Back to Back Motor Control

[Eoghann]

We are building a high inertia robot that requires very high precision on several rotary axis. We need a a system to negate the backlash and have decided that Back To Back motors would be best. Because one motor is "dragging" on the other Indramat and Siemens solutions only allow one motor to drive in one direction ie. both motors must be capable of producing the full torque required for the axis. Does anyone know of a controller that would allow torque "sharing" (so that we could have two smaller motors) between the two drives?

any help gratefully received!

 

[jbartos]

Suggestion: Visit

http://

http://www.avltech.com/Pages/RotoLokWEBpg2.html

for "zero to nearly zero backlash"
Of course, in some instances or statistically, there may happen to be a zero backlash, however, the worst case is the nearly zero backlash.

 

[jOmega]

JB:

In using a search engine to investigate "Zero Backlash" ... one of the things found would be:

Textron Power Transmission - AccuDrive, Benzlers, Cone Drive, ...
Absolute Zero Backlash. Double-enveloping ... Many Cone Drive products are
available with Absolute Zero Backlash worm gearsets. Absolute Zero ...

http://www.textronpt.com/cgi-bin/

products.cgi?prod=zero&group=worm

And there are many other such products, you'll find, that afford ZERO backlash.


One wonders if after splitting hairs, spltting atoms is the next task ..

 

[Eoghann]

For those of you intrested in the actual control system needed for these systems there is a good article on the Danaher website:
ftp://ftp.kollmorgen.com/dist/techdocs/app_prod_notes/600rdpbacklash.pdf

We are finalising the supplier list at the moment and gathering quotes. It is more than likely that NUM (

http://www.schneider-num.com)

will be chosen due to the turnkey solution they have offered. They propose a full CNC controller which also has full PLC capabilities so we no longer need a PLC for interlocking with support equipment. They have many of the Back to Back systems in operation (one in Glasgow that I shall be visiting).

 

[jbartos]

Comment on the previous posting: I visited the posted link and there was the following statement:
The backlash between both the left motor and the load, and the right motor and the load, was adjusted to be approximately 0.010” (0.4mm).
The backlash is adjustable. Apparently, it is somewhat greater than zero due to the manufacturing tolerances of the equipment.