30 research outputs found
Dynamic Active Constraints for Surgical Robots using Vector Field Inequalities
Robotic assistance allows surgeons to perform dexterous and tremor-free
procedures, but robotic aid is still underrepresented in procedures with
constrained workspaces, such as deep brain neurosurgery and endonasal surgery.
In these procedures, surgeons have restricted vision to areas near the surgical
tooltips, which increases the risk of unexpected collisions between the shafts
of the instruments and their surroundings. In this work, our
vector-field-inequalities method is extended to provide dynamic
active-constraints to any number of robots and moving objects sharing the same
workspace. The method is evaluated with experiments and simulations in which
robot tools have to avoid collisions autonomously and in real-time, in a
constrained endonasal surgical environment. Simulations show that with our
method the combined trajectory error of two robotic systems is optimal.
Experiments using a real robotic system show that the method can autonomously
prevent collisions between the moving robots themselves and between the robots
and the environment. Moreover, the framework is also successfully verified
under teleoperation with tool-tissue interactions.Comment: Accepted on T-RO 2019, 19 Page
Pose consensus based on dual quaternion algebra with application to decentralized formation control of mobile manipulators
This paper presents a solution based on dual quaternion algebra to the
general problem of pose (i.e., position and orientation) consensus for systems
composed of multiple rigid-bodies. The dual quaternion algebra is used to model
the agents' poses and also in the distributed control laws, making the proposed
technique easily applicable to time-varying formation control of general
robotic systems. The proposed pose consensus protocol has guaranteed
convergence when the interaction among the agents is represented by directed
graphs with directed spanning trees, which is a more general result when
compared to the literature on formation control. In order to illustrate the
proposed pose consensus protocol and its extension to the problem of formation
control, we present a numerical simulation with a large number of free-flying
agents and also an application of cooperative manipulation by using real mobile
manipulators
Active Constraints using Vector Field Inequalities for Surgical Robots
Robotic assistance allows surgeons to perform dexterous and tremor-free
procedures, but is still underrepresented in deep brain neurosurgery and
endonasal surgery where the workspace is constrained. In these conditions, the
vision of surgeons is restricted to areas near the surgical tool tips, which
increases the risk of unexpected collisions between the shafts of the
instruments and their surroundings, in particular in areas outside the surgical
field-of-view. Active constraints can be used to prevent the tools from
entering restricted zones and thus avoid collisions. In this paper, a vector
field inequality is proposed that guarantees that tools do not enter restricted
zones. Moreover, in contrast with early techniques, the proposed method limits
the tool approach velocity in the direction of the forbidden zone boundary,
guaranteeing a smooth behavior and that tangential velocities will not be
disturbed. The proposed method is evaluated in simulations featuring two eight
degrees-of-freedom manipulators that were custom-designed for deep
neurosurgery. The results show that both manipulator-manipulator and
manipulator-boundary collisions can be avoided using the vector field
inequalities.Comment: Accepted on ICRA 2018, 8 page
Dynamics of Serial Manipulators using Dual Quaternion Algebra
This paper presents two approaches to obtain the dynamical equations of
serial manipulators using dual quaternion algebra. The first one is based on
the recursive Newton-Euler formulation and uses twists and wrenches instead of
3D vectors, which simplifies the classic procedure by removing the necessity of
exhaustive geometrical analyses since wrenches and twists are propagated
through high-level algebraic operations. Furthermore, the proposed formulation
works for arbitrary types of joints and does not impose any particular
convention for the propagation of twists. The second approach, based on Gauss's
Principle of Least Constraint (GPLC), takes into account elements of the dual
quaternion algebra and provides a linear relationship between twists
derivatives and joint accelerations, which can be particularly useful in robot
control. Differently from other approaches based on the GPLC, which have
representational singularities or require constraints, our method does not have
those drawbacks. We present a thorough methodology to obtain the computational
cost of both algorithms and compared them with their classic counterparts.
Although our current formulations are more computationally expensive, they are
more general than their counterparts in the state of the art. Simulation
results showed that both methods are as accurate as the classic recursive
Newton-Euler algorithm.Comment: Submitted for publication (currently under review
Hybrid kinematic control for rigid body pose stabilization using dual quaternions
In this paper, we address the rigid body pose stabilization problem using dual quaternion formalism. We propose a hybrid control strategy to design a switching control law with hysteresis in such a way that the global asymptotic stability of the closed-loop system is guaranteed and such that the global attractivity of the stabilization pose does not exhibit chattering, a problem that is present in all discontinuous-based feedback controllers. Using numerical simulations, we illustrate the problems that arise from existing results in the literature—as unwinding and chattering—and verify the effectiveness of the proposed controller to solve the robust global pose stability problem
Semi-automatic needle steering system with robotic manipulator
International audienceThis paper presents a semi-automatic system for robotically assisted 2D needle steering that uses duty-cycling to perform insertions with arcs of adjustable curvature radius. It combines image feedback manually provided by an operator with an adaptive path planning strategy to compensate for system uncertainties and changes in the workspace during the procedure. Experimental results are presented to validate the proposed platform