Posts Tagged ‘Data Flow Diagram’

Best Robotic Legs Ever?

Friday, July 6th, 2012

A very interesting development has been reported by the Daily Disruption News Desk regarding robotic legs that are claimed to “fully model walking in a biologically accurate manner.” This will come as good news for spinal cord injury patients. Those of us who follow developments in artificial intelligence and robotics will likely take note as well.

I read this account with fascination, and immediately wanted to sketch out my understanding in model form. Extending the colloquialism, to a hammer, everything is a nail – to a systems engineer, everything must be modeled. As conveyed in the article, human walking is controlled by a neural network called the central pattern generator (CPG), which is anatomically located in the lumbar region. It’s purpose is to generate rhythmic muscle signals. The researchers said in its simplest form the CPG can be modeled by a neuron pair that each fire signals in alternating fashion.

To complete this model in addition to the neural architecture, the robot needs muscle-skeleton and sensory feedback components. Roughly, this system can be modeled as shown:

I could be wrong, but this is how I understand the Robotic Leg System!

Co-author of the study Dr Theresa Klein was quoted as saying “…we were able to produce a walking gait, without balance, which mimicked human walking with only a simple half-centre controlling the hips and a set of reflex responses controlling the lower limb.”

So, did you catch that? That was quite a surprising statement. Two things are totally counter intuitive to me. First, she said the robot works “without balance.” Does that mean that this robot does not need an “inner ear” to balance? Second, the CPG apparently apparently converts coarse motor commands into forces applied at the hip joint only. The “dangling part of the leg, the lower limb, just follows reflexively, implementing easily programmable commands that simple follow what is happening up stream at the hip.

Another implication of this analysis is that the brain proper plays less of a role in controlling gait that I would have guessed.

This would be a good time to confess that I could be totally wrong in my interpretation of this research and its result; I am learning as I go.

Speaking of which, the CPG model of this study is apparently a good facsimile of how gait is refined from early childhood steps through later improvement during the maturing process. The CPG in humans gets better over time as it learns the best walk to walk by repetition.

This is exciting as I can see similarities between this system and what I am learning in my Udacity.com artificial intelligence class. The evolving understanding of complex bio-mechanical systems as well as advances in AI make this a great time to be a student of such things.

Is there an OODA Loop in your Future?

Thursday, June 21st, 2012

Being out and about in today's dismal economyJohn Boyd’s OODA Loop as Data Flow Diagram by Michael LaRue presents an array of opportunities and challenges. Since the word displaced is a euphemism for laid-off/unemployed, let's face it, restoring an income stream is one of the most important of those challenges. One way or another, doing that will require some situational assessment and decision-making.

Regardless of how well an aerospace engineering degree and decades of professional experience may equip a person, there is no silver bullet solution, or natural growth path towards a comfortable future, once displaced. A person in this position has to be resourceful and purposeful in moving forward.

Presented with this exact situation myself, I wondered what decision-making framework from my prior experience might serve well? Fortunately for me, something came to mind pretty quickly, the famous OODA loop!

My exposure to this concept came while working on an enhanced threat assessment feature of the Space-Based Space Surveillance system. Don't worry, it's unclassified, or at least it was at the time.

Briefly, OODA is a method for effective decision-making which is composed of a recurring cycle of the following steps: Observe – Orient – Decide – Act. This loop was created by Air Force Colonel John Boyd for application to military tactics in aerial combat. To paraphrase, the objective is to defeat an enemy in combat, and survive, by operating at a tempo faster than their ability to effectively make their own decisions. An excellent introduction to the subject can be found within this wikipedia entry.

For a person in my position, this seems like useful strategy to employ. If you are in a similar situation and don't think it's good, then perhaps you married rich, are already otherwise financially independent, or you've got a better idea yourself. If that's the case I'd love to hear from you; let me in on your secret, please!

To illustrate the OODA Loop I've created a Data Flow Diagram. This is a notation by Tom DeMarco in his excellent book, Structured Analysis and System Specification. I've used this notation frequently, to great effect in my aerospace engineering days. Most other times I've seen it presented though, it's been in a classical flowchart style. Rather than just regurgitate that form, I thought a fresh look might be helpful.

In my next post I will outline how I've applied, and will continue to apply, this approach, to the ongoing process of recreating myself for my future.

Until then, if you've lacking for something constructive to do, at least start doing the first of the two O's – start observing your environment and your circumstances. What could be more important that being aware of where you're at?