ESD.77 FINAL PROJECT SPRING 2010 Barge Design Optimization Anonymous MIT Students Abstract— In this project, three members of the Armed Forces tested the multi-disciplinary system design optimization approach to concept evaluation on a simplified platform, a barge. A barge is a non-self propelled vessel that incorporates the basic disciplines of ship building: hydrodynamics, hydrostatics, and structural mechanics. Using four bounded design variables, we attempt to optimize the payload, in tons, that a barge could carry within the physical constraints. We conduct a design of experiments to select an initial design to further optimize. Sequential quadratic programming (SQP) was used to solve the non-linear program (NLP) in computer software MATLAB. The NLP was also solved using the genertic algorithm (GA) heurisitic. SQP converged quickly and found the optimal solution. The problem was expanded to include another objective, structural weight. The multi-objective problem was solved to create a Pareto front to show the trade-offs for each objective. The results of the study show this approach is feasible for these types of platforms and allow the opportubnity for expansion of included disciplines as well as increased fidelity of the model used. Thus, eventually, a warship or some other such complex system could be designed with this approach. Index Terms—Barge, MDO, SQP, Genetic Algorithm ——————————  —————————— 1 INTRODUCTION barge is a typically non-self propelled, flat-bottomed vessel used initially for river or canal transportation of heavy goods. Although other means of transportation have been developed since their introduction, barges are still used all over the world as a low-cost solution for carrying either low -value or heavy and bulky items. Although a barge is very simplistic compared to most of its waterborne brethren, it still presents ample oppor-tunity to experiment with balanced designs. A customer may desire to carry as much payload as possible to gain effeciencies in their transportation costs, but maximizing these payloads must be balanced by engineers to operate within the laws of physics (including stability, buoyancy, powering, resistance, structures, etc.) and balanced by financiers to operate within a customer ’s allow able lim its of cost. These two very obvious considerations alone can create quite a complex balancing act, since these forces - requirements, feasibility, cost - tend to oppose each other. 2 MOTIVATION The team ’s interest and backgrou nd in many asso-ciated disciplines has primarily motivated this project. Du ring the team ’s tenu re at Massachusetts Institu te of Technology, they have taken a range of courses inclu ding Marine Hydrodynamics, Design Principles for Ocean Ve-hicles, Principles of Naval Architecture, Power and Pro-pulsion, Structural Mechanics, Plates and Shells, Ship Structural Analysis and Design, and Ship Design and Construction. Each of these courses had one of two ap-proaches. Either the course examined a particular discip-line of ship design and mentioned that a designer should not forget other disciplines, or the course examined the design as a process and recognized the many disciplines bu t encouraged an iterative, ―throw -it-over-the-w all‖ ap-proach to converge to a point design. To further emphas-ize, even the courses that recognized the multi-disciplinary aspects of ship design only designed for con-vergence to any feasible design within the space, not nec-essarily an optimal design. Thus, the team wished to explore the possibility of an optimal design amongst each of the disciplines. We wanted to create an optimal design from a multi-disciplinary standpoint and understand the associated trade-offs within the design vector. Meanwhile, we wanted to acquire knowledge and skills by using the m e-thods and tools of this new trade. The team knew, however, that using these tools to de-sign any standard sea-going vessel would provide dimi-nishing returns due to the incredibly complex and coupled nature of the entire set of design variables. Thus, the team used a simplified, low-fidelity model on a sim-ple vessel – a barge – to demonstrate the benefit of these tools within the marine design environment. The under-standing was that the design vector could grow and the fidelity of the model could increase modularly to accom-modate increasingly complex designs for more typical ocean platforms. Indeed, two team members have the task of performing a clean slate design of a warship for the next year, so, should they incorporate these tools in the design process, the design vector will grow and the ESD.77 © 2010 IEEE ———————————————— Student A is pursuing a Naval Engineer’s Degree and an M S in Engi-neering Management through the Systems Design and Management pro-gram, both at the Massachussetts Institute of Technology in Cambridge, MA 02139. Student B i s pursuing a N aval Engineer’s Degree and an MS in Engineering Management through the Systems Design and Management program, both at the Massachussetts Institute of Technology in Cambridge, MA 02139. Student C is pursuing an MS in Operational Research at Massachu-setts Institute of Technology in Cambridge, MA 02139. A2 ESD.77 FINAL PROJECT SPRING 2010 fidelity and computational expense of the model will in-crease very quickly. This project proved a good proof of concept for the team members to grow and add variables, parameters, constraints, and fidelity to at a later date. 3 PROBLEM FORMULATION As with any vessel operating in the marine environ-ment, the designer has to deal with stability, seakeeping and structural strength issues – to name a few - all of which come from different disciplines: hydrostatics, hy-drodynamics, and structural mechanics. The team used the methods and tools of multi-disciplinary system de-sign optimization to optimize the design of a barge with respect these disciplines. The primary design objective was to maximize the payload (i.e. the cargo capacity) that the barge can effectively carry. Eventually, this project also balanced that optimization against the cost of the vessel, represented by the