Viewing and Understanding the Specifications of Pre-defined Robots

How do you view what the details of a predefined robot look like?

For eaxample, I saw the following line in an example file: load exampleRobots.mat lbr

However, when I say open exampleRobots.mat, I just see this:

baxter: [1×1 rigidBodyTree]

lbr: [1×1 rigidBodyTree]

puma1: [1×1 rigidBodyTree]

puma2: [1×1 rigidBodyTree]

How do I know what these specifications for the robots look like?

Similarly, I see example code that says to import a robot using a URDF file. However, how can I view a URDF file, and how do I know what the robot looks like?

Thanks!

Answer 1

[Karsh Tharyani]

Each of the variables above are a type of rigidBodyTree object. As a starting step to view what the underlying connectivity looks like (bodies and their joints) you can use the showdetails function. If you want to see what the "rigidBodyTree" looks like, simply call the show function on the "rigidBodyTree" object. For example,

>> showdetails(puma1)
--------------------
Robot: (6 bodies)

 Idx    Body Name   Joint Name   Joint Type    Parent Name(Idx)   Children Name(s)
 ---    ---------   ----------   ----------    ----------------   ----------------
   1           L1         jnt1     revolute             base(0)   L2(2)  
   2           L2         jnt2     revolute               L1(1)   L3(3)  
   3           L3         jnt3     revolute               L2(2)   L4(4)  
   4           L4         jnt4     revolute               L3(3)   L5(5)  
   5           L5         jnt5     revolute               L4(4)   L6(6)  
   6           L6         jnt6     revolute               L5(5)   
--------------------
>> show(puma1)

This documented example is a good reference for the same. You can also look at Build a robot step by step Topic page if you are getting started with "rigidBodyTree".

A URDF file is an XML file which captures the connectivity of the tree representing a robot. You can read more about it here. You can use your favorite editor to view the file. From MATLAB you can try viewing a sample URDF file called "sawyer.urdf". You can use the "edit" command to open and view any other URDF as well.

>> edit sawyer.urdf

Note: "sawyer.urdf" is located at "toolbox/robotics/robotmanip/exampleRobots/sawyer_description/urdf/sawyer.urdf" where the "toolbox" directory is located under your matlabroot directory.

Hope that answers your question.