Hype aside, there aren’t necessarily all that many areas where robots have the potential to step into an existing workflow and immediately provide a substantial amount of value. But one of the areas that we have seen several robotics companies jump into recently is box manipulation—specifically, using robots to unload boxes from the back of a truck, ideally significantly faster than a human. This is a good task for robots because it plays to their strengths: you can work in a semi-structured and usually predictable environment, speed, power, and precision are all valued highly, and it’s not a job that humans are particularly interested in or designed for.
One of the more novel approaches to this task comes from Dextrous Robotics, a Memphis TN-based startup led by Evan Drumwright. Drumwright was a professor at GWU before spending a few years at the Toyota Research Institute and then co-founding Dextrous in 2019 with an ex-student of his, Sam Zapolsky. The approach that they’ve come up with is to do box manipulation without any sort of suction, or really any sort of grippers at all. Instead, they’re using what can best be described as a pair of moving arms, each gripping a robotic chopstick.
We can pick up basically anything using chopsticks. If you're good with chopsticks, you can pick up individual grains of rice, and you can pick up things that are relatively large compared to the scale of the chopsticks. Your imagination is about the limit, so wouldn't it be cool if you had a robot that could manipulate things with chopsticks? —Evan Drumwright
It definitely is cool, but are there practical reasons why using chopsticks for box manipulation is a good idea? Of course there are! The nice thing about chopsticks is that they really can grip almost anything (even if you scale them up), making them especially valuable in constrained spaces where you’ve got large disparities in shapes and sizes and weights. They’re good for manipulation, too, able to nudge and reposition things with precision. And while Dextrous is initially focused on a trailer unloading task, having this extra manipulation capability will allow them to consider more difficult manipulation tasks in the future, like trailer loading, a task that necessarily happens just as often as unloading does but which is significantly more complicated to robot-ize.
Even though there are some clear advantages to Dextrous’ chopstick technique, there are disadvantages as well, and the biggest one is likely that it’s just a lot harder to use a manipulation technique like this. “The downside of the chopsticks approach is, as any human will tell you, you need some sophisticated control software to be able to operate,” Drumwright tells us. “But that’s part of what we bring to the game: not just a clever hardware design, but the software to operate it, too.”
Meanwhile, what we’ve seen so far from other companies in this space is pretty consistent use of suction systems for box handling. If you have a flat, non-permeable surface (as with most boxes), suction can work quickly and reliably and with a minimum of fancy planning. However, suction has limits form of manipulation, because it’s inherently so sticky, meaning that it can be difficult and/or time consuming to do anything with precision. Other issues with suction include its sensitivity to temperature and moisture, its propensity to ingest all the dirt it possibly can, and the fact that you need to design the suction array based on the biggest and heaviest things that you anticipate having to deal with. That last thing is a particular problem because if you also want to manipulate smaller objects, you’re left trying to do so with a suction array that’s way bigger than you’d like it to be. This is not to say that suction is inferior in all cases, and Drumwright readily admits that suction will probably prove to be a good option for some specific tasks. But chopstick manipulation, if they can get it to work, will be a lot more versatile.
Dextrous Robotics co-founders Evan Drumwright and Sam Zapolsky. Photo: Dextrous Robotics
I think there's a reason that nature has given us hands. Nature knows how to design suction devices—bats have it, octopi have it, frogs have it—and yet we have hands. Why? Hands are a superior instrument. And so, that's why we've gone down this road. I personally believe, based on billions of years of evolution, that there's a reason that manipulation is superior and that that technology is going to win out. —Evan Drumwright
Part of Dextrous’ secret sauce is an emphasis on simulation. Hardware is hard, so ideally, you want to make one thing that just works the first time, rather than having to iterate over and over. Getting it perfect on the first try is probably unrealistic, but the better you can simulate things in advance, the closer you can get. “What we’ve been able to do is set up our entire planning perception and control system so that it looks exactly like it does when that code runs on the real robot,” says Drumwright. “When we run something on the simulated robot, it agrees with reality about 95 percent of the time, which is frankly unprecedented.” Using very high fidelity hardware modeling, a real time simulator, and software that can directly transfer between sim and real, Dextrous is able to confidently model how their system performs even on notoriously tricky things to simulate, like contact and stiction. The idea is that the end result will be a system that can be developed faster while performing more complex tasks better than other solutions.
We were also wondering why this system uses smooth round chopsticks rather than something a little bit grippier, like chopsticks with a square cross section, and maybe with some higher friction something on the inside surface. Drumwright explains that the advantage of the current design is that it’s symmetrical around its rotational axis, meaning that you only need five degrees of freedom to fully control it. “What that means practically is that things can get a whole lot simpler—the control algorithms get simpler, the inverse kinematics algorithms get simpler, and importantly the number of motors that we need to drive in the robot goes down.”
Simulated version of Dextrous Robotics’ hardware. Screenshot: Dextrous Robotics
Dextrous took seed funding 18 months ago, and since then they’ve been working on both the software and hardware for their system as well as finding the time to score an NSF SBIR phase 1 grant. The above screenshot shows the simulation of the hardware they’re working towards (chopstick manipulators on two towers that can move laterally), while the Franka Panda arms are what they’re using to validate their software in the meantime. New hardware should be done imminently, and over the next year, Dextrous is looking forward to conducting paid pilots with real customers.