96,142 research outputs found
Constrained LQR Using Online Decomposition Techniques
This paper presents an algorithm to solve the infinite horizon constrained
linear quadratic regulator (CLQR) problem using operator splitting methods.
First, the CLQR problem is reformulated as a (finite-time) model predictive
control (MPC) problem without terminal constraints. Second, the MPC problem is
decomposed into smaller subproblems of fixed dimension independent of the
horizon length. Third, using the fast alternating minimization algorithm to
solve the subproblems, the horizon length is estimated online, by adding or
removing subproblems based on a periodic check on the state of the last
subproblem to determine whether it belongs to a given control invariant set. We
show that the estimated horizon length is bounded and that the control sequence
computed using the proposed algorithm is an optimal solution of the CLQR
problem. Compared to state-of-the-art algorithms proposed to solve the CLQR
problem, our design solves at each iteration only unconstrained least-squares
problems and simple gradient calculations. Furthermore, our technique allows
the horizon length to decrease online (a useful feature if the initial guess on
the horizon is too conservative). Numerical results on a planar system show the
potential of our algorithm.Comment: This technical report is an extended version of the paper titled
"Constrained LQR Using Online Decomposition Techniques" submitted to the 2016
Conference on Decision and Contro
Guaranteeing Input Tracking For Constrained Systems: Theory and Application to Demand Response
A method for certifying exact input trackability for constrained discrete
time linear systems is introduced in this paper. A signal is assumed to be
drawn from a reference set and the system must track this signal with a linear
combination of its inputs. Using methods inspired from robust model predictive
control, the proposed approach certifies the ability of a system to track any
reference drawn from a polytopic set on a finite time horizon by solving a
linear program. Optimization over a parameterization of the set of reference
signals is discussed, and particular instances of parameterization of this set
that result in a convex program are identified, allowing one to find the
largest set of trackable signals of some class. Infinite horizon feasibility of
the methods proposed is obtained through use of invariant sets, and an implicit
description of such an invariant set is proposed. These results are tailored
for the application of power consumption tracking for loads, where the operator
of the load needs to certify in advance his ability to fulfill some requirement
set by the network operator. An example of a building heating system
illustrates the results.Comment: Technical Not
Heterogeneity and Vulnerability in the Urban Informal Economy
The focus of this paper is on the low-value urban informal economy in sub-Saharan Africa. The paper presents a case study from Uganda, with the focus on secondary cities where much of the urban population growth is expected in the next decade. There is also good evidence that informality will persist within both dynamic and in slow urban economies in sub-Saharan Africa. Analysis of the results from fieldwork is presented in support of the basic argument that, as the informal economy is likely to persist there is need for a more conducive policy approach to ensure its positive contribution to the urban economic development; seen as a mainstay of Africa’s future economic development. Currently, the informal economy is considered ephemeral, with little institutional engagement, with the focus on restrictive
measures.
The paper explores the range of theoretical perspectives on the urban informal economy leading to its re-conceptualizing as part of a continuum of activities in which both formal and informal elements are interlinked. Given the need to improve productivity of activities of different constituent groups along the continuum, the aim of this paper is to develop a conceptual framework that would enable the systematic analyses and identification of the internal diversities within the informal economy. It could be used in future policy research to identify diagnostic groups for entry points. The findings from the fieldwork carried out in the cities of Mbale and Mbarara, show that there are several viable options for sustainable livelihoods, particularly in a dynamic urban center. However, while women dominate in numbers, men remain the main actors. This calls for an inclusive, gender-mainstreamed, pro-poor development policy to complement an enterprise-based approach
Metallic Triple Beam Resonator with Thick-film Printed Drive and Pickup
A triple beam resonator fabricated in 430S17 stainless steel with thick-film piezoelectric elements to drive and detect the vibrations is presented. The resonator substrate was fabricated by a simultaneous, double-sided photochemical etching technique and the thick-film piezoelectric elements were deposited by a standard screen-printing process. The combination of these two batch-fabrication processes provides the opportunity for mass production of the device at low cost. The resonator, a dynamically balanced triple beam tuning fork (TBTF) structure 23.5 mm long and 6.5 mm wide, has a favoured mode at 4.96 kHz with a Q-factor of 3630 operating in air
What is the probability that a random integral quadratic form in variables has an integral zero?
We show that the density of quadratic forms in variables over that are isotropic is a rational function of , where the rational
function is independent of , and we determine this rational function
explicitly. When real quadratic forms in variables are distributed
according to the Gaussian Orthogonal Ensemble (GOE) of random matrix theory, we
determine explicitly the probability that a random such real quadratic form is
isotropic (i.e., indefinite).
As a consequence, for each , we determine an exact expression for the
probability that a random integral quadratic form in variables is isotropic
(i.e., has a nontrivial zero over ), when these integral quadratic
forms are chosen according to the GOE distribution. In particular, we find an
exact expression for the probability that a random integral quaternary
quadratic form has an integral zero; numerically, this probability is
approximately .Comment: 17 pages. This article supercedes arXiv:1311.554
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