Re: Force feedback handwheels

Hi Les,

I have never seen such an application on a real CNC machine,
however, it seems as though Game controllers use this sort of stuff.

As for using a servo - no way would I do that - like you said, it
could in effect turn the MPG - very bad thing!

A brake makes the safest sense. If you are working with Servos
(Instead of steppers) for the axes drives, you could monitor the
current through the servo with a micro and have it apply a
proportionate amount of force to the brake. This way, the feedback
is relative to the load on the axis, not the spindle. This would
have a direct "feel" relative to the work being done. Otherwise,
just monitoring the spindle would apply braking to both X and Z
while you may only be cutting on one.

Just some thoughts - sounds like a fun project!

Chris





--- In CAD_CAM_EDM_DRO@yahoogroups.com, Les Newell <lesnewell@...>
wrote:

>
> I have been busy designing electronic hand wheels for my latest

lathe

> conversion and I have been wondering about force feedback. This

machine

> will be used half as a manual and half as a cnc so in manual mode

I want

> it to feel like a manual. It is not difficult to monitor the servo
> current. This can then be used to feed back to the wheel. There

are two

> options for generating the feedback:
>
> 1) use a servo motor on the wheel. This would be the most

realistic but

> could potentially end up back driving the wheel if you don't have

hold

> of it - a very bad idea.
>
> 2) Use a variable brake on the wheel. This is easy enough to do

using a

> simple solenoid operated brake. It also has the advantage of being
> failsafe and there is no chance of back driving the wheel.
>
> Has anyone done this or used commercial machine with force

feedback

> (assuming any manufacturer does it)? If so is it worth the effort?
>
> Les
>