1,526 research outputs found
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
Scaled bilateral teleoperation using discrete-time sliding mode controller
In this paper, the design of a discrete-time slidingmode
controller based on Lyapunov theory is presented along
with a robust disturbance observer and is applied to a piezostage
for high-precision motion. A linear model of a piezostage was
used with nominal parameters to compensate the disturbance
acting on the system in order to achieve nanometer accuracy. The
effectiveness of the controller and disturbance observer is validated
in terms of closed-loop position performance for nanometer
references. The control structure has been applied to a scaled
bilateral structure for the custom-built telemicromanipulation
setup. A piezoresistive atomic force microscope cantilever with a
built-in Wheatstone bridge is utilized to achieve the nanonewtonlevel
interaction forces between the piezoresistive probe tip and
the environment. Experimental results are provided for the
nanonewton-range force sensing, and good agreement between
the experimental data and the theoretical estimates has been
demonstrated. Force/position tracking and transparency between
the master and the slave has been clearly demonstrated after
necessary scalin
Transparency in Port-Hamiltonian-Based Telemanipulation
After stability, transparency is the major issue in the design of a telemanipulation system. In this paper, we exploit the behavioral approach in order to provide an index for the evaluation of transparency in port-Hamiltonian-based teleoperators. Furthermore, we provide a transparency analysis of packet switching scattering-based communication channels
Semi-autonomous scheme for pushing micro-objects
-In many microassembly applications, it is often
desirable to position and orient polygonal micro-objects lying on
a planar surface. Pushing micro-objects using point contact provides
more flexibility and less complexity compared to pick and
place operation. Due to the fact that in micro-world surface forces
are much more dominant than inertial forces and these forces
are distributed unevenly, pushing through the center of mass of
the micro-object will not yield a pure translational motion. In
order to translate a micro-object, the line of pushing should pass
through the center of friction. In this paper, a semi-autonomous
scheme based on hybrid vision/force feedback is proposed to push
microobjects with human assistance using a custom built telemicromanipulation
setup to achieve pure translational motion.
The pushing operation is divided into two concurrent processes:
In one process human operator who acts as an impedance
controller alters the velocity of the pusher while in contact with
the micro-object through scaled bilateral teleoperation with force
feedback. In the other process, the desired line of pushing for
the micro-object is determined continuously using visual feedback
procedures so that it always passes through the varying center of
friction. Experimental results are demonstrated to prove nanoNewton
range force sensing, scaled bilateral teleoperation with
force feedback and pushing microobjects
Function based control for bilateral systems in tele-micromanipulation
Design of a motion control system should take into
account (a) unconstrained motion performed without interaction
with environment or any other system, and (b) constrained
motion with system in contact with environment or other systems.
Control in both cases can be formulated in terms of maintaining
desired system configuration what makes essentially the same
structure for common tasks: trajectory tracking, interaction force
control, compliance control etc. The same design approach can be
used to formulate control in bilateral systems aimed to maintain
desired functional relations between human and environment
through master and slave motion systems. Implementation of
the methodology is currently being pursued with a custom built
Tele-micromanipulation setup and preliminary results concerning
force/position tracking and transparency between master and
slave are clearly demonstrated
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