A New Control Scheme For Bilateral Teleoperating Systems: Performance Evaluation And Comparison

This two-part paper presents a general method to model three-phase ac-dc converters as two-port networks for power system stability studies. Part I of the work has developed the two-port network models and identified two types of transfer characteristics that are unique to ac-dc converters and important for system stability. Part II presents the applications of the developed models in stability analysis of different power systems that use ac-dc converters, including grid integration of converter-based generation from wind, PV and other renewable sources, grid-connected dc microgrids and dc distributed power systems, high-voltage dc transmission, as well as hybrid ac-dc power systems. While impedance-based stability analysis has been studied for each of these systems, the new two-port models, especially the transfer immittance models, make it possible and easy to formulate more complete system models to include dynamics and coupling effects that have been ignored or impossible to consider in the past. The methods to study the stability of each type of systems are explained and illustrated by case studies that also highlight the effects of coupling modeled by the transfer immittances on system stability. Each case study also exemplifies a practical stability concern in converter-based power systems.

An unbalanced electric power system can occur due to unequal lines and/or loads in each phase of the system. For a system with a high level of unbalance, the assumption that the system is balanced becomes incorrect. For a case like this, the system must be analyzed using three-phase approaches because single-phase analysis techniques can no longer be used to obtain accurate results. Therefore, the development of three-phase models of all components of the electric power system, including the wind turbine generating system (WTGS), is very important so that the system can properly be analyzed and its performance can correctly be evaluated. This paper proposes a method to incorporate WTGS in a three-phase load flow analysis of an unbalanced distribution system. The proposed method is based on the previously published single-phase two-port network model. In this paper, the single-phase two-port network model is modified and extended so that it can be applied to unbalanced systems. The model is then included in the three-phase distribution system load flow (DSLF) analysis. The proposed method is validated using 12-node and 19-node distribution systems.

This work proposes an equivalent circuit model for a stand-alone three-phase self-excited induction generator (SEIG) with unbalanced load impedances. The SEIG supplying unbalanced loads is modelled by a two-port network that allows the steady-state performance of the generator to be analysed more easily and more efficiently. The proposed model is validated by experiments on a 0.5 Hp cage-type induction motor operated as a generator.

The electrical response of two-port photoconductive GaN nanowire devices was measured from 50 MHz to 33 GHz. The admittance of the nanowire devices showed an increase on the order of 10% throughout the measured frequency range after exposure to steady ultraviolet illumination. Two different two-port microwave network models were used to extract microwave circuit parameters in the photoconductive and dark states. After illumination, the GaN nanowire devices showed a measurable increase in shunt capacitance and decreases in both the contact and nanowire resistances.

In order to analyze the amplification phenomenon of harmonic currents by the traction network in an electric railway, this paper established a simplified model for traction network using T-type distributed model. Further more the conductors of the traction network were represented by a delicate multi-port model which has been reduced in ends. This model is an improvement for analyzing conductor complex compared with two-port network model. The simulation results of the resonance frequency and the amplification of harmonic currents was given by EMTP-ATP, which verified that the proposed model was an accurate and effective way for analyzing the harmonics in traction network.

Signal integrity (SI) losses in the interconnects are the disturbances coming out of their distributed nature of parasitic capacitances, resistances, and inductances at high frequency operation by A. Attartha and M. Nourani (2002). SI losses are further aggravated if multiple interconnect lines couple energy from, or to each other. Therefore, this paper aims to analyze the cross-talk coupling effects between the two interconnects, namely the aggressor and victim lines, using the ABCD two-port network model. In order to reduce the simulation time a reduced order modeling of the interconnect line is considered. Furthermore, as stated in various literatures by A. Sinha et al. (1999) the rising (or falling) input signal represented by a simple step function is not accurate enough, therefore in this paper the rising transitions and the falling transitions are represented more accurately using the exponential terms, and based on such input representation the time domain output signal voltage in presence of crosstalk noise, at the far end side of both aggressor line and victim line, is determined. Such output voltage representation is very helpful in estimating the delay, overshoot or undershoot etc., which are believed to cause SI losses in the SoC.

This paper presents a control method using an adjusting output-limiter for stable haptic rendering in a virtual environment. In a simulation of force-reflecting interaction with deformable objects in a virtual environment, a quick computation of the accurate impedance of deformable objects is rare. This is particularly true when physics-based models, such as tensor-mass models or mass-spring models, are used. The problem is aggravated if the simulation involves changes in the geometry and/or impedance of the deformation model, such as cutting or suturing. The proposed control method guarantees stable haptic interactions with deformable objects of unknown and/or varying impedance. The method is based on the time-domain passivity theorem and the two-port network model. The controller adjusts the maximum permissible force to guarantee the passivity of the haptic system at every sampling instant. The controller notes only the magnitude of the reflective force, and does not depend on properties of the employed force model. This allows the proposed control method applicable to haptic systems involving deformable objects with unknown, nonlinear, and/or time-varying impedance. Designs of the controllers are presented for impedance-type and admittance-type haptic systems. The method is also extended for multiple degrees-of-freedom.

Conventional pilot protections used for EHV/UHV ac transmission lines require data synchronization between the two terminals of transmission line, and their performances are affected by the line capacitive charging current and load conditions. To tackle these problems, this paper proposes a new pilot protection scheme based on two-port network model of ac transmission lines. The new protection scheme calculates the two-port network parameters from the online measurements via the sequence components method, and then compares the solved parameters with their setting values to distinguish the internal and external faults. It does not require the data synchronization between two terminals of the transmission line. Moreover, its performance is not affected by the line capacitive charging current and load conditions. The applicability of the proposed scheme for series compensated lines is also analyzed. Effectiveness and accuracy of the proposed protection scheme have been verified by simulation tests.

This paper presents the use of a power cable modeling approach based on the two port network theory and its application to power transformers. More specifically, it takes place in the frame of the evaluation of the capacity of the power network infrastructure to support narrowband PLC technology. In this context, a classical two-port network modeling approach of cable transfer function is transposed to other devices like LV-LV transformers. In order to evaluate the impact of derivations of the power network, a classical distribution system topology is also studied. Practically, the effect of power network components is modeled by a cascade of transmission matrices. A comparison between model results and measurement is performed to show the coherence of results.

An electric master-slave manipulator was generally used for remote control systems. Generally, the master arm has the same mechanism as the slave arm. Thus, the operator is constrained by the master arm. From such a point of view, a nonconstrained master arm with tactile feedback actuator was developed. The operator can move without constraint and feel the force or touch between slave and objects. If a tactile feedback actuator on a master arm is made from mechanical actuator, it will constrain the operator. Thus, a pneumatic balloon actuator was developed to return the touch between the slave arm and objects to the master arm. The system was experimentally produced and its performance tested and evaluated. It was found to be applicable to a nonconstrained master arm with tactile feedback actuator.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Piezoelectric stack actuators have the advantages of zero backlash and no acoustic noise, but their stroke is too small to actuate robotic links directly. Because the force available is often more than the required, the stroke of the piezoelectric stack can be amplified by a compliant mechanism at the expense of force. It is not always clear what the geometry of this compliant mechanism should be. Compliant mechanisms have parallels in biology in that they describe two-way interactions between the actuator and the environment. In this paper, we employ the concept of a two-port network model from circuit theory to describe this two-way interaction and present a method to obtain each element of the two-port model as an analytical function of physical geometric parameters for a wide class of geometries. This method makes use of Castigliano's theorem and Euler-Bernoulli linearly elastic beam theory. To our knowledge, this is the first two-port representation of a compliant mechanism that is based on analytical expressions of geometric parameters. This analytical model agrees well with finite-element method calculations. We also examine a representative case experimentally and achieve accuracies better than 18%.

The article presents the results of the investigations of the oculomotor reaction during a 24-h sleep deprivation in 10 normal male volunteers aged 25–30 years. Binocular recording of the eye movements was carried out using a VNG System VO-25 video nystagmograph. A set of methods based on video oculography, including the balancing test developed by us, as well as the investigation of saccadic and smooth tracking eye movements, was proposed. The balancing test determined the nystagmic activity; the saccade test, the saccade latent period, peak velocity, and precision; and the smooth tracking test, the average gain coefficient, and the root-mean-square error of tracking velocity and displacement. In addition to video oculography, the velocity of a simple sensorimotor reaction was measured, and subjective well-being was assessed using the self-rated well-being-activity-mood scale. The balancing test revealed balancing nystagmus whose rate of occurrence increased in marked desynchronosis. The saccades registered under these conditions revealed a significant decrease in their velocity, a less marked increase in the latent period, and degradation of precision. Sleep deprivation reduced the average gain coefficient values and increased the root-mean-square error of the velocity and displacement of smooth eye tracking.

Humans perceive their surrounding environment through five sensory channels, popularly labeled “sight,” “sound,” “taste,” “smell,” and “touch.” All of these modalities are fused together in our brains into an apparently seamless perception of our world. While we typically place the most importance on our visual sense, it is our sense of touch which provides us with much of the information necessary to modify and manipulate the world around us. This sense can be divided into two categories: the kinesthetic sense, through which we sense movement or force in muscles and joints; and the tactile sense, through which we sense shapes and textures. This chapter will focus on the use of kinesthetic sense in realistic teleoperation and virtual environment simulations. Artificial kinesthetic feedback techniques were first developed in the field of teleoperation—robot manipulators remotely controlled by human operators. In teleoperation, the perceptions from a physically remote environment must be conveyed to the human operator in a realistic manner. This differs from virtual reality in which the perceptions from a simulated environment are conveyed to the user. Thus, teleoperation and virtual environments communities share many of the same user interface issues but in teleoperation the need for detailed world modeling is less central. The earliest remote manipulation systems were operated by direct mechanical linkages and the operator viewed the workspace directly through windows (Goertz, 1964). Perhaps because of their relative simplicity and high performance, little was learned about sensory requirements for remote manipulation from these early devices. When remote manipulation was developed for long distances and mobile platforms, electronic links became mandatory. The earliest attempts drove the remote manipulator with a position signal only and no information was returned to the operator about contact force. In the original mechanical designs, force information was intrinsically available because the linkages (actually metal tape and pulley transmissions) were relatively stiff, low-mass, connections between the operator and the environment. With the shift to electronic links, the loss of kinesthetic information was immediately apparent to the operators. The first artificial kinesthetic displays arose to provide improved functionality for remote manipulators.

This paper presents an adaptive control design of a pneumatic teleoperation system that could be useful for applications like MRI-guided surgery. The system under study is special because of its reduced number of components compared to other bilateral teleoperation systems, which reduces cost and complexity. The direct fluidic connection and the force feedback that is transferred to the human operator allow the operator to feel as if s/he were having physical contact with the environment without the need for a force sensor on the slave actuator. A simulation model that allows stability and transparency assessment is presented in detail. A linear controller is optimized for various operating remote environments via transparency assessment. The linear controller leads to good results for certain operating environments, but its tuning is dependent on the impedance characteristic of the environments both on the master and slave sides. Since the system must perform under parametric uncertainties on both sides of the teleoperator, an adaptive control scheme is developed. A self-tuning regulator is designed to allow the teleoperator to cope with a variable environment. The control design is validated in simulation and yielded satisfactory performance under multiple environment settings.

In teleoperation, it is very important to have salient cooperation between the human operator and the control mechanism equipped on the remote manipulator. The cooperation becomes especially crucial when the teleoperation system is used to execute compliance tasks in which simultaneous control of both position and force may be demanded and inevitable contact with environments is encountered. In this paper, we focus on the issues of planning, execution, and coordination between the human operator and the remote controller in teleoperating a compliance task. In addition, we are also interested in how the intelligence in planning and control to be distributed between them according to the specific characteristics of a given compliance task. For the study, a VR-based (Virtual Reality) telerobotic system for compliance tasks is developed. The telerobotic system provides both haptic and visual information, and possesses a remote intelligence controller, capable of compliance control. Experiments based on various types of compliance tasks are performed for the investigation.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.