robot joint offsets required to overcome internal absolute encoder

Hi!

I now have the DH params working well.

However as LinuxCNC does not see theta values I need to offset joint1 by 90 degrees at startup so that the robot posture is a true representation  to the encoders or real word position/posture.  I can't do G5* as internally the robot limits movement to -70/+90.  I need to add 90 to the encoder value before it gets to joint.1.motor-pos-fb - is there some motor or other offset feature in the ini file I can use here?

Best practice for this?


 

can i use this somehow with a fake encoder for sim?

setp    a2-offset.offset 90
net     a2-pos-cmd            joint.1.motor-pos-cmd       a2-offset.in
net     a2-pos-cmd-comp       a2-offset.out               
net     a2-pos-fb-comp        a2-offset.fb-out            joint.1.motor-pos-fb

# --- closedloop signals ---
net a1-pos-cmd      joint.0.motor-pos-cmd  => joint.0.motor-pos-fb
# net a2-pos-cmd      joint.1.motor-pos-cmd  => joint.1.motor-pos-fb
net a3-pos-cmd      joint.2.motor-pos-cmd  => joint.2.motor-pos-fb
net a4-pos-cmd      joint.3.motor-pos-cmd  => joint.3.motor-pos-fb
net a5-pos-cmd      joint.4.motor-pos-cmd  => joint.4.motor-pos-fb
net a6-pos-cmd      joint.5.motor-pos-cmd  => joint.5.motor-pos-fb

then join up a2-pos-fb-comp with gui?

net :j0 <= joint.0.pos-fb => pyvcp.joint0 => meca500gui.joint1

# fix me change to a2-pos-fb-comp ??

net :j1 <= joint.1.pos-fb => pyvcp.joint1 => meca500gui.joint2

net :j2 <= joint.2.pos-fb => pyvcp.joint2 => meca500gui.joint3
net :j3 <= joint.3.pos-fb => pyvcp.joint3 => meca500gui.joint4
net :j4 <= joint.4.pos-fb => pyvcp.joint4 => meca500gui.joint5
net :j5 <= joint.5.pos-fb => pyvcp.joint5 => meca500gui.joint6

#net :vismach-clear <= pyvcp.vismach-clear => vismach.plotclear


Sadly I don't understand the arrows too well here in this postgui. How can I link up a2-pos-fb-comp to :j1 else it picks up the non compensated value I think.

this error out and shuts down

net :j1 <= a2-pos-fb-comp => pyvcp.joint1 => meca500gui.joint2

hi andy, i'm trying to set this up in sim mode. maybe going about it all wrong way.

kinematics fail using offset, back to the drawing board

We need a way to add back into the system the "theta" values for following so the robot poses correctly in sim and kinematics work correctly.

theta j1= neg 90
theta j5 = pos 180

I am open to guidance on how to achieve this in both sim and real.  Thanks!