Hello community! This is my first post and I am hoping the expertise and experience here can help point me in the right direction...
I'm working on a project for a robotic (duh, right?) arm with a minimum of 6 DOF and needs (would prefer) to support a max load weight of about approximately 50 lbs, when fully extended to a length of about 2 meters/6ft, give or take depending on the final hardware selection.
My question is this: Which solution would you guys recommend as far as motor choice? I'd prefer steppers for the finer positioning, but I know that servos have - typically - a stronger holding torque. Any ideas are welcome. I know that for weight like this I'm bordering on small industrial capacity. Perhaps geared steppers?
you will have multiple thousands of dollars wrapped up in an arm able to hold 50lbs at 6ft?
I realize my initial comment is rather negative. I wouldn’t even begin to have an idea about the motor required. There are formulas that will give you an idea. The other thing you need to consider is the mass of the arm/actuator/end effector + the mass you plan on moving. Your “elbow” actuator will be moving 75 to 100 lbs. Your “shoulder” will be moving 100 to 125 lbs. Mind you my numbers are just SWAG, but, I reiterate, you are asking for some pretty serious hardware.
My apologies for not actually answering your question. I guess I just got caught up in the impression you seem to be biting off more than you can maybe chew.
I’m thinking about building I’m thinking about building a roughly life sized human arm for SA-Groucho. I think it will be lucky to bring me one plate or a single bottle. I’m thinking about using a wheelchair motor for the shoulder and perhaps Torxis servos for the rest.
One thing to remember is that using heavy motors means that the other motors have to lift those motors in addition to the weight of the arm. You can help with this by keeping as many as possible near or at the base of the arm. I like large robots, but I wouldn’t try a 50 lb lift from a six foot long arm. I’ve built an arm before, but it lifted only ounces in addition to its own weight.
Just curious: what is the arm for? And how are you planning on powering it?
Another thought for motors: the Dynamixel Pro series, but they are extremely expensive ($1,000 US each). Also using A/C motors will probably be much less expensive.
How fast do you need the arm to move? You could make clever use of worm gears and have a large toothed gear at the joint that is driven by a worm gear mounted to a motor. The torque of the motor will be multiplied by how ever many teeth are on the joint gear, and as a bonus the load on the arm won’t back drive the motor when you turn off power to it. The drawback is the speed of the motor will be divided by the number of teeth on the large gear. You could also print out a wheel encoder disk and use that for position feedback on the gear joint position.
