rigidBodyTree

Create tree-structured robot

Description

The rigidBodyTree is a representation of the connectivity of rigid bodies with joints. Use this class to build robot manipulator models in MATLAB^®. If you have a robot model specified using the Unified Robot Description Format (URDF), use importrobot to import your robot model.

A rigid body tree model is made up of rigid bodies as rigidBody objects. Each rigid body has a rigidBodyJoint object associated with it that defines how it can move relative to its parent body. Use setFixedTransform to define the fixed transformation between the frame of a joint and the frame of one of the adjacent bodies. You can add, replace, or remove rigid bodies from the model using the methods of the RigidBodyTree class.

Robot dynamics calculations are also possible. Specify the Mass, CenterOfMass, and Inertia properties for each rigidBody in the robot model. You can calculate forward and inverse dynamics with or without external forces and compute dynamics quantities given robot joint motions and joint inputs. To use the dynamics-related functions, set the DataFormat property to "row" or "column".

For a given rigid body tree model, you can also use the robot model to calculate joint angles for desired end-effector positions using the robotics inverse kinematics algorithms. Specify your rigid body tree model when using inverseKinematics or generalizedInverseKinematics.

The show method supports visualization of body meshes. Meshes are specified as .stl files and can be added to individual rigid bodies using addVisual. Also, by default, the importrobot function loads all the accessible .stl files specified in your URDF robot model.

Creation

Syntax

robot = rigidBodyTree

robot = rigidBodyTree("MaxNumBodies",N,"DataFormat",dataFormat)

Description

robot = rigidBodyTree creates a tree-structured robot object. Add rigid bodies to it using addBody.

robot = rigidBodyTree("MaxNumBodies",N,"DataFormat",dataFormat) specifies an upper bound on the number of bodies allowed in the robot when generating code. You must also specify the DataFormat property as a name-value pair.

Properties

NumBodies — Number of bodies

integer

This property is read-only.

Number of bodies in the robot model (not including the base), returned as an integer.

Bodies — List of rigid bodies

cell array of handles

This property is read-only.

List of rigid bodies in the robot model, returned as a cell array of handles. Use this list to access specific RigidBody objects in the model. You can also call getBody to get a body by its name.

BodyNames — Names of rigid bodies

cell array of string scalars | cell array of character vectors

This property is read-only.

Names of rigid bodies, returned as a cell array of character vectors.

BaseName — Name of robot base

'base' (default) | string scalar | character vector

Name of robot base, returned as a string scalar or character vector.

Gravity — Gravitational acceleration experienced by robot

[0 0 0] m/s² (default) | [x y z] vector

Gravitational acceleration experienced by robot, specified as an [x y z] vector in meters per second squared. Each element corresponds to the acceleration of the base robot frame in that direction.

DataFormat — Input/output data format for kinematics and dynamics functions

"struct" (default) | "row" | "column"

Input/output data format for kinematics and dynamics functions, specified as "struct", "row", or "column". To use dynamics functions, you must use either "row" or "column".

Object Functions

Dynamics

centerOfMass	Center of mass position and Jacobian
externalForce	Compose external force matrix relative to base
forwardDynamics	Joint accelerations given joint torques and states
geometricJacobian	Geometric Jacobian for robot configuration
gravityTorque	Joint torques that compensate gravity
inverseDynamics	Required joint torques for given motion
massMatrix	Joint-space mass matrix
velocityProduct	Joint torques that cancel velocity-induced forces

Kinematics

getTransform	Get transform between body frames
homeConfiguration	Get home configuration of robot
randomConfiguration	Generate random configuration of robot

Collision Checking

checkCollision

Check if robot is in collision

Modify Rigid Body Tree Structure

addBody	Add body to robot
addSubtree	Add subtree to robot
getBody	Get robot body handle by name
removeBody	Remove body from robot
replaceBody	Replace body on robot
replaceJoint	Replace joint on body
subtree	Create subtree from robot model

Utilities

copy	Copy robot model
show	Show robot model in figure
showdetails	Show details of robot model
writeAsFunction	Create rigidBodyTree code generating function

Examples

Attach Rigid Body and Joint to Rigid Body Tree

Add a rigid body and corresponding joint to a rigid body tree. Each rigidBody object contains a rigidBodyJoint object and must be added to the rigidBodyTree using addBody.

Create a rigid body tree.

rbtree = rigidBodyTree;

Create a rigid body with a unique name.

body1 = rigidBody('b1');

Create a revolute joint. By default, the rigidBody object comes with a fixed joint. Replace the joint by assigning a new rigidBodyJoint object to the body1.Joint property.

jnt1 = rigidBodyJoint('jnt1','revolute');
body1.Joint = jnt1;

Add the rigid body to the tree. Specify the body name that you are attaching the rigid body to. Because this is the first body, use the base name of the tree.

basename = rbtree.BaseName;
addBody(rbtree,body1,basename)

Use showdetails on the tree to confirm the rigid body and joint were added properly.

showdetails(rbtree)

--------------------
Robot: (1 bodies)

 Idx    Body Name   Joint Name   Joint Type    Parent Name(Idx)   Children Name(s)
 ---    ---------   ----------   ----------    ----------------   ----------------
   1           b1         jnt1     revolute             base(0)   
--------------------

Build Manipulator Robot Using Denavit-Hartenberg Parameters

Use the Denavit-Hartenberg (DH) parameters of the Puma560® robot to build a robot. Each rigid body is added one at a time, with the child-to-parent transform specified by the joint object.

The DH parameters define the geometry of the robot with relation to how each rigid body is attached to its parent. For convenience, setup the parameters for the Puma560 robot in a matrix [1]. The Puma robot is a serial chain manipulator. The DH parameters are relative to the previous row in the matrix, corresponding to the previous joint attachment.

dhparams = [0   	pi/2	0   	0;
            0.4318	0       0       0
            0.0203	-pi/2	0.15005	0;
            0   	pi/2	0.4318	0;
            0       -pi/2	0   	0;
            0       0       0       0];

Create a rigid body tree object to build the robot.

robot = rigidBodyTree;

Create the first rigid body and add it to the robot. To add a rigid body:

1. Create a rigidBody object and give it a unique name.

2. Create a rigidBodyJoint object and give it a unique name.

3. Use setFixedTransform to specify the body-to-body transformation using DH parameters. The last element of the DH parameters, theta, is ignored because the angle is dependent on the joint position.

4. Call addBody to attach the first body joint to the base frame of the robot.

body1 = rigidBody('body1');
jnt1 = rigidBodyJoint('jnt1','revolute');

setFixedTransform(jnt1,dhparams(1,:),'dh');
body1.Joint = jnt1;

addBody(robot,body1,'base')

Create and add other rigid bodies to the robot. Specify the previous body name when calling addBody to attach it. Each fixed transform is relative to the previous joint coordinate frame.

body2 = rigidBody('body2');
jnt2 = rigidBodyJoint('jnt2','revolute');
body3 = rigidBody('body3');
jnt3 = rigidBodyJoint('jnt3','revolute');
body4 = rigidBody('body4');
jnt4 = rigidBodyJoint('jnt4','revolute');
body5 = rigidBody('body5');
jnt5 = rigidBodyJoint('jnt5','revolute');
body6 = rigidBody('body6');
jnt6 = rigidBodyJoint('jnt6','revolute');

setFixedTransform(jnt2,dhparams(2,:),'dh');
setFixedTransform(jnt3,dhparams(3,:),'dh');
setFixedTransform(jnt4,dhparams(4,:),'dh');
setFixedTransform(jnt5,dhparams(5,:),'dh');
setFixedTransform(jnt6,dhparams(6,:),'dh');

body2.Joint = jnt2;
body3.Joint = jnt3;
body4.Joint = jnt4;
body5.Joint = jnt5;
body6.Joint = jnt6;

addBody(robot,body2,'body1')
addBody(robot,body3,'body2')
addBody(robot,body4,'body3')
addBody(robot,body5,'body4')
addBody(robot,body6,'body5')

Verify that your robot was built properly by using the showdetails or show function. showdetails lists all the bodies in the MATLAB® command window. show displays the robot with a given configuration (home by default). Calls to axis modify the axis limits and hide the axis labels.

showdetails(robot)

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

 Idx    Body Name   Joint Name   Joint Type    Parent Name(Idx)   Children Name(s)
 ---    ---------   ----------   ----------    ----------------   ----------------
   1        body1         jnt1     revolute             base(0)   body2(2)  
   2        body2         jnt2     revolute            body1(1)   body3(3)  
   3        body3         jnt3     revolute            body2(2)   body4(4)  
   4        body4         jnt4     revolute            body3(3)   body5(5)  
   5        body5         jnt5     revolute            body4(4)   body6(6)  
   6        body6         jnt6     revolute            body5(5)   
--------------------

show(robot);
axis([-0.5,0.5,-0.5,0.5,-0.5,0.5])
axis off

References

[1] Corke, P. I., and B. Armstrong-Helouvry. “A Search for Consensus among Model Parameters Reported for the PUMA 560 Robot.” Proceedings of the 1994 IEEE International Conference on Robotics and Automation, IEEE Computer. Soc. Press, 1994, pp. 1608–13. DOI.org (Crossref), doi:10.1109/ROBOT.1994.351360.

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)   
--------------------

Specify Dynamics Properties to Rigid Body Tree

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)

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

Compute Forward Dynamics Due to External Forces on Rigid Body Tree Model

Calculate the resultant joint accelerations for a given robot configuration with applied external forces and forces due to gravity. A wrench is applied to a specific body with the gravity being specified for the whole robot.

Load a KUKA iiwa 14 robot model from the Robotics System Toolbox™ loadrobot. The robot is specified as a rigidBodyTree object.

Set the data format to "row". For all dynamics calculations, the data format must be either "row" or "column".

Set the gravity. By default, gravity is assumed to be zero.

kukaIIWA14 = loadrobot("kukaIiwa14",DataFormat="row",Gravity=[0 0 -9.81]);

Get the home configuration for the kukaIIWA14 robot.

q = homeConfiguration(kukaIIWA14);

Specify the wrench vector that represents the external forces experienced by the robot. Use the externalForce function to generate the external force matrix. Specify the robot model, the end effector that experiences the wrench, the wrench vector, and the current robot configuration. wrench is given relative to the "iiwa_link_ee_kuka" body frame, which requires you to specify the robot configuration, q.

wrench = [0 0 0.5 0 0 0.3];
fext = externalForce(kukaIIWA14,"iiwa_link_ee_kuka",wrench,q);

Compute the resultant joint accelerations due to gravity, with the external force applied to the end-effector "iiwa_link_ee_kuka" when kukaIIWA14 is at its home configuration. The joint velocities and joint torques are assumed to be zero (input as an empty vector []).

qddot = forwardDynamics(kukaIIWA14,q,[],[],fext)

qddot = 1×7

   -0.0023   -0.0112    0.0036   -0.0212    0.0067   -0.0075  499.9920

Compute Inverse Dynamics from Static Joint Configuration

Use the inverseDynamics function to calculate the required joint torques to statically hold a specific robot configuration. You can also specify the joint velocities, joint accelerations, and external forces using other syntaxes.

Load an Omron eCobra-600 from the Robotics System Toolbox™ loadrobot, specified as a rigidBodyTree object. Set the gravity property and ensure the data format is set to "row". For all dynamics calculations, the data format must be either "row" or "column".

robot = loadrobot("omronEcobra600", DataFormat="row", Gravity=[0 0 -9.81]);

Generate a random configuration for robot.

q = randomConfiguration(robot);

Compute the required joint torques for robot to statically hold that configuration.

tau = inverseDynamics(robot,q)

tau = 1×4

    0.0000    0.0000  -19.6200         0

Compute Joint Torque to Counter External Forces

Use the externalForce function to generate force matrices to apply to a rigid body tree model. The force matrix is an m-by-6 vector that has a row for each joint on the robot to apply a six-element wrench. Use the externalForce function and specify the end effector to properly assign the wrench to the correct row of the matrix. You can add multiple force matrices together to apply multiple forces to one robot.

To calculate the joint torques that counter these external forces, use the inverseDynamics function.

Load a Universal Robots UR5e from the Robotics System Toolbox™ loadrobot, specified as a rigidBodyTree object. Update the gravity and set the data format to "row". For all dynamics calculations, the data format must be either "row" or "column"

manipulator = loadrobot("universalUR5e", DataFormat="row", Gravity=[0 0 -9.81]);
showdetails(manipulator)

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

 Idx                Body Name                         Joint Name                         Joint Type                Parent Name(Idx)   Children Name(s)
 ---                ---------                         ----------                         ----------                ----------------   ----------------
   1                     base         base_link-base_fixed_joint                              fixed                    base_link(0)   
   2        base_link_inertia        base_link-base_link_inertia                              fixed                    base_link(0)   shoulder_link(3)  
   3            shoulder_link                 shoulder_pan_joint                           revolute            base_link_inertia(2)   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)   flange(9)  
   9                   flange                     wrist_3-flange                              fixed                 wrist_3_link(8)   tool0(10)  
  10                    tool0                       flange-tool0                              fixed                       flange(9)   
--------------------

Get the home configuration for manipulator.

q = homeConfiguration(manipulator);

Set external force on shoulder_link. The input wrench vector is expressed in the base frame.

fext1 = externalForce(manipulator,"shoulder_link",[0 0 0.0 0.1 0 0]);

Set external force on the end effector, tool0. The input wrench vector is expressed in the tool0 frame.

fext2 = externalForce(manipulator,"tool0",[0 0 0.0 0.1 0 0],q);

Compute the joint torques required to balance the external forces. To combine the forces, add the force matrices together. Joint velocities and accelerations are assumed to be zero (input as []).

tau = inverseDynamics(manipulator,q,[],[],fext1+fext2)

tau = 1×6

   -0.0233  -52.4189  -14.4896   -0.0100    0.0100   -0.0000

Display Robot Model with Visual Geometries

You can import robots that have .stl files associated with the Unified Robot Description format (URDF) file to describe the visual geometries of the robot. Each rigid body has an individual visual geometry specified. The importrobot function parses the URDF file to get the robot model and visual geometries. The function assumes that visual geometry and collision geometry of the robot are the same and assigns the visual geometries as collision geometries of corresponding bodies.

Use the show function to display the visual and collision geometries of the robot model in a figure. You can then interact with the model by clicking components to inspect them and right-clicking to toggle visibility.

Import a robot model as a URDF file. The .stl file locations must be properly specified in this URDF. To add other .stl files to individual rigid bodies, see addVisual.

robot = importrobot('iiwa14.urdf');

Visualize the robot with the associated visual model. Click bodies or frames to inspect them. Right-click bodies to toggle visibility for each visual geometry.

show(robot,Visuals="on",Collisions="off");

Visualize the robot with the associated collision geometries. Click bodies or frames to inspect them. Right-click bodies to toggle visibility for each collision geometry.

show(robot,Visuals="off",Collisions="on"); 

More About

Dynamics Properties

When working with robot dynamics, specify the information for individual bodies of your manipulator robot using these properties of the rigidBody objects:

• Mass — Mass of the rigid body in kilograms.

• CenterOfMass — Center of mass position of the rigid body, specified as a vector of the form [x y z]. The vector describes the location of the center of mass of the rigid body, relative to the body frame, in meters. The centerOfMass object function uses these rigid body property values when computing the center of mass of a robot.

• Inertia — Inertia of the rigid body, specified as a vector of the form [Ixx Iyy Izz Iyz Ixz Ixy]. The vector is relative to the body frame in kilogram square meters. The inertia tensor is a positive definite matrix of the form:

  

  The first three elements of the Inertia vector are the moment of inertia, which are the diagonal elements of the inertia tensor. The last three elements are the product of inertia, which are the off-diagonal elements of the inertia tensor.

For information related to the entire manipulator robot model, specify these rigidBodyTree object properties:

• Gravity — Gravitational acceleration experienced by the robot, specified as an [x y z] vector in m/s². By default, there is no gravitational acceleration.

• DataFormat — The input and output data format for the kinematics and dynamics functions, specified as "struct", "row", or "column".

Dynamics Equations

Manipulator rigid body dynamics are governed by this equation:

$$\frac{d}{dt}\left[\begin{array}{c}q\\ \dot{q}\end{array}\right]=\left[\begin{array}{c}\dot{q}\\ M{(q)}^{-1}\left(-C(q,\dot{q})\dot{q}-G(q)-J{(q)}^T{f}_{Ext}+\tau \right)\end{array}\right]$$

also written as:

$$M(q)\ddot{q}=-C(q,\dot{q})\dot{q}-G(q)-J{(q)}^T{f}_{Ext}+\tau$$

where:

• $$M(q)$$ — is a joint-space mass matrix based on the current robot configuration. Calculate this matrix by using the massMatrix object function.

• $$C(q,\dot{q})$$ — are the Coriolis terms, which are multiplied by $$\dot{q}$$ to calculate the velocity product. Calculate the velocity product by using by the velocityProduct object function.

• $$G(q)$$ — is the gravity torques and forces required for all joints to maintain their positions in the specified gravity Gravity. Calculate the gravity torque by using the gravityTorque object function.

• $$J(q)$$ — is the geometric Jacobian for the specified joint configuration. Calculate the geometric Jacobian by using the geometricJacobian object function.

• $$f_{Ext}$$ — is a matrix of the external forces applied to the rigid body. Generate external forces by using the externalForce object function.

• $$\tau$$ — are the joint torques and forces applied directly as a vector to each joint.

• $$q,\dot{q},\ddot{q}$$ — are the joint configuration, joint velocities, and joint accelerations, respectively, as individual vectors. For revolute joints, specify values in radians, rad/s, and rad/s², respectively. For prismatic joints, specify in meters, m/s, and m/s².

To compute the dynamics directly, use the forwardDynamics object function. The function calculates the joint accelerations for the specified combinations of the above inputs.

To achieve a certain set of motions, use the inverseDynamics object function. The function calculates the joint torques required to achieve the specified configuration, velocities, accelerations, and external forces.

References

[1] Craig, John J. Introduction to Robotics: Mechanics and Control. Reading, MA: Addison-Wesley, 1989.

[2] Siciliano, Bruno, Lorenzo Sciavicco, Luigi Villani, and Giuseppe Oriolo. Robotics: Modelling, Planning and Control. London: Springer, 2009.

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

R2024a: Static memory allocation support

These rigidBodyTree object functions now support static memory sizes for code generation by disabling dynamic memory allocation.

• centerOfMass

• externalForce

• forwardDynamics

• geometricJacobian

• gravityTorque

• inverseDynamics

• massMatrix

• velocityProduct

• getTransform

• homeConfiguration

• randomConfiguration

For more information about disabling dynamic memory allocation, see Set Dynamic Memory Allocation Threshold (MATLAB Coder).

R2019b: rigidBodyTree was renamed

The rigidBodyTree object was renamed from robotics.RigidBodyTree. Use rigidBodyTree for all object creation.