frameinfo

Frame information

Since R2025a

Syntax

frame = frameinfo(rb,framename)

Description

frame = frameinfo(rb,framename) returns a structure containing framename frame's information, containing its name, parent frame name, relative transformation of the frame with respect to the parent frame, and child frame names.

Examples

Work with Frames in Rigid Body Robot Model

This example showcases how to manage frames within a rigid body, covering operations such as adding, removing, and updating frames, as well as retrieving transforms between them.

Create a rigid body robot model and display initial frame information.

A rigid body can contain multiple frames used to define coordinate systems for attaching sensors, tools, or other components.

rb = rigidBody('rb');
rbFrame = frameinfo(rb, 'rb')

rbFrame = struct with fields:
              Name: 'rb'
    RigidTransform: [4×4 double]
       ParentFrame: ''
       ChildFrames: {1×0 cell}

Add a new frame named test to the rigid body rb, defining its position with a translation relative to the root frame rb.

addFrame(rb, 'test', 'rb', trvec2tform([1 2 3]));

Next, add another frame, test1, which is positioned relative to the newly added frame test using a combination of translation and rotation.

Each frame is defined by its name, parent frame, and rigid transform.

addFrame(rb, 'test1', 'test', trvec2tform([1 2 3]));

Display information about these added frames to verify their properties and confirm their placement within the rigid body.

testFrame = frameinfo(rb, 'test1')

testFrame = struct with fields:
              Name: 'test1'
    RigidTransform: [4×4 double]
       ParentFrame: 'test'
       ChildFrames: {1×0 cell}

You can also remove frames, which updates the frame tree to maintain its kinematic structure. Remove the frame test and observe its effect on test1 frame.

% Remove frame 'test'
removeFrame(rb, 'test');

% Check updated frame information for 'test1'
frameAfterRemove = frameinfo(rb, 'test1')

frameAfterRemove = struct with fields:
              Name: 'test1'
    RigidTransform: [4×4 double]
       ParentFrame: 'rb'
       ChildFrames: {1×0 cell}

Now, modify existing frames by updating their properties, such as the name, parent frame, or rigid transform.

First, rename test1 frame to test2.

updateFrame(rb, 'test1', 'Name', 'test2');

Add a new frame test3 and update test2 to use it as the parent frame.

addFrame(rb, 'test3', 'rb', trvec2tform([1 1 1]));
updateFrame(rb, 'test2', 'ParentFrame', 'test3', ...
    'RigidTransform', trvec2tform([1 2 3]));

Display updated frame information.

frameAfterUpdate = frameinfo(rb, 'test2')

frameAfterUpdate = struct with fields:
              Name: 'test2'
    RigidTransform: [4×4 double]
       ParentFrame: 'test3'
       ChildFrames: {1×0 cell}

Input Arguments

rb — Rigid body

rigidBody object

Rigid body, specified as a rigidBody object.

framename — Name of frame to be queried

string scalar | character vector

Name of the frame to be queried, specified as a string scalar or character vector.

Data Types: char | string

Output Arguments

frame — Frame information

struct

Information of the frame specified by framename, returned as a structure containing these fields:

• Name — Name of the queried frame in the rigid body, specified as a string scalar or character vector.

• RigidTransform — Rigid body transform of the queried frame in the rigid body, specified as 4-by-4 homogeneous transformation.

• ParentFrame — Name of the parent frame of the queried frame in the rigid body, as a string scalar or character vector.

• ChildFrames — Name of the child frames of the queried frame in the rigid body, specified as a cell array.

Data Types: struct

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.

Version History

Introduced in R2025a