Would there be any benefit to not try to replicate human movement directly? For example, maybe balance would be easier by adding a "tail" that drags along behind with a small wheel under it.
I would think that the main benefits that people would look for over a wheel chair, are being able to go over uneven surfaces / stairs, and being at the right height to reach things.
I'm imagining a system where the user is strapped to a seat of a machine with the legs slightly bent and in front, and and the machine's two legs maneuver by telescoping. That way, you need one motor to control how far a leg is extended, and another one to control forward swing. The tail would help with balance, and also hold the battery pack.
Very briefly, the things holding back exos are
- regulatory process is a five year process, minimum, so anything coming out today is using at least 5 year old designs etc, and also means fewer players can afford to undergo the process (fda, patents, etc)
- state of the art is held back by poor designs and construction methods
- lack of focus/v.c $$ in the field
I suspect within the next decade we will see a revolution in this field, but for now, this is what we've got.