giant robots

[neodarkstar]

I've got part of an idea figured out.(i had one of those aha moments)
human framed robots using disc joints for simple joints(legs, elbows, fingers) and a series of push and pull hydraulic pistons for complex joints(shoulder, legs hips,neck, wrists)
the issue i keep running into is supporting weight.
so i'm posting it to put it out there for others to further

 

[Cognisant]

By "disc joint" do you mean some kind of hinge?

the issue i keep running into is supporting weight.

Think about suspension, it'll also protect your actuators from shocks and vibration.

 

[ItsRelative]

Think we are not far from reverse-engineering human ball joint artificially, it's material question and carbon nanotubes as bones would work great.
I like how evolution has found so ingenious solutions already, like using pressured fluid so that 2 parts of the joint wont make contact, kinda reminds of rebelling magnets. I wonder what could be strong and elastic enough to keep those fluids in the joint while having enough pressure to support whatever it's supporting.
When joint is done just use hydraulics or some form of artificial muscles and you have something that works like human arm.

 

[neodarkstar]

By "disc joint" do you mean some kind of hinge?


Think about suspension, it'll also protect your actuators from shocks and vibration.

yes i meant hinge but it would need more control than a free swinging hinge (since the goal is to imitate the human body) again push pull using hydraulic actuators
and suspension could work in place of muscles.

Think we are not far from reverse-engineering human ball joint artificially, it's material question and carbon nanotubes as bones would work great.
I like how evolution has found so ingenious solutions already, like using pressured fluid so that 2 parts of the joint wont make contact, kinda reminds of rebelling magnets. I wonder what could be strong and elastic enough to keep those fluids in the joint while having enough pressure to support whatever it's supporting.
When joint is done just use hydraulics or some form of artificial muscles and you have something that works like human arm.

for fluid maybe a scaled version of motor oil pumpimg through a sponge like lining around the contact points thereby lubricating the joint(need a better idea thats a bit lower maintainence) and carbon nano tubes as bones works perfectly

 

[Cognisant]

Two hinges, like one of those X shaped tire irons but with pins instead of nut sockets, and if we lay this X down and put a swivel above it (like a halo) and one underneath, there you go the equivalent of a ball joint.

Now adding actuators to this, thats really tricky.

 

[neodarkstar]

Two hinges, like one of those X shaped tire irons but with pins instead of nut sockets, and if we lay this X down and put a swivel above it (like a halo) and one underneath, there you go the equivalent of a ball joint.

Now adding actuators to this, thats really tricky.

great idea!
fyi clarification:by actuators i meant the push pull piston like item(simple in and out directionality)

 

[Cognisant]

for fluid maybe a scaled version of motor oil pumpimg through a sponge like lining around the contact points thereby lubricating the joint(need a better idea thats a bit lower maintainence) and carbon nano tubes as bones works perfectly

Atm the only way to get carbon nano tubes is to make your own, in other words it's not happening, luckily Aluminium is more than adequate and relatively cheap

Hydrulics are awesome but impractical, just take a look at a digger or something, those pistons have a lot of power but that's not where the power comes from, it comes from the massive engine on the back of the machine, yeah.

Whatever the T-800 uses, it's not hydrulics, more likely a solenoid of some kind.

 

[Cognisant]

great idea! that works perfectly but then how does the x move?

It itself doesn’t.

On the end of each arm is a pin, pins on opposite sides of the X attach to the same frame piece, so two will attach to the equivalent of the pelvis while the other two attach to the equivalent of the femur, in effect you get two hinges in the same place providing freedom of motion in different directions.

With that one swivel lets the whole thing rotate (so the leg can be pointed diagonally from the pelvis) and another allows the leg itself to rotate within this motion (which enables us to sit down with crossed legs, for example, but it's also a key part of the walking motion).

 

[neodarkstar]

It itself doesn’t.

On the end of each arm is a pin, pins on opposite sides of the X attach to the same frame piece, so two will attach to the equivalent of the pelvis while the other two attach to the equivalent of the femur, in effect you get two hinges in the same place providing freedom of motion in different directions.

With that one swivel lets the whole thing rotate (so the leg can be pointed diagonally from the pelvis) and another allows the leg itself to rotate within this motion (which enables us to sit down with crossed legs, for example, but it's also a key part of the walking motion).

ah i get it now and it doesn't have to be hydraulics it not the tech that would move it'd be the combination of push and pull managed by a logic board and/or control program

 

[dark]

Two hinges, like one of those X shaped tire irons but with pins instead of nut sockets, and if we lay this X down and put a swivel above it (like a halo) and one underneath, there you go the equivalent of a ball joint.

Now adding actuators to this, thats really tricky.

That is called a universal joint in mechanics, they suck on the most part to be honest. That type of joint in the automotive world is almost obsolete. Although the Germans stopped using those about 30 years ago.

 

[Cognisant]

*hugs dark, in sentiment*

 

[dark]

For joints, you may be interested in looking at how BMW does it on their drive shafts. Depending on the movement of the joints, if minimal, a flexjoint is superb I believe, though they do make really good universal joint like joints for movement that needs to be larger.

My reasons for universal joints not working in robots is quite simple. Universal joints are not designed to have that much pressure on them like it would if used for a knee and such. Joints that are under a lot of pressure can be found in the suspension of an automobile. I would look at joints for an independent rear suspension vehicle, though sometimes they aren't joints, but some are. But the movement is typically limited because of shock absorbers and springs. Take a look at the suspension of off road vehicles, they have a lot of movement.

 

[Cognisant]

I'm thinking biped, approximately 60kg, don't you think a universal joint could work if the design was solid enough? 2cm of solid steel can hold a lot of weight...
(I have no idea how much)

 

[dark]

The only problem I see is that U-joints are designed and have been designed for horizontal movement. They wear down from that, if the pressure were to be placed vertically, then the joints would wear down quicker unless something can be figured out to avoid that. It is less the X part of it than the bearings or whatever is used to connect that to the two parts. I am sure one could create a heavy duty universal joint, support it with shock absorbers and various springs, but the movement would be limited. But that would be fine if that is done multiple times. Though the main problem I see is that to make something like this move would require too many engines. So you couldn't make it too heavy duty, because that would just take more energy.

I hate to actually agree with Ockham's Razor, but the simple design seems like it would work the best here. Take things like shoulders. Then the bones in that connects the top of the arm to the lower, I know there are terms that I don't know. Designs like this seem to work well. While knees seem to fail even in us.