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Remove inverse kinematics constraints

Since R2020a



removeConstraints(viztree)removes the constraint stored at the last index of the Constraints property of the interactiveRigidBodyTree object, viztree.

removeConstraints(viztree,index) removes the constraints with the specified indices.


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Use the interactiveRigidBodyTree object to manually move around a robot in a figure. The object uses interactive markers in the figure to track the desired poses of different rigid bodies in the rigidBodyTree object.

Load Robot Model

Use the loadrobot function to access provided robot models as rigidBodyTree objects.

robot = loadrobot("atlas");

Visualize Robot and Save Configurations

Create an interactive tree object and associated figure, specifying the loaded robot model and its left hand as the end effector.

viztree = interactiveRigidBodyTree(robot,"MarkerBodyName","l_hand");

Click and drag the interactive marker to change the robot configuration. You can click and drag any of the axes for linear motion, rotate the body about an axis using the red, green, and blue circles, and drag the center of the interactive marker to position it in 3-D space.

The interactiveRigidBodyTree object uses inverse kinematics to determine a configuration that achieves the desired end-effector pose. If the associated rigid body cannot reach the marker, the figure renders the best configuration from the inverse kinematics solver.

Programmatically set the current configuration. Assign a vector of length equal to the number of nonfixed joints in the RigidBodyTree to the Configuration property.

currConfig = homeConfiguration(viztree.RigidBodyTree);
currConfig(1:10) = [ 0.2201 -0.1319 0.2278 -0.3415 0.4996 ...
                     0.0747 0.0377 0.0718 -0.8117 -0.0427]';
viztree.Configuration = currConfig;

Save the current robot configuration in the StoredConfigurations property.


To switch the end effector to a different rigid body, right-click the desired body in the figure and select Set body as marker body. Use this process to select the right hand frame.

You can also set the MarkerBodyName property to the specific body name.

viztree.MarkerBodyName = "r_hand";

Move the right hand to a new position. Set the configuration programmatically. The marker moves to the new position of the end effector.

currConfig(1:18) = [-0.1350 -0.1498 -0.0167 -0.3415 0.4996 0.0747
                     0.0377 0.0718 -0.8117 -0.0427 0 0.4349 
                    -0.5738 0.0563 -0.0095 0.0518 0.8762 -0.0895]';
viztree.Configuration = currConfig;

Save the current configuration.


Add Constraints

By default, the robot model respects only the joint limits of the rigidBodyJoint objects associated with the RigidBodyTree property. To add constraints, generate Robot Constraint objects and specify them as a cell array in the Constraints property. To see a list of robotic constraints, see Inverse Kinematics. Specify a pose target for the pelvis to keep it fixed to the home position. Specify a position target for the right foot to be raised in front front and above its current position.

fixedWaist = constraintPoseTarget("pelvis");
raiseRightLeg = constraintPositionTarget("r_foot","TargetPosition",[1 0 0.5]);

Apply these constraints to the interactive rigid body tree object as a cell array. The right leg in the resulting figure changes position.

viztree.Constraints = {fixedWaist raiseRightLeg};                               

Notice the change in position of the right leg. Save this configuration as well.


Play Back Configurations

To play back configurations, iterate through the stored configurations index and set the current configuration equal to the stored configuration column vector at each iteration. Because configurations are stored as column vectors, use the second dimension of the matrix.

for i = 1:size(viztree.StoredConfigurations,2)
    viztree.Configuration = viztree.StoredConfigurations(:,i);

Input Arguments

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Interactive rigid body tree robot model visualization, specified as an interactiveRigidBodyTree object.

Index locations to remove configurations, specified as a positive integer or vector of positive integers.

Data Types: double

Version History

Introduced in R2020a