Techno Dolly Need advice on controller

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12 May 2014 02:45 #46825 by Knoxvisuals
I am building a medium sized robots camera crane. I will need a 5 axis controller and most likely belt drive so I can teach it what I want to do.

I have the base built and the parts for the robotic arm are under the bench or on order.
I need guidance and information on the CNC type stepper motors and controller that can LEARN my manual movements. This is a self funded project ,so funds are limited..within reason.

I need guidance to the right source , so I can learn how to make this thing function.

The arm is balanced. weights are used to keep everything in balance. it may have to lift 15 pounds.

The x axis will be the extendable arm
the y axis will rotate the column
the z axis will cause the camera end to go up and down.
the 4th axis will cause the column to rise and lower about 30 incheW
the fith axis will run a motor that pulls a cable under neath to pull the whole thing on its 27 ft track. We will run a cable to a drum on a stepper motor under the rig.

Bottom line: I want to physically teach the robot arm to move where I want it to, then replay.

No drawing to be used as in CNC.

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12 May 2014 05:32 #46829 by PCW
One note:

You probably do not want step motors since you need feedback from the axis position
if you expect to teach the robot arm by moving it by hand. Step motors also have a fair
amount of residual torque when powered down which may interfere with smooth manual
motion. Servo motors would be more appropriate (but more expensive)

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13 May 2014 07:12 #46857 by andypugh

I need guidance and information on the CNC type stepper motors and controller that can LEARN my manual movements.


AS PCW has said, this looks more like a job for servos, though you might be able to use stepper motors with encoders on them.

Ideally for this application you would probably want to be using absolute encoders, to avoid the need for a homing procedure prior to teaching.

It is apparently possible to get quadrature pulses out of steppers when they are unpowered, but the voltage level depends strongly on movement speed, so some serious buffering would be needed. You would probably still lose counts during very slow movements.

Do you have any feel for the torque/power that will be needed? There is a vendor in South Korea on eBay who always has a lot of servos and drives on offer at reasonable prices. But "reasonable" still does mean cheap.
stores.ebay.com/FA-PARTS/SERVO-DRIVE-AMP...html?_fsub=456141017
I have never actually bought anything from him, though I have been tempted.

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