getTransform

Get transform between body frames

Syntax

transform = getTransform(robot,configuration)

transform = getTransform(robot,configuration,bodyname)

transform = getTransform(robot,configuration,framename)

transform = getTransform(robot,configuration,sourcebody,targetbody)

transform = getTransform(robot,configuration,sourceframe,targetframe)

Description

transform = getTransform(robot,configuration) computes the transform for every frame in the rigid body tree with respect to the robot base frame, using the specified robot configuration configuration.

transform = getTransform(robot,configuration,bodyname) computes the transform that converts points in the bodyname frame to the robot base frame, using the specified robot configuration.

transform = getTransform(robot,configuration,framename) computes the transform that converts points in the framename frame to the robot base frame, using the specified robot configuration.

transform = getTransform(robot,configuration,sourcebody,targetbody) computes the transform that converts points from the source body frame to the target body frame, using the specified robot configuration.

transform = getTransform(robot,configuration,sourceframe,targetframe) computes the homogenous transformation matrix that transforms points in the source frame to the target frame, using the specified robot configuration.

Examples

Get Transform Between Frames for Robot Configuration

Get the transform between two frames for a specific robot configuration.

Load a Yaskawa Motoman MH-5 manipulator from the Robotics System Toolbox™ loadrobot.

motoman = loadrobot("yaskawaMotomanMH5");
showdetails(motoman)

--------------------
Robot: (6 bodies)

 Idx     Body Name     Joint Name     Joint Type     Parent Name(Idx)   Children Name(s)
 ---     ---------     ----------     ----------     ----------------   ----------------
   1        link_s        joint_s       revolute         base_link(0)   link_l(2)  
   2        link_l        joint_l       revolute            link_s(1)   link_u(3)  
   3        link_u        joint_u       revolute            link_l(2)   link_r(4)  
   4        link_r        joint_r       revolute            link_u(3)   link_b(5)  
   5        link_b        joint_b       revolute            link_r(4)   link_t(6)  
   6        link_t        joint_t       revolute            link_b(5)   
--------------------

Get the transform between the "link_l" and "link_t" bodies of the motoman robot given a specific configuration. The transform converts points in "link_l" frame to the "link_t" frame.

q = randomConfiguration(motoman);
show(motoman,q);

transform = getTransform(motoman,q,"link_l","link_t")

transform = 4×4

    0.7787    0.0961   -0.6199    0.3115
    0.5256    0.4396    0.7283   -0.4624
    0.3425   -0.8930    0.2918   -0.1886
         0         0         0    1.0000

Input Arguments

robot — Robot model

rigidBodyTree object

Robot model, specified as a rigidBodyTree object.

configuration — Robot configuration

structure array

Robot configuration, specified as a structure array with joint names and positions for all the bodies in the robot model. You can generate a configuration using homeConfiguration(robot), randomConfiguration(robot), or by specifying your own joint names and positions in a structure array.

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

framename — Frame name

string scalar | character vector

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

Data Types: char | string

targetbody — Target body name

string scalar | character vector

Target body name, specified as a character vector. This body must be on the robot model specified in robot. The target frame is the coordinate system you want to transform points into.

Data Types: char | string

sourcebody — Source body name

string scalar | character vector

Source body name, specified as a string scalar or character vector. This body must be on the robot model specified in robot. The source frame is the coordinate system you want points transformed from.

Data Types: char | string

targetframe — Target frame name

string scalar | character vector

Target frame name, specified as a character vector. This frame must be on the robot model specified in robot. The target frame is the coordinate system you want to transform points into.

Data Types: char | string

sourceframe — Source frame name

string scalar | character vector

Source frame name, specified as a string scalar or character vector. This frame must be on the robot model specified in robot. The source frame is the coordinate system you want points transformed from.

Data Types: char | string

Output Arguments

transform — Homogeneous transform

4-by-4 matrix

Homogeneous transform, returned as a 4-by-4 matrix.

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

R2025a: Specify frame name in getTransform method

The getTransform method now accepts either body names or frame names in the input arguments to compute the transform between them.

R2024a: Static memory allocation support

getTransform now supports code generation with disabled dynamic memory allocation. For more information about disabling dynamic memory allocation, see Set Dynamic Memory Allocation Threshold (MATLAB Coder).