removeBody

Remove body from robot

Syntax

removeBody(robot,bodyname)

newSubtree = removeBody(robot,bodyname)

Description

removeBody(robot,bodyname) removes the body and all subsequently attached bodies from the robot model.

newSubtree = removeBody(robot,bodyname) returns the subtree created by removing the body and all subsequently attached bodies from the robot model.

Examples

Modify a Robot Rigid Body Tree Model

Make changes to an existing rigidBodyTree object. You can get replace joints, bodies and subtrees in the rigid body tree.

Load an ABB IRB-120T manipulator from the Robotics System Toolbox™ loadrobot. It is specified as a rigidBodyTree object.

manipulator = loadrobot("abbIrb120T");

View the robot with show and read the details of the robot using showdetails.

show(manipulator);

showdetails(manipulator)

--------------------
Robot: (8 bodies)

 Idx     Body Name            Joint Name            Joint Type     Parent Name(Idx)   Children Name(s)
 ---     ---------            ----------            ----------     ----------------   ----------------
   1          base        base_link-base                 fixed         base_link(0)   
   2        link_1               joint_1              revolute         base_link(0)   link_2(3)  
   3        link_2               joint_2              revolute            link_1(2)   link_3(4)  
   4        link_3               joint_3              revolute            link_2(3)   link_4(5)  
   5        link_4               joint_4              revolute            link_3(4)   link_5(6)  
   6        link_5               joint_5              revolute            link_4(5)   link_6(7)  
   7        link_6               joint_6              revolute            link_5(6)   tool0(8)  
   8         tool0          joint6-tool0                 fixed            link_6(7)   
--------------------

Get a specific body to inspect the properties. The only child of the link_3 body is the link_4 body. You can copy a specific body as well.

body3 = getBody(manipulator,"link_3");
childBody = body3.Children{1}

childBody = 
  rigidBody with properties:

            Name: 'link_4'
           Joint: [1x1 rigidBodyJoint]
            Mass: 1.3280
    CenterOfMass: [0.2247 1.5000e-04 4.1000e-04]
         Inertia: [0.0028 0.0711 0.0723 1.3052e-05 -1.3878e-04 -6.6037e-05]
          Parent: [1x1 rigidBody]
        Children: {[1x1 rigidBody]}
         Visuals: {'Mesh Filename link_4.stl'}
      Collisions: {'Mesh Filename link_4.stl'}

body3Copy = copy(body3);

Replace the joint on the link_3 body. You must create a new Joint object and use replaceJoint to ensure the downstream body geometry is unaffected. Call setFixedTransform if necessary to define a transform between the bodies instead of with the default identity matrices.

newJoint = rigidBodyJoint("prismatic");
replaceJoint(manipulator,"link_3",newJoint);

showdetails(manipulator)

--------------------
Robot: (8 bodies)

 Idx     Body Name            Joint Name            Joint Type     Parent Name(Idx)   Children Name(s)
 ---     ---------            ----------            ----------     ----------------   ----------------
   1          base        base_link-base                 fixed         base_link(0)   
   2        link_1               joint_1              revolute         base_link(0)   link_2(3)  
   3        link_2               joint_2              revolute            link_1(2)   link_3(4)  
   4        link_3             prismatic                 fixed            link_2(3)   link_4(5)  
   5        link_4               joint_4              revolute            link_3(4)   link_5(6)  
   6        link_5               joint_5              revolute            link_4(5)   link_6(7)  
   7        link_6               joint_6              revolute            link_5(6)   tool0(8)  
   8         tool0          joint6-tool0                 fixed            link_6(7)   
--------------------

Remove an entire body and get the resulting subtree using removeBody. The removed body is included in the subtree.

subtree = removeBody(manipulator,"link_4")

subtree = 
  rigidBodyTree with properties:

     NumBodies: 4
        Bodies: {[1x1 rigidBody]  [1x1 rigidBody]  [1x1 rigidBody]  [1x1 rigidBody]}
          Base: [1x1 rigidBody]
     BodyNames: {'link_4'  'link_5'  'link_6'  'tool0'}
      BaseName: 'link_3'
       Gravity: [0 0 0]
    DataFormat: 'struct'

show(subtree);

Remove the modified link_3 body. Add the original copied link_3 body to the link_2 body, followed by the returned subtree. The robot model remains the same. See a detailed comparison through showdetails.

removeBody(manipulator,"link_3");
addBody(manipulator,body3Copy,"link_2")
addSubtree(manipulator,"link_3",subtree)

showdetails(manipulator)

--------------------
Robot: (8 bodies)

 Idx     Body Name            Joint Name            Joint Type     Parent Name(Idx)   Children Name(s)
 ---     ---------            ----------            ----------     ----------------   ----------------
   1          base        base_link-base                 fixed         base_link(0)   
   2        link_1               joint_1              revolute         base_link(0)   link_2(3)  
   3        link_2               joint_2              revolute            link_1(2)   link_3(4)  
   4        link_3               joint_3              revolute            link_2(3)   link_4(5)  
   5        link_4               joint_4              revolute            link_3(4)   link_5(6)  
   6        link_5               joint_5              revolute            link_4(5)   link_6(7)  
   7        link_6               joint_6              revolute            link_5(6)   tool0(8)  
   8         tool0          joint6-tool0                 fixed            link_6(7)   
--------------------

Input Arguments

robot — Robot model

rigidBodyTree object

Robot model, specified as a rigidBodyTree object.

bodyname — Body name

string scalar | character vector

Body name, specified as a string scalar character vector. This body must be on the robot model specified in robot.

Data Types: char | string

Output Arguments

newSubtree — Robot subtree

rigidBodyTree object

Robot subtree, returned as a rigidBodyTree object. This new subtree uses the parent name of the body specified by bodyname as the base name. All bodies that are attached in the previous robot model (including the body with bodyname specified) are added to the subtree.

Extended Capabilities

C/C++ Code Generation

Generate C and C++ code using MATLAB® Coder™.

Usage notes and limitations:

When creating the rigidBodyTree object, use the syntax that specifies the MaxNumBodies as an upper bound for adding bodies to the robot model. You must also specify the DataFormat property as a name-value pair. For example:

robot = rigidBodyTree("MaxNumBodies",15,"DataFormat","row")

To minimize data usage, limit the upper bound to a number close to the expected number of bodies in the model. All data formats are supported for code generation. To use the dynamics functions, the data format must be set to "row" or "column".

The show and showdetails functions do not support code generation.

Version History

Introduced in R2016b