Mehmet İsmet Can Dede

Modification of the Wave Variable Technique for Teleoperation Systems Experiencing Communication Loss

Researchers have studied teleoperation systems essentially for implementation in critical tasks. Although teleoperation systems require stability apriori, time delays over the communications lines become a major source of instability. During the last two decades several researchers have focused on the time delay problem. The wave variable technique is one of the teleoperation controllers developed to ensure stability under time delays. In this paper, a modified algorithm of the wave variable technique is introduced. The purpose of the modification is to ensure that the slave manipulator tracks the position demand of the master even if there is a communication loss or the wave variable technique fails for a limited time period.

Fault‐tolerant teleoperation systems design

Purpose – The objective of this study is to enhance the usage of teleoperation fields, such as in nuclear site decommissioning or nuclear waste disposal, by designing a stable, dependable and fault‐tolerant teleoperation system in the face of “extraordinary” conditions. These “extraordinary” conditions can be classified as variable time delays in communications lines, usage of different robotic systems, component failures and changes in the system parameters during task execution.Design/methodology/approach – This paper first gives a review of teleoperation systems developed earlier. Later, fault tolerance is proposed for use in teleoperation systems at the processor, actuator, sub‐system, and system levels. Position/force control algorithms are recommended to address stability issues when there is a loss in communications. Various other controls are also introduced to overcome the instability experienced when there is a time delay in the communications line.Findings – Finally, this work summarizes the te...

Design of a haptic device for teleoperation and virtual reality systems

Haptics technology has increased the precision and telepresence of the teleoperation and precision of the in-house robotic applications by force and surface information feedback. Force feedback is achieved through sending back the pressure and force information via a haptic device as the information is created or measured at the point of interest. In order to configure such a system, design, analysis and production processes of a haptic device, which is suitable for that specific application, becomes important. Today, haptic devices find use in assistive surgical robotics and most of the teleoperation systems. These devices are also extensively utilized in simulators to train medical and military personnel. The objective of this work is to design a haptic device with a new structure that has the potential to increase the precision of the robotic operation. Thus, literature is reviewed and possible robot manipulator designs are investigated to increase the precision in haptics applications. As a result of the investigations, conceptual designs are developed. Ultimately, final design is selected and produced after it is investigated in computer-aided-design (CAD) environment and its kinematic and structural analyses are carried out.

A study on multiple degree-of-freedom force reflecting teleoperation

This article reviews the wave variable method as it applies to multi-degree-of-freedom teleoperation systems. To demonstrate the effect of wave variables on the stability of a time-delayed multidegree-of-freedom system, initial simulation results on a three-axis robot are presented. Also the multidegree-of-freedom teleoperation system model developed in the Matlab/spl copy/ environment is described. This model, used in numerical simulations, is also utilized in real-time implementation of the controller.

Derivation of Input/Output Relationships for the Bennett 6R Linkages Based on the Method of Decomposition

The Bennett overconstrained 6R linkages are the double-planar, the double-spherical and the plano-spherical 6R linkages. These mechanisms are obtained by combining simple planar and/or spherical mechanisms and then removing one of the common links. This paper presents the derivation of the input/output relationships for these mechanisms using the decomposition method. This method is based on writing the input/output equations for the two imaginary loops comprising the 6R mechanism and then eliminating the imaginary joint variable. It is found that the resulting input/output equations contain up to 4th power of trigonometric terms, such as cos4 θ.

Trajectory Planning of Redundant Planar Mechanisms for Reducing Task Completion Duration

In the industry there is always a demand to shorten the task completion durations in order to maximize the efficiency of the operation. This work aims to provide a solution to minimize the task completion duration for planar tasks by introducing kinematic redundancy. An example setting of a redundant planar mechanism is considered and an algorithm developed for resolving redundancy order to minimize task completion duration is discussed based on this mechanism.

A Comparative Study on Application of Decomposition Method in Function Generation Synthesis of Over-Constrained Mechanisms

Double-spherical six-bar linkage is one of the Bennett over-constrained 6R linkages. Kinematic synthesis of such linkages can be tedious and impossible to solve for analytically. In order to cope with higher number of unknowns in these types of linkages, decomposition method is a valuable tool. This paper focuses on the function generation synthesis of double-spherical six-bar linkage. Two procedures for applying decomposition method are explained. Two numerical studies are conducted for both procedures to evaluate the performance of each procedure.

Tracking Performance Of An Identical Master-Slave Teleoperation System Under Variable Time Delays

Teleoperation system performance suffers from the delays in communication lines. These delays are usually variable time delays. The customary wave variable technique used for constant time delays cannot provide satisfactory results to stabilize the system under variable delays. Another problem is observed in the position tracking performance of the limited-workspace teleoperation systems. Although wave variable technique is proven to track position demands successfully under constant time delays given that there is no communication failure, position tracking performance also degrades under variable delays. In this paper, a new controller is proposed to stabilize the system and enhance position tracking performance under variable time delays. This proposed controller is then applied to an identical master-slave teleoperation configuration which qualifies as a limited-workspace teleoperation system.

Extending model-mediation method to multi-degree-of-freedom teleoperation systems experiencing time delays in communication

In this study, a bilateral teleoperation control algorithm is developed in which the model-mediation method is integrated with an impedance controller. The model-mediation method is also extended to three-degrees-of-freedom teleoperation. The aim of this controller is to compensate for instability issues and excessive forcing applied to the slave environment stemming from time delays in communication. The proposed control method is experimentally tested with two haptic desktop devices. Test results indicate that stability and passivity of the bilateral teleoperation system is preserved under variable time delays in communication. It is also observed that safer interactions of the slave system with its environment can be achieved by utilizing an extended version of the model-mediation method with an impedance controller.

Alternating error effects on decomposition method in function generation synthesis

In approximate function generation synthesis methods, error between the desired function’s output and designed mechanism’s output oscillate about zero error while crossing the zero error margin at precision points. The common goal of these methods is to minimize the error within the selected working region of the mechanism. For mechanisms like Bennett overconstrained six-revolute jointed linkages that have relatively large number of construction parameters, it is a difficult task to solve for them at once. Decomposition method enables to divide such linkages into two loops and independently solve for each loop with less construction parameters. Although some approximation methods are proven to produce smaller errors than others for a single-loop synthesis, in this work, it is shown that smaller errors are not guaranteed for a certain method when used along with decomposition method. Numerical examples indicate that in decomposition method, more attention should be given to the alternation of the error of each decomposed mechanism, rather than the approximation method used.