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An industrial robot today uses measurements of its joint positions and models of its kinematics and dynamics to estimate and control its end-effector position. Substantially better end-effector position estimation and control performance would be obtainable if direct measurements of its end-effector position were also used. The subject of this paper is extended Kalman filtering for precise estimation of the position of the end-effector of a robot using, in addition to the usual measurements of the joint positions, direct measurements of the end-effector position. The estimation performances of extended Kalman filters are compared in applications to a planar two-axis robotic arm with very flexible links. The comparisons shed new light on the dependence of extended Kalman filter estimation performance on the quality of the model of the arm dynamics that the extended Kalman filter operates with. KEY WORDS—extended Kalman filter, estimation, flexible links, robot 1
David B. Rathbun Pulse Width Control for Precise Positioning of Structurally Flexible Systems Subject to Stiction and Coulomb Friction
Pulse Width Control for Precise Positioning of Structurally Flexible Systems Subject to Stiction and Coulomb Friction
Piecewise-Linear-Gain Pulse Width Control for Precise Positioning of Structurally Flexible Systems Subject to Stiction and Coulomb Friction
Evaluation of Two Complementary Modeling Approaches for Fiber-Reinforced Soft Actuators
Roboticists have been seeking to address this situation in recent years
through the use of soft robots. Unfortunately, identifying appropriate models
for the complete analysis and investigation of soft robots for design and
control purposes can be problematic. This paper seeks to address this challenge
by proposing two complementary modeling techniques for a particular type of
soft robotic actuator known as a Fiber-Reinforced Elastomeric Enclosure (FREE).
We propose that researchers can leverage multiple models to fill gaps in the
understanding of the behavior of soft robots. We present and evaluate both a
dynamic, lumped-parameter model and a finite element model to extend
understanding of the practicability of FREEs in soft robotic applications. The
results with the lumped-parameter model demonstrate that it predicts the actual
rotational motion of a FREE with at most 4% error when a closed-loop controller
is embedded in the system. Additionally, finite element analysis was used to
study FREE design parameters as well as the workspace achieved with a module
comprised of multiple FREEs. Our finite element results indicate that
variations in the material properties of the elastic enclosure of a FREE are
more significant than variations in fiber properties. Finally, finite element
results show that a 30-degree difference in winding angle dramatically alters
the shape of the workspace generated by four FREEs assembled into a module.
Concludingly, comments are made about the relative advantages and limitations
of lumped-parameter and finite element models of FREEs and FREE modules in
providing useful insights into their behavior