How can I change the base position of universalUR10 robot model

Code:

ur10 = loadrobot('universalUR10');

ur10Moved = rigidBodyTree;

rb = rigidBody('newBaseForUR10');

rb.Joint.setFixedTransform(trvec2tform([3,0,0]));

ur10Moved.addBody(rb, 'base');

ur10Moved.addSubtree('newBaseForUR10', ur10);

show(ur10);

xlim([-2 4])

zlim([0, 1.5])

hold on

show(ur10Moved);

Error:

The name of the body, base, has already been used in the robot. Use a different name for the body.

when I use a different name, i got this error:

Body with name bbase is not found. Check the BodyNames property of the rigidBodyTree object to get a list of body names.

Answer 1

[Hannes Daepp]

This issue is because the default base name in a new rigidBodyTree is "base", which is also a rigid body in the loaded UR10.

This is evident when you first create the new rigid body tree:

ur10Moved = rigidBodyTree

ur10Moved = 
  rigidBodyTree with properties:

     NumBodies: 0
        Bodies: {1×0 cell}
          Base: [1×1 rigidBody]
     BodyNames: {1×0 cell}
      BaseName: 'base'
       Gravity: [0 0 0]
    DataFormat: 'struct'

ur10Moved.BaseName

ans = 'base'

As you can see, the BaseName property of UR10 is already set to "base". Then when you load the UR10, it too has a body named "base":

ur10 = loadrobot('universalUR10');
ur10.showdetails

--------------------
Robot: (10 bodies)

 Idx             Body Name                            Joint Name                            Joint Type             Parent Name(Idx)   Children Name(s)
 ---             ---------                            ----------                            ----------             ----------------   ----------------
   1             base_link                           world_joint                                 fixed                     world(0)   base(2)  shoulder_link(3)  
   2                  base            base_link-base_fixed_joint                                 fixed                 base_link(1)   
   3         shoulder_link                    shoulder_pan_joint                              revolute                 base_link(1)   upper_arm_link(4)  
   4        upper_arm_link                   shoulder_lift_joint                              revolute             shoulder_link(3)   forearm_link(5)  
   5          forearm_link                           elbow_joint                              revolute            upper_arm_link(4)   wrist_1_link(6)  
   6          wrist_1_link                         wrist_1_joint                              revolute              forearm_link(5)   wrist_2_link(7)  
   7          wrist_2_link                         wrist_2_joint                              revolute              wrist_1_link(6)   wrist_3_link(8)  
   8          wrist_3_link                         wrist_3_joint                              revolute              wrist_2_link(7)   ee_link(9)  tool0(10)  
   9               ee_link                        ee_fixed_joint                                 fixed              wrist_3_link(8)   
  10                 tool0        wrist_3_link-tool0_fixed_joint                                 fixed              wrist_3_link(8)   
--------------------

Since body names must be unique, these two rigid body tree objects cannot be combined as-is.

However, the base name is not fixed after construction, so an easy way to get around this issue would be to change the base name in the new rigid body tree that you are creating so that there are no conflicts once the UR10 is added. That is:

% Load the UR10 from the robot library
ur10 = loadrobot('universalUR10');

% Create the new rigid body tree with a new base name
ur10Moved = rigidBodyTree;
ur10Moved.BaseName = 'newBase';

% Add a new custom base to the renamed base
rb = rigidBody('newBaseForUR10');
rb.Joint.setFixedTransform(trvec2tform([3,0,0]));
ur10Moved.addBody(rb, ur10Moved.BaseName);

Then you should be able to add the UR10 as a subtree without any issue

ur10Moved.addSubtree('newBaseForUR10', ur10);

[hussein saied]

Thank you so much for your answer, it solved my problem.

Good luck