Thursday, October 21, 2021

Bending Robots – Are they Better than other Robots?

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So, Is not it very interesting? the Famous YouTuber Derek Muller, owner of Veritasium recently released a video on youtube about bending robots. So, he went to Stanford and met Zach Hammond and his Bending Robot. Derek asked him about the functionality of the soft robot.

So, you can kind of chain the rolls together in the robot to roll it around in any environment. this rolling is known as Punctuated Rolling Locomotion. In this motion it is kind of stuck on a face until it tips over and now it is on a new face. And then it can continue to move its center of gravity. Once the center of gravity exits the support polygon or the base, then it tips over one of the edges of the face.

This is a different soft robot made out of flexible tubing. The design of this robot was to mimic the way a turtle walks. Where diagonally legs move together. Compressed air entirely powers its movement. And the interesting part about this robot is that it does not require any electronics. All of the circuitry of this robot is pneumatic. This means the robot can be used in places like mines, where electronics could spark an explosion, or in the strong magnetic fields around MRI machines. But the question arises,

For operation around humans, there is not much damage a soft robot can do to you! Because the fundamental structure of this robot is compliant, there is only some maximum that it could ever exert on me. So it is inherently safe to be operating around people.

In the answer to the question about who did build the robot, Zach said that he and another grad student build the entire robot on their own.

It took almost one month to build all the soft components along with the robot.

The main structural members of this robot are fabric tubes inflated with air. The red tube of the robot is nylon fabric and then internally there is a polyethylene tube that provides the airtightness. The tubes are inflated to about six PSI above atmospheric. So it’s almost one and a half atmospheres. Each tube passes through pairs of rollers connected to a motor. The rollers pinch the tube so it bends kind of like a pinched straw. Add the rods and then we have this like high friction material wrapped around the rods.

And then that coupled with the fact that we have this pressurized tube that’s kind of pushing the membrane of the tube into the rollers, prevents us from slipping. By driving the motor, it changes the length of the tubes. Kind of like when a clown creates a twist in a balloon and then folds that balloon into a balloon animal. The difference between what the clown does and what we do is that there is some passage of air between adjacent segments of the tube. So that as the robot drives around, we are not pressurizing the segments of the tube.

This robot is made of four inflated tubes, each one connected to a pair of motors, forming triangular sides. They think that they kind of look like sausage links when put together, that is why they have named the robot after different types of sausages. So the one that he showed is called Polish, another one is Chorizo, there are a linguica and Kielbasa over there somewhere.

The shape of the robot is called Octahedron because if you draw line between this kind of kinematic joints in the robot, that will look like a octahedron.

Driving the motors together allows the robot to dramatically change shape. It can get very tall or short and squat. But since the tubes themselves don’t change in length, the overall perimeter of the robot, the length of all the edges combined doesn’t change. So, the robot is considered isoparametric.

The hard robots are used to are strong and precise. Their actions are accurate and repeatable. But they are also heavy and they can’t really change their volume dramatically. But the soft robot is still capable of carrying a heavy load.

The robot is operated by using a GUI in MATLAB. It enables the owner to just put in the positions that he wants the robots to move in inches and then send them out. There is another other functionality of some like stored configurations to send to the robots.

Soft robots also have the advantage of shape changing. They generally can become tall to go over obstacles or short to fit under obstructions. So, if there is some rocks that it didn’t see or that it wanted to roll over, It could simply do that and the compliance of the tubes would simply just bend around that disturbance.

One of the nice things about this type of robotic structures is that they can shrink down their volume very drastically. And because volume on rockets is such ans expensive premium. Being able to have a robot that can pack down small for transport is very valuable. So NASA was at one point looking into trust robots for exactly that reason. And they’ve contacted Zach since they’ve made this robot to explore different ideas for space exploration projects.

So, one of the things that they’re thinking about doing is deploying robots underneath a sheet of ice. So they’re gonna drill through this sheet of ice and then deposit a robot through what is a kind of a small diameter hole. And so if you can have a robot that can change its volume very drastically or be disassembled and then reassembled to form like a much larger structure. Then you can have large robots that are able to fit through the tight spaces. And be deployed in kind of difficult to access areas.

The robots are like some kind of octopus as they use their shape-changing ability and their compliance to squeeze through tight passageways, and then also to wrap their body around objects. So for example, they can open jars with their tentacles, and of the things we want to use this robot for is grasping and manipulating objects.

So, this robot is even capable of picking objects up off the ground.

Because of the compliance of the tubes, it has a natural ability to grasp and manipulate objects because as its does so, the tubes bend ever so slightly, which increases the contact area and distributes evenly, the forces that are exerted on the objects.

© Veritasium

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