The Cartesian Hand: In-Hand Manipulation with All-Linear Fingers (generalroboticslab.com)
37 pointsby AareyBaba2 days ago8 comments
chuckledog 2 hours ago
Reminds me a bit of the TARS robot from Interstellar. It was portrayed as a highly capable robot with limited articulation. (CASE too) https://interstellarfilm.fandom.com/wiki/Robot
Animats 4 hours ago
It works best on problems which are strongly Cartesian. The chopsticks demo shows the limitations of this. The gripper can pick up two chopsticks, but it can't do much with them, because it can't rotate them to bring them together at the points.
But it seems to be good for lab equipment with simple geometry.
Also, where are the motors? Inside the gripper, or at the other end of cables?
octoberfranklin 3 hours ago
Rotational screw-on caps are not Cartesian, and this excels at dealing with them.
I'm very impressed with this.
Re: chopsticks, oh but it can! It can roll one chopstick between one pair of grippers. Do that while holding the tip against a fixed object and you'll tilt the chopstick. Once you get the tips touching, it can use them.
The motors are inside those chonky things just outside the fingertips. I'm guessing hobby servos, which are tiny cheap and strong.
varjag 2 hours ago
Still there are fundamental limitations. Holding a bowl full of liquid, a heavy jug with a rounded handle etc.
octoberfranklin 37 minutes ago
What would be the problem with a bowl of liquid?
The balancing there comes from the wrist joint, not the fingers. Obviously this device is supposed to be mounted on a wrist joint that can rotate (pitch+yaw). Wrist joints are pretty well-understood these days.
Rounded handle I don't see the problem unless the hole is too small for one of the fingers.
varjag 7 minutes ago
Holding a rounded handle with a rectangular profile slider is inherently unstable as it's extremely sensitive to the pinch point.
And the bowl has a radius that make orthogonal grip impractical.
octoberfranklin 3 hours ago
One of the challenging parts of imitating human hands is that our hands sense through the same surface which deforms as we bend our fingers. We don't have good robotic devices that can do that.
This sidesteps the problem: the surface that contacts the object is flat and never bends, so you can apply a huge variety of very detailed grid sensors to it.
The "rolling between the fingers" trick is ultimately what eliminates the need for deformation.
SCAQTony 4 hours ago
...or AI assisted robotic surguries