| 1. |
- Ali-Eldin, Ahmed, et al.
(författare)
-
Efficient provisioning of bursty scientificworkloads on the cloud using adaptive elasticity control
- 2012
-
Konferensbidrag (refereegranskat)abstract
- Elasticity is the ability of a cloud infrastructure to dynamically change theamount of resources allocated to a running service as load changes. We build anautonomous elasticity controller that changes the number of virtual machinesallocated to a service based on both monitored load changes and predictions offuture load. The cloud infrastructure is modeled as a G/G/N queue. This modelis used to construct a hybrid reactive-adaptive controller that quickly reactsto sudden load changes, prevents premature release of resources, takes intoaccount the heterogeneity of the workload, and avoids oscillations. Using simulations with Web and cluster workload traces, we show that our proposed controller lowers the number of delayed requests by a factor of 70 for the Web traces and 3 for the cluster traces when compared to a reactive controller. Ourcontroller also decreases the average number of queued requests by a factor of 3 for both traces, and reduces oscillations by a factor of 7 for the Web traces and 3 for the cluster traces. This comes at the expense of between 20% and 30% over-provisioning, as compared to a few percent for the reactive controller.
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
- Freidovich, Leonid, et al.
(författare)
-
Friction compensation based on LuGre model
- 2006
-
Ingår i: 45th IEEE Conference on Decision and Control. - New York : IEEE. - 1-4244-0171-2 ; s. 3837-3842
-
Konferensbidrag (refereegranskat)abstract
- We consider a tracking problem for mechanical systems. It is assumed that feedback controller is designed neglecting some disturbances, which could be approximately modeled by a dynamic LuGre friction model. We are interested to derive an additive observer-based compensator to annihilate or reduce the influence of such a disturbance. We exploit a recently suggested approach for observer design for LuGre-friction-model-based compensation. In order to follow this technique, it is necessary to know the Lyapunov function for the unperturbed system, parameters of the dynamic friction model, and to have certain structural property satisfied. The case when this property is passivity with respect to the matching disturbance related to the given Lyapunov function is illustrated in the paper with an example of a DC-motor. The main contribution is some new insights into numerical real time implementation of friction compensators for various LuGre-type models. The other contribution, built upon the main one, is experimental verification of the suggested observer design procedure.
|
|
| 5. |
- Shiriaev, Anton, et al.
(författare)
-
Criteria for Global Stability of Coupled Systems with Application to Robust Output Feedback Design for Active Surge Control
- 2009
-
Konferensbidrag (refereegranskat)abstract
- The well-known and commonly accepted finite dimensional model qualitatively describing surge instabilities in centrifugal (and axial) compressors is considered. The problem of global output feedback stabilization for it is solved. The solution relies on two new criteria for global stability proposed for a class of nonlinear systems exploiting quadratic constraints for infinite sector nonlinearities. Two families of robust output feedback controllers are proposed. Controllers from the first family ensure global exponential stabilization. The ones from the second family provide integral action but only ensure local exponential and global asymptotic stability. Performance is verified by simulations.
|
|
| 6. |
- Shiriaev, Anton, et al.
(författare)
-
Separation Principle for a Class of Nonlinear Feedback Systems Augmented with Observers
- 2008
-
Konferensbidrag (refereegranskat)abstract
- The paper suggests conditions for presence of quadratic Lyapunov functions for nonlinear observer based feedback systems with an input nonlinearity in the feedback path. Provided that the system using state feedback satisfies the circle criterion (i.e., when all states can be measured), we show that stability of the extended system with output feedback control from a (full state) Luenberger-type observer may be concluded using the circle criterion. As another result, we state a separation principle for a class of feedback systems with an input nonlinearity.When only local stability results can be stated, our method provides an estimate of the region of attraction.
|
|
| 7. |
- Shiriaev, Anton, et al.
(författare)
-
Virtual-constraints-based design of stable oscillations of Furuta pendulum
- 2006
-
Ingår i: Proceedings of the 45th IEEE conference on decision and control. - New York : IEEE. - 1-4244-0171-2 ; s. 6144-6149
-
Konferensbidrag (refereegranskat)abstract
- We consider a special benchmark mechanical system with two degrees of freedom and underactuation degree one. Furuta Pendulum consists of an arm, rotating in the horizontal plane, and a pendulum, attached to the end of the arm freely and moving in the vertical plane. Our goal is to create and partially shape stable oscillations of the pendulum. The approach is based on the idea of stabilization of a particular virtual holonomic constraint, imposed on the configuration coordinates. We describe here a step-by-step design procedure in details. Our approach is illustrated through successful experimental tests.
|
|
