321 research outputs found
Robustifying Event-Triggered Control to Measurement Noise
While many event-triggered control strategies are available in the
literature, most of them are designed ignoring the presence of measurement
noise. As measurement noise is omnipresent in practice and can have detrimental
effects, for instance, by inducing Zeno behavior in the closed-loop system and
with that the lack of a positive lower bound on the inter-event times,
rendering the event-triggered control design practically useless, it is of
great importance to address this gap in the literature. To do so, we present a
general framework for set stabilization of (distributed) event-triggered
control systems affected by additive measurement noise. It is shown that, under
general conditions, Zeno-free static as well as dynamic triggering rules can be
designed such that the closed-loop system satisfies an input-to-state practical
set stability property. We ensure Zeno-freeness by proving the existence of a
uniform strictly positive lower-bound on the minimum inter-event time. The
general framework is applied to point stabilization and consensus problems as
particular cases, where we show that, under similar assumptions as the original
work, existing schemes can be redesigned to robustify them to measurement
noise. Consequently, using this framework, noise-robust triggering conditions
can be designed both from the ground up and by simple redesign of several
important existing schemes. Simulation results are provided that illustrate the
strengths of this novel approach
Co-design of a controller and its digital implementation: the MOBY-DIC2 toolbox for embedded model predictive control
Several software tools are available in the literature for the design and embedded implementation of linear model predictive control (MPC), both in its implicit and explicit (either exact or approximate) forms. Most of them generate C code for easy implementation on a microcontroller, and the others can convert the C code into hardware description language code for implementation on a field programmable gate array (FPGA). However, a unified tool allowing one to generate efficient embedded MPC for an FPGA, starting from the definition of the plant and its constraints, was still missing. The MOBY-DIC2 toolbox described in this brief bridges this gap. To illustrate its functionalities, the tool is exploited to embed the controller and observer for a real buck power converter in an FPGA. This implementation achieves a latency of about 30 µs with the implicit controller and 240 μs with the approximate explicit controller
Observer designs for experimental non-smooth and discontinuous systems
This brief presents the design and implementation of observer design strategies for experimental non-smooth continuous and discontinuous systems. First, a piece-wise linear observer is implemented for an experimental setup consisting of a harmonically excited flexible steel beam with a one-sided support which can be considered as a benchmark for a class of flexible mechanical systems with one-sided restoring characteristics. Second, an observer is developed for an experimental setup that describes a dynamic rotor system which is a benchmark for motion systems with friction and flexibility. In both cases, the implemented observers guarantee global asymptotic stability of the estimation error dynamic in theory. Simulation and experimental results are presented to demonstrate the performance of the observers in practice. These results support the use of (switched) observers to achieve state reconstruction for such non-smooth and discontinuous mechanical systems
Constraint-Adaptive MPC for linear systems: A system-theoretic framework for speeding up MPC through online constraint removal
Reducing the computation time of model predictive control (MPC) is important,
especially for systems constrained by many state constraints. In this paper, we
propose a new online constraint removal framework for linear systems, for which
we coin the term constraint-adaptive MPC (ca-MPC). In so-called exact ca-MPC,
we adapt the imposed constraints by removing, at each time-step, a subset of
the state constraints in order to reduce the computational complexity of the
receding-horizon optimal control problem, while ensuring that the closed-loop
behavior is {\em identical} to that of the original MPC law. We also propose an
approximate ca-MPC scheme in which a further reduction of computation time can
be accomplished by a tradeoff with closed-loop performance, while still
preserving recursive feasibility, stability, and constraint satisfaction
properties. The online constraint removal exploits fast backward and forward
reachability computations combined with optimality properties
The key driver method
This chapter is a re-worked version of a paper for the International Conference on System Engineering and Applications (ICSSEA) 2006
Urgency-aware optimal routing in repeated games through artificial currencies
When people choose routes minimizing their individual delay, the aggregate congestion can be much higher compared to that experienced by a centrally-imposed routing. Yet centralized routing is incompatible with the presence of self-interested users. How can we reconcile the two? In this paper we address this question within a repeated game framework and propose a fair incentive mechanism based on artificial currencies that routes selfish users in a system-optimal fashion, while accounting for their temporal preferences. We instantiate the framework in a parallel-network whereby users commute repeatedly (e.g., daily) from a common start node to the end node. Thereafter, we focus on the specific two-arcs case whereby, based on an artificial currency, the users are charged when traveling on the first, fast arc, whilst they are rewarded when traveling on the second, slower arc. We assume the users to be rational and model their choices through a game where each user aims at minimizing a combination of today's discomfort, weighted by their urgency, and the average discomfort encountered for the rest of the period (e.g., a week). We show that, if prices of artificial currencies are judiciously chosen, the routing pattern converges to a system-optimal solution, while accommodating the users’ urgency. We complement our study through numerical simulations. Our results show that it is possible to achieve a system-optimal solution whilst significantly reducing the users’ perceived discomfort when compared to a centralized optimal but urgency-unaware policy
Projection-based Controllers with Inherent Dissipativity Properties
Projection-based Controllers (PBCs) are currently gaining traction in both
scientific and engineering communities. In PBCs, the input-output signals of
the controller are kept in sector-bounded sets by means of projection. In this
paper, we will show how this projection operation can be used to induce useful
passivity or general dissipativity properties on broad classes of (unprojected)
nonlinear controllers that otherwise would not have these properties. The
induced dissipativity properties of PBC will be exploited to guarantee
asymptotic stability of negative feedback interconnections of passive nonlinear
plants and suitably designed PBC, under mild conditions. Proper generalizations
to so-called -dissipativity will be presented as well. For
illustrating the effectiveness of PBC control design via these passivity-based
techniques, two numerical examples are provided.Comment: to be presented at IEEE CDC 2023 (Singapore
Lattice Boltzmann for Binary Fluids with Suspended Colloids
A new description of the binary fluid problem via the lattice Boltzmann
method is presented which highlights the use of the moments in constructing two
equilibrium distribution functions. This offers a number of benefits, including
better isotropy, and a more natural route to the inclusion of multiple
relaxation times for the binary fluid problem. In addition, the implementation
of solid colloidal particles suspended in the binary mixture is addressed,
which extends the solid-fluid boundary conditions for mass and momentum to
include a single conserved compositional order parameter. A number of simple
benchmark problems involving a single particle at or near a fluid-fluid
interface are undertaken and show good agreement with available theoretical or
numerical results.Comment: 10 pages, 4 figures, ICMMES 200
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