a robot/rc crane

[ruben301088]

Hi, I wanna start building a robot, and at that, this is my first.
My goal is to build a small crane; no bigger than what will fit on my desk. However, I need it to be able to lift stuff. I have the LEGO nxt 2.0 set, and have tried a couple of solutions, but when lifting, it puts way too much strain on the servos, obviously.

So, I wanted to ask the forum, what would be the best/cheapest/easiest approach. At the moment, I am looking at pneumatics, since it is safe and the concept makes sense to my inexperienced person, although, as far as i've gathered, the parts aren't exactly cheap.

Also, if I build an RC pneumatic crane thingy, It will take a lot of sensors to make it autonomous, since there are very limited measuring controls on pneumatic pumps, where servos offer much more control.

Any advice is appreciated.

Oh, and probably worth mentioning, the crane is more like an arm. Im imagining three jointed, where the first joint is at the base, and the third is at the very end, where the hand is. It should have a grabbing hand instead og a string with a hook.... So more of an arm than a crane, I guess.

I intend to operate it with my pyMCU, running the software on a connected computer.

Ruben

[newInRobotics]

My goal is to build a small crane; no bigger than what will fit on my desk.

It all depends on the size of Your table then 

I have the LEGO nxt 2.0 set, and have tried a couple of solutions, but when lifting, it puts way too much strain on the servos, obviously.

Yeah, servos are not exactly what they use in real-life cranes/robotic arms. You probably want to look at stepper motors.

So, I wanted to ask the forum, what would be the best/cheapest/easiest approach. At the moment, I am looking at pneumatics, since it is safe and the concept makes sense to my inexperienced person, although, as far as i've gathered, the parts aren't exactly cheap.

Best, cheapest and easiest are miles away from each other, moreover doesn't go well with pneumatics  Pneumatic systems are expensive, bulky and not very precise (at least not something that can be achieved easily, although possible).

Oh, and probably worth mentioning, the crane is more like an arm. Im imagining three jointed, where the first joint is at the base, and the third is at the very end, where the hand is. It should have a grabbing hand instead og a string with a hook.... So more of an arm than a crane, I guess.

Crane and robotic arm are very different in terms of design. Light to medium weight cranes normally have one or two prismatic joints to increase/decrease reach, hydraulic strut to set angle, and base that is rotated most likely with hydro-motor. Heavy cranes are vertical and use pulley system for reach, and another pulley system together with counter-weight for lifting; all is driven by huge electric motors or diesel engine. Robotic arms normally have rotating base, and stepper motor at each joint, some have prismatic joints as well; these robotic arms have ability to "freeze" at any given point without "jittering" - thanks to stepper motors, you cannot achieve that with servos.

So, what help exactly do You need? 

[ruben301088]

It sounds like stepper motors are exactly what i need. From what i gather they can handle a lot of pressure if i pick the right size. Also, they seem to provide almost complete control, since i can switch between each step. A brilliant suggestion.

That might actually be all i needed to know

Thanks for taking the time to offer such a thorough answer
Oh, and yes, from your way of describing them, the arm is what i want to do, not the crane. Now i just need to find a place to get the parts i need I live in Denmark, Europe