Task Space Motion Model
Model rigid body tree motion given task-space inputs
Libraries:
Robotics System Toolbox /
Manipulator Algorithms
Description
The Task Space Motion Model block models the closed-loop task-space motion
of a manipulator, specified as a rigidBodyTree
object. The motion model behavior
is defined using proportional-derivative (PD) control.
For more details about the equations of motion, see Task-Space Motion Model.
Examples
Follow Task Space Trajectory in Simulink
Use a Task Space Motion Model to follow a task space trajectory.
Ports
Input
refPose — Desired end-effector pose
4-by-4 matrix
Homogenous transformation matrix representing the desired end-effector pose, specified in meters.
refVel — Desired end-effector velocities
6-element vector
6-element vector representing the desired linear and angular velocities of the end effector, specified in meters per second and radians per second.
FExt — External forces
6-by-m matrix
6-by-m matrix representing external forces, where each column
is a wrench in the form [Fx; Fy; Fz; Tx; Ty; Tz]
.
Fx
, Fy
, and Fz
are the
forces in the x-, y-, and
z-axes, in Newtons. Tx
, Ty
,
and Tz
are the torques about the x-,
y-, and z-axes, in Newton-meters.
m is the number of bodies in the rigidBodyTree
object in the Rigid body
tree parameter. Each of the m wrenches act on the
rigid body frame of the corresponding index in the rigid body tree. For example, the
third column of FExt
specifies the wrench acting on the third
rigid body in the rigid body tree.
Dependencies
To enable this port, set the Show external
force input
parameter to on
.
Output
q — Joint positions
n-element vector
Joint positions output as an n-element vector in radians or
meters, where n is the number of nonfixed joints in the rigidBodyTree
object in the Rigid body
tree
parameter.
qd — Joint velocities
n-element
Joint velocities output as an n-element vector in radians per
second or meters per second, where n is the number of nonfixed
joints in the rigidBodyTree
object in the Rigid body
tree
parameter.
qdd — Joint accelerations
n-element
Joint accelerations output as an n-element in radians per
second squared or meters per second squared, where n is the number
of nonfixed joints in the rigidBodyTree
object in the Rigid body
tree
parameter.
Parameters
Rigid body tree — Rigid body tree
twoJointRigidBodyTree
object (default) | RigidBodyTree
object
Robot model, specified as a RigidBodyTree
object. You can also
import a robot model from an URDF (Unified Robot Description Formation) file using
importrobot
.
The default robot model, twoJointRigidBodyTree
, is a robot with
revolute joints and two degrees of freedom.
End effector — End effector body
tool
(default)
This parameter defines the body that will be used as the end effector, and for which
the task space motion is defined. The property must correspond to a body name in the
rigidBodyTree
object of the property.
Click Select body to select a body from the
rigidBodyTree
. If the rigidBodyTree
is updated
without also updating the end effector, the body with the highest index is assigned by
default.
Proportional gain — Proportional gain for PD Control
500*eye(6)
(default) | 6-by-6 matrix
Proportional gain for proportional-derivative (PD) control, specified as a 6-by-6 matrix.
Derivative gain — Derivative gain for PD Control
100*eye(6)
(default) | 6-by-6 matrix
Derivative gain for proportional-derivative (PD) control, specified as a 6-by-6 matrix.
Joint damping — Damping ratios
[1 1]
(default) | n-element vector | scalar
Damping ratios on each joint, specified as a scalar or n-element
vector, where n is the number of nonfixed joints in the rigidBodyTree
object in the Rigid body
tree
parameter.
Show external force input — Display FExt
port
off
(default) | on
Click the check-box to enable this parameter to input external forces using the
FExt
port.
Initial joint configuration — Initial joint positions
0
(default) | n-element vector | scalar
Initial joint positions, specified as a n-element vector or
scalar in radians. n is the number of nonfixed joints in the rigidBodyTree
object in the Rigid body
tree
parameter.
Initial joint velocities — Initial joint velocities
0
(default) | n-element vector | scalar
Initial joint velocities, specified as a n-element vector or
scalar in radians per second. n is the number of nonfixed joints in
the rigidBodyTree
object in the Rigid body
tree
parameter.
Simulate using — Type of simulation to run
Interpreted execution
(default) | Code generation
Interpreted execution
— Simulate model using the MATLAB® interpreter. For more information, see Interpreted Execution vs. Code Generation (Simulink).Code generation
— Simulate model using generated C code. The first time you run a simulation, Simulink® generates C code for the block. The C code is reused for subsequent simulations, as long as the model does not change.
Tunable: No
References
[1] Craig, John J. Introduction to Robotics: Mechanics and Control. Upper Saddle River, NJ: Pearson Education, 2005.
[2] Spong, Mark W., Seth Hutchinson, and Mathukumalli Vidyasagar. Robot Modeling and Control. Hoboken, NJ: Wiley, 2006.
Extended Capabilities
C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.
Version History
Introduced in R2019bR2024a: Static memory allocation support
Task Space Motion Model 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).
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