run AMCL.

<http://www.ros.org/wiki/navigation/Tutorials/RobotSetup#Base_Local_Planner_Configuration>Hope
this helps,

Eitan

On Wed, Nov 3, 2010 at 4:51 AM, #TAN ZHI PING# <TANZ0066@e.ntu.edu.sg>wrote:

>   Hi all,
>
> I am currently using the Move_base program to move the Pioneer robot and
> encountered some difficulties
>
> 1) Instead of moving in a straight line as shown in the global path, the
> robot moved in a s-shaped direction.
> 2) Using a empty map as global map, the robot constantly banged on the wall
> despite obstacles detection using  laser scan.
>
> Thank in advance for your kind advice.
>
> With thank,
> Zhiping
>
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