A new structure of Morse's dynamic certainty equivalent adaptive controllers with a dynamic high gain feedback compensator in the continuous-time, single-input single-output linear time-invariant plant is proposed in this paper. The boundedness of all the signals in the closed-loop system and the convergence of the output error are proved. Furthermore, the mean square tracking error and L∞ bounds on the tracking error are obtained. According to the performance bounds, it is shown that an arbitrary improved zero-state transient performance can be obtained. Finally a numerical example is illustrated in order to show the effectiveness of the proposed method.
We propose a WWW cache control mechanism that adapts the traffic of satellite links and latency to retrieve a WWW object for the user. To prefetch a WWW object effectively reduces the latency of a satellite link; however, this technique also generates massive traffic and should be controlled. We use a control mechanism where the rim cache will decide whether to prefetch an object after observing the current traffic of satellite links in real time. The cache then decides which object should be prefetched, based on the users' access patterns. In addition, the hub cache distributes the frequently-accessed objects with multicast transmissions and improves hit ratio on rim caches. We adopted the mechanism for the AI3 satellite network, which connects several research organizations in Asia, and conclude that the proposed system improved the hit ratio of the cache 15% while reducing the mean retrieval time of an object 20%, compared to a conventional cache system.
To construct an optimal regulator for a wheeled vehicle, we need a viscosity solution of the Hamilton-Jacobi partial differential equation (HJ-PDE). In this paper, we propose a new method to have the viscosity solution of the HJ-PDE more quickly by applying a new searching method which uses a sequence of random inputs. This method reduces the number of searching points and makes calculation time faster than the previous method. Next, we propose a method to have the viscosity solution for obstacle avoidance. From the theoretical result of optimal control with state constraints, we can get the viscosity solution which avoids obstacles optimally. Then we make sure that an optimal solution can be obtained analytically by the finite difference numerical approximation of the HJ-PDE. This new result gives us an optimal solution without searching. Finally, the effectiveness of control results calculated from proposed methods are confirmed through simulations.
For a pendulum system whose weight is transferred up and down, a vibration control method is proposed using a nonnegative function like the mechanical energy of the pendulum. That is, a condition that makes the time derivative of the function nonpositive is derived and a design method of the controller for l (l represents the length of the pendulum) is developed on the basis of the condition. The condition is expressed in terms of the sign condition of i and shows that the Coriolis force is used to damp the oscillations of the pendulum. The limit of performance achieved under a constrained stroke of l is also given. The controller is easily designed with a servo system that consists of a 2nd-order lag and a bang-bang input obtained from the pendulum trajectory. Numerical experiments are performed to examine the validity of the proposed method.
Virtual enterprise is a temporary alliance of enterprises that come together to share skills, core competencies or resources in order to better respond to cope with demand of customers, and whose cooperation is supported by computer networks. It is very important and difficult activity in forming a virtual enterprise to select appropriate business partners, because each enterprise considers not only pursuing its profit but also sharing the risk to join the virtual enterprise. In this study, we focus on the negotiation process in virtual enterprise formulation as the basic research to clarify its effective management. We develop a computer simulation model to form a virtual enterprise through multiple negotiations amongst several potential members in the negotiation domain, and finally clarify the formulation dynamism with the negotiation process.