replaceBody

Replace body on robot

Syntax

replaceBody(robot,bodyname,newbody)

Description

replaceBody(robot,bodyname,newbody) replaces the body in the robot model with the new body. All properties of the body are updated accordingly, except the Parent and Children properties. The rest of the robot model is unaffected.

example

Examples

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Specify Dynamics Properties to Rigid Body Tree

Open Live Script

To use dynamics functions to calculate joint torques and accelerations, specify the dynamics properties for the rigidBodyTree object and rigidBody.

Create a rigid body tree model. Create two rigid bodies to attach to it.

robot = rigidBodyTree('DataFormat','row');
body1 = rigidBody('body1');
body2 = rigidBody('body2');

Specify joints to attach to the bodies. Set the fixed transformation of body2 to body1. This transform is 1m in the x-direction.

joint1 = rigidBodyJoint('joint1','revolute');
joint2 = rigidBodyJoint('joint2');
setFixedTransform(joint2,trvec2tform([1 0 0]))
body1.Joint = joint1;
body2.Joint = joint2;

Specify dynamics properties for the two bodies. Add the bodies to the robot model. For this example, basic values for a rod (body1) with an attached spherical mass (body2) are given.

body1.Mass = 2;
body1.CenterOfMass = [0.5 0 0];
body1.Inertia = [0.001 0.67 0.67 0 0 0];

body2.Mass = 1;
body2.CenterOfMass = [0 0 0];
body2.Inertia = 0.0001*[4 4 4 0 0 0];

addBody(robot,body1,'base');
addBody(robot,body2,'body1');

Compute the center of mass position of the whole robot. Plot the position on the robot. Move the view to the xy plane.

comPos = centerOfMass(robot);

show(robot);
hold on
plot(comPos(1),comPos(2),'or')
view(2)

Figure contains an axes object. The axes object with xlabel X, ylabel Y contains 6 objects of type patch, line. One or more of the lines displays its values using only markers These objects represent base, body1, body2.

Change the mass of the second body. Notice the change in center of mass.

body2.Mass = 20;
replaceBody(robot,'body2',body2)

comPos2 = centerOfMass(robot);
plot(comPos2(1),comPos2(2),'*g')
hold off

Figure contains an axes object. The axes object with xlabel X, ylabel Y contains 7 objects of type patch, line. One or more of the lines displays its values using only markers These objects represent base, body1, body2.

Input Arguments

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`robot` — Robot model
`rigidBodyTree` object

Robot model, specified as a rigidBodyTree object. The rigid body is added to this object and attached at the rigid body specified by bodyname.

`bodyname` — Body name
string scalar | character vector

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

Data Types: char | string

`newbody` — Rigid body
`rigidBody` object

Rigid body, specified as a rigidBody object.

Extended Capabilities

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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