Russ Tedrake on Underactuated Robotics, Control, Dynamics, and the Zen of Barefoot Movement

This episode features Russ Tedrake, an MIT roboticist and VP of Robotics Research at Toyota Research Institute, discussing his work on controlling complex, underactuated, and stochastic robotic systems. Tedrake highlights the beauty and efficiency of passive dynamic walkers, such as those built by Steve Collins and Andy Ruina, which leverage gravity and mechanics to achieve graceful, human-like motion without active control. He contrasts this with traditional control methods that often try to counteract natural dynamics, advocating for a more "zen" approach where robots work with, rather than against, physics. The conversation also delves into the fascinating phenomenon of dead fish swimming upstream by resonating with water vortices, illustrating the profound role of mechanics in biological efficiency.\n\nTedrake draws a crucial distinction between control (active energy input via motors) and mechanics (passive dynamics, springs, dampers), arguing that the line between them is often blurred and that the importance of dynamics in biological systems is frequently underestimated. He cites examples like bone remodeling in the human body as an adaptation of mechanics, not just brain control. The discussion touches upon the challenges and motivations behind bipedal robot design, acknowledging that while it's a difficult control problem, the human form is compelling for robots operating in environments built for humans. He also cautions against flawed evolutionary arguments, emphasizing the role of random events and survival in harsh conditions over steady-state efficiency.\n\nFrom a practical standpoint, Tedrake shares his personal experience and insights from barefoot running, which he adopted after studying biomechanics. He emphasizes that barefoot running provides immediate feedback on gait flaws, encouraging a softer, more protective landing that prioritizes long-term joint health over speed or distance. His advice for aspiring barefoot runners is to start slowly and listen to the body's signals. He also describes his unique commute, which often involves running, biking, or even rowing, as a vital time for thinking, decompressing, and achieving mental clarity, demonstrating a personal integration of his philosophy of movement and efficiency into daily life.\n\nUltimately, the conversation explores the broader implications of understanding and harnessing natural dynamics, both in robotics and in human movement. It suggests that by allowing physics to do most of the work, systems can achieve greater elegance and efficiency. This perspective extends beyond engineering to personal well-being, where mindful engagement with one's body and environment can lead to sustainable practices and a deeper appreciation for the intricate interplay of mechanics, control, and adaptation in the world around us.

I think the most beautiful motion of a robot has to be the passive dynamic walkers.

You don't have to do that you can just let go let physics do most of the work.

The dead fish basically starts swimming upstream it's completely dead no brain no motors no control but it somehow the mechanics of the fish resonate with the vortex street and it starts swimming upstream.

I mean I think part of the point is that we shouldn't draw a line as as clearly as we tend to.

The idea that somehow it's only our brain that's adapting or evolving is not right.

I think the most compelling one is that the world is built for the human form and if you want a robot to work in the world we have today then you know having a human form is a pretty good way to go.

If you take your shoes off then if you hit hard with your foot at all then it hurts you don't like run 10 miles and then and then realize you've done something some damage you have immediate feedback telling you that you've done something that's that's maybe sub-optimal and you change your gait.

Your foot has as many muscles and sensors as your hand does right sensors ooh okay and we do amazing things with our hands and we stick our foot in a big solid shoe right so there's I think you know when you're barefoot you're you're just giving yourself more proprioception and that's why you're more aware of some of the gait flaws and stuff like this.

I think I am better at work because I take time to think on the way in so I plan my day around it and I I rarely feel that those are really in at odds.

The clarity of thought that some of the more mathematical control theory can bring to even very complex messy looking problems is really it really had a big impact on me.