Robotic Arm Motor Selection

[YAN-1]

Hi everyone. I am about to start working on a project in which I will build a simple robotic arm with 3 joints and probably a gripper. I need some help with finding the appropriate motors for the joints. I need servos with their driving circuits so that I can control them from PICs. The arm won't have to deal with large loads; just maybe hold a glass of water and move it but I guess they have to be low-speed, high-torque motors. Can you please direct me to what motors are usually used in such applications? Thanks a lot.

Nichola V. Abdo

 

[bloody-orc]

normal "student versions" are using standard servos. high power ones use pneumatics/hydraulics. you can use DC motors with wormgears to give a lot of power and slow speed. also then you need sone controlcircuit to position it right. you cant use steppers, they have wery low power and are huge, BUT they are precise.

 

[YAN-1]

Well thanks but can you please direct me to certain servos with ready control circuits that I just connect to a microcontroller like a PIC 16F877 and send a PWM signal for instance? There are many motors out there but I need those that are usually used in robotics and robotic arms. I'd appreciate any advice from anyone with experience in this field. Thanks again.

Nichola V. Abdo

 

[bloody-orc]

please tell us what is slow speed and large loads. a cup of water is actually pretty heavy you know. and if you have please send us the plans of your arm. you could use all servos as they are controlled via one wire that you send pulses in (+ power supply so it makes 3 wires in total per servo). there are mini servos than can take 1.2kg on a 1cm "arm", then there are normal standard servos that can take 3kg and then there are high power ones that can take 6 or 12 or something like that on a 1cm rod/arm. also the size and power consumption increase.

When you want to use normal DC motors (what are sometimes smaller and have more torque) then you also need to build a H-Bridge between the motor and uController.

I hope this is more helpful for you.

 

[YAN-1]

Thanks. Well actually I don't have the plans yet. I am required to build an arm with a shoulder, an elbow, a wrist, and a gripper. The load is small since this is just for demostration purposes. But I think the servo at the shoulder has to be the largest because it will carry the entire arm and the other motors. I would prefer servos over normal DC motor because I don't want to get into the building process of driving circuits and H-bridges becuase this is not the purpose of the project. What is your advice? Thanks.

 

[bloody-orc]

then i suggest geting yourself some servos. most of them can be standard 3kg servos but for the shoulder (and maybe even for the elbow alsi) i suggest something bigger. like 6kg servo or so. then it is all about mechanics. Where to get those servos you ask? from your local electronics suplyeror if they dont have it from online electronics stores. (cand name you any certain onses though)