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This paper presents a robust adaptive control strategy for nonlinear teleoperation systems. The controller is based on estimation of the impedance of human hand as well as that of the environment. The mentioned system is subjected to unmodeled dynamics, time-varying parameters and external force disturbances. The upper bound for the norm of disturbances and system uncertainties are not used in the...
In this paper, a robust output feedback control strategy is proposed for a nonlinear teleoperation system which can deal with stability as well as transparency despite the variable time‐delay and uncertain dynamics. The proposed approach is composed of two steps. First, local Lyapunov based adaptive controllers are applied to both master and slave sides in order to suppress the nonlinearities in the...
In this paper a novel approach is proposed for interaction force estimation between a non-passive soft tissue in contact with end effector of a robot. It is necessary to understand the real behavior of living organs of the body in the robotic surgeries to do a better operation especially in cases of tele-operation surgery. In addition, this interaction force to the surgeon should be fed back in a...
This paper investigates three-dimensional dynamic model of underactuated spherical wheel mobile robot (Ballbot) in the presence of input coupling and friction. The way of how such a robot moves is considered and an approach is proposed for accurate trajectory generation for linear and circular paths. Due to the high reliability of the approach, no position feedback is used and it is simulated open-loop...
Control of Flexible-link Manipulators Using Neural Networks addresses the difficulties that arise in controlling the end-point of a manipulator that has a significant amount of structural flexibility in its links. The non-minimum phase characteristic, coupling effects, nonlinearities, parameter variations and unmodeled dynamics in such a manipulator all contribute to these difficulties. Control strategies...
This paper presents a novel approach to determine and realize the virtual fixture stiffness matrix. Generally, for characterizing the stiffness matrix, stiffness of each direction needs to be known. Here, by the help of screw theory, stiffness matrix is obtained and afterwards, an impedance control strategy is employed to realize it. In addition, the extension of the proposed virtual fixture algorithm...
BackgroundRestorative dentistry simulation is one of the most challenging applications involving virtual reality and haptics. This paper presents a haptics‐based tooth drilling simulator for dental education.
MethodsUnlike the existing methods, the force model is based on physical properties which consider the geometrical model of the tool. In order to provide uniform force feedback from tooth layers,...
This paper addresses bilateral control of a nonlinear teleoperation system with flexible-link slave manipulator. For this purpose, due to the non-minimum phase behavior of flexible-link manipulators, tip position tracking of the slave manipulator is performed based on the output redefinition method. Moreover, to compensate the uncertainties, a robustifying term is considered in the controller. However,...
In this paper, the problem of a bilateral teleoperation system in contact with active environment is considered. The human operator is assumed to be nonpassive, and the network is subject to unsymmetrical constant time delay. Two new nonlinear terms are added to the common PD control strategy in order to deal with the active impedance appeared in the closed loop system. The master/slave robots are...
In this paper, the stability and tracking control problem of a task space nonlinear bilateral teleoperation system is addressed interacting with a unknown environment. The controllers consist of adaptive controller and nonlinear disturbance observer to deal with uncertain dynamic model of manipulators, environmental and operators forces, respectively, in the presence of time delay. In order to estimate...
The force estimation problem in robotic systems is studied in this paper. To isolate the effects of external disturbance on force estimation, a neural network based nonlinear disturbance observer is proposed. Hence, unlike existing force observers in the literature, force estimation in the presence of external disturbances is guaranteed. Based on the Lyapunov stability criterion, sufficient conditions...
This paper deals with output synchronization problem in nonlinear multi-agent systems. The main contribution of the paper is to guarantee output synchronization in the network while the dynamics of agents exhibit non-minimum phase behavior. To achieve this goal, a control signal is presented for each agent consisting of two terms. The first term is a linear function of each agent states employed in...
The experimental results for the implementation of a fuzzy tracking controller on a macro-micro manipulator (M3) are shown and compared to those of a joint-PD controller. The test bed is a nonlinear nonminimum-phase MIMO system with a complex dynamic model and pronounced joint frictions. The controller belongs to a class of fuzzy controllers based on Lyapunov-function reasoning. The control strategy...
Humanoid robots play an important role in the future life. The main contribution of this paper is to design and prototype a humanoid robot that is going to be employed in the study of such systems as well as robotics competitions. Eighteen servomotors are utilized as the actuators. A camera sensor is used to get visual feedback. An accelerometer sensor is utilized to determine the physical state of...
In this paper, the problem of stability and tracking performance of FRVF (Forbidden Region Virtual Fixture) for bilateral nonlinear teleoperation systems is studied in presence of varying time delay. It is proved that PD-like controllers can stabilize the teleoperation systems with FRVF in slave side and variable time delay in communication channels. It is also proved by proposed Lyapunov-Krasovskii's...
Series resonant converters with high frequency operation property play important role in small and light weight power supply design. In this paper robust controller synthesis by linear matrix inequality approach is presented for series resonant converters. The achieved controller has been designed based on a multi input — multi output model of the converter. Moreover, it reveals output voltage regulation...
This paper deals with the problem of designing an observer-based adaptive tracking controller for a class of uncertain nonlinear systems. A neural network-based observer estimates states of the system and a neural network-based controller is designed to approximate input control signal. The estimated states by the observer are inputs of the controller and two neural networks (NNs) interact together...
In this paper, the problem of path planning for needle insertion into a soft tissue is considered. A new method is proposed which does not have the disadvantage and difficulties of the previous methods, namely disability in modeling short distances or 3D path planning complexities. In the proposed method by dividing the primary path into short plane paths and assuming a point near each obstacle as...
In this paper, performance of a new axial-flux interior permanent-magnet eddy-current coupler is analyzed, for which a magnetic equivalent circuit is also developed. The design considerations of the device are also presented. The proposed structure have advantageous over the couplers with surface-mounted PMs, e.g., the PMs are protected by the frame, there is no centrifugal force on PMs, the reaction...
Herein, a rotating interior permanent-magnet radial-flux eddy-current coupler is studied. In the proposed coupler, permanent-magnets (PMs) located inside the inner rotating part of the coupler are orthogonal to the air-gap, and a copper sheet is paced on the inner surface of the outer rotating part. It is worth noting that in this structure, besides utilizing the rectangular-shaped PM, there is no...
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