[MUSIC] Welcome to week three of our robotics MOOC. In this week, we'll be thinking about taking those primitives of week two and putting together, attaching limbs to bodies, and getting them to start to behave. The first half hour of this week concerns itself with what limbs can do, what they can't do, and how to think about their capabilities, first of all in motion, and second of all at work. What do I mean by that? In 3.1.1, we'll review kinematics, which is the study of limbs in motion. What are the mobility properties of the limbs without thinking about how they achieve those motions in time? Then in the second segment of this half hour, we'll review the way in which Newton's laws, when they attach to the masses that are constrained by these complicated linkages, how those laws create very complicated and interesting dynamical effects such as I talked about in the original discussion of animal mobility. It will turn out that when animals run, they turn themselves into pogo sticks. Remember that slip template from week two? You're going to see it here in many, many different incarnations. In bipeds, in quadrupeds, in six legged runners, in many legged runners. You're going to see how the kinematics of these linkages get transformed into pogo sticks by the animal coordination that we try to be inspired about and build into our robots. Here is an example of a machine that doesn't look like the pogo stick, but it's built to run as a composition of pogo sticks and leap like a coordinated single pogo stick. Stay tuned. We won't talk about this composition yet. That's for week four, but that's where we're headed. The second half hour of this week will be concerned with designs of bodies. How do we attach these wonderful limbs to bodies to get complicated robots that can do interesting tasks for us? We'll start with sprawled posture runners. Very strongly informed by what our friends in biomechanics and integrated biology can tell us about how the arthropods do it. Well, many, many, many engineers and even hobbyist have been inspired by the sprawled posture of arthropods, which are the most successful animals on the planet if you consider their weight and biomass, but we'll be focusing on a machine that doesn't look anything like a cockroach yet is bio-inspired and borrows the principals of the cockroach so that when it starts running, it is able to traverse these very, very broken and unstable landscapes. The first time that that had been achieved by any legged machine. We'll move from hexopods to quadrupeds, four-legged machines, and we'll spend some time talking about the marvelous quadrupeds that have been pioneered by our friends at Boston Dynamics founded by Marc Raibert, the very person who taught us about pogo sticking the robots. We'll spend some time talking about how Marc and his engineers have built those pogo sticks into these quadrupeds. Finally, we'll introduce bipeds, and we'll distinguish between bipeds that have many, many, many, many degrees of actuated freedom such as this anthropomorphic design to the left and those machines that are much, much more inspired by the mechanics of running such as the ATRIAS machine built by Professor Hurst at Oregon State University. We will spend a fair bit of time thinking about how to take those principles and extract them away from either the anthropomorphic or the mere pogo sticking designs into designs of bodies that are much, much more versatile but still embody these pogo sticking dynamical principles. Here's a leaping machine built by Ms. Anna Brill with Avik De, in our GRASP Laboratory over the last year, showing how to get leaping behaviors out of a tailed biped that is called the Jerboa, about which you'll hear much more in week four. Welcome to week three. We're going to spend the week putting the bodies together and thinking about how what we learned about dynamics and controls and kinematics can begin to inform our design of behaviors.