I'm consistently impressed by Seeed Studio's support for various levels of DIY in their products. I realize that many of the products are not totally original, but what I find interesting and original about the company is their interest in diy-accessibility and partnering with companies like Trmnl [0]. It's somewhere in between Raspberry Co, Adafruit, Pimoroni, and the like.
The LeRobot / SO-ARM101 uses $9 motors [1] has 5 degrees of freedom and is available with all parts for $300 [2] fully assembled. They don't quote a payload, reach, speed or repeatability. Their target market is people who want to play around with things like imitation learning outside of simulation at the lowest possible price, and who don't care about payload, reach, speed or repeatability.
The reBot Arm B601 uses $150 motors [3] has 6 degrees of freedom and a kit with all parts is $1200 [4] not assembled. They claim a 1.5kg payload, 650mm reach, and 0.2mm repeatability - numbers that are good for the price, if true (take that 0.2mm with a pinch of salt). It has no brakes, so don't lift anything you're not willing to drop. Obviously it doesn't compare to a $40,000 industrial arm, but for the price you wouldn't expect it to.
They actually describe it as "6+1 degrees of freedom" [1] with the gripper being the "+1" - so it's got base, shoulder, elbow, wrist1, wrist2, wrist3, and gripper.
This is a conventional way of describing things. Traditionally robot arms come with a "tool flange" where you attach your own "end effector" (which might be a gripper, or a suction cup, or a welding gun, or a paint sprayer, or whatever) and we count the degrees of freedom before the tool flange separately from those after the tool flange.
Occasionally robots come with 7 degrees of freedom [2] which gives you more options for reaching the same tool flange position. This can be useful in certain applications, like working around obstacles in the environment. It's uncommon though.
It should be noted that 6 degrees of freedom is the minimum that enables reaching any point with any orientation of the effector, while 7 degrees of freedom is what a human arm has with the shoulder fixed, which enables reaching some points even around some obstacles that would block a 6 degrees of freedom arm.
Including the movements of the shoulder, a human arm has 9 degrees of freedom, but the additional 2 degrees of freedom do not provide a new capability, they just extend the range of possible motions beyond that limited by the joints of the other degrees of freedom.
An arm with many degrees of freedom, like an octopus arm, could reach some places even when having to avoid many obstacles.
His point is that the robot has split the kinematics to have 3 DOF for position near the base and 3 orientation DOF on the wrist.
This still gives you 6 DOF on the end effector, which is pretty good, but overall the arm design is restricted in its ability to route around obstacles.
This downside has an upside though. Since every cartesian position has exactly one pose for the first 3 DOF, the inverse kinematics are simpler and you do not run into singularities for basic position control when maintaining a constant orientation.
I'm sorry, I was confused. This arm appear to have wrist pitch and yaw "backwards" from standard split forearm configuration, and I mistook the wrist yaw motor to be something else.
Although, it does still worry me that there don't seem to be a lot of footage of this arm with that axis away from its neutral position...
Have any companies you recommend? We’ve been looking for something to automate part loading/unloading on a CNC, don’t have the budget for a UR yet but have been looking for something around 10K-20K
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[0] https://github.com/Seeed-Projects/reBot-DevArm/blob/main/LIC...
0. https://www.hackster.io/news/seeed-partners-with-trmnl-s-rya...
The reBot Arm B601 uses $150 motors [3] has 6 degrees of freedom and a kit with all parts is $1200 [4] not assembled. They claim a 1.5kg payload, 650mm reach, and 0.2mm repeatability - numbers that are good for the price, if true (take that 0.2mm with a pinch of salt). It has no brakes, so don't lift anything you're not willing to drop. Obviously it doesn't compare to a $40,000 industrial arm, but for the price you wouldn't expect it to.
[1] https://www.aliexpress.com/item/1005008284773473.html [2] https://www.seeedstudio.com/SO-ARM-101-Assembled-Kit-Pro-p-6... [3] https://www.aliexpress.com/item/1005008012684745.html [4] https://www.seeedstudio.com/reBot-Arm-B601-DM-Bundle.html
https://www.compart.com/en/unicode/U+1F9BE
so, six variables that produce a posture. 6DoF.
but explaining this makes me feel like i'm missing some deeper meaning in your comment?
This is a conventional way of describing things. Traditionally robot arms come with a "tool flange" where you attach your own "end effector" (which might be a gripper, or a suction cup, or a welding gun, or a paint sprayer, or whatever) and we count the degrees of freedom before the tool flange separately from those after the tool flange.
Occasionally robots come with 7 degrees of freedom [2] which gives you more options for reaching the same tool flange position. This can be useful in certain applications, like working around obstacles in the environment. It's uncommon though.
[1] https://www.seeedstudio.com/reBot-Arm-B601-DM-Bundle.html [2] https://explicit-robotics.github.io/exp_robot/kuka_LBR_iiwa7...
Including the movements of the shoulder, a human arm has 9 degrees of freedom, but the additional 2 degrees of freedom do not provide a new capability, they just extend the range of possible motions beyond that limited by the joints of the other degrees of freedom.
An arm with many degrees of freedom, like an octopus arm, could reach some places even when having to avoid many obstacles.
This still gives you 6 DOF on the end effector, which is pretty good, but overall the arm design is restricted in its ability to route around obstacles.
This downside has an upside though. Since every cartesian position has exactly one pose for the first 3 DOF, the inverse kinematics are simpler and you do not run into singularities for basic position control when maintaining a constant orientation.
Although, it does still worry me that there don't seem to be a lot of footage of this arm with that axis away from its neutral position...
we have a bunch at work, happy to chat about them (email in profile), they are about 10k
$830 for just the motors