In this paper we consider a link serving multiple service classes. We evaluate the properties of the link admission control policies that are obtained from an efficient scheme proposed by Krishnan and Hubner. The Kris...
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In this paper we consider a link serving multiple service classes. We evaluate the properties of the link admission control policies that are obtained from an efficient scheme proposed by Krishnan and Hubner. The Krishnan and Hubner approach suggests efficient calculations of state-dependent routing criteria for multi-rate networks through state-space aggregation. Through simple examples we show that it is possible that the approximations made in the approach might lead to degraded performance, instead of the expected improvement. We outline and discuss a possible extension to the Krishnan and Hubner approach in an effort to address this problem.
In this paper, we extend the observer/control strategies previously published in [18] to an n-link, serially connected, direct drive, rigid link, revolute robot operating in the presence of nonlinear friction effects ...
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In this paper, we extend the observer/control strategies previously published in [18] to an n-link, serially connected, direct drive, rigid link, revolute robot operating in the presence of nonlinear friction effects modeled by the Lu-Gre model. In addition, we also present a new adaptive control technique for compensating for the nonlinear parameterizabIe Stribeck effects. Specifically, an adaptive observer/controller scheme is developed which contains a feedforward approximation of the Stribeck effects. This feedforward approximation is used in a composite controller/observer strategy which forces the average square integral of the position tracking error to an arbitrarily small value.
In this paper, we consider the vibration suppression control of flexible arms by using sliding mode method. The vibration motion of the flexible arm has infinite number of modes. The higher order modes of the flexible...
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In this paper, we consider the vibration suppression control of flexible arms by using sliding mode method. The vibration motion of the flexible arm has infinite number of modes. The higher order modes of the flexible arm are considered as the disturbances. Since the payload mass is usually unknown, the model uncertainties usually exist. The sliding surface is designed such that the dynamics on the surface is stable under the sliding mode control. The robustness of sliding mode control is effectively employed to compensate the model uncertainties and the disturbances. For different payloads, experimental results show that the robustness of the proposed method is superior to that of the traditional pole-placement methods.
Under `Free Flight,' each individual aircraft will have the first responsibility to resolve its own conflicts. Therefore, a centralized air traffic controller (ATC) will issue a resolution command only when a phys...
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Under `Free Flight,' each individual aircraft will have the first responsibility to resolve its own conflicts. Therefore, a centralized air traffic controller (ATC) will issue a resolution command only when a physical conflict would be unavoidable if the ATC did not do so. Regarding the operation of an ATC under `Free Flight,' hence, determining when the ATC should issue a resolution command would be one of the most important problems. This paper presents a systematic and efficient algorithm as a solution to this problem. This algorithm is based on the well-known Semi-Definite Program (SDP) relaxation method.
An alternative approach to identify suspension system models using neuro-fuzzy technique is presented in this paper. Structure and design scheme based on this approach will be briefly discussed, which includes an adap...
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An alternative approach to identify suspension system models using neuro-fuzzy technique is presented in this paper. Structure and design scheme based on this approach will be briefly discussed, which includes an adaptive network employed as a building block, and the back-propagation gradient method as well as least square estimator as a hybrid learning rule. The objective is to represent the suspension dynamics by a set of fuzzy rules representation. By using this approach, the nonlinear characteristics of the suspension system can also be accommodated. Experimental evaluation of the proposed technique has been conducted using an input-output data collected from a running test vehicle. Observations by comparing the model responses with the actual output measurements revealed that satisfactory model matching were obtained which means that the models have captured the real basic features of the vehicle suspension dynamic characteristics.
In this paper, we present recent results of using a Kohonen neural network to detect and classify faults occurring in a dynamic system. The measured outputs from the system are first used in a Kalman filter to generat...
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In this paper, we present recent results of using a Kohonen neural network to detect and classify faults occurring in a dynamic system. The measured outputs from the system are first used in a Kalman filter to generate residual vectors that serve as fault indicators. As the residuals are generated they can be sent one-by-one to the Kohonen network, both the Kalman filter and the Kohonen network operating on-line in real time. The Kohonen network detects and categorizes the fault, since the residual vectors serve as signatures for different types of faults. The Kohonen network starts with a few pre-designated categories, each category representing a fault type. As more and more residual vectors become available, the Kohonen network opens new categories for residuals that do not have a good enough match with any of the existing categories. The concept is illustrated by an application example that uses actual fault data commercially recorded by the utilities in Texas.
Experimental testing is an important step in the verification of control strategies. In the case of civil engineering structural controlsystems, small scale testing is commonly used to demonstrate key concepts and me...
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Experimental testing is an important step in the verification of control strategies. In the case of civil engineering structural controlsystems, small scale testing is commonly used to demonstrate key concepts and methods. Large or full scale testing is expensive and only a handful of facilities exist in the world. Thus, some researchers have considered experimental techniques which focus on the control device itself, and emulate the behavior of the structure with a simulator. The concern is that these techniques do not account for the interaction between the control device and the structure. This issue will be examined herein. In a numerical example, the behavior of the control device when tested independently will be compared to that of the device when it is used to control a structure.
The Furuta pendulum is used to evaluate a friction compensator based on the dynamic LuGre friction model. The effect of friction compensation is very well illustrated by reduction of limit cycles when stabilizing the ...
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The Furuta pendulum is used to evaluate a friction compensator based on the dynamic LuGre friction model. The effect of friction compensation is very well illustrated by reduction of limit cycles when stabilizing the pendulum. The observer based LuGre friction compensator is compared with classical Coulomb and Stiction compensator schemes. Existing analysis of the LuGre observer is extended to observer based friction compensation in general linear state feedback control of linear time invariant systems where friction enters the system at the input. In particular this observer based friction compensation is applicable on the pendulum. The performance of the LuGre compensator was found to be similar to that of the Stiction compensator. Important differences is the smooth control signal obtained from the LuGre observer, and that it uses less prior information.
In this paper, passive walking of the eight-legged robot Quartet that has simple straight legs, and is also constrained to have two degrees of freedom for the simplicity of its motion, is described. It is known that a...
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In this paper, passive walking of the eight-legged robot Quartet that has simple straight legs, and is also constrained to have two degrees of freedom for the simplicity of its motion, is described. It is known that a legged robot can continue to walk down a slight slope steadily without any actuation if appropriate initial conditions are given. Since no control input except for gravitational torque is applied to the robot, more natural gaits compared with those of conventional actuated walking robots are expected. In walking simulation, bifurcation that occurs along with the increase of slope angle and finally leads to chaotic gait is discussed. In walking experiment, some kind of trajectory stability can be observed.
The occurrence of flooding in the absorption column of the Rectisol process at Sasol Synthetic Fuels was predicted as part of the overall Advanced control Project on the Rectisol unit. The flooding predictor was used ...
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The occurrence of flooding in the absorption column of the Rectisol process at Sasol Synthetic Fuels was predicted as part of the overall Advanced control Project on the Rectisol unit. The flooding predictor was used as a controlled variable in a multivariable controller with an objective function that maximizes the gas throughput. Data from the Rectisol process corresponding to several different flooding scenarios was analyzed. Results show that the neural network differential pressure predictor was accurate. However, the linear differential pressure predictor performed quite poorly. This indicates that sufficient nonlinear dynamical effects in the Rectisol process exist to warrant the use of a nonlinear model.
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