Add some « fictive » axis on 3-axis machine

Hi everyone,

In the framework of a phD, I want to modify the trajectory of milling in “real-time” (or on-line, during process).
We have a 3-axis Cincinnati Sabre Milacron fully functional with LinuxCNC (with Motenc axis drive).
The idea is to to add two fictive axis (U and V), which are not pilotable but can modify positions values of X and Y (in the goal fo feint the machine en modify the trajectory).

Some questions :
- Have you already see (or try) this type of configuration with fictive axis, which use of entry point without any motor, and can modify another axis data ?
- Do I have to modify the file trivkins.c and rebuilt LinuxCNC ? Or just modify hal file of motenc.hal ?
- For trivkins, do I have to modify just like this ? :
double x = joint[0] + joints [6];
double y = joint[1] + joints [7];
pos->tran.x = x;
pos->tran.y = y;
.
.
.
pos->u = "exterior data";
pos->v = "exterior data"


joints[0] = pos->tran.x - pos->tran.u;
joints[1] = pos->tran.y - pos->tran.v;

- I have to modify other file?
- Can I update data of fictive axis in real-time (with rotary coder) but no motor?

Thanks in advance for your answers.
Don’t hesitate to ask some questions in English (or French) for more details.

(For my presentation and first post on forum LinuxCNC, and to see some answer to my request, you can go under this link : www.linuxcnc.org/index.php/french/forum/46-francais/28479#52533)

you would need to modify trivkins.c and re-compile linuxcnc
or copy trivkins to a different name and then add to the linuxcnc source , you would need to modify the makefile also .

then add the fictional axis to your ini file and treat as normal

Ok. Thank you for you reply.

For now, I'll try just to modify HAL file (like andypugh said : www.linuxcnc.org/index.php/french/forum/46-francais/28479#52539) because it seems to be more simple than modify trivkins.c and re-compile. And if i haven't the results that i need, i will modify kinematics like you say.