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Articulated Hand: Low-Cost Prototyping with LEGO
One of the interests of the Open Prosthetics Project is to develop low cost prototyping platforms to encourage experimentation and collaboration on new concepts, both for control systems and mechanisms. One of our favorite prototyping tools is the LEGO construction system. We think that LEGO parts can offer a flexible and inexpensive method for developing complete mechatronic devices for research and development.
John Bergmann has made great progress in developing an advanced mechanism for a LEGO hand, complete with fully articulated fingers and opposable thumbs at a scale similar to that of the average male hand. He has put together some great documentation of his construction techniques for the basic hand.
At present this hand is not powered, however, John has been working a next revision of the device that includes a functional wrist with cable actuators. We encourage others to look at John’s design and consider collaborating with him to continue the development of this platform. Once a functional power system is integrated the device could serve as an excellent plant to be controlled by a low-cost myoelectric or acoustic myography sensor system.
Gluing a structure like this together could make it strong enough even for limited use. Experts say that Oatey All-Purpose Glue works well. We have yet to give it a try, although we can say that it can be frustrating to have a model come apart when you try to use it.
Development of a LEGO-based sensor platform is another area of interest. We believe that a complete, low-cost myoelectric sensor system could be built using LEGO Minstorms NXT controllers. Creating an NXT-based sensor platform combined with a hand mechanism such as John’s would result in a complete LEGO-based reference design for less than $500 in materials.
Given the small number of upper-extremity prosthetic clients, a toy that uses myoelectric technology could spur some interesting developments. Also, LEGO products are accessible in ways that many things in the world of hardware are not. The existence of a complete myoelectric platform like this would significantly lower barriers to participation in research and development and aid in accelerating collaboration by using inexpensive, readily available parts for implementation.
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