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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Stabilization of Asymmetric Bilateral Teleoperation Systems with Time-Varying Delays

Hilliard, Trent 10 August 2012 (has links)
A novel control scheme for asymmetric bilateral teleoperation systems is developed based on linear models of the hardware, with two scenarios considered: i) only an upper bound on the time delay and ii) an upper and lower bounds on the time delay. Lyapunov based methods are used with linear matrix inequalities to prove that the system error is bounded between the manipulators. To ensure stability, a master side impedance matching controller is used. Simulations were conducted using the Matlab and Simulink platform to run the LMI code and simulate the system. Experiments were then conducted using actual hardware to verify the results, with deviations from imulation results. The variations were due to non-linearities in the hardware and model parameter approximation errors. Finally, suggestions for future work are made.
2

Stable bilateral teleoperation with time-varying delays

Yang, Yuan 12 July 2017 (has links)
A teleoperation system is a master-slave robotic system in which the master and slave robots are at different geographical locations and synchronize their motions through the communication channel, with the goal of enabling the human operator to interact with a remote environment. The two primary objectives of bilateral teleoperation systems, position tracking and force feedback, are necessary for providing the user with high fidelity telepresence. However, time delays in communication channels impede the realization of the two objectives and even destabilize the system. To guarantee stability and improve performance, several damping injection-based controllers have been developed in this thesis for two channel and four channel teleoperation systems. For two channel teleoperation, an adaptive bounded state feedback controller has firstly been proposed to address teleoperation with time-varying delays, model uncertainties and bounded actuations. Next, a simplified and augmented globally exponentially convergent velocity observer has been designed and incorporated in the conventional P+d control to obtain stable bilateral teleoperation without using velocity measurements. Then, the more challenging bounded output feedback control problem has been solved by combining the bounded state feedback control and output feedback control two techniques with more conservative control gains. In four channel teleoperation, a hybrid damping and stiffness adjustment strategy has been introduced to tightly constrain the master and slave robots and achieve robust stability. Further, the nonsingular version is developed to conquer the singularity problem in the hybrid strategy, which has been proved to avoid unexpected torque spikes due to the singularity problem at zero velocities. Besides, this thesis has also provided a reduced-order controller to guarantee position coordination for arbitrarily large position errors and maintain the tight coupling between the master and slave sites. After concluding all the research results, future study directions are pointed out at the end of this thesis. / Graduate
3

Consensus in multi-agent systems and bilateral teleoperation with communication constraints

Wu, Jian 01 March 2013 (has links)
With the advancement of communication technology, more and more control processes happen in networked environment. This makes it possible for us to deploy multiple systems in a spatially distributed way such that they could finish certain tasks collaboratively. While it brings about numerous advantages over conventional control, challenges arise in the mean time due to the imperfection of communication. This thesis is aimed to solve some problems in cooperative control involving multiple agents in the presence of communication constraints. Overall, it is comprised of two main parts: Distributed consensus in multi-agent systems and bilateral teleoperation. Chapter 2 to Chapter 4 deal with the consensus problem in multi-agent systems. Our goal is to design appropriate control protocols such that the states of a group of agents will converge to a common value eventually. The robustness of multi-agent systems against various adverse factors in communication is our central concern. Chapter 5 copes with bilateral teleoperation with time delays. The task is to design control laws such that synchronization is reached between the master plant and slave plant. Meanwhile, transparency should be maintained within an acceptable level. Chapter 2 investigates the consensus problem in a multi-agent system with directed communication topology. The time delays are modeled as a Markov chain, thus more characteristics of delays are taken into account. A delay-dependent approach has been proposed to design the Laplacian matrix such that the system is robust against stochastic delays. The consensus problem is converted into stabilization of its equivalent error dynamics, and the mean square stability is employed to characterize its convergence property. One feature of Chapter 2 is redesign of the adjacency matrix, which makes it possible to adjust communication weights dynamically. In Chapter 3, average consensus in single-integrator agents with time-varying delays and random data losses is studied. The interaction topology is assumed to be undirected. The communication constraints lie in two aspects: 1) time-varying delays that are non-uniform and bounded; 2) data losses governed by Bernoulli processes with non-uniform probabilities. By considering the upper bounds of delays and probabilities of packet dropouts, sufficient conditions are developed to guarantee that the multi-agent system will achieve consensus. Chapter 4 is concerned with the consensus problem with double-integrator dynamics and non-uniform sampling. The communication topology is assumed to be fixed and directed. With the adoption of time-varying control gains and the theory on stochastic matrices, we prove that when the graph has a directed spanning tree and the control gains are properly selected, consensus will be reached. Chapter 5 deals with bilateral teleoperation with probabilistic time delays. The delays are from a finite set and each element in the set has a probability of occurrence. After defining the tracking error between the master and slave, the input-to-state stability is used to characterize the system performance. By taking into account the probabilistic information in time delays and using the pole placement technique, the teleoperation system has achieved better position tracking and enhanced transparency. / Graduate
4

Distributed control of multi-robot teleoperation: connectivity preservation and authority dispatch

Yang, Yuan 03 May 2021 (has links)
The frequent occurrences of natural and technological disasters have incurred grave loss of life and damage to property. For mitigating the miserable aftermaths, multi-robot teleoperation systems have been developed and deployed to cooperate with human rescuers in post-earthquake scenarios, and to sample, monitor and clean pollutants in marine environments. With a bidirectional communication channel, human users can deliver commands/requests to guide the motions of the remote robots, and can receive visual/audio feedback to supervise the status of the remote environment, throughout multi-robot teleoperation. Furthermore, the remote robots can send force feedback to human operators to improve their situational awareness and task performance. This way, a closed-loop multi-robot teleoperation system becomes bilateral in which coordinated robots physically interact and exchange energy with human users, and hence needs to be rendered passive for safe human-robot interaction. Beyond guaranteeing closed-loop passivity, the control of a bilateral multi-robot teleoperation system faces two challenging problems: preserving the communication connectivity of the remote robots; and dispatching the teleoperation authority to multiple human users. Because wireless transmission of radio/acoustic signals between the remote robots is constrained by their distances, bilateral multi-robot teleoperation control must coordinate the motions of the remote robots appropriately so as to maintain their communication network connected. Further, multiple human users can send possibly conflicting teleoperation commands to the remote robots, a distributed authority dispatch algorithm is thus needed for the remote robot network to recognize and follow the most urgent user commands at runtime. This thesis develops an energy shaping strategy to preserve the connectivity of the remote robots, and to dispatch control authority over the remote robots to human users, during bilateral multi-robot teleoperation. Chapter 1 introduces the application background of multi-robot teleoperation as well as the state-of-the-art development in related research areas. In Chapter 2, a dynamic interconnection and damping strategy is proposed to reduce and constrain the position error between the local and remote robots to any prescribed bound during bilateral teleoperation. Chapter 3 derives a gradient plus damping control from a bounded potential function and then unifies it into an indirect coupling framework to preserve all communication links of an autonomous multi-robot system with time-varying delays and bounded actuation. On these bases, Chapter 4 develops a dynamic feedforward-feedback passivation strategy to preserve all communication links and thus the connectivity of the tree network of the remote robots while rendering the bilateral multi-robot teleoperation close loop passive. Specifically, by blending the sliding variable in Chapter 2 with the bounded potential function in Chapter 3, the dynamic passivation strategy decomposes the dynamics of the remote robots into a power-preserving interconnection of two subsystems, and regulates the energy behaviour of each subsystem to preserve the tree communication connectivity of the remote robots. To handle time-varying communication delays, the strategy further transforms the communication channels between the local and remote robots into a dynamic controller for passivating bilateral teleoperation. Superior to existing controls, the strategy using a bounded potential function can circumvent numerical instability, reduce noise sensitivity and facilitate future extensions to accommodate robot actuator saturation. On the other side, Chapter 5 designs a distributed and exponentially convergent winners-take-all authority dispatch algorithm that activates the teleoperation of only human users with the most urgent requests in real time. After formulating the problem as a constrained quadratic program, we employ an exact penalty function method to construct a distributed primal-dual dynamical system that can solve the problem at an exponential rate. Because the equilibrium of the system changes with user requests, we then interconnect the dynamical system with physical robot dynamics in a power-preserving way, and passivate closed-loop multi-robot teleoperation using multiple storage functions from a switched system perspective. Finally, Chapter 6 provides some conclusive remarks and two problems regarding connectivity preservation and authority dispatch for future study. / Graduate
5

Enhanced Bilateral Teleoperation using Generalized Force/Position Mapping

Malysz, Pawel 09 1900 (has links)
<p> The performance index in teleoperation, transparency, is often defined as linear scaling of force and position between the master/ operator and slave/ environment. Motivated by applications involving soft tissue manipulation such as robotic surgery, the transparency objective is generalized in this thesis to include static nonlinear and linear-time-invariant filter mappings between the master I slave position and force signals. Lyapunov-based adaptive motion/ force controllers are proposed to achieve the generalized transparency objectives. Using Lyapunov stability theory the mapped position and force tracking errors are shown to converge in the presence of dynamic uncertainty in the master I slave robots and user I environment dynamics. Given a priori known bounds on unknown dynamic parameters, a framework for robust stability analysis is proposed that uses stability of Lur'ePostinkov systems and Nyquist/Bode envelopes of interval plant systems. Methods for finding the required Nyquist/Bode envelopes are presented in this thesis. A comprehensive stability analysis is performed under different sets of generalized mappings. For nonlinear mapping of either position or force, robust stability depends on stability of an equivalent Lur'e-Postinikov system. Stability results of such systems are discussed in this thesis. In particular, the on and off-axis circle theorems are utilized. Using these theorems, sufficient teleoperation stability regions are obtained that are far less conservative than those obtained from passivity. In the special case of LTI filtered force and position mappings the exact robust stability regions are obtained by showing stability of the relevant closed-loop characteristic polynomial. The proposed robust stability test uses the phase values of a limited set of extremal polynomials. </p> <P> To demonstrate the utility of the generalized performance measures, a stiffness discrimination tele-manipulation task is considered in which the user compares and contrasts the stiffness of soft environments via haptic exploration in the presence and absence of visual feedback. Using adaptive psychophysical perception experiments a nonlinear force mapping is shown to enhance stiffness discrimination thresholds. The design guidelines for this enhanced nonlinear force mapping are reported in this thesis. Generalized nonlinear and linear filtered mappings are achieved in experiments with a two-axis teleoperation system where the details of implementation are given. </p> / Thesis / Master of Applied Science (MASc)
6

Adaptive Fuzzy Logic Control for Time-Delayed Bilateral Teleoperation

Zhu, Jiayi 23 January 2012 (has links)
In recent years, teleoperation has shown great potentials in different fields such as spatial, mining, under-water, etc. When teleoperation is required to be bilateral, the time delay induced by a potentially large physical distance prevents a good performance of the controller, especially in case of contact. When bilateral teleoperation is introduced to the field of medicine, a new challenge arises: the controller needs to be used in both hard and soft environments. For example, in the context of telesurgery, the robot can enter in contact with both bone (hard) and organ (soft). In an attempt to enrich existing controller designs to better suit the medical needs, an adaptive fuzzy logic controller is designed in this text. It simulates human intelligence and adapts the controller to environments of different stiffness coefficients. It is compared to three other classical controllers used in the field of bilateral teleopeartion and demonstrates very interesting potential.
7

Adaptive Fuzzy Logic Control for Time-Delayed Bilateral Teleoperation

Zhu, Jiayi 23 January 2012 (has links)
In recent years, teleoperation has shown great potentials in different fields such as spatial, mining, under-water, etc. When teleoperation is required to be bilateral, the time delay induced by a potentially large physical distance prevents a good performance of the controller, especially in case of contact. When bilateral teleoperation is introduced to the field of medicine, a new challenge arises: the controller needs to be used in both hard and soft environments. For example, in the context of telesurgery, the robot can enter in contact with both bone (hard) and organ (soft). In an attempt to enrich existing controller designs to better suit the medical needs, an adaptive fuzzy logic controller is designed in this text. It simulates human intelligence and adapts the controller to environments of different stiffness coefficients. It is compared to three other classical controllers used in the field of bilateral teleopeartion and demonstrates very interesting potential.
8

Performance evaluation of real-time bilateral teleoperation systems with wired and wireless network simulation

Liao, Stephen 20 December 2012 (has links)
This thesis presents a general simulation framework used for evaluating the performance of bilateral teleoperation systems under consistent and controllable network conditions. A teleoperation system is where an operator uses a master device to control a slave robot through a communication link. The communication link between the master and slave has an important impact on the system performance. Network emulation using ns-2 has been proposed as a way of simulating the communication link. It allows for the network conditions to be controlled and for repeatable results. The proposed setup was used to test the performance of a hydraulic actuator under various conditions of wired and wireless networks. Three control schemes were evaluated using various combinations of time delay and packet loss. The system was also tested simulating wireless communication between the master and slave to determine the effects of transmission power and distance on the performance of the system.
9

Performance evaluation of real-time bilateral teleoperation systems with wired and wireless network simulation

Liao, Stephen 20 December 2012 (has links)
This thesis presents a general simulation framework used for evaluating the performance of bilateral teleoperation systems under consistent and controllable network conditions. A teleoperation system is where an operator uses a master device to control a slave robot through a communication link. The communication link between the master and slave has an important impact on the system performance. Network emulation using ns-2 has been proposed as a way of simulating the communication link. It allows for the network conditions to be controlled and for repeatable results. The proposed setup was used to test the performance of a hydraulic actuator under various conditions of wired and wireless networks. Three control schemes were evaluated using various combinations of time delay and packet loss. The system was also tested simulating wireless communication between the master and slave to determine the effects of transmission power and distance on the performance of the system.
10

Adaptive Fuzzy Logic Control for Time-Delayed Bilateral Teleoperation

Zhu, Jiayi 23 January 2012 (has links)
In recent years, teleoperation has shown great potentials in different fields such as spatial, mining, under-water, etc. When teleoperation is required to be bilateral, the time delay induced by a potentially large physical distance prevents a good performance of the controller, especially in case of contact. When bilateral teleoperation is introduced to the field of medicine, a new challenge arises: the controller needs to be used in both hard and soft environments. For example, in the context of telesurgery, the robot can enter in contact with both bone (hard) and organ (soft). In an attempt to enrich existing controller designs to better suit the medical needs, an adaptive fuzzy logic controller is designed in this text. It simulates human intelligence and adapts the controller to environments of different stiffness coefficients. It is compared to three other classical controllers used in the field of bilateral teleopeartion and demonstrates very interesting potential.

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