"The Problems With Humanoid Robots"

Humanoid robots are certainly having their day. We are seeing a flood of articles and think pieces discussing how these mechanical men are about to change our lives any day now. What’s much harder to find are serious discussions about whether making a robot look like a human makes any sense. This post by Brad Porter, someone with considerable experience making robots that actually do things, is a good start.

There are three specific problems with humanoid robots. One first I believe will be overcome with continued advances in AI. The second might be overcome with enough investor dollars. The third is the Achilles heel.

1. The AI isn’t there yet. We lack the generalized controls necessary for robust balancing systems to work in production environments.
2. Hardware investments when the AI isn’t there are bad investments. The dollars required to bring a humanoid robot to production quality are likely to be well over $1B invested.
3. Biomimicry isn’t the right approach. Humanoid robots aren’t the right design solution for most production tasks.

Stephen Boyd, one of the true luminaries in the space of controls research and engineering gave an interesting talk. In fairness to Dr. Boyd, I’ll summarize my take-aways which may be different than what he hoped to convey. But overall the talk compared a number of controls techniques, including reinforcement learning, and articulated clearly how they could be reduced to problems of convex optimization, greatly simplifying the problem space. But then he said something interesting (paraphrasing, but hoping I got this right), “so just get the dimensionality under 6 and these problems become classically solvable.” That was a big a-ha for me. This is exactly what we do in robotics. We reduce the dimensionality of the problem down below 6 degrees of control actuation and we derive a controller using some combination of math, convex optimization, RL or equivalent techniques. Quad-copter drones are 4 degrees of actuation and generally an IMU. Cars are throttle, brake, steer. Airplanes are generally aileron, rudder, elevator, throttle. What Agility has done beautifully is simplify the physics of walking such that the controller can be modeled as a spring-mass system. What Boston Dynamics has done, impressively, is demonstrated the ability to transition from one control regime to another seamlessly, but each controller is simplified. Successful hand controllers in production have reduced the dimensionality with eigenhands, or lower-dimensional controls spaces.

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As I said up front, I think advances in ML/AI will address this problem. We will eventually get more robust robotics controllers, but there’s a reasonable argument that this problem is as hard, or maybe even harder given the open-ended nature of the world, as developing a self-driving car. For instance, self-driving cars are passively stable. They don’t care if they’re transporting liquids or solids, mass sloshing doesn’t affect them. But if a humanoid robot is carrying a box with a bowling ball in it, the controls problem just got very very hard. Humans stabilize our bodies with a lot of different muscles, including our neck muscles which subtly refine the position of our head to keep our center of mass above our feet. That’s super hard to do! And look, we still can’t put a timeline on robust AI for self-driving cars.

 

This brings us to our second problem. Hardware is expensive. And complex hardware is really expensive. Combining complex hardware engineering costs with open-ended, unsolved AI problems, means the funding requirements are open-ended. And it’s not like you can do some work with a humanoid without solving the balancing problem. I suppose some humanoids are just using a wheeled base, but they’re not intrinsically stable… their center of mass is still too high to be safe.

Is there enough money in the venture ecosystem to make a dent in this? Probably, though Softbank has some of the deepest pockets and thrown a lot of money at robots. Google as well. The returns for those investments to date are more than a little disappointing.

But the biggest problem is that humanoids are the wrong solution for most tasks. Not all tasks, I do think Disney’s animatronic actors will become more and more sophisticated and impressive. In Toyko, there’s a hotel where animatronic dinosaurs check you in. An animatronic human might be a little friendlier than a dinosaur. But when it comes to doing real work in the world around us, biomimicry isn’t the answer.

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Wheels are the right answer in logistics, in manufacturing, in hospitals, in airports, in stadiums, on the sidewalk, in office complexes, and in nearly every commercial environment. Also, passive stability, having at least 3 points of contact on the ground, preferably 4, is extremely valuable. Keeping the payload inside the cone of stability rather than cantilevered in front of a robot is better as well.