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Branch and bound based coordinate search filter algorithm for nonsmooth nonconvex mixed-integer nonlinear programming problems

Publication . Fernandes, Florbela P.; Costa, Fernanda P.M.; Fernandes, Edite M.G.P.

A mixed-integer nonlinear programming problem (MINLP) is a problem with continuous and integer variables and at least, one nonlinear function. This kind of problem appears in a wide range of real applications and is very difficult to solve. The difficulties are due to the nonlinearities of the functions in the problem and the integrality restrictions on some variables. When they are nonconvex then they are the most difficult to solve above all. We present a methodology to solve nonsmooth nonconvex MINLP problems based on a branch and bound paradigm and a stochastic strategy. To solve the relaxed subproblems at each node of the branch and bound tree search, an algorithm based on a multistart strategy with a coordinate search filter methodology is implemented. The produced numerical results show the robustness of the proposed methodology.

2014Conference object

Open access

Multiple solutions of mixed variable optimization by multistart hooke and jeeves filter method

Publication . Costa, M. Fernanda P.; Fernandes, Florbela P.; Fernandes, Edite M.G.P.; Rocha, Ana Maria A.C.

In this study, we propose a multistart method based on an extended version of the Hooke and Jeeves (HJ) algorithm for computing multiple solutions of mixed variable optimization problems. The inequality and equality constraints of the problem are handled by a ﬁlter set methodology. The basic ideas present in the HJ algorithm, namely the exploratory and pattern moves, are extended to consider two objective functions and to handle continuous and integer variables simultaneously. This proposal is integrated into a multistart method as a local search procedure that is repeatedly invoked to converge to diﬀerent global and non-global optimal solutions starting from randomly generated points. To avoid repeated convergence to previously computed solutions, the concept of region of attraction of an optimizer is implemented. The performance of the new method is tested on benchmark problems. Its eﬀectiveness is emphasized by a comparison with a well-known solver.

2014Journal article

Open access

Combining gait optimization with passive system to increase the energy efficiency of a humanoid robot walking movement

Publication . Pereira, Ana I.; Lima, José; Costa, Paulo Gomes da

There are several approaches to create the Humanoid robot gait planning. This problem presents a large number of unknown parameters that should be found to make the humanoid robot to walk. Optimization in simulation models can be used to find the gait based on several criteria such as energy minimization, acceleration, step length among the others. The energy consumption can also be reduced with elastic elements coupled to each joint. The presented paper addresses an optimization method, the Stretched Simulated Annealing, that runs in an accurate and stable simulation model to find the optimal gait combined with elastic elements. Final results demonstrate that optimization is a valid gait planning technique.

2015Conference object

Open access

Project-based learning: an environment to prepare IT students for an industry career

Publication . Alves, Luís M.; Ribeiro, Pedro; Machado, Ricardo J.

The lack of preparation of Software Engineering (SE) graduates for a professional career is a common complaint raised by industry practitioners. One approach to solving, or at least mitigating, this problem is the adoption of the Project-Based Learning (PBL) training methodology. Additionally, the involvement of students in real industrial projects, incorporated as a part of the formal curriculum, is a well-accepted means for preparing students for their professional careers. The authors involve students from BSc, MSc, and PhD degrees in Computing in developing a software project required by a real client. This chapter explains the educational approach to training students for industry by involving them with real clients within the development of software projects. The educational approach is mainly based on PBL principles. With the approach, the teaching staff is responsible for creating an environment that enhances communications, teamwork, management, and engineering skills in the students involved.

2018Book part

Restricted access

Solving multilocal optimization problems with a recursive parallel search of the feasible region

Publication . Pereira, Ana I.; Rufino, José

Stretched Simulated Annealing (SSA) combines simulated annealing with a stretching function technique, in order to solve multilocal programming problems. This work explores an approach to the parallelization of SSA, named PSSA-HeD, based on a recursive heterogeneous decomposition of the feasible region and the dynamic distribution of the resulting subdomains by the processors involved. Three PSSAHeD variants were implemented and evaluated, with distinct limits on the recursive search depth, offering different levels of numerical and computational efficiency. Numerical results are presented and discussed.

2014Conference object

Open access