Sunday, July 8, 2012

Most Biologically Accurate Model of Human Walking

The press release a couple of days ago the work that Theresa Klein and I did has really caught the world's  imagination.  It also caught me off guard. My cell phone started ringing at 7:00 am the day before the press release with people asking for interviews.  It was fun, we were covered by the AFP the Paris news agency, and BBC Radio up all night... and various other places.

Before looking at the video, which you can see here, I would recommend either reading the article. Or the summary of the results published at the National Health Services in Britain here.

The point of the work was to create a physical model of the walking system in a human being. That includes getting the biomechanics right. We had to build a system with  essential elements of the biomechanics of the lower human limb. That alone was difficult starting from scratch.

We used a 3-D printer from Dimension. It took me about 5 years for my students and I to master building robots using a 3-d printer.  There were a lot of techniques we learned on the way. One day, I hope to publish all of the tricks that allowed us to do this.

Next we had to build muscle like actuators that used tendons to pull on the limb. Easy right? well, we had to sense the force in the tendons. Theresa went through many iterations until she invented a sensor that was accurate but durable enough to be used in a robot. When I say many I mean many iteration. Robotics is nothing if not about persistence.

Theresa then had to experiment with building neural circuits. Typically, neurorobot in the past have used dynamical equations that produce oscillations... not really neurons... we used Izhikevich spiking neurons which we felt are much more like what you would see in the true spinal cord.

I have been working with building spiking neural networks for some time now. We have even built a series of ASIC chips that implement the dynamics of neurons in collaboration with our colleagues at Johns Hopkins. We have used those chips to control movement in animals.

What we needed was a platform to figure out how the entire neuro-mechanical-sensory system interacts. So, if we one day want to restore locomotion, we need to have some basic understanding of walking.

Now, why is this important to science? Biologist collect lots of data about the bits and pieces of locomotory system, but they don't know if they put all of the pieces together if the system will actually work as in a human or animal. They can never know if the elements they have uncovered are both "Necessary and Sufficient."  That is where robots can really help.

So our work does just that, we took what we knew about biology then had to fill in details where details were missing (think Jurassic park :-)) . And we were able to get walking using ONLY suggestions from biology. No gimmicks.

So, that is why I think the work is cool and it is relevant SCIENTIFICALLY.

Now, a lot of people have compared what we have done to PetMan. And one commentator implied that we where trying to play "catch up."

Well, Petman has been extremely well funded, and had practical, engineering goals. We did our work on our own dime and some funds provided by the University of Arizona (thank you!).  I am sure the ratio of spending is something like 1000:1. To be perfectly honest, initial funding for the core concepts behind this  work was provided by Tom McKenna of the Office of Naval Research years ago. He got me going in the direction of building biologically inspired humanoids. Dr. McKenna has been the most important force in legged locomotion over the past several decades in the United States PERIOD.  Now Gill Pratt at Darpa is really making a push, but I think Dr. Pratt's charter is more towards building systems with direct military importance. Perhaps I can persuade Darpa to do a neuro-prosthetics program for the lower limb like they funded for upper limb prosthesis. that would be cool!

Like I said, funding is hard to get for this kind of work. In this country engineers don't care about the biology at all. And biologist are skeptical of "engineers" encroaching on their turf competing for very limited funds in biology... which I totally understand.  Really, only a handful of places around the country have been able to make a living in this biologically inspired walking robot paradigm. I would say the oldest program was  at Case Western Reserve and that work is still being continued by Roger Quinn and Roy Ritzmann and colleagues.

But, non-the-less, Theresa and I  felt this work was important and we put our own money sweat and time into building it. She preserved for years... I am proud of her. Unfortunately, the experience left her jaded about research.  She had fantastic opportunities to continue this work when she graduated  and a possibly brilliant research career ahead of her but, she decided to go into industry, ultimately.

It is a loss to science.

It is telling that most attention to this work has come from overseas... internationally... where I think they understand interdisciplinary research a bit better.

But, I think I will continue this work somehow.  I have gotten many letters from people and seen many comments on sites that indicate that people see this robot as hope that one day we will be able to restore locomotion in people with spinal cord injury. Of course,  the robot we built is just a tool for understanding. We still need the medical experts to make it real.

No comments:

Post a Comment