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Office Ergonomics: Active Sitting

In my previous post “Office Ergonomics: Why Sitting Will Kill You” I discuss the physiological adaptations that your body experiences when spending long hours sitting. (See also “Another 1,001 Reasons to Avoid Sitting“) This post builds on that and explores some healthy approaches to sitting which will help minimize the negative effects.

Support Causes Atrophy

Figure 1. NASA astronaut Tracy Caldwell Dyson and Russian cosmonauts Alexander Skvortsov, and Mikhail Kornienko, Sept 26, 2010. The micro-gravity of space has left their bodies weak.

My biggest concern with much of the design and marketing around ergonomics equipment is the short-term focus on supporting your body in ways that will lead to further atrophy and weakness. A disturbingly common approach is to proudly announce how ergonomic chairs will protect your health through “anti-gravity support.”  While it sounds initially compelling that your tired sore back needs more support, this approach can lead to a dangerous downward spiral of further atrophy and dependence on support. Have you ever seen an astronaut after they return from a long stay in space?  They do not stride out of their space ship boldly like Buck Rogers — rather they are often assisted straight into a wheel chair. (See Figure 1) Without the need to counter-act gravity on a daily basis, their bodies have efficiently reduced muscle bulk to save energy and they are unable to stand up safely after landing.  This occurs despite significant time and effort spent exercising while in orbit, as discussed on this NASA webpage:

Exercise is the number one health priority in space, said Don Hagan, director of exercise physiology at Johnson Space Center. “No other activity except eating and sleeping is given that much priority. Two and a half hours each day are devoted to fitness.”

Why is it so important for astronauts to exercise while they’re in space? If astronauts don’t exercise, their bodies start losing bone and muscle. Bone and muscle loss mean decreased size and strength, and can reduce an astronaut’s ability to do work because it makes them weak.

Weakened astronauts would be less able to do tasks while in space, Hagan says. Also, if there were an emergency, the astronauts would need to be in good shape to get out of the Space Shuttle or Space Station quickly. Once they land on Earth, weakened muscles and bones would make walking difficult.

Gravity is your friend — it keeps you strong! If you remove the requirement to exert yourself and engage your body by using supports such as back rests, your body will naturally adapt and become weaker. Instead of following this downward spiral of weakness we can practice Active Sitting where we learn to engage and move our muscles while sitting.  To do this in a healthy manner we will need to address Alignment, Motion, and Physical Conditioning.

Back Rests and Alignment

The first alignment principle to understand is that the tilt of your pelvis has a direct impact on the curvature of your spine.  If your pelvis is in an upright neutral position, it is very easy for your spine to hold itself upright —  this is how we have evolved to move through the world.  On the other hand, if your pelvis is tilted backwards, then your spine must curve strongly to keep your back upright and your head up (Figure 2).  This takes effort and will exhaust you quickly.

Figure 2. (A) It is easiest for the spine to support the upper body when the pelvis is in a neutral upright position. When the pelvis is tilted forward (B) the lower back strains to keep the body from collapsing forward. We often unconsciously reduce the strain by using external support, such as leaning on our elbows. (C) When the pelvis is tilted backwards we need to engage our core, like holding a sit-up, to keep from falling over backwards. Since this is tiring, we often use backrests to stay upright, causing our bodies to weaken.

Sadly, many chairs, even “ergonomic” ones, are designed such that your pelvis tilts backwards and throws your back into the backrest. Chairs that naturally tilt backwards further exacerbate this tendency. Granted, these chairs feel comfortable because they naturally force you to depend upon the support of the backrest, and that is relaxing.  But, as discussed above, such dependence upon support will lead to atrophy and deeper dependence.

You want a chair that naturally holds your pelvis in a neutral upright position and makes it easy to hold your spine up. This will make it easier to sit up without continual use of the backrest, enabling your back to stay active and strong.  In fact, a backrest should be exactly what its name implies — a tool used to rest your back when it is tired, not something that you use continually the entire time you are sitting. So, when you are looking at a new chair, look to see that the seat pan is flat and does not cause your pelvis to tip forward or backwards.

Likewise, if a chair is too low and your knees end up higher than your hips, it will be very hard to sit without back support. Thus, you want a chair where your knees are even with, or lower than, your hips. Some chairs have sculpted seat-pans which combine a flat section for the pelvis and formed areas for the legs making it easier for the knees to be slightly lower than the hips without the chair cutting into the back of the legs. This is a good design feature, but has to be properly fit to your body size.

Figure 3 An example of slouched sitting. Notice the rounded back and thrust forward head. Don’t sit like this.

Buying the right chair is only part of the solution. A good chair will make it easy for you to sit with good alignment, but you can have poor alignment while sitting in the best chair. Good alignment requires active attention and knowledge, and an active and strong core. Learning how to find a healthy neutral pose for your pelvis and spine is a topic that you will continue to refine and perfect for many years. I’m still getting better at this, and I’ve been thinking about it for a long time! The following are a couple good resources that I’ve found which I recommend reading:

And finally, remember that if you are sitting without a backrest it is essential to maintain a good posture!  If your head is forward and/or your back is rounded (Figure 3), you are putting unhealthy strain on your body.

Staying in Motion

In my previous post about sitting I discussed the changes to your muscles which occur when you sit in a static position.  Your body actively lays down collagen fibers and glues muscles together — a process which is reversed by keeping the muscles in motion.  In general, this is a smart thing for the body to do because muscles that are not actively being used become more rigid and thus require less energy.  Yet when we sit in a static posture all day, we end up with glued together rigid muscles that do not serve us well when we try to stand up and walk around. It is also worth remembering that our brain has primarily evolved to coordinate motion (The Brain is For Motion), and staying active keeps us alert and mentally engaged with our bodies.

Active Sitting helps avoid tight muscles by keeping our body dynamic.  Instead of passively relaxing into a backrest, or rigidly holding a static “correct” pose, Active Sitting is about staying in motion all day long.  When our pelvis is upright we are well balanced and free to move our body as we work.  I often find myself moving and dancing in my chair slightly as I work and listen to music. Once I lean back into my backrest or lean forward onto my elbows, I notice that I move less. Such small motions may not look like”exercise,” but they do have a significant impact on our health.  Primarily these motions keep our muscles dynamically active — engaging and relaxing, and lengthening and shortening — a process which keeps them from binding up and turning off.

We can take this approach one step further by intentionally destabilizing the surface we are sitting on and requiring our body to actively balance and dynamically adjust its posture the entire time we are sitting. The easiest way to do this is by sitting on an air filled sitting disc.  When sitting on these discs your body actively tries to keep your head level (to simplify vision processing) by constantly adjusting and balancing long chains of muscles to compensate for your weight shifting with each motion you make. Using a sitting disc can turn the simple act of rotating your head into a full body action, engaging muscles all the way from your head to your feet. It is this type of dynamic engagement that keeps our muscles alive and active!


There are many air-filled exercise discs out on the market and I have tried a few of them. The first ones I used were intended for standing balance exercises, such as this one. While they were a good place to start, I found that they were not wide enough for my seat and were too tall. I eventually found the 15 sitting disc from FitBall, which has been my favorite disc so far.  It is wider, so my sit-bones fit on it, and has a lower profile, which is ideal for sitting. I have also recently found an even wider sitting disc the 24 disc from AeroMat  which I think would be great for larger folks like myself (I’m 6’6″ tall), but I have not yet tried it. Finally, some friends have spoken well of the Fitter First 15 Sitting Disc.

A sitting disc is easy and inexpensive to incorporate into your existing office setup and to start exploring Active Sitting.  It is important to note that you should not expect to sit on them continuously for the whole day.  Rather, use them for half an hour at a time, taking them on and off your chair throughout the day. Since they make active use of your core muscles, once you fatigue it is easy to unconsciously prop yourself up somehow and circumvent the destabilization that the disc offers.

Take Your Time To Train

When I first started practicing Active Sitting, I would try sitting without using my backrest for 30 minutes or less. Like any new sport, you have to train and condition your body for the activity. Besides simply building up strength and endurance in your back and core muscles, it is likely that you will have to stretch and lengthen muscles that are chronically tight from years of passive sitting. When I started my hips were too tight and my pelvis would stay rotated backwards making it difficult to sit with a neutral pelvis (See Figure 4 and discussion in my previous post). Until I was able to loosen my hips and legs enough to find a neutral pelvis, I found it very hard to sit without back support.

Figure 4 Short hamstrings contribute to tight hips and limited flexion. This combination of short hamstrings and limited hip flexion can pull your pelvis into a backward tilt, making it difficult to sit with a neutral pelvis — even in the best fitting chair.

Even now, after many years of Active Sitting, I still find that I get tired and cannot sit all day without using a backrest. So, don’t feel like you have to be able to do this for eight hours straight — that is really challenging!  My solution is to have a variety of different ways to work — from standing, to sitting on a tall saddle stool, to sitting on a regular chair with a sit disc, to simply collapsing back into the backrest and resting while continuing to work. Whenever I feel myself becoming tired of one pose, I switch to a different one. Sometimes I just lay down on my back on the floor to relax for a while.

It is worth remembering that this is a life long practice with many interdependent aspects.  You cannot simply rip the backrest off your chair and suddenly find freedom. You need to start with the body you have today and figure out what is the best path forward for you. Despite all the problems with atrophy and dependence that supportive devices cause, they can be the right short term solution. When you break your leg, using crutches is a good idea.  Doctors will try to get you back to weight bearing as quickly as possible so that your leg muscles do not atrophy — a quick process that happens in a matter of weeks!  The same is true of back support.  If you are in crisis — if your back is actively in daily pain — you may need better support in the short term.  The key is to understand that the support is not the long-term solution — it is only useful to help you while you initiate the strengthening and healing process.  Ultimately, the right solution is to have a strong, flexible, and active body, and to use equipment that helps you stay active, strong, and in good alignment.

The process of strengthening and healing your body after a life time of sitting is a complex topic beyond the scope of this post, but which I hope to discuss in detail as I continue to write. The good news is that it is possible!  Our bodies are amazingly adaptable and will adjust to a change in our daily patterns. The more aware and knowledgeable we are of our bodies, the better we can be at healing ourselves.  But even with lots of knowledge and physical conditioning I have found that I sometime need further help and have gained great benefit from regular bodywork such as chiropractic adjustments, massages, and acupuncture.  Finally, I’ve benefited from active physical training by excellent teachers I have found in the Anusara Yoga community and a number of physical therapists I have worked with.  For a short introduction to alignment principals of Anusara Yoga, and how the physical practice relates to our mental and emotional lives, see my previous post “Melt Your Heart”. So, have fun regaining use of your body while you sit, and I will follow this up with more posts on saddle stools, sit-stand desks, and many more tips for staying healthy while working.

Posted in Bodies, Ergonomics.

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What Can the Study of Human and Robotic Motion Teach Us About Our Brains and Bodies?

Note: I have posted a video of a recent version of this talk (May 2012).

Greetings Readers!

Over the last number of months I have been giving an hour long presentation which has been *very* well received. My goal is to highlight exciting insights into how we humans function and help you understand yourself.

Below is the Abstract and below that you will find copies of the slides.

“What Can the Study of Human and Robotic Motion Teach Us About Our Brains and Bodies?”
Abstract:
There is a fundamental connection between understanding our daily human experience and researching robotics.  This connection is Motion.  Because our brains exist to coordinate motion, if we wish to understand how we think, feel, and relate to others, we should start by understanding how we move.  Robotics is also fundamentally a science of Motion, spanning the range from motor controllers to advanced algorithms for world modeling and deciding where to move to.  This talk will integrate lessons learned from many robotics systems (both NASA built robots and others), and emerging theories of human physiology and neuroscience to paint an integrated picture of how our brains and bodies work together to create coordinated actions in a messy dynamic world.  In the process we will see that unlike computers, our brains are organized around timing, rhythm, and synchronization, and that human qualities like self-awareness may be the side effect of the computational requirements of intentional motion.

Bio:
Vytas is a Senior Robotics Researcher in the Intelligent Robotics Group within the Intelligent Systems Division at NASA Ames Research Center. He is currently leading efforts within the group to develop new biologically inspired approaches to robotic systems which interact safely with humans and the environment. Recently, Vytas lead development and field-testing of the Footfall Planning Software, which enables operators to plan walking sequences over complex terrain for the ATHLETE family of six-legged lunar robots. Prior to that Vytas was the Manager of the ArmLab, where he investigated non-dexterous robotic manipulation of the environment.

Vytas has been developing new robotic technologies and leading start-ups since he graduated from Stanford University in 1998. Most recently he took at 1.5-year break from NASA to be the CTO of Apisphere Inc, a Berkeley based startup that built a cloud-based system for delivering location triggered services to mobile devices. His first start-up in 1998 was Mobot Inc., which built fully autonomous robotic tour guides for museums — some of the first publicly, deployed social robots to autonomously interact with the public.

In parallel with his career in Robotics Research, Vytas has been a life-long student of human motion in many forms, including yoga, dance, martial arts, and (consequently) many forms of physical therapy.

Upcoming events where I will share this talk:

I’ve given this talk in the following Venues:

Please contact me if you would like me to present this at your own event. It is intended for the general public.

Posted in Bodies, Brains, Robots, Tensegrity.

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Office Ergonomics: Why Sitting Will Kill You

Sitting is bad for you.  I’m sorry to say, but it really is that simple. Our bodies are designed to move and run and to be active, while sitting causes them to atrophy and fall apart.  Yet, most of us are professional sitters — getting paid to sit for most of the day at a desk and work on computers.  I know that I would rather be dancing or riding my bike, but I can pay my bills a lot more effectively by sitting at a computer.  So, how can we work at our desks and be as healthy to our bodies as possible? This is the first of a series of posts on Office Ergonomics where I explore basic physiology, anatomy, and alignment principles, review my favorite equipment (and explain why), and discuss various actions you can take if you are currently experiencing pain while at work.

Your Body Adapts

The first principle to understand is that your body (and brain) physically adapts to how you use it.  We all know about sport specific adaptation — like bikers who develop strong leg muscles, or rock climbers who have strong arms.  While stronger muscles sound like a great result, adaptations that help you specialize for a specific task may make it more difficult for you to do other tasks. I know weight lifters who bench press enormous amounts of weight, but who can not cross their arms in front of their body any more. As athletes train daily for the specialized set of actions required by their sport, they become very good at those actions, but can throw their bodies out of balance leaving them prone to injury when doing other things.  This is one reason that cross-training is popular and helps prevents injuries — it keeps an athletes body prepared for a more general set of motions and avoids overly specializing for a single set of actions.  Now, take a moment to think about how much time you spend sitting every day.  Besides being at work, you might sit in your car commuting, then sit while eating at each meal, then you also sit while watching TV or surfing the internet reading blogs like this one. How much time do you actually spend moving?  Your body adapts to whatever you do, so if you spend long hours every day sitting your body will adapt to be better at sitting and possible worse at other things — like walking! So, always remember to cross-train for sitting and include as much motion in your day as possible.  Along with motion, knowledge about the adaptions will help you understand the impacts of sitting, and they fall into three major categories: muscle atrophy, muscle shortening, and fascia binding.

Muscle Atrophy

Muscle atrophy is a concept that most of us are aware of. We know that if we do not use our muscles, they will get weaker.  It takes constant energy to feed muscle bulk, and our bodies are efficient — if we are not using the muscle it naturally starts to atrophy since it is a wasteful use of resources to maintain unneeded muscle.  The primary daily use of our muscles is to move us around while counteracting gravity.  Because gravity is so omni-present we tend not to think much about it, but it is a constant and significant force that we expend a lot of energy engaging with.  Sitting passively we reduce the need to counteract gravity and do not demand much out of our bodies – leading to atrophied muscles and weakness.  Weak muscles are a problem because they will leave your joints unstable and prone to injury, or otherwise pulled out of alignment by other chronically short, tight muscles.

Muscle Shortening

Besides adapting your muscle bulk, your body also adapts the length of your muscles. Your muscles are strongest in the middle of their range of motion, loosing power at extremes of extension or contraction.  Therefore, it is most efficient for the natural resting length of your muscles to be in the middle of the normal range of motion that you experience. This adaptation allows the muscle to have the most power for the least effort through the majority of expected motions.  Therefore, your body will literally change its shape to accommodate the poses and movements that you normally experience.

Figure 2. Tight hip flexors pull your pelvis away from neutral alignment into an anterior tilt, which strains the lower back.

Figure 1. The iliacus and the psoas together make the iliopsoas, a deep and powerful hip flexor

All the time we spend sitting at desks and sitting at home encourages a pattern of shortened hip flexors.  One of our most important and powerful hip flexors is the iliopsoas (Figure 1), a two headed muscle which runs from the inside of our lower spine and the top of our pelvis down to the upper portions of our femur bone. With the pelvis fixed in place, contracting this muscle causes you to lift your leg (like a seated pose).  Conversely, when standing with the femur bone fixed in place, contracting the iliopsoas causes the pelvis to tilt forward (anterior rotation — figure 2a). Therefore, when you sit all day the iliopsoas is held in a shorted position (Figure 3b) and slowly adapts over the years causing your pelvis to tilt forward (anterior rotation) and putting a lot of pressure on your lower back.  Thus, your adaption to sitting has made it more difficult for your body to stand upright because that requires your iliopsoas to be in a longer looser pose (figure 3a).

Figure 3 Muscles shorten when you sit.

The shortening of the hip flexors is only one of the problems caused by sitting. The hamstrings, which are the largest and most powerful muscles in the body, also become shorter. The hamstrings connect from the bottom of the pelvis to the upper portions of the tibia (shin bone — figure 4).  Thus, sitting with your knees bent your hamstrings hold a shorter pose than required while standing (figure 3).  Since the hamstrings attach to the back of your pelvis, they pull your pelvis in the opposite direction as your hip flexors.  This can cause the lower back to flatten past the point of a healthy neutral spine and can be a source of many lower back complaints.

Figure 4. The hamstrings connect from the bottom of the pelvis to the top of the tibia (shin bone).

The shortening of the hip flexors and the hamstrings tilt the pelvis in different directions. While you might think, “great! Its all in balance!” it is not.  As the hamstrings and the iliopsoas fight each other they both get tighter and tighter. This reduces the range of motion of your pelvis and locks it into place, often far from a healthy “neutral” pose (Figure 2b).  It is a vicious feedback cycle that makes it increasingly difficult to achieve a healthy alignment, even when you try, since the tight locked muscles will keep pulling you back out of alignment. When you want to unlock stuck hips, the solution is, of course, a combination of knowledge, stretching, strengthening, and bodywork. Think of this as cross-training so that you can be good at both sitting and walking.

Fascia Binding

In another earlier post (Fascia, Collagen, Motion, and Bodywork) I discuss how our body is constantly laying down new collagen fibers, somewhat at random.  As we move we break the fibers that grow between the moving surfaces of our muscles.  Thus, the body adapts to its usage by stiffening up sections that don’t move much and keeping smooth sliding surfaces in the areas that see lots of motion. Like our body efficiently letting unused muscles atrophy, the body uses this process to save energy on muscles that are held chronically tight. When keeping a muscle constantly clenched, the slow build up of the collagen fibers is similar to a tree trunk becoming more fibrous and woody. As the muscle binds up and gets stiff, the body spends less energy clenching the muscle and instead passively relies on the tree trunk it just grew. Thus, when spending most of our time sitting, our muscles slowly glue together in that pose, decreasing our range of motion and eventually getting so stuck together that we can no longer get the muscles unstuck simply by moving. For more on this, see my earlier post.

Why Sitting Will Kill You

The good news is that you are unlikely to keel over and die directly as a result of sitting.  Sitting kills as an indirect result of the physical adaptations it causes. As your body adapts to sitting and becomes less well suited for other activities, like standing and walking, you increase your likelihood of a major injury.  Having tight, weak muscles may still be sufficient to get you through your typical day — shuffling from work desk, to car, to couch, to bed — the danger is when the unexpected happens.  When you slip, trip, or otherwise have a sudden need for your body to perform, you need a strong, flexible, reactive body to be able to catch yourself safely. Everyone trips, everyone slips, the unexpected is guaranteed to happen eventually, and if you are too tight and weak to catch yourself you end up falling and breaking something like your hip or arm, or throwing out your back.  These injuries can directly kill you or cause a severe degradation in your quality of life.  The most frustrating is when the injuries cause you to tighten up even more and you further limit your physical activity — starting the downward spiral that leads to further injury and physical decline.

There are many ways to avoid this sort of downward spiral. Staying active, exercising, strengthening, stretching, and managing your weight are all well-known goals (more on them eventually). Think of this as cross training for sitting!  Knowledge is the best place to start — so you can guide your physical efforts well.  To learn more about how specific muscles move your body in use-dependent ways, I highly recommend reading the Anatomy of Movement. This is the best book I’ve found for someone who wants to learn about their own anatomy and start to understand which muscles make which motions.  It is an easy and accessible read which I think everyone should take a look at. To read more about how short tight muscles can disrupt your tension network and cause problems throughout your entire body, please see my earlier post on Fascia, Bones, and Muscles.  Finally, it would be a good idea to get up and go stretch and walk around right now! Here is a good introduction to stretching following the principles of Anusara Yoga. (See also my earlier post on Anusara: “Melt Your Heart”.)

Keeping with my current focus on Office Ergonomics, my next post will discuss Active Sitting and how we can minimize the undesirable adaptations caused by long hours at the desk.  On the sidebar to the right of this post I’ve added a few quick reviews for the items I personally use, and will give more detailed discussion in future posts.


Since I wrote this post, I have gathered more studies and articles on the topic and written a review in this recent post: “Another 1,001 Reasons to Avoid Sitting“.

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Walking, Vision, and Self-Awareness

In my last post on  Robots, NASA, and The Future of Space Exploration I discussed the NASA-wide Robotics Field Test that I participated in this summer.  My project, which I worked on with my colleague DW Wheeler, was to demonstrate planning and control of the ATHLETE Robot walking over a rocky terrain using the “Footfall Planning” software we have been developing for the last four years.

I’m interested in robotics in order to learn about our own lives and experiences from the effort of designing machines that can handle similar challenges to what we face on a daily basis. One of these challenges is the simple task of walking. Decomposing the act of walking, what are the fundamental problems which must be solved?  A four-meter tall, six legged robot with wheels on the ends of its legs and electric motors instead of muscles is very different from a flesh and bones human. Yet, despite the differences, digging into the problem of walking you expose the underlying aspects which are independent of metal, flesh, two legs, four legs, or even six.

Of the many insights that came from developing the FootFall Planner, I am fascinated about the connection between walking and self-awareness.  Sharing this connection starts by describing the ATHLETE robot and then giving an overview of how walking is commanded.

About ATHLETE

ATHLETE Standing to full Height at the D-RATS 2010 Field Test

ATHLETE Standing to full height at the D-RATS 2010 Field Test

ATHLETE is an awe-inspiring robot to work with, and I consider myself privileged to have collaborated with the team from NASA’s Jet Propulsion Laboratory in California (JPL) that built the robot. Being designed to help construct a lunar base and carry large pieces of infrastructure from the lander long distances across complex lunar terrain, ATHLETE is large and impressive. The current second-generation prototype is one half the anticipated lunar scale. The robot stands to a maximum height of just over four meters, and has a payload capacity of 450 kg in Earth gravity.  Each of its six legs has seven joints, and a wheel at the end that allows it to drive over smooth terrain and walk over rough terrain. This duality of movement style is ideal for robots operating in unstructured natural environments. The most appropriate mode of locomotion can be selected depending on the conditions. Driving provides fast, energy efficient motion but is limited to smooth terrain, while walking is slower and less efficient but also more robust to obstacles and challenging terrain.

How ATHLETE Walks

In general, walking is composed of many tasks including: taking a single purposeful step, generating rhythmic gaits, and using sensory feedback to feel the force of contact with the ground and dynamically balancing even as the ground shifts underfoot (such as when on sand or soft dirt). In the FootFall Planner we worked on taking purposeful steps and generating gait sequences for the 6 legs. In this post I will focus on the process for taking a single intentional step. The process starts by using ATHLETE’s cameras to build a model of the surrounding terrain, then projecting the robots current pose into the terrain model, and then planning a sequence of motions and trajectories for each leg joint such that the robot avoids hitting itself or any part of the terrain.

View of the Apollo 15 landing site showing Hadley Rille, Hadley C crater, and the Appenine Mountains. This 3D view was created from original Apollo orbital images using the NASA Ames Stereo Pipeline.

Most of the cameras on ATHLETE come in pairs, like a pair of eyes. After requesting images to be taken, each returned stereo pair is processed to build a 3D model of the terrain. We do this by using a piece of open source software called the Ames Stereo Pipeline, which is part of the NASA Vision Workbench. These tools were built in our research group, The Intelligent Robotics Group, and are designed to provide flexible and extensible support for advanced computer vision algorithms.  Our group uses these vision tools for tasks as diverse as building 3D models of the Moon and Mars from satellite data, to robotic navigation tasks where local 3D terrain models are needed so the robot can plan a safe route around rocks and other hazards.

In the FootFall Planning System, once ATHLETE has taken images and the local 3D terrain model is built, the operator can select a new location on the ground to move a leg to. This initiates the motion planning process which takes the terrain model, the current configuration of the robot, and the desired foot placement and starts searching through a seven-dimensional space of possible leg positions until it finds an efficient motion plan which avoids any collisions with itself or the terrain.  The search space is seven-dimensional because the leg has seven joints, each of which can be controlled through a range of motion.  As each potential position of the leg is evaluated a collision-checking algorithm takes the proposed position of the leg and determines if the robot would be in collision with itself or the terrain.  Once the motion planner finds a sequence of collision-free motions that achieve the desired foot placement, a command sequence is returned to the operator who can inspect the planned motions and preview the results on a virtual model of the robot.  If the command sequence looks safe it can be sent to the robot for actual execution.

Self Awareness

Self-imaging: Stereo reconstruction will include the legs as part of the terrain. In this image the front leg has been moved aside in order to highlight the impact it had on the terrain model.  The colors of the terrain indicate which parts are reachable (green) by the leg.

This algorithmic process suddenly becomes philosophically interesting when the robot can see its own legs and feet in its camera images.  Implementing 3D terrain modeling algorithms naively results in everything that is visible in the camera image being modeled as part of the terrain.  Thus, if part of the leg and foot are visible, they end up in the terrain model and the motion planner treats them as obstacles and will not let the robot move through those spaces.  But since that is exactly where the leg currently stands, the motion planner complains that the robot is already in collision and cannot move in any direction safely. This confusion stems from the fact that the robot knows where its own body is in space, but it does not recognize its own body in the images of the surrounding terrain.

The solution to this is to implement algorithms which can identify the robots limbs in the images, remove them, and then build the terrain map that is used by the motion planner. In other words, the robot must be able to visually distinguish between Self and Other in its field of view.  This can be done by combining a projection of the robots knowledge of its leg position into the camera image, and using that location as the starting point for a process that decides which pixels in the image are part of the leg and which are not.  Once all the pixels that are part of the robot are removed from the image, the remaining terrain can be processed and motions safely planned.

Unlike ATHLETE, we humans do not necessarily place our feet with such careful attention when we walk — we usually do not look directly at our feet and instead rely heavily on rhythmic gaits and our ability to dynamically balance ourselves.  But when we use our hands to manipulate the world we often take a similar purposeful approach of looking, modeling, and reasoning about our motions.  In fact, looking at the six legged ATHLETE, one can think of the way it walks as being very similar to a large hand grasping the ground and walking by manipulating the ground with its six fingers.

Origins of Self-Consciousness?

The philosophically exciting aspect of this work is that it shows how the basic computational requirements of moving purposefully through the world require the ability to differentiate between Self and Other.  It appears that we do this for many different tasks: from walking, to manipulating objects, to how we can distinguish our own voice from all the other sounds we hear. I even read some papers which indicate that when we feel pressure on our skin from touching another object, we experience the same contact force differently if it is generated externally or as a result of our own motion. So, in every sensory modality that we have, we find the same need to separate Self from Other in order to make use of the data.

And what would happen if we were not able to separate Self from Other? In the following TED talk Jill Taylor, a Neuroanatomist, describes her experience of having a stroke, and how that gave her profound insight into the nature of Self and Other. Around 8 minutes into the talk she discusses the moment when she lost her ability to differentiate her own arm from the surrounding scene.  As she describes it, the experience is beautiful — she loses the sense of her own body and identity and feels completely connected to everything — but those moments also leave her completely incapacitated. During waves of normal thought she regains her sense of Self and is able to perform tasks, like saving her life by calling for help.

If the ability to differentiate Self from Other evolved in order to enable intentional motion and manipulation in the physical world, it seems possible that this capability for modeling ones Self separate from the environment has been built upon and used in increasingly complex ways over the generations.  Increasing this “self-modeling” capability allows us to reason about potential outcomes of actions and become better predictors of how we can influence the surrounding environment. Building on the same principles, a really complex model of ourselves enables us to reason about our own thinking, and optimize basic behaviors. That capacity for self-reflection allows us to question how much attention we should give to our model of Self and how much attention should we give to our connection with Other. After all, while it is clearly functional to be able to think separately about our Self from the environment, we do not exist in isolation, and our hearts seem to sing the brightest when we experience connection.

Further Technical Reading

If you would like to dig deeper into the FootFall Planning System, we have written a number of papers that describe the algorithms and technologies in much greater detail.  The first paper listed below gives a good overview of the system as it was in 2008, and the following papers go into greater detail on specific aspects. A new paper that summarizes the entire 4 year project has just been submitted to the Journal of Field Robotics, and will hopefully be accepted for publication later this year.

Vytas SunSprial, Daniel Chavez-Clemente, Michael Broxton, Leslie Keely, Patrick Milhelich, “FootFall: A Ground Based Operations Toolset Enabling Walking for the ATHLETE Rover,” In proceedings, AIAA Space2008, San Diego, California, Sept. 2008.

Dawn Wheeler, Daniel Chavez-Clemente, Vytas SunSpiral, “FootSpring: A Compliance Model for the ATHLETE Family of Robots,” In proceedings, 10th International Symposium on Artificial Intelligence, Robotics and Automation in Space, (i-SAIRAS 2010). Sapporo, Japan, August 2010.

T. Smith, D. Chavez-Clemente, “A Practical Comparison of Motion Planning Techniques for Robotic Legs in Environments with Obstacles,” In Proceedings of the Third IEEE International Conference on Space Mission Challenges for Information Technology. Pasadena, CA. July 2009.

Tristan Smith, Javier Barreiro, David Smith, Vytas Sunspiral, Daniel Chavez, “Athlete’s Feet: Multi-Resolution Planning for a Hexapod Robot.” In proceedings, International Conference on Automated Planning and Scheduling (ICAPS), Sydney, Australia, Sept. 2008.


I would like to end with a formal disclaimer –I do not work for NASA (I’m employed by a contracting company — Stinger Ghaffarian Technologies Inc.), and this blog is written as a personal project.

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