The Triple Delta Robot Arm (and Leg)

delta By now you’d think we’ve seen just about every means of robotic actuator possible. We have Cartesian bots, Stewart platforms, SCARA bots, Delta bots, and even some exceedingly bizarre linkages from [Nicholas Seward]. We’re not done with odd robotic arms, it seems, and now we have Delta-ish robots that can move outside their minimum enclosed volume. They’re fresh from the workshop of [Aad van der Geest], and he’s calling them double and triple Deltas.

Previous Delta robots have used three universal joints to move the end effector up and down, and side to side. They’re extremely fast and are a great design for 3D printers and pick and place machines, but they do have a limitation: the tip of a single Delta can not move much further than the base of the robot.

By adding more parallelograms to a Delta, [Aad] greatly increases working volume of a his robots. One of the suggested uses for this style of bot is for palletizers, demonstrated in the video below by stacking Jenga blocks. There is another very interesting application: legs. There’s footage of a small, simple triple Delta scooting around the floor, supported by wire training wheels below. It makes a good cat toy, but we’d love to see a bipedal robot with this style of legs.

17 thoughts on “The Triple Delta Robot Arm (and Leg)

  1. I’d like to know how the positional accuracy decreases with every additional linkage.
    Every additional linkage would also increase the amount of force the motor needs to exert.
    Very cool though, kudos

    1. Well, I think the decreases in resolution or strength of the linkage could be compensated for easily enough by changing how it’s driven. I think that for applications that needed the extra range of motion it would be an OK tradeoff to make.

  2. Man, I love that arm design. And if that’s not the cutest damn robot I’ve ever seen, I don’t know what is. I wonder how many delta segments can be stacked before it becomes completely inoperable.

    This seems like one of the few arms that would work as a suitable universal one-size-fits all arm, except in high torque requirements. You could also chain the arms together, with multiple servo sets, it would be possible to reach around things if you did that.
    …I want one…

  3. Well done!

    I was kind of hoping for a truly “stacked” delta system – eg, several deltas working in series, one hanging from the next. With that (hellish though it might be to actually put together- though hydraulics/flex-rod linkages might help) you could create a reasonably useful industrial tentacle.

  4. Very nice design and demonstration. BTW, does anyone recall the name or link for the two servo robot that had two loops of wire on the ground. One servo would lift up one loop and the other would rotate the body relative to the loop still on the ground. It was a very novel idea and was fun to watch. I would like to build one but can’t recall the post even after looking and searching for some time. Thanks in advance for any ideas on locating the post.

  5. “By adding more parallelograms to a Delta, [Aad] greatly increases working volume of a his robots.”
    If he had just made the dimensions of the linkages larger, it would achieve the same thing. 3x 1″ linkages is the same as 1x 3″ linkage. Draw the vector diagram to see.
    It does reduce the required operating volume, but doesn’t magically make the parallel arms move further.

    1. Walk 3 blocks down the road, turn right, walk three blocks.
      Walk 1 block down the road, turn right, walk 1 block, turn left,
      Walk 1 block down the road, turn right, walk 1 block, turn left
      Walk 1 block down the road, turn right, walk 1 block, turn left

      Which one is more elegant?

      1. Neither. “Elegant” is subjective — but mostly is based on how “well” a problem is solved, and you didn’t post enough information to make that call. Maybe one of those paths is easier because there aren’t any steep hills, sidewalks, or there’s less traffic. Or there’s a better shade one way and blazing hot sun the other.

        1. Agreed, I was thinking about this problem yesterday while having a conversation with a coworker about different distance metrics. In abstract spaces, use of the Manhattan distance doesn’t matter too much, but when you try to use it for routing delivery trucks you run into problems as it’s important to factor in the number of turns and I believe left turns are more costly on average than right turns.

    2. If you make the arms longer you will need a lot of empty space around your robot. For example the palletizer arms would hit the roof if you want to stack to the same height.

  6. Very nice. I’m working on a something similar, an arm consisting of two Canfield joints in series. The eventual robot will be two of these arms, facing each other, one for holding the workpiece and the other holding a tool.

  7. Love it, a fantastic compact robotic arm/leg, all without a wrist/elbow. I guess the next step is to add an wrist and and extended claw/hand and see the possibilities…
    A single larger delta, I think, can do the same range, but this version made it ‘slimmer’…

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