4 Presentations

• 
  10:30 AM - 10:55 AM

  Service systems with adjustable speed

  • Eman Almehdawe, presenter, University of Regina

  We investigate a fluid model of a service system, in which customers are discharged at an adjustable speed, which influences the proportion of customers that require rework after a delay. We formulate the model as a delay-differential equation. We study the transient and steady-state behavior of the system occupancy in four different regimes and we obtain conditions under which speedup reduces average occupancy.

• 
  10:55 AM - 11:20 AM

  Factorization-free methods for computed tomography

  • Maxime Mclaughlin, presenter, Polytechnique Montreal
  • Dominique Orban, GERAD - Polytechnique Montréal

  We study a tomographic reconstruction problem in cylindrical coordinates. A change of variables involving a Fourier matrix attempts to improve the conditioning of the Hessian but introduces linear inequality constraints. The scale and density of the problem call for factorization-free methods. We argue that projections into the feasible set can be computed efficiently by solving a bound-constrained least-squares problem with a fast linear operator. In this talk, we focus on a Barzilai-Borwein projected gradient method and a trust-region projected Newton method. We compare two solvers for the projection subproblem: a two-metric projection algorithm and a trust-region projected Newton method. The performance of several combinations is assessed using synthetic data on the reconstruction problem.

• 
  11:20 AM - 11:45 AM

  Extremum-Seeking Guidance on SO(3) Using a Kalman Filter

  • Alex Walsh, University of Michigan
  • James Richard Forbes, presenter, McGill University

  Extremum-seeking guidance endeavours to drive the output of a system to the extremum of an unknown objective function. This paper proposes an extremum-seeking guidance algorithm for constrained subsets of SO(3). The algorithm is enabled by a novel constrained Kalman filter, and is demonstrated on a spacecraft attitude guidance problem.

• 
  11:45 AM - 12:10 PM

  Controller Design for Regional Pole and Zero Placement using Linear Matrix Inequalities and the Modified Minimum Gain Lemma

  • Ryan Caverly, presenter, University of Michigan
  • James Richard Forbes, McGill University

  This talk presents controller synthesis methods involving linear matrix inequalities that place closed-loop zeros in the open left-half complex plane. This prevents nonminimum phase closed-loop behaviour, often characterized by a response that initially moves in the opposite direction from a desired set point before asymptotically reaching the desired set point.