In recent years, increased interest in parallel robots has been observed. Their control with modern theory, such as the computed-torque method, has, however been restrained, essentially due to the difficulty in establ...
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In recent years, increased interest in parallel robots has been observed. Their control with modern theory, such as the computed-torque method, has, however been restrained, essentially due to the difficulty in establishing a simple dynamic model that can be calculated in real time. In this paper;a simple method based on the virtual work principle is proposed for modeling parallel robots. The mass matrix of the robot needed for decoupling control strategies, does not explicitly appear in the formulation;however it can be computed separately, based on kinetic energy considerations. The method is applied to the DELTA parallel robot, leading to a very efficient model that has been implemented in a real-time computed-torque control algorithm.
The dynamic behaviors of a damped satellite with partially-filled liquid which is subjected to external disturbance are studied in this paper. The Lyapunov direct method is used to obtain conditions of stability of th...
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The dynamic behaviors of a damped satellite with partially-filled liquid which is subjected to external disturbance are studied in this paper. The Lyapunov direct method is used to obtain conditions of stability of the equilibrium point of the system. A co-dimension one bifurcation analysis for the autonomous system is carried out near the degenerate point. It is found that Hopf bifurcation occurs in the system by center manifold theory. By applying numerical results, phase diagrams, power spectrum, Poincare maps, and Lyapunov exponents are presented to observe periodic and chaotic motions. The effect of the parameter changes in the system can be found in the bifurcation and parametric diagrams. For global analysis, the basins of attraction of each attractor of the system are located by employing the modified interpolated cell mapping (MICM) method. Finally, several methods, the delayed feedback control, the addition of constant motor torque, the addition of periodic force, and adaptive control algorithm are used to control chaos effectively. (C) 1998 Academic Press.
Relying on the possibility of generating a second-order sliding motion by using, as control, the first derivative of the control signal instead of the actual control, a new solution to the problem of chattering elimin...
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Relying on the possibility of generating a second-order sliding motion by using, as control, the first derivative of the control signal instead of the actual control, a new solution to the problem of chattering elimination in variable structure control (VSC) is presented. Such a solution, inspired by the classical bang-bang optimal control strategy, is first depicted and expressed in terms of a control algorithm by introducing a suitable auxiliary problem involving a second-order uncertain system with unavailable velocity. Then, the applicability of the algorithm is extended, via suitable modifications, to the case of nonlinear systems with uncertainties of more general types. The proposed algorithm does not require the use of observers and differential inequalities and can be applied in practice by exploiting such commercial components as peak detectors or other approximated methods to evaluate the change of the sign of the derivative of the quantity accounting for the distance to the sliding manifold.
Three control algorithms are developed to stabilize an underactuated two-link robot at its unstable inverted position. The well-known linear quadratic regulator is described first. Next, a stabilization control law us...
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Three control algorithms are developed to stabilize an underactuated two-link robot at its unstable inverted position. The well-known linear quadratic regulator is described first. Next, a stabilization control law using partial feedback linearization is developed where the reference trajectories for the linearized degrees of freedom are designed by analyzing the zero dynamics. The linear quadratic regulator and partial feedback linearization control algorithms both assume an exact dynamic model. To deal with modeling inaccuracies, a robust controller using sliding mode concepts is supplied. Numerical simulations are presented. (C) 1998 John Wiley & Sons, Inc.
The authors describe how novel sensors and control algorithmsembedded in today's domestic appliances make them smart enough toestimate the size and dirtiness of a load of clothes tossed in a washeror to determine ...
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The authors describe how novel sensors and control algorithmsembedded in today's domestic appliances make them smart enough toestimate the size and dirtiness of a load of clothes tossed in a washeror to determine whether water in a pot on the stove is boiling. Theyargue that, as semiconductor costs come down, such appliances will geteven smarter
This paper reviews an active control algorithm adopted for an active-passive composite tuned mass damper, which is a unique vibration control device equipped into an office building in Tokyo in 1993. The main purpose ...
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This paper reviews an active control algorithm adopted for an active-passive composite tuned mass damper, which is a unique vibration control device equipped into an office building in Tokyo in 1993. The main purpose of this device is to subdue the response motion of tall buildings under random disturbances such as wind pressures and small earthquakes. The main topics in this paper are: (1) the principle of the acceleration feedback algorithm, (2) the expected control performance, (3) the multi-modal control algorithm, (4) the observed performance of the applications using the algorithm.
In order to meet the Quality-Of-Service (QOS) requirements of the VOD (Video-On-Demand) service, and, on the other hand, to maximize the system throughput (revenue), it is essential that the admission control algorith...
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In order to meet the Quality-Of-Service (QOS) requirements of the VOD (Video-On-Demand) service, and, on the other hand, to maximize the system throughput (revenue), it is essential that the admission control algorithm be carefully designed, In this paper, two new types of admission control schemes for the VOD service are proposed. They are the Enhanced strict Admission Control (ESAC) and the Probabilistic Admission Control. (PAC). In the ESAC schemes, we propose to use more statistics (of small amount and easily pre-calculated) than the peak frame size of the stored video information to strictly guarantee the QOS requirement and to achieve potentially much higher throughput. In the PAC schemes, we propose to use similar statistics ins used in the ESAC schemes to achieve even higher throughput at the cost of some small and controllable likelihood of lost/overdue data. The admission control problems are formulated as feasibility problems where different systems of simultaneous equations are considered. For each admission control scheme, if the corresponding system of simultaneous equations has a feasible solution, then admit the call request;otherwise, reject the call. Special structures of the systems are identified so as to facilitate the development of optimal real-time admission control algorithms. Efficient optimal algorithms are also proposed to calculate the minimal buffer requirement For a given performance objective.
A fuzzy logic controller that drives a crank turning apparatus is presented. A crank turning operation with unknown initial conditions is an example of a contact operation a mechanical manipulator often finds challeng...
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A fuzzy logic controller that drives a crank turning apparatus is presented. A crank turning operation with unknown initial conditions is an example of a contact operation a mechanical manipulator often finds challenging. The apparatus presented in this manuscript uses a fuzzy logic controller that results in a simple structure and a readily realizable algorithm. computer simulations and experimental studies demonstrate favorable results offering an effective control algorithm. (C) 1998 John Wiley & Sons, Inc.
In this paper we study three popular on-line disk scheduling algorithms, FCFS, SSTF, and LOOK, using competitive analysis. Our results show that, in a competitive sense, the performance of LOOK is better than those of...
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In this paper we study three popular on-line disk scheduling algorithms, FCFS, SSTF, and LOOK, using competitive analysis. Our results show that, in a competitive sense, the performance of LOOK is better than those of SSTF and FCFS. As a by-product, our analysis also reveals quantitatively the role played by the size of the window, which in our model is a waiting buffer that holds a fixed number of requests waiting to be serviced next. The window, in some sense, offers the lookahead ability which is mentioned in several on-line problems.
This paper presents a method to verify the correctness of protocols and distributed algorithms. The method compares a state graph of the implementation with a specification which is a state graph representing the desi...
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This paper presents a method to verify the correctness of protocols and distributed algorithms. The method compares a state graph of the implementation with a specification which is a state graph representing the desired abstract behavior. The steps in the specification correspond to atomic transactions, which are not atomic in the implementation. The method relies on an aggregation function, which is a type of abstraction function that aggregates the steps of each transaction in the implementation into a single atomic transaction in the specification. The key idea in defining the aggregation function is that it must complete atomic transactions which have committed but are not finished. This paper illustrates the method on a directory-based cache coherence protocol developed for the Stanford FLASH multiprocessor. The coherence protocol consisting of more than a hundred different kinds of implementation steps has been reduced to a specification with six kinds of atomic transactions. Based on the reduced behavior, it is very easy to prove crucial properties of the protocol including data consistency of cached copies at the user level. This is the first correctness proof verified by a theorem-prover for a cache coherence protocol of this complexity. The aggregation method is also used to prove that the reduced protocol satisfies a desired memory consistency model.
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