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“The Cargo Transphere” and Pugh Method overview

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“The Cargo Transphere” is a concept I have proposed for military cargo field transfer system and that “won” out of other concepts by the rules of “Pugh” during one of Systems Engineering exercises (it was a non-secret couple-hours exercise, so I can bring it here).

Prior to the concept description, here is a brief overview of Pugh if you are not familiar with (which is more important than this particular example). It is also sometimes called a “Decision Matrix” or “Concept Selection Matrix”:

During one of stages of conceptual design, there is a need in trade-off analysis. Let’s say you have already got to several primary concepts. At this stage you would like to narrow your set to couple of best concepts. There are several ways to do so, while the Pugh method is an extremely simple, brief and efficient one. Here is how it works – you make a table, where for each primary concept you’ve got a column. Then you have to bring multiple criteria, related to the functional and business perspectives, risks, characteristics of scenarios (usually you already should have ones at this stage), MTBFs… bottom line every general, but important criterion can play. Each criterion gets one row in the table. You choose one of the concepts as a reference for comparison and name it “Datum”. Then you go and compare per criterion over all other concepts and sign if the concept characteristics are better/worse/or kind of similar in meeting the criterion. You can use (+/-/s) or any other sign in each cell. You can use also values since this is what you are going to do at the next stage – sum each column, while “better” gets “+1”, “worse” gets “-1” and “similar” is weighted as “+0”. You can use other values in some cases – for example if the concept is “the best” out of all for some criterion, you can assign “+2”. Now you sum all and – voilà you’ve got the winner!

Well from this kind of simplicity you can only complicate your method. For example sometimes you can add couple of criteria that are “must have” and separate them from others that are not. It is done purposely, since once some of concepts does not meet a basic need, there is no need to proceed in comparison.

pugh

In some cases I have seen, on top of “Sum”, there are added “Soft” characteristics that are adding some bias to the weight of the concept. For example “Novelty”, “Elegance”, “Politics” etc…

Please mind that “Datum” has to be chosen carefully since it should not be at the corner a priori. Try to take some solution that seems to be somewhere in the middle (you can grossly see some other concepts that are better and some that are worse than this). No worry – even if you see that apparently it is at the corner (all others got “-” or “+”), you can choose it and rerun the analysis. Not critical though. Why is it done?

Here is why. The purpose of “Pugh” is not only to choose the best concepts, but also make an improvements of those concepts by “characteristics adoption” of other superior concepts where it is possible. So the work can be done in several iterations, every time improving the primary concepts.

That’s all… As simple as it sounds, it might take couple hours and, no – most of New Product Developers are not doing even this… at least those that I know (hope I am mistaken as a general statement).

Ok. Here we go – I promised the concept. General goal was to develop a product of cargo transfer for military purposes with some constraints, so soldiers could use it in a field. In this scenario, 100kg cargo, packaged volume 1m^3, enabling in <5 minutes, deployment in <5 seconds, filed conditions – desert, self weight <20kg, extremely low noise and activity footprint.

So here is the concept:

Name: “The Cargo Transphere”

Concept symbol:  symbol

Description: An inflated spheres around the cargo with motor system in between two rubber spheres that is causing the system to roll on the ground automatically. At the time of application the space around the cargo is inflated while the cargo is held within, attached to strings, connected to the inner sphere. Locomotive units, which include electro-motors, electro-accumulators and mechanical parts, are moving in-between two spheres and by applying the angular momentum, are causing the whole system to roll. Inner surface of external sphere is rough to maximize the friction with the locomotive unit.   Control and communication modules are located within the system and are responsible for control of the movement, getting the feedback from the soldier, positioning systems, cameras and central base. The operational extraction of the cargo or its partial exposure is possible by automatic or manual relaxation of “the Navel” aperture. Complex control of the movement systems is done to avoid collision between locomotive modules and with the “Navel”. The navigation is done in several modes – fully automatic based on the reference point, follow-the-soldier mode and manual mode. Based on need (leak/post-access refill) the internal balloon with compressed gas can be used to inflate the spheres and increase the pressure. In case of manual mode, the accumulators are charged by the system (oh, I will vomit if I will write that it is charged by solar surface of the sphere). In “system damaged” scenario, the locomotive units can be taken out to reduce the weight of the system (special “Navel” mode) and used in a fully manual matter. External surface material is designed to change the trajectory of the bullets to exit through the external sphere without impacting the internal. Holes from bullets can be detected by changed color of the surface and after a patch application by soldier and self-inflation, the system can continue the functionality. The system can be used on a low inclination surface, including water.

Dimensions: Diameter of the system is 2 meters,  space between spheres is 30 cm

Schematics:

the system

 

As usual , thanks for reading and hope you enjoyed and/or learned something 🙂

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Author: Andrey Gabdulin

www.gabdulin.com Product Development

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