Arms

[jaspinall]

Sooooo....been a very long time since posting on here

I've still got JARPod under wraps, boxed away waiting for spring...

However, my next immediate project is going to be a 5 or 6 DOF arm. We need one in work to do a specific job, been looking around commercial solutions and the prices are just *scary* (to say the least!)

Given we have in house CNC and Solidworks, I'm in the process of gleaning as much info looking at robotic arm photos around the net... Got some really useful ideas...

Matt, a question for you. Your hexapod drive circuitry and complementary software - how easy would it be to adapt the software to control arms?

[Matt Denton]

Hi Jason,

Well if your using PWM servos then you could use the p.Brain with the SSC code to drive them form a serial port, but not sure how useful this would be, as you would still need to do the IK for the 6 DOF arm! Plus you would only be using 6 of the 24 channels, also if your building a big arm then you may need more resolution and position feedback.

[jaspinall]

Hi Matt

Yes, it's my intention to use PWM servos at the moment as the arm will be moving some incredibly light material between four stations on a 140 degree arc. Infact, the material being moved is around 5g, so, as long as the servos can move the arm around itself, the load shouldn't pose any issues.

I did read somewhere where someone has hacked PWM servos, taking the potentiometer out of the servo, ripping it open, glueing a magnet to the spindle, and installing some magnetic flux detecting IC (forget the exact details, but it increases the accuracy/resolution quite nicely) - will have to dig the link out for them... Whether or not I need to bump up the accuracy of the servos remains to be seen.

I'd quite like to use the p.Brain, but currently know diddly squat about SSC code :/ You done any "arm" work in your field Matt?

It terms of size, I'm guessing when fully stretched out in the vertical, the arm will stand between 300 and 400mm high... My initial design attempts are concentrating around the gripper, which needs parallel movement to hold a disc of plastic 50mm in diameter...