13,438 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
Efficient Transport Protocol for Networked Haptics Applications
The performance of haptic application is highly sensitive to communication delays and losses of data. It implies several constraints in developing networked haptic applications. This paper describes a new internet protocol called Efficient Transport Protocol (ETP), which aims at developing distributed interactive applications. TCP and UDP are transport protocols commonly used in any kind of networked communication, but they are not focused on real time application. This new protocol is focused on reducing roundtrip time (RTT) and inter packet gap (IPG). ETP is, therefore, optimized for interactive applications which are based on processes that are continuously exchanging data.ETP protocol is based on a state machine that decides the best strategies for optimizing RTT and IPG. Experiments have been carried out in order to compare this new protocol and UDP
Teleoperation of passivity-based model reference robust control over the internet
This dissertation offers a survey of a known theoretical approach and novel experimental results in establishing a live communication medium through the internet to host a virtual communication environment for use in Passivity-Based Model Reference Robust Control systems with delays. The controller which is used as a carrier to support a robust communication between input-to-state stability is designed as a control strategy that passively compensates for position errors that arise during contact tasks and strives to achieve delay-independent stability for controlling of aircrafts or other mobile objects. Furthermore the controller is used for nonlinear systems, coordination of multiple agents, bilateral teleoperation, and collision avoidance thus maintaining a communication link with an upper bound of constant delay is crucial for robustness and stability of the overall system. For utilizing such framework an elucidation can be formulated by preparing site survey for analyzing not only the geographical distances separating the nodes in which the teleoperation will occur but also the communication parameters that define the virtual topography that the data will travel through. This survey will first define the feasibility of the overall operation since the teleoperation will be used to sustain a delay based controller over the internet thus obtaining a hypothetical upper bound for the delay via site survey is crucial not only for the communication system but also the delay is required for the design of the passivity-based model reference robust control. Following delay calculation and measurement via site survey, bandwidth tests for unidirectional and bidirectional communication is inspected to ensure that the speed is viable to maintain a real-time connection. Furthermore from obtaining the results it becomes crucial to measure the consistency of the delay throughout a sampled period to guarantee that the upper bound is not breached at any point within the communication to jeopardize the robustness of the controller. Following delay analysis a geographical and topological overview of the communication is also briefly examined via a trace-route to understand the underlying nodes and their contribution to the delay and round-trip consistency. To accommodate the communication channel for the controller the input and output data from both nodes need to be encapsulated within a transmission control protocol via a multithreaded design of a robust program within the C language. The program will construct a multithreaded client-server relationship in which the control data is transmitted. For added stability and higher level of security the channel is then encapsulated via an internet protocol security by utilizing a protocol suite for protecting the communication by authentication and encrypting each packet of the session using negotiation of cryptographic keys during each session
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
Central controller for hybrid control over network
In this paper, a central controller for position/force
hybrid control over network is proposed. In the proposed method,
the central controller receives position and force information
from each plant. Then, the central controller generates acceleration
references for each plant by using a hybrid controller and a
dead time compensator. As an application, bilateral control with
communication delay is implemented. And some simulations and
experiments verify the validity of the proposed method
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