6,318 research outputs found
Disturbance Decoupling in Nonlinear Impulsive Systems
International audienceThis work deals with the problem of structural disturbance decoupling by state feedback for nonlinear impulsive systems. The dynamical systems addressed exhibit a hybrid behavior characterized by a nonlinear continuous-time state evolution interrupted by abrupt discontinuities at isolated time instants. The problem considered consists in finding a state feedback such that the system output is rendered totally insensitive to the disturbance. Both the case of static state feedback and that of dynamic state feedback are considered. A necessary and sufficient condition for the existence of a static state feedback that solves the problem in the multivariable case is proven by defining suitable tools in the context of the differential geometric approach. The situation concerning solvability by a dynamic state feedback is examined in the framework of the differntial algeraic approach. A necessary and sufficient solvaility condition is conjectured and discussed
Fast Reachable Set Approximations via State Decoupling Disturbances
With the recent surge of interest in using robotics and automation for civil
purposes, providing safety and performance guarantees has become extremely
important. In the past, differential games have been successfully used for the
analysis of safety-critical systems. In particular, the Hamilton-Jacobi (HJ)
formulation of differential games provides a flexible way to compute the
reachable set, which can characterize the set of states which lead to either
desirable or undesirable configurations, depending on the application. While HJ
reachability is applicable to many small practical systems, the curse of
dimensionality prevents the direct application of HJ reachability to many
larger systems. To address computation complexity issues, various efficient
computation methods in the literature have been developed for approximating or
exactly computing the solution to HJ partial differential equations, but only
when the system dynamics are of specific forms. In this paper, we propose a
flexible method to trade off optimality with computation complexity in HJ
reachability analysis. To achieve this, we propose to simplify system dynamics
by treating state variables as disturbances. We prove that the resulting
approximation is conservative in the desired direction, and demonstrate our
method using a four-dimensional plane model.Comment: in Proceedings of the IEE Conference on Decision and Control, 201
A robust PID autotuning method for steam/water loop in large scale ships
During the voyage of the ship, disturbances from the sea dynamics are frequently changing, and the ship's operation mode is also varied. Hence, it is necessary to have a good controller for steam/water loop, as the control task is becoming more challenging in large scale ships. In this paper, a robust proportional-integral-derivative (PID) autotuning method is presented and applied to the steam/water loop based on single sine tests for every sub-loop in the steam/water loop. The controller is obtained during which the user-defined robustness margins are guaranteed. Its performance is compared against other PID autotuners, and results indicate its superiority
Virtual Constraints and Hybrid Zero Dynamics for Realizing Underactuated Bipedal Locomotion
Underactuation is ubiquitous in human locomotion and should be ubiquitous in
bipedal robotic locomotion as well. This chapter presents a coherent theory for
the design of feedback controllers that achieve stable walking gaits in
underactuated bipedal robots. Two fundamental tools are introduced, virtual
constraints and hybrid zero dynamics. Virtual constraints are relations on the
state variables of a mechanical model that are imposed through a time-invariant
feedback controller. One of their roles is to synchronize the robot's joints to
an internal gait phasing variable. A second role is to induce a low dimensional
system, the zero dynamics, that captures the underactuated aspects of a robot's
model, without any approximations. To enhance intuition, the relation between
physical constraints and virtual constraints is first established. From here,
the hybrid zero dynamics of an underactuated bipedal model is developed, and
its fundamental role in the design of asymptotically stable walking motions is
established. The chapter includes numerous references to robots on which the
highlighted techniques have been implemented.Comment: 17 pages, 4 figures, bookchapte
Quantum Internal Model Principle: Decoherence Control
In this article, we study the problem of designing a Decoherence Control for
quantum systems with the help of a scalable ancillary quantum control and
techniques from geometric control theory, in order to successfully and
completely decouple an open quantum system from its environment. We
re-formulate the problem of decoherence control as a disturbance rejection
scheme which also leads us to the idea of Internal Model Principle for quantum
control systems which is first of its kind in the literature.
It is shown that decoupling a quantum disturbance from an open quantum
system, is possible only with the help of a quantum controller which takes into
account the model of the environmental interaction. This is demonstrated for a
simple 2-qubit system wherein the effects of decoherence are completely
eliminated. The theory provides conditions to be imposed on the controller to
ensure perfect decoupling. Hence the problem of decoherence control naturally
gives rise to the quantum internal model principle which relates the
disturbance rejecting control to the model of the environmental interaction.
Classical internal model principle and disturbance decoupling focus on
different aspects viz. perfect output tracking and complete decoupling of
output from external disturbances respectively. However for quantum systems,
the two problems come together and merge in order to produce an effective
platform for decoherence control. In this article we introduce a seminal
connection between disturbance decoupling and the corresponding analog for
internal model principle for quantum systems.Comment: Submitted to IEEE Transactions on Automatic Control, Mar 15 2010. A
basic introduction appeared in 46th IEEE CDC 2007. Acknowledgements: The
authors would like to thank the Center for Quantum Information Science and
Technology at Tsinghua University, R.-B. Wu, J. Zhang, J.-W. Wu, M. Jiang,
C.-W. Li and G.-L. Long for their valuable comments and suggestion
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