262 research outputs found
Control in the operational space of bilateral teleoperators with time-delays and without velocity measurements¿
This paper proposes a control scheme in the operational space for bilateral teleoperation systems composed of heterogeneous robots (kinematically and dynamically different) without velocity sensors and considering variable time-delays in the interconnection. The proposed control scheme use a second order dynamical controller that back-propagates damping to the local and the remote manipulators. Under the assumptions that the human operator and the environment define passive maps from force to velocity, it is proved that velocities and pose (position and orientation) errors between the local and the remote manipulators are bounded. Moreover, in the case that the human and the environment forces are zero, the velocities and pose errors converge asymptotically to zero. The proposed approach employs, the singularity-free, unit-quaternions to represent the orientation of the end-effectors. The performance of the proposed controller is illustrated via simulations with a teleoperation system composed of robots with 3-DoF and 7-DoF.Peer ReviewedPostprint (published version
Novel observers for compensation of communication delay in bilateral control systems
The problem of communication delay in bilateral or
teleoperation systems is even more emphasized with the use of the
internet for communication, which may give rise to loss of
transparency and even instability. To address the problem,
numerous methods have been proposed. This study is among the
few recent studies taking a disturbance observer approach to the
problem of time delay, and introduces a novel sliding-mode
observer to overcome specifically the effects of communication
delay in the feedback loop. The observer operates in combination
with a PD+ controller which controls the system dynamics, while
also compensating load torque uncertainties on the slave side. To
this aim, an EKF based load estimation algorithm is performed on
the slave side. The performance of this approach is tested with
computer simulations for the teleoperation of a 1-DOF robotic
arm. The simulations reveal an acceptable amount of accuracy
and transparency between the estimated slave and actual slave
position under both constant and random measurement delay and
variable and step-type load variations on the slave side,
motivating the use of the approach for internet-based bilateral
control systems
A framework for robotized teleoperated tasks
"Premio al mejor artículo presentado en ROBOT 2011" atorgat pel Grupo de Robótica, Visión y Control de la Universidad de Sevilla, la Universidad Pablo Olavide i el Centro Avanzado de Tecnologías Aeroespaciales.Teleoperation systems allow the extension of the
human operator’s sensing and manipulative capability into a
remote environment to perform tasks at a distance, but the
time-delays in the communications affect the stability and
transparency of such systems. This work presents a teleoperation
framework in which some novel tools, such as nonlinear
controllers, relational positioning techniques, haptic guiding
and augmented reality, are used to increase the sensation
of immersion of the human operator in the remote site.
Experimental evidence supports the advantages of the proposed
framework.Award-winningPostprint (published version
Stability Analysis of Teleoperation System by State Convergence with Variable Time Delay
We propose a novel control scheme for bilateral teleoperation of n degree-of-freedom (DOF) nonlinear robotic systems with time-varying communication delay. A major contribution from this work lies in the demonstration that the structure of a state convergence algorithm can be also applied to nth-order nonlinear teleoperation systems. By choosing a Lyapunov Krasovskii functional, we show that the local-remote teleoperation system is asymptotically stable.
The time delay of communication channel is assumed to be unknown and randomly time varying, but the upper bounds of the delay interval and the derivative of the delay are assumed to be known
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